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• What are most demanded web-development languages today for startups?

  - by Liston Catch

  What technologies are in demand nowaydas for web-development for web-startups? For frontend its all clear: HTML5, JS, AJAX, JQuery. But what about backend? What languages (and frameworks) should I consider using? I am not asking "which language is best", I just need a list of modern languages and frameworks (and not Pascal, Delphi or Basic) which are demanded and well-payed. UPD: I totally decline the "it's all about logic, not about language. language is just a tool" concept. While THEORETICALLY it's true, in reality the time you need to study required frameworks is counted by months, so language DOES matter indeed. That's why I made this topic UPD 2: Mason Wheeler, so you seriously advice me to go for Delphi? You think its DEMANDED nowadays? Or you just tell me an exception which only confirms the rule? It's like "one guy won 100,000,000$ in lottery. Just for you to know that lottery is not a bad way to earn money."

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• Sendmail Failing to Forward Locally Addressed Mail to Exchange Server

  - by DomainSoil

  I've recently gained employment as a web developer with a small company. What they neglected to tell me upon hire was that I would be administrating the server along with my other daily duties. Now, truth be told, I'm not clueless when it comes to these things, but this is my first rodeo working with a rack server/console.. However, I'm confident that I will be able to work through any solutions you provide. Short Description: When a customer places an order via our (Magento CE 1.8.1.0) website, a copy of said order is supposed to be BCC'd to our sales manager. I say supposed because this was a working feature before the old administrator left. Long Description: Shortly after I started, we had a server crash which required a server restart. After restart, we noticed a few features on our site weren't working, but all those have been cleaned up except this one. I had to create an account on our server for root access. When a customer places an order, our sites software (Magento CE 1.8.1.0) is configured to BCC the customers order email to our sales manager. We use a Microsoft Exchange 2007 Server for our mail, which is hosted on a different machine (in-house) that I don't have access to ATM, but I'm sure I could if needed. As far as I can tell, all other external emails work.. Only INTERNAL email addresses fail to deliver. I know this because I've also tested my own internal address via our website. I set up an account with an internal email, made a test order, and never received the email. I changed my email for the account to an external GMail account, and received emails as expected. Let's dive into the logs and config's. For privacy/security reasons, names have been changed to the following: domain.com = Our Top Level Domain. email.local = Our Exchange Server. example.com = ANY other TLD. OLDadmin = Our previous Server Administrator. NEWadmin = Me. SALES@ = Our Sales Manager. Customer# = A Customer. Here's a list of the programs and config files used that hold relevant for this issue: Server: > [root@www ~]# cat /etc/centos-release CentOS release 6.3 (final) Sendmail: > [root@www ~]# sendmail -d0.1 -bt < /dev/null Version 8.14.4 ========SYSTEM IDENTITY (after readcf)======== (short domain name) $w = domain (canonical domain name) $j = domain.com (subdomain name) $m = com (node name) $k = www.domain.com > [root@www ~]# rpm -qa | grep -i sendmail sendmail-cf-8.14.4-8.e16.noarch sendmail-8.14-4-8.e16.x86_64 nslookup: > [root@www ~]# nslookup email.local Name: email.local Address: 192.168.1.50 hostname: > [root@www ~]# hostname www.domain.com /etc/mail/access: > [root@www ~]# vi /etc/mail/access Connect:localhost.localdomain RELAY Connect:localhost RELAY Connect:127.0.0.1 RELAY /etc/mail/domaintable: > [root@www ~]# vi /etc/mail/domaintable # /etc/mail/local-host-names: > [root@www ~]# vi /etc/mail/local-host-names # /etc/mail/mailertable: > [root@www ~]# vi /etc/mail/mailertable # /etc/mail/sendmail.cf: > [root@www ~]# vi /etc/mail/sendmail.cf ###################################################################### ##### ##### DO NOT EDIT THIS FILE! Only edit the source .mc file. ##### ###################################################################### ###################################################################### ##### $Id: cfhead.m4,v 8.120 2009/01/23 22:39:21 ca Exp $ ##### ##### $Id: cf.m4,v 8.32 1999/02/07 07:26:14 gshapiro Exp $ ##### ##### setup for linux ##### ##### $Id: linux.m4,v 8.13 2000/09/17 17:30:00 gshapiro Exp $ ##### ##### $Id: local_procmail.m4,v 8.22 2002/11/17 04:24:19 ca Exp $ ##### ##### $Id: no_default_msa.m4,v 8.2 2001/02/14 05:03:22 gshapiro Exp $ ##### ##### $Id: smrsh.m4,v 8.14 1999/11/18 05:06:23 ca Exp $ ##### ##### $Id: mailertable.m4,v 8.25 2002/06/27 23:23:57 gshapiro Exp $ ##### ##### $Id: virtusertable.m4,v 8.23 2002/06/27 23:23:57 gshapiro Exp $ ##### ##### $Id: redirect.m4,v 8.15 1999/08/06 01:47:36 gshapiro Exp $ ##### ##### $Id: always_add_domain.m4,v 8.11 2000/09/12 22:00:53 ca Exp $ ##### ##### $Id: use_cw_file.m4,v 8.11 2001/08/26 20:58:57 gshapiro Exp $ ##### ##### $Id: use_ct_file.m4,v 8.11 2001/08/26 20:58:57 gshapiro Exp $ ##### ##### $Id: local_procmail.m4,v 8.22 2002/11/17 04:24:19 ca Exp $ ##### ##### $Id: access_db.m4,v 8.27 2006/07/06 21:10:10 ca Exp $ ##### ##### $Id: blacklist_recipients.m4,v 8.13 1999/04/02 02:25:13 gshapiro Exp $ ##### ##### $Id: accept_unresolvable_domains.m4,v 8.10 1999/02/07 07:26:07 gshapiro Exp $ ##### ##### $Id: masquerade_envelope.m4,v 8.9 1999/02/07 07:26:10 gshapiro Exp $ ##### ##### $Id: masquerade_entire_domain.m4,v 8.9 1999/02/07 07:26:10 gshapiro Exp $ ##### ##### $Id: proto.m4,v 8.741 2009/12/11 00:04:53 ca Exp $ ##### # level 10 config file format V10/Berkeley # override file safeties - setting this option compromises system security, # addressing the actual file configuration problem is preferred # need to set this before any file actions are encountered in the cf file #O DontBlameSendmail=safe # default LDAP map specification # need to set this now before any LDAP maps are defined #O LDAPDefaultSpec=-h localhost ################## # local info # ################## # my LDAP cluster # need to set this before any LDAP lookups are done (including classes) #D{sendmailMTACluster}$m Cwlocalhost # file containing names of hosts for which we receive email Fw/etc/mail/local-host-names # my official domain name # ... define this only if sendmail cannot automatically determine your domain #Dj$w.Foo.COM # host/domain names ending with a token in class P are canonical CP. # "Smart" relay host (may be null) DSemail.local # operators that cannot be in local usernames (i.e., network indicators) CO @ % ! # a class with just dot (for identifying canonical names) C.. # a class with just a left bracket (for identifying domain literals) C[[ # access_db acceptance class C{Accept}OK RELAY C{ResOk}OKR # Hosts for which relaying is permitted ($=R) FR-o /etc/mail/relay-domains # arithmetic map Karith arith # macro storage map Kmacro macro # possible values for TLS_connection in access map C{Tls}VERIFY ENCR # who I send unqualified names to if FEATURE(stickyhost) is used # (null means deliver locally) DRemail.local. # who gets all local email traffic # ($R has precedence for unqualified names if FEATURE(stickyhost) is used) DHemail.local. # dequoting map Kdequote dequote # class E: names that should be exposed as from this host, even if we masquerade # class L: names that should be delivered locally, even if we have a relay # class M: domains that should be converted to $M # class N: domains that should not be converted to $M #CL root C{E}root C{w}localhost.localdomain C{M}domain.com # who I masquerade as (null for no masquerading) (see also $=M) DMdomain.com # my name for error messages DnMAILER-DAEMON # Mailer table (overriding domains) Kmailertable hash -o /etc/mail/mailertable.db # Virtual user table (maps incoming users) Kvirtuser hash -o /etc/mail/virtusertable.db CPREDIRECT # Access list database (for spam stomping) Kaccess hash -T<TMPF> -o /etc/mail/access.db # Configuration version number DZ8.14.4 /etc/mail/sendmail.mc: > [root@www ~]# vi /etc/mail/sendmail.mc divert(-1)dnl dnl # dnl # This is the sendmail macro config file for m4. If you make changes to dnl # /etc/mail/sendmail.mc, you will need to regenerate the dnl # /etc/mail/sendmail.cf file by confirming that the sendmail-cf package is dnl # installed and then performing a dnl # dnl # /etc/mail/make dnl # include(`/usr/share/sendmail-cf/m4/cf.m4')dnl VERSIONID(`setup for linux')dnl OSTYPE(`linux')dnl dnl # dnl # Do not advertize sendmail version. dnl # dnl define(`confSMTP_LOGIN_MSG', `$j Sendmail; $b')dnl dnl # dnl # default logging level is 9, you might want to set it higher to dnl # debug the configuration dnl # dnl define(`confLOG_LEVEL', `9')dnl dnl # dnl # Uncomment and edit the following line if your outgoing mail needs to dnl # be sent out through an external mail server: dnl # define(`SMART_HOST', `email.local')dnl dnl # define(`confDEF_USER_ID', ``8:12'')dnl dnl define(`confAUTO_REBUILD')dnl define(`confTO_CONNECT', `1m')dnl define(`confTRY_NULL_MX_LIST', `True')dnl define(`confDONT_PROBE_INTERFACES', `True')dnl define(`PROCMAIL_MAILER_PATH', `/usr/bin/procmail')dnl define(`ALIAS_FILE', `/etc/aliases')dnl define(`STATUS_FILE', `/var/log/mail/statistics')dnl define(`UUCP_MAILER_MAX', `2000000')dnl define(`confUSERDB_SPEC', `/etc/mail/userdb.db')dnl define(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnl define(`confAUTH_OPTIONS', `A')dnl dnl # dnl # The following allows relaying if the user authenticates, and disallows dnl # plaintext authentication (PLAIN/LOGIN) on non-TLS links dnl # dnl define(`confAUTH_OPTIONS', `A p')dnl dnl # dnl # PLAIN is the preferred plaintext authentication method and used by dnl # Mozilla Mail and Evolution, though Outlook Express and other MUAs do dnl # use LOGIN. Other mechanisms should be used if the connection is not dnl # guaranteed secure. dnl # Please remember that saslauthd needs to be running for AUTH. dnl # dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl dnl define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl dnl # dnl # Rudimentary information on creating certificates for sendmail TLS: dnl # cd /etc/pki/tls/certs; make sendmail.pem dnl # Complete usage: dnl # make -C /etc/pki/tls/certs usage dnl # dnl define(`confCACERT_PATH', `/etc/pki/tls/certs')dnl dnl define(`confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl dnl define(`confSERVER_CERT', `/etc/pki/tls/certs/sendmail.pem')dnl dnl define(`confSERVER_KEY', `/etc/pki/tls/certs/sendmail.pem')dnl dnl # dnl # This allows sendmail to use a keyfile that is shared with OpenLDAP's dnl # slapd, which requires the file to be readble by group ldap dnl # dnl define(`confDONT_BLAME_SENDMAIL', `groupreadablekeyfile')dnl dnl # dnl define(`confTO_QUEUEWARN', `4h')dnl dnl define(`confTO_QUEUERETURN', `5d')dnl dnl define(`confQUEUE_LA', `12')dnl dnl define(`confREFUSE_LA', `18')dnl define(`confTO_IDENT', `0')dnl dnl FEATURE(delay_checks)dnl FEATURE(`no_default_msa', `dnl')dnl FEATURE(`smrsh', `/usr/sbin/smrsh')dnl FEATURE(`mailertable', `hash -o /etc/mail/mailertable.db')dnl FEATURE(`virtusertable', `hash -o /etc/mail/virtusertable.db')dnl FEATURE(redirect)dnl FEATURE(always_add_domain)dnl FEATURE(use_cw_file)dnl FEATURE(use_ct_file)dnl dnl # dnl # The following limits the number of processes sendmail can fork to accept dnl # incoming messages or process its message queues to 20.) sendmail refuses dnl # to accept connections once it has reached its quota of child processes. dnl # dnl define(`confMAX_DAEMON_CHILDREN', `20')dnl dnl # dnl # Limits the number of new connections per second. This caps the overhead dnl # incurred due to forking new sendmail processes. May be useful against dnl # DoS attacks or barrages of spam. (As mentioned below, a per-IP address dnl # limit would be useful but is not available as an option at this writing.) dnl # dnl define(`confCONNECTION_RATE_THROTTLE', `3')dnl dnl # dnl # The -t option will retry delivery if e.g. the user runs over his quota. dnl # FEATURE(local_procmail, `', `procmail -t -Y -a $h -d $u')dnl FEATURE(`access_db', `hash -T<TMPF> -o /etc/mail/access.db')dnl FEATURE(`blacklist_recipients')dnl EXPOSED_USER(`root')dnl dnl # dnl # For using Cyrus-IMAPd as POP3/IMAP server through LMTP delivery uncomment dnl # the following 2 definitions and activate below in the MAILER section the dnl # cyrusv2 mailer. dnl # dnl define(`confLOCAL_MAILER', `cyrusv2')dnl dnl define(`CYRUSV2_MAILER_ARGS', `FILE /var/lib/imap/socket/lmtp')dnl dnl # dnl # The following causes sendmail to only listen on the IPv4 loopback address dnl # 127.0.0.1 and not on any other network devices. Remove the loopback dnl # address restriction to accept email from the internet or intranet. dnl # DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl dnl # dnl # The following causes sendmail to additionally listen to port 587 for dnl # mail from MUAs that authenticate. Roaming users who can't reach their dnl # preferred sendmail daemon due to port 25 being blocked or redirected find dnl # this useful. dnl # dnl DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl dnl # dnl # The following causes sendmail to additionally listen to port 465, but dnl # starting immediately in TLS mode upon connecting. Port 25 or 587 followed dnl # by STARTTLS is preferred, but roaming clients using Outlook Express can't dnl # do STARTTLS on ports other than 25. Mozilla Mail can ONLY use STARTTLS dnl # and doesn't support the deprecated smtps; Evolution <1.1.1 uses smtps dnl # when SSL is enabled-- STARTTLS support is available in version 1.1.1. dnl # dnl # For this to work your OpenSSL certificates must be configured. dnl # dnl DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl dnl # dnl # The following causes sendmail to additionally listen on the IPv6 loopback dnl # device. Remove the loopback address restriction listen to the network. dnl # dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnl dnl # dnl # enable both ipv6 and ipv4 in sendmail: dnl # dnl DAEMON_OPTIONS(`Name=MTA-v4, Family=inet, Name=MTA-v6, Family=inet6') dnl # dnl # We strongly recommend not accepting unresolvable domains if you want to dnl # protect yourself from spam. However, the laptop and users on computers dnl # that do not have 24x7 DNS do need this. dnl # FEATURE(`accept_unresolvable_domains')dnl dnl # dnl FEATURE(`relay_based_on_MX')dnl dnl # dnl # Also accept email sent to "localhost.localdomain" as local email. dnl # LOCAL_DOMAIN(`localhost.localdomain')dnl dnl # dnl # The following example makes mail from this host and any additional dnl # specified domains appear to be sent from mydomain.com dnl # MASQUERADE_AS(`domain.com')dnl dnl # dnl # masquerade not just the headers, but the envelope as well dnl FEATURE(masquerade_envelope)dnl dnl # dnl # masquerade not just @mydomainalias.com, but @*.mydomainalias.com as well dnl # FEATURE(masquerade_entire_domain)dnl dnl # MASQUERADE_DOMAIN(domain.com)dnl dnl MASQUERADE_DOMAIN(localhost.localdomain)dnl dnl MASQUERADE_DOMAIN(mydomainalias.com)dnl dnl MASQUERADE_DOMAIN(mydomain.lan)dnl MAILER(smtp)dnl MAILER(procmail)dnl dnl MAILER(cyrusv2)dnl /etc/mail/trusted-users: > [root@www ~]# vi /etc/mail/trusted-users # /etc/mail/virtusertable: > [root@www ~]# vi /etc/mail/virtusertable [email protected] [email protected] [email protected] [email protected] /etc/hosts: > [root@www ~]# vi /etc/hosts 127.0.0.1 localhost.localdomain localhost ::1 localhost6.localdomain6 localhost6 192.168.1.50 email.local I've only included the "local info" part of sendmail.cf, to save space. If there are any files that I've missed, please advise so I may produce them. Now that that's out of the way, lets look at some entries from /var/log/maillog. The first entry is from an order BEFORE the crash, when the site was working as expected. ##Order 200005374 Aug 5, 2014 7:06:38 AM## Aug 5 07:06:39 www sendmail[26149]: s75C6dqB026149: from=OLDadmin, size=11091, class=0, nrcpts=2, msgid=<[email protected]>, relay=OLDadmin@localhost Aug 5 07:06:39 www sendmail[26150]: s75C6dXe026150: from=<[email protected]>, size=11257, class=0, nrcpts=2, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 07:06:39 www sendmail[26149]: s75C6dqB026149: [email protected],=?utf-8?B?dGhvbWFzICBHaWxsZXNwaWU=?= <[email protected]>, ctladdr=OLDadmin (501/501), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=71091, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s75C6dXe026150 Message accepted for delivery) Aug 5 07:06:40 www sendmail[26152]: s75C6dXe026150: to=<[email protected]>,<[email protected]>, delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=161257, relay=email.local. [192.168.1.50], dsn=2.0.0, stat=Sent ( <[email protected]> Queued mail for delivery) This next entry from maillog is from an order AFTER the crash. ##Order 200005375 Aug 5, 2014 9:45:25 AM## Aug 5 09:45:26 www sendmail[30021]: s75EjQ4O030021: from=OLDadmin, size=11344, class=0, nrcpts=2, msgid=<[email protected]>, relay=OLDadmin@localhost Aug 5 09:45:26 www sendmail[30022]: s75EjQm1030022: <[email protected]>... User unknown Aug 5 09:45:26 www sendmail[30021]: s75EjQ4O030021: [email protected], ctladdr=OLDadmin (501/501), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=71344, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknown Aug 5 09:45:26 www sendmail[30022]: s75EjQm1030022: from=<[email protected]>, size=11500, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 09:45:26 www sendmail[30021]: s75EjQ4O030021: to==?utf-8?B?S2VubmV0aCBCaWViZXI=?= <[email protected]>, ctladdr=OLDadmin (501/501), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=71344, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s75EjQm1030022 Message accepted for delivery) Aug 5 09:45:26 www sendmail[30021]: s75EjQ4O030021: s75EjQ4P030021: DSN: User unknown Aug 5 09:45:26 www sendmail[30022]: s75EjQm3030022: <[email protected]>... User unknown Aug 5 09:45:26 www sendmail[30021]: s75EjQ4P030021: to=OLDadmin, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=42368, relay=[127.0.0.1] [127.0.0.1], dsn=5.1.1, stat=User unknown Aug 5 09:45:26 www sendmail[30022]: s75EjQm3030022: from=<>, size=12368, class=0, nrcpts=0, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 09:45:26 www sendmail[30021]: s75EjQ4P030021: s75EjQ4Q030021: return to sender: User unknown Aug 5 09:45:26 www sendmail[30022]: s75EjQm5030022: from=<>, size=14845, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 09:45:26 www sendmail[30021]: s75EjQ4Q030021: to=postmaster, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=43392, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s75EjQm5030022 Message accepted for delivery) Aug 5 09:45:26 www sendmail[30025]: s75EjQm5030022: to=root, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=45053, dsn=2.0.0, stat=Sent Aug 5 09:45:27 www sendmail[30024]: s75EjQm1030022: to=<[email protected]>, delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=131500, relay=email.local. [192.168.1.50], dsn=2.0.0, stat=Sent ( <[email protected]> Queued mail for delivery) To add a little more, I think I've pinpointed the actual crash event. ##THE CRASH## Aug 5 09:39:46 www sendmail[3251]: restarting /usr/sbin/sendmail due to signal Aug 5 09:39:46 www sm-msp-queue[3260]: restarting /usr/sbin/sendmail due to signal Aug 5 09:39:46 www sm-msp-queue[29370]: starting daemon (8.14.4): queueing@01:00:00 Aug 5 09:39:47 www sendmail[29372]: starting daemon (8.14.4): SMTP+queueing@01:00:00 Aug 5 09:40:02 www sendmail[29465]: s75Ee2vT029465: Authentication-Warning: www.domain.com: OLDadmin set sender to root using -f Aug 5 09:40:02 www sendmail[29464]: s75Ee2IF029464: Authentication-Warning: www.domain.com: OLDadmin set sender to root using -f Aug 5 09:40:02 www sendmail[29465]: s75Ee2vT029465: from=root, size=1426, class=0, nrcpts=1, msgid=<[email protected]>, relay=OLDadmin@localhost Aug 5 09:40:02 www sendmail[29464]: s75Ee2IF029464: from=root, size=1426, class=0, nrcpts=1, msgid=<[email protected]>, relay=OLDadmin@localhost Aug 5 09:40:02 www sendmail[29466]: s75Ee23t029466: from=<[email protected]>, size=1784, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 09:40:02 www sendmail[29466]: s75Ee23t029466: to=<[email protected]>, delay=00:00:00, mailer=local, pri=31784, dsn=4.4.3, stat=queued Aug 5 09:40:02 www sendmail[29467]: s75Ee2wh029467: from=<[email protected]>, size=1784, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost.localdomain [127.0.0.1] Aug 5 09:40:02 www sendmail[29467]: s75Ee2wh029467: to=<[email protected]>, delay=00:00:00, mailer=local, pri=31784, dsn=4.4.3, stat=queued Aug 5 09:40:02 www sendmail[29464]: s75Ee2IF029464: to=OLDadmin, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31426, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s75Ee23t029466 Message accepted for delivery) Aug 5 09:40:02 www sendmail[29465]: s75Ee2vT029465: to=OLDadmin, ctladdr=root (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31426, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (s75Ee2wh029467 Message accepted for delivery) Aug 5 09:40:06 www sm-msp-queue[29370]: restarting /usr/sbin/sendmail due to signal Aug 5 09:40:06 www sendmail[29372]: restarting /usr/sbin/sendmail due to signal Aug 5 09:40:06 www sm-msp-queue[29888]: starting daemon (8.14.4): queueing@01:00:00 Aug 5 09:40:06 www sendmail[29890]: starting daemon (8.14.4): SMTP+queueing@01:00:00 Aug 5 09:40:06 www sendmail[29891]: s75Ee23t029466: to=<[email protected]>, delay=00:00:04, mailer=local, pri=121784, dsn=5.1.1, stat=User unknown Aug 5 09:40:06 www sendmail[29891]: s75Ee23t029466: s75Ee6xY029891: DSN: User unknown Aug 5 09:40:06 www sendmail[29891]: s75Ee6xY029891: to=<[email protected]>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=33035, dsn=2.0.0, stat=Sent Aug 5 09:40:06 www sendmail[29891]: s75Ee2wh029467: to=<[email protected]>, delay=00:00:04, mailer=local, pri=121784, dsn=5.1.1, stat=User unknown Aug 5 09:40:06 www sendmail[29891]: s75Ee2wh029467: s75Ee6xZ029891: DSN: User unknown Aug 5 09:40:06 www sendmail[29891]: s75Ee6xZ029891: to=<[email protected]>, delay=00:00:00, xdelay=00:00:00, mailer=local, pri=33035, dsn=2.0.0, stat=Sent Something to note about the maillog's: Before the crash, the msgid included localhost.localdomain; after the crash it's been domain.com. Thanks to all who take the time to read and look into this issue. I appreciate it and look forward to tackling this issue together.

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• MySQL: Pacemaker cannot start the failed master as a new slave?

  - by quanta

  I'm going to setup failover for MySQL replication (1 master and 1 slave) follow this guide: https://github.com/jayjanssen/Percona-Pacemaker-Resource-Agents/blob/master/doc/PRM-setup-guide.rst Here're the output of crm configure show: node serving-6192 \ attributes p_mysql_mysql_master_IP="192.168.6.192" node svr184R-638.localdomain \ attributes p_mysql_mysql_master_IP="192.168.6.38" primitive p_mysql ocf:percona:mysql \ params config="/etc/my.cnf" pid="/var/run/mysqld/mysqld.pid" socket="/var/lib/mysql/mysql.sock" replication_user="repl" replication_passwd="x" test_user="test_user" test_passwd="x" \ op monitor interval="5s" role="Master" OCF_CHECK_LEVEL="1" \ op monitor interval="2s" role="Slave" timeout="30s" OCF_CHECK_LEVEL="1" \ op start interval="0" timeout="120s" \ op stop interval="0" timeout="120s" primitive writer_vip ocf:heartbeat:IPaddr2 \ params ip="192.168.6.8" cidr_netmask="32" \ op monitor interval="10s" \ meta is-managed="true" ms ms_MySQL p_mysql \ meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true" globally-unique="false" target-role="Master" is-managed="true" colocation writer_vip_on_master inf: writer_vip ms_MySQL:Master order ms_MySQL_promote_before_vip inf: ms_MySQL:promote writer_vip:start property $id="cib-bootstrap-options" \ dc-version="1.0.12-unknown" \ cluster-infrastructure="openais" \ expected-quorum-votes="2" \ no-quorum-policy="ignore" \ stonith-enabled="false" \ last-lrm-refresh="1341801689" property $id="mysql_replication" \ p_mysql_REPL_INFO="192.168.6.192|mysql-bin.000006|338" crm_mon: Last updated: Mon Jul 9 10:30:01 2012 Stack: openais Current DC: serving-6192 - partition with quorum Version: 1.0.12-unknown 2 Nodes configured, 2 expected votes 2 Resources configured. ============ Online: [ serving-6192 svr184R-638.localdomain ] Master/Slave Set: ms_MySQL Masters: [ serving-6192 ] Slaves: [ svr184R-638.localdomain ] writer_vip (ocf::heartbeat:IPaddr2): Started serving-6192 Editing /etc/my.cnf on the serving-6192 of wrong syntax to test failover and it's working fine: svr184R-638.localdomain being promoted to become the master writer_vip switch to svr184R-638.localdomain Current state: Last updated: Mon Jul 9 10:35:57 2012 Stack: openais Current DC: serving-6192 - partition with quorum Version: 1.0.12-unknown 2 Nodes configured, 2 expected votes 2 Resources configured. ============ Online: [ serving-6192 svr184R-638.localdomain ] Master/Slave Set: ms_MySQL Masters: [ svr184R-638.localdomain ] Stopped: [ p_mysql:0 ] writer_vip (ocf::heartbeat:IPaddr2): Started svr184R-638.localdomain Failed actions: p_mysql:0_monitor_5000 (node=serving-6192, call=15, rc=7, status=complete): not running p_mysql:0_demote_0 (node=serving-6192, call=22, rc=7, status=complete): not running p_mysql:0_start_0 (node=serving-6192, call=26, rc=-2, status=Timed Out): unknown exec error Remove the wrong syntax from /etc/my.cnf on serving-6192, and restart corosync, what I would like to see is serving-6192 was started as a new slave but it doesn't: Failed actions: p_mysql:0_start_0 (node=serving-6192, call=4, rc=1, status=complete): unknown error Here're snippet of the logs which I'm suspecting: Jul 09 10:46:32 serving-6192 lrmd: [7321]: info: rsc:p_mysql:0:4: start Jul 09 10:46:32 serving-6192 lrmd: [7321]: info: RA output: (p_mysql:0:start:stderr) Error performing operation: The object/attribute does not exist Jul 09 10:46:32 serving-6192 crm_attribute: [7420]: info: Invoked: /usr/sbin/crm_attribute -N serving-6192 -l reboot --name readable -v 0 The full logs: http://fpaste.org/AyOZ/ The strange thing is I can starting it manually: export OCF_ROOT=/usr/lib/ocf export OCF_RESKEY_config="/etc/my.cnf" export OCF_RESKEY_pid="/var/run/mysqld/mysqld.pid" export OCF_RESKEY_socket="/var/lib/mysql/mysql.sock" export OCF_RESKEY_replication_user="repl" export OCF_RESKEY_replication_passwd="x" export OCF_RESKEY_test_user="test_user" export OCF_RESKEY_test_passwd="x" sh -x /usr/lib/ocf/resource.d/percona/mysql start: http://fpaste.org/RVGh/ Did I make something wrong?

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• Installing Lubuntu 14.04.1 forcepae fails

  - by Rantanplan

  I tried to install Lubuntu 14.04.1 from a CD. First, I chose Try Lubuntu without installing which gave: ERROR: PAE is disabled on this Pentium M (PAE can potentially be enabled with kernel parameter "forcepae" ... Following the description on https://help.ubuntu.com/community/PAE, I used forcepae and tried Try Lubuntu without installing again. That worked fine. dmesg | grep -i pae showed: [ 0.000000] Kernel command line: file=/cdrom/preseed/lubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- forcepae [ 0.008118] PAE forced! On the live-CD session, I tried installing Lubuntu double clicking on the install button on the desktop. Here, the CD starts running but then stops running and nothing happens. Next, I rebooted and tried installing Lubuntu directly from the boot menu screen using forcepae again. After a while, I receive the following error message: The installer encountered an unrecoverable error. A desktop session will now be run so that you may investigate the problem or try installing again. Hitting Enter brings me to the desktop. For what errors should I search? And how? Finally, I rebooted once more and tried Check disc for defects with forcepae option; no errors have been found. Now, I am wondering how to find the error or whether it would be better to follow advice c in https://help.ubuntu.com/community/PAE: "Move the hard disk to a computer on which the processor has PAE capability and PAE flag (that is, almost everything else than a Banias). Install the system as usual but don't add restricted drivers. After the install move the disk back." Thanks for some hints! Perhaps some of the following can help: On Lubuntu 12.04: cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 13 model name : Intel(R) Pentium(R) M processor 1.50GHz stepping : 6 microcode : 0x17 cpu MHz : 600.000 cache size : 2048 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr mce cx8 mtrr pge mca cmov clflush dts acpi mmx fxsr sse sse2 ss tm pbe up bts est tm2 bogomips : 1284.76 clflush size : 64 cache_alignment : 64 address sizes : 32 bits physical, 32 bits virtual power management: uname -a Linux humboldt 3.2.0-67-generic #101-Ubuntu SMP Tue Jul 15 17:45:51 UTC 2014 i686 i686 i386 GNU/Linux lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 12.04.5 LTS Release: 12.04 Codename: precise cpuid eax in eax ebx ecx edx 00000000 00000002 756e6547 6c65746e 49656e69 00000001 000006d6 00000816 00000180 afe9f9bf 00000002 02b3b001 000000f0 00000000 2c04307d 80000000 80000004 00000000 00000000 00000000 80000001 00000000 00000000 00000000 00000000 80000002 20202020 20202020 65746e49 2952286c 80000003 6e655020 6d756974 20295228 7270204d 80000004 7365636f 20726f73 30352e31 007a4847 Vendor ID: "GenuineIntel"; CPUID level 2 Intel-specific functions: Version 000006d6: Type 0 - Original OEM Family 6 - Pentium Pro Model 13 - Stepping 6 Reserved 0 Brand index: 22 [not in table] Extended brand string: " Intel(R) Pentium(R) M processor 1.50GHz" CLFLUSH instruction cache line size: 8 Feature flags afe9f9bf: FPU Floating Point Unit VME Virtual 8086 Mode Enhancements DE Debugging Extensions PSE Page Size Extensions TSC Time Stamp Counter MSR Model Specific Registers MCE Machine Check Exception CX8 COMPXCHG8B Instruction SEP Fast System Call MTRR Memory Type Range Registers PGE PTE Global Flag MCA Machine Check Architecture CMOV Conditional Move and Compare Instructions FGPAT Page Attribute Table CLFSH CFLUSH instruction DS Debug store ACPI Thermal Monitor and Clock Ctrl MMX MMX instruction set FXSR Fast FP/MMX Streaming SIMD Extensions save/restore SSE Streaming SIMD Extensions instruction set SSE2 SSE2 extensions SS Self Snoop TM Thermal monitor 31 reserved TLB and cache info: b0: unknown TLB/cache descriptor b3: unknown TLB/cache descriptor 02: Instruction TLB: 4MB pages, 4-way set assoc, 2 entries f0: unknown TLB/cache descriptor 7d: unknown TLB/cache descriptor 30: unknown TLB/cache descriptor 04: Data TLB: 4MB pages, 4-way set assoc, 8 entries 2c: unknown TLB/cache descriptor On Lubuntu 14.04.1 live-CD with forcepae: cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 13 model name : Intel(R) Pentium(R) M processor 1.50GHz stepping : 6 microcode : 0x17 cpu MHz : 600.000 cache size : 2048 KB physical id : 0 siblings : 1 core id : 0 cpu cores : 1 apicid : 0 initial apicid : 0 fdiv_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov clflush dts acpi mmx fxsr sse sse2 ss tm pbe bts est tm2 bogomips : 1284.68 clflush size : 64 cache_alignment : 64 address sizes : 36 bits physical, 32 bits virtual power management: uname -a Linux lubuntu 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:12 UTC 2014 i686 i686 i686 GNU/Linux lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 14.04.1 LTS Release: 14.04 Codename: trusty cpuid CPU 0: vendor_id = "GenuineIntel" version information (1/eax): processor type = primary processor (0) family = Intel Pentium Pro/II/III/Celeron/Core/Core 2/Atom, AMD Athlon/Duron, Cyrix M2, VIA C3 (6) model = 0xd (13) stepping id = 0x6 (6) extended family = 0x0 (0) extended model = 0x0 (0) (simple synth) = Intel Pentium M (Dothan B1) / Celeron M (Dothan B1), 90nm miscellaneous (1/ebx): process local APIC physical ID = 0x0 (0) cpu count = 0x0 (0) CLFLUSH line size = 0x8 (8) brand index = 0x16 (22) brand id = 0x16 (22): Intel Pentium M, .13um feature information (1/edx): x87 FPU on chip = true virtual-8086 mode enhancement = true debugging extensions = true page size extensions = true time stamp counter = true RDMSR and WRMSR support = true physical address extensions = false machine check exception = true CMPXCHG8B inst. = true APIC on chip = false SYSENTER and SYSEXIT = true memory type range registers = true PTE global bit = true machine check architecture = true conditional move/compare instruction = true page attribute table = true page size extension = false processor serial number = false CLFLUSH instruction = true debug store = true thermal monitor and clock ctrl = true MMX Technology = true FXSAVE/FXRSTOR = true SSE extensions = true SSE2 extensions = true self snoop = true hyper-threading / multi-core supported = false therm. monitor = true IA64 = false pending break event = true feature information (1/ecx): PNI/SSE3: Prescott New Instructions = false PCLMULDQ instruction = false 64-bit debug store = false MONITOR/MWAIT = false CPL-qualified debug store = false VMX: virtual machine extensions = false SMX: safer mode extensions = false Enhanced Intel SpeedStep Technology = true thermal monitor 2 = true SSSE3 extensions = false context ID: adaptive or shared L1 data = false FMA instruction = false CMPXCHG16B instruction = false xTPR disable = false perfmon and debug = false process context identifiers = false direct cache access = false SSE4.1 extensions = false SSE4.2 extensions = false extended xAPIC support = false MOVBE instruction = false POPCNT instruction = false time stamp counter deadline = false AES instruction = false XSAVE/XSTOR states = false OS-enabled XSAVE/XSTOR = false AVX: advanced vector extensions = false F16C half-precision convert instruction = false RDRAND instruction = false hypervisor guest status = false cache and TLB information (2): 0xb0: instruction TLB: 4K, 4-way, 128 entries 0xb3: data TLB: 4K, 4-way, 128 entries 0x02: instruction TLB: 4M pages, 4-way, 2 entries 0xf0: 64 byte prefetching 0x7d: L2 cache: 2M, 8-way, sectored, 64 byte lines 0x30: L1 cache: 32K, 8-way, 64 byte lines 0x04: data TLB: 4M pages, 4-way, 8 entries 0x2c: L1 data cache: 32K, 8-way, 64 byte lines extended feature flags (0x80000001/edx): SYSCALL and SYSRET instructions = false execution disable = false 1-GB large page support = false RDTSCP = false 64-bit extensions technology available = false Intel feature flags (0x80000001/ecx): LAHF/SAHF supported in 64-bit mode = false LZCNT advanced bit manipulation = false 3DNow! PREFETCH/PREFETCHW instructions = false brand = " Intel(R) Pentium(R) M processor 1.50GHz" (multi-processing synth): none (multi-processing method): Intel leaf 1 (synth) = Intel Pentium M (Dothan B1), 90nm

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• Solaris 10 branded zone VM Templates for Solaris 11 on OTN

  - by jsavit

  Early this year I wrote the article Ours Goes To 11 which describes the ability to import Solaris 10 systems into a "Solaris 10 branded zone" under Oracle Solaris 11. I did this using Solaris 11 Express, and the capability remains in Solaris 11 with only slight changes. This important tool lets you painlessly inhaling a Solaris Container from Solaris 10 or entire Solaris 10 systems ("the global zone") into virtualized environments on a Solaris 11 OS. Just recently, Oracle provided Oracle VM Templates for Oracle Solaris 10 Zones to let you create Solaris 10 branded zones for Solaris 11 even if you don't currently have access to install media or a running Solaris 10 system. To use this, just download the Oracle VM Template for Oracle Solaris Zone 10 from OTN at http://www.oracle.com/technetwork/server-storage/solaris11/downloads/virtual-machines-1355605.html. This page contains images of Oracle Solaris 10 8/11 (the recent update to Solaris 10) in SPARC and x86 formats suitable for creating branded zones. The same page also has a VirtualBox image you can download for a complete Solaris 10 install in a guest virtual machine you can run on any host OS that supports VirtualBox. Both sets of downloads provide a quick - and extremely easy - way to set up a virtual Solaris 10 environment. In the case of the Oracle VM Templates, they illustrate several advanced features of Solaris 11. To start, just go to the above link, download the template for the hardware platform (SPARC or x86) you want, and download the README file also linked from that page. Install prerequisites The README file tells you to install the prerequisite Solaris 11 package that implements the Solaris 10 brand. Then you can install instances of zones with that brand. # pkg install pkg:/system/zones/brand/brand-solaris10 Packages to install: 1 Create boot environment: No Create backup boot environment: Yes DOWNLOAD PKGS FILES XFER (MB) Completed 1/1 44/44 0.4/0.4 PHASE ACTIONS Install Phase 74/74 PHASE ITEMS Package State Update Phase 1/1 Image State Update Phase 2/2 That took only a few minutes, and didn't require a reboot. Install the Solaris 10 zone Now it's time to run the downloaded template file. First make it executable via the chmod command, of course. I found that (unlike stated in the README) there was no need to rename the downloaded file to remove the .bin. When you run it you provide several parameters to describe the zone configuration: -a IP address - the IP address and optional netmask for the zone. This is the only mandatory parameter. -z zonename - the name of the zone you would like to create. -i interface - the package will create an exclusive-IP zone using a virtual NIC (vnic) based on this physical interface. In my case, I have a NIC called rge0. -p PATH - specifies the path in which you want the zoneroot to be placed. In my case, I have a ZFS dataset mounted at /zones, and this will create a zoneroot at /zones/s10u10. Kicking it off, you will see a copyright message, and then messages showing progress building the zone, which only takes a few minutes. # ./solaris-10u10-x86.bin -p /zones -a 192.168.1.100 -i rge0 -z s10u10 ... ... Checking disk-space for extraction Ok Extracting in /export/home/CDimages/s10zone/bootimage.ihaqvh ... 100% [===============================] Checking data integrity Ok Checking platform compatibility The host and the image do not have the same Solaris release: host Solaris release: 5.11 image Solaris release: 5.10 Will create a Solaris 10 branded zone. Warning: could not find a defaultrouter Zone won't have any defaultrouter configured IMAGE: ./solaris-10u10-x86.bin ZONE: s10u10 ZONEPATH: /zones/s10u10 INTERFACE: rge0 VNIC: vnicZBI13379 MAC ADDR: 2:8:20:5c:1a:cc IP ADDR: 192.168.1.100 NETMASK: 255.255.255.0 DEFROUTER: NONE TIMEZONE: US/Arizona Checking disk-space for installation Ok Installing in /zones/s10u10 ... 100% [===============================] Using a static exclusive-IP Attaching s10u10 Booting s10u10 Waiting for boot to complete booting... booting... booting... Zone s10u10 booted The zone's root password has been set using the root password of the local host. You can change the zone's root password to further harden the security of the zone: being root, log into the zone from the local host with the command 'zlogin s10u10'. Once logged in, change the root password with the command 'passwd'. The nifty part in my opinion (besides being so easy), is that the zone was created as an exclusive-IP zone on a virtual NIC. This network configuration lets you enforce traffic isolation from other zones, enforce network Quality of Service, and even let the zone set its own characteristics like IP address and packet size. Independence of the zone's network characteristics from the global zone is one of the enhancements in Solaris 10 that make it easier to consolidate zones while preserving their autonomy, yet provide control in a consolidated environment. Let's see what the virtual network environment looks like by issuing commands from the Solaris 11 global zone. First I'll use Old School ifconfig, and then I'll use the new ipadm and dladm commands. # ifconfig -a4 lo0: flags=2001000849<UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 rge0: flags=1004943<UP,BROADCAST,RUNNING,PROMISC,MULTICAST,DHCP,IPv4> mtu 1500 index 2 inet 192.168.1.3 netmask ffffff00 broadcast 192.168.1.255 ether 0:14:d1:18:ac:bc vboxnet0: flags=201000843<UP,BROADCAST,RUNNING,MULTICAST,IPv4,CoS> mtu 1500 index 3 inet 192.168.56.1 netmask ffffff00 broadcast 192.168.56.255 ether 8:0:27:f8:62:1c # dladm show-phys LINK MEDIA STATE SPEED DUPLEX DEVICE yge0 Ethernet unknown 0 unknown yge0 yge1 Ethernet unknown 0 unknown yge1 rge0 Ethernet up 1000 full rge0 vboxnet0 Ethernet up 1000 full vboxnet0 # dladm show-link LINK CLASS MTU STATE OVER yge0 phys 1500 unknown -- yge1 phys 1500 unknown -- rge0 phys 1500 up -- vboxnet0 phys 1500 up -- vnicZBI13379 vnic 1500 up rge0 s10u10/vnicZBI13379 vnic 1500 up rge0 s10u10/net0 vnic 1500 up rge0 # dladm show-vnic LINK OVER SPEED MACADDRESS MACADDRTYPE VID vnicZBI13379 rge0 1000 2:8:20:5c:1a:cc random 0 s10u10/vnicZBI13379 rge0 1000 2:8:20:5c:1a:cc random 0 s10u10/net0 rge0 1000 2:8:20:9d:d0:79 random 0 # ipadm show-addr ADDROBJ TYPE STATE ADDR lo0/v4 static ok 127.0.0.1/8 rge0/_a dhcp ok 192.168.1.3/24 vboxnet0/_a static ok 192.168.56.1/24 lo0/v6 static ok ::1/128 Log into the zone The install step already booted the zone, so lets log into it. Notice how you have to be appropriately privileged to log into a zone. This is my home system so I'm being a bit cavalier, but in a production environment you can give granular control of who can login to which zones. Voila! a Solaris 10 environment under a Solaris 11 kernel. Notice the output from the uname -a and ifconfig commands, and output from a ping to a nearby host. $ zlogin s10u10 zlogin: You lack sufficient privilege to run this command (all privs required) savit@home:~$ sudo zlogin s10u10 Password: [Connected to zone 's10u10' pts/5] Oracle Corporation SunOS 5.10 Generic Patch January 2005 # uname -a SunOS s10u10 5.10 Generic_Virtual i86pc i386 i86pc # ifconfig -a4 lo0: flags=2001000849 mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 vnicZBI13379: flags=1000843 mtu 1500 index 2 inet 192.168.1.100 netmask ffffff00 broadcast 192.168.1.255 ether 2:8:20:5c:1a:cc # bash bash-3.2# ifconfig -a lo0: flags=2001000849 mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 vnicZBI13379: flags=1000843 mtu 1500 index 2 inet 192.168.1.100 netmask ffffff00 broadcast 192.168.1.255 ether 2:8:20:5c:1a:cc bash-3.2# ping 192.168.1.2 192.168.1.2 is alive For fun, I configured Apache (setting its configuration file in /etc/apache2) and brought it up. Easy - took just a few minutes. bash-3.2# svcs apache2 STATE STIME FMRI disabled 12:38:46 svc:/network/http:apache2 bash-3.2# svcadm enable apache2 Summary In just a few minutes, I built a functioning virtual Solaris 10 environment under by Solaris 11 system. It was... easy! While I can still do it the manual way (creating and using a system archive), this is a low-effort way to create a Solaris 10 zone on Solaris 11.

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• Unable to ssh out anywhere - ssh_exchange_identification

  - by Chowlett

  I have a setup where I'm running Ubuntu 11.10 as a VirtualBox guest under a Windows 7 host, behind a restrictive corporate firewall. I have set up NAT from the host port 22 to Ubuntu's port 22; IT inform me that they have opened port 22 outbound for the host machine's IP address. I have run ssh-keygen -t rsa, and am trying to test the setup by connecting to github and another known ssh server. In both cases the connect is refused with ssh_exchange_identification: Connection closed by remote host. Full -vvv log is below. Is this possibly still due to the corporate firewall? If so, what else might I need to request from them? Any other ideas what might be wrong and how to fix it? ~$ ssh -Tvvv [email protected] OpenSSH_5.8p1 Debian-7ubuntu1, OpenSSL 1.0.0e 6 Sep 2011 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug2: ssh_connect: needpriv 0 debug1: Connecting to github.com [207.97.227.239] port 22. debug1: Connection established. debug3: Incorrect RSA1 identifier debug3: Could not load "/home/chris/.ssh/id_rsa" as a RSA1 public key debug2: key_type_from_name: unknown key type '-----BEGIN' debug3: key_read: missing keytype debug2: key_type_from_name: unknown key type 'Proc-Type:' debug3: key_read: missing keytype debug2: key_type_from_name: unknown key type 'DEK-Info:' debug3: key_read: missing keytype debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug3: key_read: missing whitespace debug2: key_type_from_name: unknown key type '-----END' debug3: key_read: missing keytype debug1: identity file /home/chris/.ssh/id_rsa type 1 debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048 debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048 debug1: identity file /home/chris/.ssh/id_rsa-cert type -1 debug1: identity file /home/chris/.ssh/id_dsa type -1 debug1: identity file /home/chris/.ssh/id_dsa-cert type -1 debug1: identity file /home/chris/.ssh/id_ecdsa type -1 debug1: identity file /home/chris/.ssh/id_ecdsa-cert type -1 ssh_exchange_identification: Connection closed by remote host Edit: Requested diagnostics: ~$ ls -la ~/.ssh total 16 drwx------ 2 chris chris 4096 2012-03-30 13:12 . drwxr-xr-x 29 chris chris 4096 2012-03-30 13:25 .. -rw------- 1 chris chris 1766 2012-03-30 13:12 id_rsa -rw-r--r-- 1 chris chris 409 2012-03-30 13:12 id_rsa.pub

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• Raid 5 mdadm Problem - Help Please

  - by user66260

  My Raid 5 array (4 1tb Disks WD10EARS) had was showing as degraded. I looked and one of the disks wasnt installed, so i re-added it with the mdadm add command. the array is now showing as (null)Array , but cant be mounted if i run: root@warren-P5K-E:/home/warren# sudo mdadm --misc --detail /dev/md0 I get: mdadm: cannot open /dev/md0: No such file or directory and running: root@warren-P5K-E:/home/warren# cat /proc/mdstat gives me: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] unused devices: < none > The data is very important root@warren-P5K-E:/home/warren# mdadm --examine /dev/sda /dev/sda: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b792 - correct Events : 1 Number Major Minor RaidDevice State this 1 8 0 1 spare /dev/sda 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdb /dev/sdb: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7a0 - correct Events : 1 Number Major Minor RaidDevice State this 0 8 16 0 spare /dev/sdb 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# oot@warren-P5K-E:/home/warren# mdadm --examine /dev/sdc /dev/sdc: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7b4 - correct Events : 1 Number Major Minor RaidDevice State this 2 8 32 2 spare /dev/sdc 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdd /dev/sdd: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7c6 - correct Events : 1 Number Major Minor RaidDevice State this 3 8 48 3 spare /dev/sdd 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd That on the 4 drives.

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• Self-signed certificates for a known community

  - by costlow

  Recently announced changes scheduled for Java 7 update 51 (January 2014) have established that the default security slider will require code signatures and the Permissions Manifest attribute. Code signatures are a common practice recommended in the industry because they help determine that the code your computer will run is the same code that the publisher created. This post is written to help users that need to use self-signed certificates without involving a public Certificate Authority. The role of self-signed certificates within a known community You may still use self-signed certificates within a known community. The difference between self-signed and purchased-from-CA is that your users must import your self-signed certificate to indicate that it is valid, whereas Certificate Authorities are already trusted by default. This works for known communities where people will trust that my certificate is mine, but does not scale widely where I cannot actually contact or know the systems that will need to trust my certificate. Public Certificate Authorities are widely trusted already because they abide by many different requirements and frequent checks. An example would be students in a university class sharing their public certificates on a mailing list or web page, employees publishing on the intranet, or a system administrator rolling certificates out to end-users. Managed machines help this because you can automate the rollout, but they are not required -- the major point simply that people will trust and import your certificate. How to distribute self-signed certificates for a known community There are several steps required to distribute a self-signed certificate to users so that they will properly trust it. These steps are: Creating a public/private key pair for signing. Exporting your public certificate for others Importing your certificate onto machines that should trust you Verify work on a different machine Creating a public/private key pair for signing Having a public/private key pair will give you the ability both to sign items yourself and issue a Certificate Signing Request (CSR) to a certificate authority. Create your public/private key pair by following the instructions for creating key pairs.Every Certificate Authority that I looked at provided similar instructions, but for the sake of cohesiveness I will include the commands that I used here: Generate the key pair.keytool -genkeypair -alias erikcostlow -keyalg EC -keysize 571 -validity 730 -keystore javakeystore_keepsecret.jks Provide a good password for this file. The alias "erikcostlow" is my name and therefore easy to remember. Substitute your name of something like "mykey." The sigalg of EC (Elliptical Curve) and keysize of 571 will give your key a good strong lifetime. All keys are set to expire. Two years or 730 days is a reasonable compromise between not-long-enough and too-long. Most public Certificate Authorities will sign something for one to five years. You will be placing your keys in javakeystore_keepsecret.jks -- this file will contain private keys and therefore should not be shared. If someone else gets these private keys, they can impersonate your signature. Please be cautious about automated cloud backup systems and private key stores. Answer all the questions. It is important to provide good answers because you will stick with them for the "-validity" days that you specified above.What is your first and last name?  [Unknown]:  First LastWhat is the name of your organizational unit?  [Unknown]:  Line of BusinessWhat is the name of your organization?  [Unknown]:  MyCompanyWhat is the name of your City or Locality?  [Unknown]:  City NameWhat is the name of your State or Province?  [Unknown]:  CAWhat is the two-letter country code for this unit?  [Unknown]:  USIs CN=First Last, OU=Line of Business, O=MyCompany, L=City, ST=CA, C=US correct?  [no]:  yesEnter key password for <erikcostlow>        (RETURN if same as keystore password): Verify your work:keytool -list -keystore javakeystore_keepsecret.jksYou should see your new key pair. Exporting your public certificate for others Public Key Infrastructure relies on two simple concepts: the public key may be made public and the private key must be private. By exporting your public certificate, you are able to share it with others who can then import the certificate to trust you. keytool -exportcert -keystore javakeystore_keepsecret.jks -alias erikcostlow -file erikcostlow.cer To verify this, you can open the .cer file by double-clicking it on most operating systems. It should show the information that you entered during the creation prompts. This is the file that you will share with others. They will use this certificate to prove that artifacts signed by this certificate came from you. If you do not manage machines directly, place the certificate file on an area that people within the known community should trust, such as an intranet page. Import the certificate onto machines that should trust you In order to trust the certificate, people within your known network must import your certificate into their keystores. The first step is to verify that the certificate is actually yours, which can be done through any band: email, phone, in-person, etc. Known networks can usually do this Determine the right keystore: For an individual user looking to trust another, the correct file is within that user’s directory.e.g. USER_HOME\AppData\LocalLow\Sun\Java\Deployment\security\trusted.certs For system-wide installations, Java’s Certificate Authorities are in JAVA_HOMEe.g. C:\Program Files\Java\jre8\lib\security\cacerts File paths for Mac and Linux are included in the link above. Follow the instructions to import the certificate into the keystore. keytool -importcert -keystore THEKEYSTOREFROMABOVE -alias erikcostlow -file erikcostlow.cer In this case, I am still using my name for the alias because it’s easy for me to remember. You may also use an alias of your company name. Scaling distribution of the import The easiest way to apply your certificate across many machines is to just push the .certs or cacerts file onto them. When doing this, watch out for any changes that people would have made to this file on their machines. Trusted.certs: When publishing into user directories, your file will overwrite any keys that the user has added since last update. CACerts: It is best to re-run the import command with each installation rather than just overwriting the file. If you just keep the same cacerts file between upgrades, you will overwrite any CAs that have been added or removed. By re-importing, you stay up to date with changes. Verify work on a different machine Verification is a way of checking on the client machine to ensure that it properly trusts signed artifacts after you have added your signing certificate. Many people have started using deployment rule sets. You can validate the deployment rule set by: Create and sign the deployment rule set on the computer that holds the private key. Copy the deployment rule set on to the different machine where you have imported the signing certificate. Verify that the Java Control Panel’s security tab shows your deployment rule set. Verifying an individual JAR file or multiple JAR files You can test a certificate chain by using the jarsigner command. jarsigner -verify filename.jar If the output does not say "jar verified" then run the following command to see why: jarsigner -verify -verbose -certs filename.jar Check the output for the term “CertPath not validated.”

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• install Ubuntu and remove Windows 7

  - by dani

  I'm using Windows 7 on my laptop (2GB RAM, 250 GB HDD). I want to install Ubuntu and remove Windows 7. I have Partitioned my laptop into 2 partitions: , C Drive - 105 GB and D Drive - 145 GB. I want to install Ubuntu on C drive all my data in D drive, no backup I have already selected the "Try something else option " /dev/sdb /dev/sdb1 ntfs 104855 MB unknown C drive /dev/sdb5 ntfs 145192 MB unknown D drive I need help using the "Try Something Else" Option My course of action: laptop power on bootubuntu nextsomething elsepartition.

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• TCP port are filtered in VirtualBox

  - by iUngi

  I'm running Ubuntu using VirtualBox to test a server application, but I couldn't get it work the communication. I used nmap to check whether the port is open or not: nmap -T4 -n vbip -p 30000 Host is up (0.00061s latency). PORT STATE SERVICE 30000/tcp filtered unknown when I'm checking the port inside the VirtualBox, than the port is open Host is up (0.00061s latency). PORT STATE SERVICE 30000/tcp open unknown I'm using bridge connection, does the VB filter the ports?

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• How to show Windows System Reserved partition using Ubuntu live dvd?

  - by Veeggon

  All questions in this site ask how to "hide"! I want to fix my boot (fix mrb wont work, I have GPT Disk) by changing some files at Windows System Reserved. GParted shows the following partitions (but Nautilus doesn't): **/dev/sda1 - file system: Unknown - 128Mb - flags: msftres** (this one shows *"Warning: Unable to detect file system! Possible reasons: -file system is damaged -file system is unknown to GParted -there is no file system available (unformated -the device entry /dev/sda1 is missing)"*) **/dev/sda2 - file system: fat32 -100Mb - flags: boot** **/dev/sda3 - file system: ntfs - 500Gb**

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• Not able to get graphs on screen with gnuplot

  - by user81194

  I have installed 12.04 along with Windows 7 and also installed gnuplot 4.6.0. When I type gnuplot on the terminal, I am getting the error message: Terminal type set to unknown. When I tried plot sin(x), the graph does not appear on the screen. However, I am able to make a postscript file. I tried set terminal 'x11', system responds with: unknown or ambiguous terminal. Please help me solve this problem.

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• Red Gate Coder interviews: Alex Davies

  - by Michael Williamson

  Alex Davies has been a software engineer at Red Gate since graduating from university, and is currently busy working on .NET Demon. We talked about tackling parallel programming with his actors framework, a scientific approach to debugging, and how JavaScript is going to affect the programming languages we use in years to come. So, if we start at the start, how did you get started in programming? When I was seven or eight, I was given a BBC Micro for Christmas. I had asked for a Game Boy, but my dad thought it would be better to give me a proper computer. For a year or so, I only played games on it, but then I found the user guide for writing programs in it. I gradually started doing more stuff on it and found it fun. I liked creating. As I went into senior school I continued to write stuff on there, trying to write games that weren’t very good. I got a real computer when I was fourteen and found ways to write BASIC on it. Visual Basic to start with, and then something more interesting than that. How did you learn to program? Was there someone helping you out? Absolutely not! I learnt out of a book, or by experimenting. I remember the first time I found a loop, I was like “Oh my God! I don’t have to write out the same line over and over and over again any more. It’s amazing!” When did you think this might be something that you actually wanted to do as a career? For a long time, I thought it wasn’t something that you would do as a career, because it was too much fun to be a career. I thought I’d do chemistry at university and some kind of career based on chemical engineering. And then I went to a careers fair at school when I was seventeen or eighteen, and it just didn’t interest me whatsoever. I thought “I could be a programmer, and there’s loads of money there, and I’m good at it, and it’s fun”, but also that I shouldn’t spoil my hobby. Now I don’t really program in my spare time any more, which is a bit of a shame, but I program all the rest of the time, so I can live with it. Do you think you learnt much about programming at university? Yes, definitely! I went into university knowing how to make computers do anything I wanted them to do. However, I didn’t have the language to talk about algorithms, so the algorithms course in my first year was massively important. Learning other language paradigms like functional programming was really good for breadth of understanding. Functional programming influences normal programming through design rather than actually using it all the time. I draw inspiration from it to write imperative programs which I think is actually becoming really fashionable now, but I’ve been doing it for ages. I did it first! There were also some courses on really odd programming languages, a bit of Prolog, a little bit of C. Having a little bit of each of those is something that I would have never done on my own, so it was important. And then there are knowledge-based courses which are about not programming itself but things that have been programmed like TCP. Those are really important for examples for how to approach things. Did you do any internships while you were at university? Yeah, I spent both of my summers at the same company. I thought I could code well before I went there. Looking back at the crap that I produced, it was only surpassed in its crappiness by all of the other code already in that company. I’m so much better at writing nice code now than I used to be back then. Was there just not a culture of looking after your code? There was, they just didn’t hire people for their abilities in that area. They hired people for raw IQ. The first indicator of it going wrong was that they didn’t have any computer scientists, which is a bit odd in a programming company. But even beyond that they didn’t have people who learnt architecture from anyone else. Most of them had started straight out of university, so never really had experience or mentors to learn from. There wasn’t the experience to draw from to teach each other. In the second half of my second internship, I was being given tasks like looking at new technologies and teaching people stuff. Interns shouldn’t be teaching people how to do their jobs! All interns are going to have little nuggets of things that you don’t know about, but they shouldn’t consistently be the ones who know the most. It’s not a good environment to learn. I was going to ask how you found working with people who were more experienced than you… When I reached Red Gate, I found some people who were more experienced programmers than me, and that was difficult. I’ve been coding since I was tiny. At university there were people who were cleverer than me, but there weren’t very many who were more experienced programmers than me. During my internship, I didn’t find anyone who I classed as being a noticeably more experienced programmer than me. So, it was a shock to the system to have valid criticisms rather than just formatting criticisms. However, Red Gate’s not so big on the actual code review, at least it wasn’t when I started. We did an entire product release and then somebody looked over all of the UI of that product which I’d written and say what they didn’t like. By that point, it was way too late and I’d disagree with them. Do you think the lack of code reviews was a bad thing? I think if there’s going to be any oversight of new people, then it should be continuous rather than chunky. For me I don’t mind too much, I could go out and get oversight if I wanted it, and in those situations I felt comfortable without it. If I was managing the new person, then maybe I’d be keener on oversight and then the right way to do it is continuously and in very, very small chunks. Have you had any significant projects you’ve worked on outside of a job? When I was a teenager I wrote all sorts of stuff. I used to write games, I derived how to do isomorphic projections myself once. I didn’t know what the word was so I couldn’t Google for it, so I worked it out myself. It was horrifically complicated. But it sort of tailed off when I started at university, and is now basically zero. If I do side-projects now, they tend to be work-related side projects like my actors framework, NAct, which I started in a down tools week. Could you explain a little more about NAct? It is a little C# framework for writing parallel code more easily. Parallel programming is difficult when you need to write to shared data. Sometimes parallel programming is easy because you don’t need to write to shared data. When you do need to access shared data, you could just have your threads pile in and do their work, but then you would screw up the data because the threads would trample on each other’s toes. You could lock, but locks are really dangerous if you’re using more than one of them. You get interactions like deadlocks, and that’s just nasty. Actors instead allows you to say this piece of data belongs to this thread of execution, and nobody else can read it. If you want to read it, then ask that thread of execution for a piece of it by sending a message, and it will send the data back by a message. And that avoids deadlocks as long as you follow some obvious rules about not making your actors sit around waiting for other actors to do something. There are lots of ways to write actors, NAct allows you to do it as if it was method calls on other objects, which means you get all the strong type-safety that C# programmers like. Do you think that this is suitable for the majority of parallel programming, or do you think it’s only suitable for specific cases? It’s suitable for most difficult parallel programming. If you’ve just got a hundred web requests which are all independent of each other, then I wouldn’t bother because it’s easier to just spin them up in separate threads and they can proceed independently of each other. But where you’ve got difficult parallel programming, where you’ve got multiple threads accessing multiple bits of data in multiple ways at different times, then actors is at least as good as all other ways, and is, I reckon, easier to think about. When you’re using actors, you presumably still have to write your code in a different way from you would otherwise using single-threaded code. You can’t use actors with any methods that have return types, because you’re not allowed to call into another actor and wait for it. If you want to get a piece of data out of another actor, then you’ve got to use tasks so that you can use “async” and “await” to await asynchronously for it. But other than that, you can still stick things in classes so it’s not too different really. Rather than having thousands of objects with mutable state, you can use component-orientated design, where there are only a few mutable classes which each have a small number of instances. Then there can be thousands of immutable objects. If you tend to do that anyway, then actors isn’t much of a jump. If I’ve already built my system without any parallelism, how hard is it to add actors to exploit all eight cores on my desktop? Usually pretty easy. If you can identify even one boundary where things look like messages and you have components where some objects live on one side and these other objects live on the other side, then you can have a granddaddy object on one side be an actor and it will parallelise as it goes across that boundary. Not too difficult. If we do get 1000-core desktop PCs, do you think actors will scale up? It’s hard. There are always in the order of twenty to fifty actors in my whole program because I tend to write each component as actors, and I tend to have one instance of each component. So this won’t scale to a thousand cores. What you can do is write data structures out of actors. I use dictionaries all over the place, and if you need a dictionary that is going to be accessed concurrently, then you could build one of those out of actors in no time. You can use queuing to marshal requests between different slices of the dictionary which are living on different threads. So it’s like a distributed hash table but all of the chunks of it are on the same machine. That means that each of these thousand processors has cached one small piece of the dictionary. I reckon it wouldn’t be too big a leap to start doing proper parallelism. Do you think it helps if actors get baked into the language, similarly to Erlang? Erlang is excellent in that it has thread-local garbage collection. C# doesn’t, so there’s a limit to how well C# actors can possibly scale because there’s a single garbage collected heap shared between all of them. When you do a global garbage collection, you’ve got to stop all of the actors, which is seriously expensive, whereas in Erlang garbage collections happen per-actor, so they’re insanely cheap. However, Erlang deviated from all the sensible language design that people have used recently and has just come up with crazy stuff. You can definitely retrofit thread-local garbage collection to .NET, and then it’s quite well-suited to support actors, even if it’s not baked into the language. Speaking of language design, do you have a favourite programming language? I’ll choose a language which I’ve never written before. I like the idea of Scala. It sounds like C#, only with some of the niggles gone. I enjoy writing static types. It means you don’t have to writing tests so much. When you say it doesn’t have some of the niggles? C# doesn’t allow the use of a property as a method group. It doesn’t have Scala case classes, or sum types, where you can do a switch statement and the compiler checks that you’ve checked all the cases, which is really useful in functional-style programming. Pattern-matching, in other words. That’s actually the major niggle. C# is pretty good, and I’m quite happy with C#. And what about going even further with the type system to remove the need for tests to something like Haskell? Or is that a step too far? I’m quite a pragmatist, I don’t think I could deal with trying to write big systems in languages with too few other users, especially when learning how to structure things. I just don’t know anyone who can teach me, and the Internet won’t teach me. That’s the main reason I wouldn’t use it. If I turned up at a company that writes big systems in Haskell, I would have no objection to that, but I wouldn’t instigate it. What about things in C#? For instance, there’s contracts in C#, so you can try to statically verify a bit more about your code. Do you think that’s useful, or just not worthwhile? I’ve not really tried it. My hunch is that it needs to be built into the language and be quite mathematical for it to work in real life, and that doesn’t seem to have ended up true for C# contracts. I don’t think anyone who’s tried them thinks they’re any good. I might be wrong. On a slightly different note, how do you like to debug code? I think I’m quite an odd debugger. I use guesswork extremely rarely, especially if something seems quite difficult to debug. I’ve been bitten spending hours and hours on guesswork and not being scientific about debugging in the past, so now I’m scientific to a fault. What I want is to see the bug happening in the debugger, to step through the bug happening. To watch the program going from a valid state to an invalid state. When there’s a bug and I can’t work out why it’s happening, I try to find some piece of evidence which places the bug in one section of the code. From that experiment, I binary chop on the possible causes of the bug. I suppose that means binary chopping on places in the code, or binary chopping on a stage through a processing cycle. Basically, I’m very stupid about how I debug. I won’t make any guesses, I won’t use any intuition, I will only identify the experiment that’s going to binary chop most effectively and repeat rather than trying to guess anything. I suppose it’s quite top-down. Is most of the time then spent in the debugger? Absolutely, if at all possible I will never debug using print statements or logs. I don’t really hold much stock in outputting logs. If there’s any bug which can be reproduced locally, I’d rather do it in the debugger than outputting logs. And with SmartAssembly error reporting, there’s not a lot that can’t be either observed in an error report and just fixed, or reproduced locally. And in those other situations, maybe I’ll use logs. But I hate using logs. You stare at the log, trying to guess what’s going on, and that’s exactly what I don’t like doing. You have to just look at it and see does this look right or wrong. We’ve covered how you get to grip with bugs. How do you get to grips with an entire codebase? I watch it in the debugger. I find little bugs and then try to fix them, and mostly do it by watching them in the debugger and gradually getting an understanding of how the code works using my process of binary chopping. I have to do a lot of reading and watching code to choose where my slicing-in-half experiment is going to be. The last time I did it was SmartAssembly. The old code was a complete mess, but at least it did things top to bottom. There wasn’t too much of some of the big abstractions where flow of control goes all over the place, into a base class and back again. Code’s really hard to understand when that happens. So I like to choose a little bug and try to fix it, and choose a bigger bug and try to fix it. Definitely learn by doing. I want to always have an aim so that I get a little achievement after every few hours of debugging. Once I’ve learnt the codebase I might be able to fix all the bugs in an hour, but I’d rather be using them as an aim while I’m learning the codebase. If I was a maintainer of a codebase, what should I do to make it as easy as possible for you to understand? Keep distinct concepts in different places. And name your stuff so that it’s obvious which concepts live there. You shouldn’t have some variable that gets set miles up the top of somewhere, and then is read miles down to choose some later behaviour. I’m talking from a very much SmartAssembly point of view because the old SmartAssembly codebase had tons and tons of these things, where it would read some property of the code and then deal with it later. Just thousands of variables in scope. Loads of things to think about. If you can keep concepts separate, then it aids me in my process of fixing bugs one at a time, because each bug is going to more or less be understandable in the one place where it is. And what about tests? Do you think they help at all? I’ve never had the opportunity to learn a codebase which has had tests, I don’t know what it’s like! What about when you’re actually developing? How useful do you find tests in finding bugs or regressions? Finding regressions, absolutely. Running bits of code that would be quite hard to run otherwise, definitely. It doesn’t happen very often that a test finds a bug in the first place. I don’t really buy nebulous promises like tests being a good way to think about the spec of the code. My thinking goes something like “This code works at the moment, great, ship it! Ah, there’s a way that this code doesn’t work. Okay, write a test, demonstrate that it doesn’t work, fix it, use the test to demonstrate that it’s now fixed, and keep the test for future regressions.” The most valuable tests are for bugs that have actually happened at some point, because bugs that have actually happened at some point, despite the fact that you think you’ve fixed them, are way more likely to appear again than new bugs are. Does that mean that when you write your code the first time, there are no tests? Often. The chance of there being a bug in a new feature is relatively unaffected by whether I’ve written a test for that new feature because I’m not good enough at writing tests to think of bugs that I would have written into the code. So not writing regression tests for all of your code hasn’t affected you too badly? There are different kinds of features. Some of them just always work, and are just not flaky, they just continue working whatever you throw at them. Maybe because the type-checker is particularly effective around them. Writing tests for those features which just tend to always work is a waste of time. And because it’s a waste of time I’ll tend to wait until a feature has demonstrated its flakiness by having bugs in it before I start trying to test it. You can get a feel for whether it’s going to be flaky code as you’re writing it. I try to write it to make it not flaky, but there are some things that are just inherently flaky. And very occasionally, I’ll think “this is going to be flaky” as I’m writing, and then maybe do a test, but not most of the time. How do you think your programming style has changed over time? I’ve got clearer about what the right way of doing things is. I used to flip-flop a lot between different ideas. Five years ago I came up with some really good ideas and some really terrible ideas. All of them seemed great when I thought of them, but they were quite diverse ideas, whereas now I have a smaller set of reliable ideas that are actually good for structuring code. So my code is probably more similar to itself than it used to be back in the day, when I was trying stuff out. I’ve got more disciplined about encapsulation, I think. There are operational things like I use actors more now than I used to, and that forces me to use immutability more than I used to. The first code that I wrote in Red Gate was the memory profiler UI, and that was an actor, I just didn’t know the name of it at the time. I don’t really use object-orientation. By object-orientation, I mean having n objects of the same type which are mutable. I want a constant number of objects that are mutable, and they should be different types. I stick stuff in dictionaries and then have one thing that owns the dictionary and puts stuff in and out of it. That’s definitely a pattern that I’ve seen recently. I think maybe I’m doing functional programming. Possibly. It’s plausible. If you had to summarise the essence of programming in a pithy sentence, how would you do it? Programming is the form of art that, without losing any of the beauty of architecture or fine art, allows you to produce things that people love and you make money from. So you think it’s an art rather than a science? It’s a little bit of engineering, a smidgeon of maths, but it’s not science. Like architecture, programming is on that boundary between art and engineering. If you want to do it really nicely, it’s mostly art. You can get away with doing architecture and programming entirely by having a good engineering mind, but you’re not going to produce anything nice. You’re not going to have joy doing it if you’re an engineering mind. Architects who are just engineering minds are not going to enjoy their job. I suppose engineering is the foundation on which you build the art. Exactly. How do you think programming is going to change over the next ten years? There will be an unfortunate shift towards dynamically-typed languages, because of JavaScript. JavaScript has an unfair advantage. JavaScript’s unfair advantage will cause more people to be exposed to dynamically-typed languages, which means other dynamically-typed languages crop up and the best features go into dynamically-typed languages. Then people conflate the good features with the fact that it’s dynamically-typed, and more investment goes into dynamically-typed languages. They end up better, so people use them. What about the idea of compiling other languages, possibly statically-typed, to JavaScript? It’s a reasonable idea. I would like to do it, but I don’t think enough people in the world are going to do it to make it pick up. The hordes of beginners are the lifeblood of a language community. They are what makes there be good tools and what makes there be vibrant community websites. And any particular thing which is the same as JavaScript only with extra stuff added to it, although it might be technically great, is not going to have the hordes of beginners. JavaScript is always to be quickest and easiest way for a beginner to start programming in the browser. And dynamically-typed languages are great for beginners. Compilers are pretty scary and beginners don’t write big code. And having your errors come up in the same place, whether they’re statically checkable errors or not, is quite nice for a beginner. If someone asked me to teach them some programming, I’d teach them JavaScript. If dynamically-typed languages are great for beginners, when do you think the benefits of static typing start to kick in? The value of having a statically typed program is in the tools that rely on the static types to produce a smooth IDE experience rather than actually telling me my compile errors. And only once you’re experienced enough a programmer that having a really smooth IDE experience makes a blind bit of difference, does static typing make a blind bit of difference. So it’s not really about size of codebase. If I go and write up a tiny program, I’m still going to get value out of writing it in C# using ReSharper because I’m experienced with C# and ReSharper enough to be able to write code five times faster if I have that help. Any other visions of the future? Nobody’s going to use actors. Because everyone’s going to be running on single-core VMs connected over network-ready protocols like JSON over HTTP. So, parallelism within one operating system is going to die. But until then, you should use actors. More Red Gater Coder interviews

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• Suggestion on algorithm to distribute objects of different value

  - by Unknown

  Hello, I have the following problem: Given N objects of different values (N < 30, and the values are multiple of a "k" constant, i.e. k, 2k, 3k, 4k, 6k, 8k, 12k, 16k, 24k and 32k), I need an algorithm that will distribute all items to M players (M <= 6) in such a way that the total value of the objects each player gets is as even as possible (in other words, I want to distribute all objects to all players in the fairest way possible). I don't need (pseudo)code to solve this (also, this is not a homework :) ), but I'll appreciate any ideas or links to algorithms that could solve this. Thanks!

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• Spinlocks, How Much Useful Are They?

  - by unknown

  How often do you find yourself actually using spinlocks in your code? How common is it to come across a situation where using a busy loop actually outperforms the usage of locks? Personally, when I write some sort of code that requires thread safety, I tend to benchmark it with different synchronization primitives, and as far as it goes, it seems like using locks gives better performance than using spinlocks. No matter for how little time I actually hold the lock, the amount of contention I receive when using spinlocks is far greater than the amount I get from using locks (of course, I run my tests on a multiprocessor machine). I realize that it's more likely to come across a spinlock in "low-level" code, but I'm interested to know whether you find it useful in even a more high-level kind of programming?

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• Convert Byte Array into Bitset

  - by Unknown

  I have a byte array generated by a random number generator. I want to put this into the STL bitset. Unfortunately, it looks like Bitset only supports the following constructors: A string of 1's and 0's like "10101011" An unsigned long. (my byte array will be longer) The only solution I can think of now is to read the byte array bit by bit and make a string of 1's and 0's. Does anyone have a more efficient solution?

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• DatagGridViewColumn.DataPropertyName to an array element?

  - by unknown

  Hi there, I'm using a DataGridView binding its datasource to a List, and specifying the properties for each column. An example would be: DataGridViewTextBoxColumn colConcept = new DataGridViewTextBoxColumn(); DataGridViewCell cell4 = new DataGridViewTextBoxCell(); colConcept.CellTemplate = cell4; colConcept.Name = "concept"; colConcept.HeaderText = "Concept"; colConcept.DataPropertyName = "Concept"; colConcept.Width = 200; this.dataGridViewBills.Columns.Add(colConcept); {... assign other colums...} And finally this.dataGridViewBills.DataSource=billslist; //billslist is List<Bill> Obviously Class Bill has a Property called Concept, as well as one Property for each column. Well, now my problem, is that Bill should have and Array/List/whateverdynamicsizecontainer of strings called Years. Let's assume that every Bill will have the same Years.Count, but this only known at runtime.Thus, I can't specify properties like Bill.FirstYear to obtain Bill.Years[0], Bill.SecondYear to obtain Bills.Years[1]... etc... and bind it to each column. The idea, is that now I want to have a grid with dynamic number of colums (known at runtime), and each column filled with a string from the Bill.Years List. I can make a loop to add columns to the grid at runtime depending of Bill.Years.Count, but is possible to bind them to each of the strings that the Bill.Years List contains??? I'm not sure if I'm clear enough. The result ideally would be something like this, for 2 bills on the list, and 3 years for each bill: --------------------------------------GRID HEADER------------------------------- NAME CONCEPT YEAR1 YEAR2 YEAR3 --------------------------------------GRID VALUES------------------------------- Bill1 Bill1.Concept Bill1.Years[0] Bill1.Years[1] Bill1.Years[2] Bill2 Bill2.Concept Bill2.Years[0] Bill2.Years[1] Bill2.Years[2] I can always forget the datasource, and write each cell manually, as the MSFlexGrid used to like, but if possible, I would like to use the binding capabilities of the DataGridView. Any ideas? Thanks a lot.

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• OpenCV to use in memory buffers or file pointers

  - by The Unknown

  The two functions in openCV cvLoadImage and cvSaveImage accept file path's as arguments. For example, when saving a image it's cvSaveImage("/tmp/output.jpg", dstIpl) and it writes on the disk. Is there any way to feed this a buffer already in memory? So instead of a disk write, the output image will be in memory. I would also like to know this for both cvSaveImage and cvLoadImage (read and write to memory buffers). Thanks! My goal is to store the Encoded (jpeg) version of the file in Memory. Same goes to cvLoadImage, I want to load a jpeg that's in memory in to the IplImage format.

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• How does Gmail do comet on Opera?

  - by Unknown

  I would like to know how Gmail (or anyone else) does comet on Opera. Here is what I know so far from my experiments. It doesn't use the event-source tag which is broken in Opera 10.51. It doesn't use iframe which displays a spinning throbber and a busy mouse cursor. It doesn't use responseText on xmlhttprequest when readyState = 3 which is known to be broken on Opera. I tried seeing how it was done in mibbit and etherpad, and I found that they both use long-polling.

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• How to stop GHC from generating intermediate files?

  - by unknown

  When compiling a haskell source file via ghc --make foo.hs GHC always leaves behind a variety of intermediate files other than foo.exe. These are foo.hi and foo.o. I often end up having to delete the .hi and .o files to avoid cluttering up the folders. Is there a command line option for GHC not to leave behind its intermediate files? (When asked on #haskell, the best answer I got was ghc --make foo.hs && rm foo.hi foo.o.

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• Strange beep when using cout

  - by Unknown

  Hello everyone, today when I was working on some code of mine I came across a beeping sound when printing a buffer to the screen. Here's the mysterious character that produces the beep: '' I don't know if you can see it, but my computer beeps when I try to print it like this: cout<<(char)7<<endl; Another point of interest is that the 'beep' doesn't originate from my on board beeper, but from my headphone/speaker Is this just my computer or there something wrong with the cout function? EDIT: But then why does printing this character produce the beep sound? does that mean that I could send other such characters through the cout function to produce different effects?

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• How to (legitimately) access files after putting self into chrooted sandbox?

  - by unknown google user

  Changing a Linux C++ program which gives the user limited file access. Thus the program chroots itself to a sandbox with the files the user can get at. All worked well. Now, however, the program needs to access some files for its own needs (not the user's) but they are outside the sandbox. I know chroot allows access to files opened before the chroot but in this case the needed files could a few among many hundreds so it is obviously impractical to open them all just for the couple that might be required. Is there any way to get at the files?

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• throw exception

  - by Unknown

  Why can't you throw an InterruptedException in the following way: try { System.in.wait(5) //Just an example } catch (InterruptedException exception) { exception.printStackTrace(); //On this next line I am confused as to why it will not let me throw the exception throw exception; } I went to http://java24hours.com, but it didn't tell me why I couldn't throw an InterruptedException. If anyone knows why, PLEASE tell me! I'm desperate! :S

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• Python interpreter with Linux Screen

  - by Unknown

  I was working with Python with a Linux terminal screen. When I typed: help(somefunction) It printed the appropriate output, but then my screen was stuck, and at the bottom of the terminal was "(end)". How do I get unstuck? Thanks in advance.

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• Get e-mail Contacts from exchange 2007 in C#

  - by unknown (google)

  Is anybody know how to pull contact list from Microsoft Exchange 2007 using c#?

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