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• Windows 7 BSOD - ntoskrnl?

  - by Ken Mason

  2 new HP Pavilion notebooks with 7 Home Premium pre-loaded with Norton. My first act was to use the Norton Removal Tool and load ZoneAlarm free and AVG Free. Frequent random BSOD's ever since...I found my way into Debug and have had various reports regarding ntoskrnl, depending on the status of symbols. It's been many years since I played with (DOS 3.x) debug, so this has been a considerable fumble. Excerpts follow and any insights would be greatly appreciated, as I am not a developer: ADDITIONAL_DEBUG_TEXT: Use '!findthebuild' command to search for the target build information. If the build information is available, run '!findthebuild -s ; .reload' to set symbol path and load symbols. MODULE_NAME: nt FAULTING_MODULE: fffff8000305d000 nt DEBUG_FLR_IMAGE_TIMESTAMP: 4b88cfeb BUGCHECK_STR: 0x7f_8 CUSTOMER_CRASH_COUNT: 1 DEFAULT_BUCKET_ID: VISTA_DRIVER_FAULT CURRENT_IRQL: 0 LAST_CONTROL_TRANSFER: from fffff800030ccb69 to fffff800030cd600 STACK_TEXT: fffff80004d6fd28 fffff800030ccb69 : 000000000000007f 0000000000000008 0000000080050033 00000000000006f8 : nt+0x70600 fffff80004d6fd30 000000000000007f : 0000000000000008 0000000080050033 00000000000006f8 fffff80003095e58 : nt+0x6fb69 fffff80004d6fd38 0000000000000008 : 0000000080050033 00000000000006f8 fffff80003095e58 0000000000000000 : 0x7f fffff80004d6fd40 0000000080050033 : 00000000000006f8 fffff80003095e58 0000000000000000 0000000000000000 : 0x8 fffff80004d6fd48 00000000000006f8 : fffff80003095e58 0000000000000000 0000000000000000 0000000000000000 : 0x80050033 fffff80004d6fd50 fffff80003095e58 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000 : 0x6f8 fffff80004d6fd58 0000000000000000 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000 : nt+0x38e58 STACK_COMMAND: kb FOLLOWUP_IP: nt+70600 fffff800`030cd600 48894c2408 mov qword ptr [rsp+8],rcx SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: nt+70600 FOLLOWUP_NAME: MachineOwner IMAGE_NAME: ntoskrnl.exe BUCKET_ID: WRONG_SYMBOLS Followup: MachineOwner ...................................................................... 0: kd !lmi nt Loaded Module Info: [nt] Module: ntkrnlmp Base Address: fffff8000305d000 Image Name: ntkrnlmp.exe Machine Type: 34404 (X64) Time Stamp: 4b88cfeb Sat Feb 27 00:55:23 2010 Size: 5dc000 CheckSum: 545094 Characteristics: 22 perf Debug Data Dirs: Type Size VA Pointer CODEVIEW 25, 19c65c, 19bc5c RSDS - GUID: {7E9A3CAB-6268-45DE-8E10-816E3080A3B7} Age: 2, Pdb: ntkrnlmp.pdb CLSID 4, 19c658, 19bc58 [Data not mapped] Image Type: FILE - Image read successfully from debugger. ntkrnlmp.exe Symbol Type: PDB - Symbols loaded successfully from symbol server. d:\debugsymbols\ntkrnlmp.pdb\7E9A3CAB626845DE8E10816E3080A3B72\ntkrnlmp.pdb Load Report: public symbols , not source indexed d:\debugsymbols\ntkrnlmp.pdb\7E9A3CAB626845DE8E10816E3080A3B72\ntkrnlmp.pdb 0: kd !analyze -v * Bugcheck Analysis * * UNEXPECTED_KERNEL_MODE_TRAP (7f) This means a trap occurred in kernel mode, and it's a trap of a kind that the kernel isn't allowed to have/catch (bound trap) or that is always instant death (double fault). The first number in the bugcheck params is the number of the trap (8 = double fault, etc) Consult an Intel x86 family manual to learn more about what these traps are. Here is a portion of those codes: If kv shows a taskGate use .tss on the part before the colon, then kv. Else if kv shows a trapframe use .trap on that value Else .trap on the appropriate frame will show where the trap was taken (on x86, this will be the ebp that goes with the procedure KiTrap) Endif kb will then show the corrected stack. Arguments: Arg1: 0000000000000008, EXCEPTION_DOUBLE_FAULT Arg2: 0000000080050033 Arg3: 00000000000006f8 Arg4: fffff80003095e58 Debugging Details: BUGCHECK_STR: 0x7f_8 CUSTOMER_CRASH_COUNT: 1 DEFAULT_BUCKET_ID: VISTA_DRIVER_FAULT PROCESS_NAME: System CURRENT_IRQL: 2 LAST_CONTROL_TRANSFER: from fffff800030ccb69 to fffff800030cd600 STACK_TEXT: fffff80004d6fd28 fffff800030ccb69 : 000000000000007f 0000000000000008 0000000080050033 00000000000006f8 : nt!KeBugCheckEx fffff80004d6fd30 fffff800030cb032 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000 : nt!KiBugCheckDispatch+0x69 fffff80004d6fe70 fffff80003095e58 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000 : nt!KiDoubleFaultAbort+0xb2 fffff880089efc60 0000000000000000 : 0000000000000000 0000000000000000 0000000000000000 0000000000000000 : nt!SeAccessCheckFromState+0x58 STACK_COMMAND: kb FOLLOWUP_IP: nt!KiDoubleFaultAbort+b2 fffff800`030cb032 90 nop SYMBOL_STACK_INDEX: 2 SYMBOL_NAME: nt!KiDoubleFaultAbort+b2 FOLLOWUP_NAME: MachineOwner MODULE_NAME: nt IMAGE_NAME: ntkrnlmp.exe DEBUG_FLR_IMAGE_TIMESTAMP: 4b88cfeb FAILURE_BUCKET_ID: X64_0x7f_8_nt!KiDoubleFaultAbort+b2 BUCKET_ID: X64_0x7f_8_nt!KiDoubleFaultAbort+b2 Followup: MachineOwner I tried running Rootkit Revealer but I don't think it works on x64 systems. Similarly Blacklight seems to have aged off. I'm running Sophos Anti-Rootkit now. So far so good...

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• How to diagnose computer lockup/freezing problem

  - by Scott Mitchell

  I built a desktop computer a couple years back with the following specs: CPU: Intel Core 2 Quad Q9300 Yorkfield 2.5GHz 6MB L2 Cache LGA 775 95W Quad-Core Processor BX80580Q9300 Motherboard: EVGA 122-CK-NF68-T1 LGA 775 NVIDIA nForce 680i SLI ATX Intel Motherboard Video Card: Two EVGA 256-P2-N758-TR GeForce 8600GT SCC 256MB 128-bit GDDR3 PCI Express x16 SLI Supported Video Card PSU: SeaSonic S12 Energy Plus SS-550HT 550W ATX12V V2.3 / EPS12V V2.91 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply Memory: Two G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model F2-6400CL5D-4GBPQ Since its inception, the machine has periodically locked up, the regularlity having varied over the years from once a day to once a month. Typically, lockups happen once every few days. By "lockup" I mean my computer just freezes. The screen locks up, I can't move the mouse. Hitting keys on my keyboard that normally turn LEDs on or off on the keyboard (such as Caps Lock) no longer turn the LEDs on or off. If there was music playing at the time of the lockup, noise keeps coming out of the speakers, but it's just the current frequency/note that plays indefinitely. There is no BSOD. When such a lockup occurs I have to do a hard reboot by either turning off the computer or hitting the reset button. I have the most recent version of the NVIDIA hardware drivers, and update them semi-regularly, but that hasn't seemed to help. I am currently using Windows 7 x64, but was previously using Windows Server 2003 x64 and having the same lockup issues. My guess is that it's somehow video driver or motherboard related, but I don't know how to go about diagnosing this problem to narrow down which of the two is the culprit. Additional information re: cooling Regarding cooling... I've not installed any after-market cooling systems aside from two regular fans I scavenged from an older computer. The fan atop the CPU is the one that shipped with it. One of the two scavenged fans I added it located at the bottom tower of the corner, in an attempt to create some airflow from front to back. The second fan is pointed directly at the two video cards. SpeedFan installation and readings Per studiohack's suggestion, I installed SpeedFan, which provided the following temperature readings: GPU: 63C GPU: 65C System: 76C CPU: 64C AUX: 36C Core 0: 78C Core 1: 76C Core 2: 79C Core 3: 79C Update #3: Another Lockup :-( Well, I had another lockup last night. :-( SpeedFan reported the CPU temp at 38 C when it happened, and there was no spike in temperature leading up to the freeze. One thing I notice is that the freeze seems more likely to happen if I am watching a video. In fact, of the last 5 freezes over the past month, 4 of them have been while watching a video on Flickr. Not necessarily the same video, but a video nevertheless. I don't know if this is just coincidence or if it means anything. (As an aside, each night before bedtime my 2 year old daughter sits on my lap and watches some home videos on Flickr and, in the last month, has learned the phrase, "Uh oh, computer broke.") Update #4: MemTest86 and 3DMark06 Test Results: Per suggestions in the comments, I ran the MemTest86 overnight and it cycled through the 8 GB of memory 5 times without error. I also ran the 3DMark06 test without a problem (see my scores at http://3dmark.com/3dm06/15163549). So... what now? :-) Any further suggestions on what to check? Is there some way to get a stack trace or something when the computer locks like that? Thanks

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• UFW as an active service on Ubuntu

  - by lamcro

  Every time I restart my computer, and check the status of the UFW firewall (sudo ufw status), it is disabled, even if I then enable and restart it. I tried putting sudo ufw enable as one of the startup applications but it asks for the sudo password every time I log on, and I'm guessing it does not protect anyone else who logs on my computer. How can I setup ufw so it is activated when I turn on my computer, and protects all accounts? Update I just tried /etc/init.d/ufw start, and it activated the firewall. Then I restarted the computer, and again it was disabled. content of /etc/ufw/ufw.conf # /etc/ufw/ufw.conf # # set to yes to start on boot ENABLED=yes # set to one of 'off', 'low', 'medium', 'high' LOGLEVEL=full content of /etc/default/ufw # /etc/default/ufw # # Set to yes to apply rules to support IPv6 (no means only IPv6 on loopback # accepted). You will need to 'disable' and then 'enable' the firewall for # the changes to take affect. IPV6=no # Set the default input policy to ACCEPT, ACCEPT_NO_TRACK, DROP, or REJECT. # ACCEPT enables connection tracking for NEW inbound packets on the INPUT # chain, whereas ACCEPT_NO_TRACK does not use connection tracking. Please note # that if you change this you will most likely want to adjust your rules. DEFAULT_INPUT_POLICY="DROP" # Set the default output policy to ACCEPT, ACCEPT_NO_TRACK, DROP, or REJECT. # ACCEPT enables connection tracking for NEW outbound packets on the OUTPUT # chain, whereas ACCEPT_NO_TRACK does not use connection tracking. Please note # that if you change this you will most likely want to adjust your rules. DEFAULT_OUTPUT_POLICY="ACCEPT" # Set the default forward policy to ACCEPT, DROP or REJECT. Please note that # if you change this you will most likely want to adjust your rules DEFAULT_FORWARD_POLICY="DROP" # Set the default application policy to ACCEPT, DROP, REJECT or SKIP. Please # note that setting this to ACCEPT may be a security risk. See 'man ufw' for # details DEFAULT_APPLICATION_POLICY="SKIP" # By default, ufw only touches its own chains. Set this to 'yes' to have ufw # manage the built-in chains too. Warning: setting this to 'yes' will break # non-ufw managed firewall rules MANAGE_BUILTINS=no # # IPT backend # # only enable if using iptables backend IPT_SYSCTL=/etc/ufw/sysctl.conf # extra connection tracking modules to load IPT_MODULES="nf_conntrack_ftp nf_nat_ftp nf_conntrack_irc nf_nat_irc" Update Followed your advise and ran update-rc.d with no luck. lester@mcgrath-pc:~$ sudo update-rc.d ufw defaults update-rc.d: warning: /etc/init.d/ufw missing LSB information update-rc.d: see <http://wiki.debian.org/LSBInitScripts> Adding system startup for /etc/init.d/ufw ... /etc/rc0.d/K20ufw -> ../init.d/ufw /etc/rc1.d/K20ufw -> ../init.d/ufw /etc/rc6.d/K20ufw -> ../init.d/ufw /etc/rc2.d/S20ufw -> ../init.d/ufw /etc/rc3.d/S20ufw -> ../init.d/ufw /etc/rc4.d/S20ufw -> ../init.d/ufw /etc/rc5.d/S20ufw -> ../init.d/ufw lester@mcgrath-pc:~$ ls -l /etc/rc?.d/*ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc0.d/K20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc1.d/K20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc2.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc3.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc4.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc5.d/S20ufw -> ../init.d/ufw lrwxrwxrwx 1 root root 13 2009-12-20 20:34 /etc/rc6.d/K20ufw -> ../init.d/ufw

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• Openldap/Sasl/GSSAPI on Debian: Key table entry not found

  - by badbishop

  The goal: to make an OpenLDAP server to authenticate using Kerberos V via GSSAPI Setup: several virtual machines running on freshly installed/updated Debian Squeeze A master KDC server kdc.example.com A LDAP server, running OpenLDAP ldap.example.com The problem: tom@ldap:~$ ldapsearch -b 'dc=example,dc=com' SASL/GSSAPI authentication started ldap_sasl_interactive_bind_s: Other (e.g., implementation specific) error (80) additional info: SASL(-1): generic failure: GSSAPI Error: Unspecified GSS failure. Minor code may provide more information (Key table entry not found) One might suggest to add that bloody keytab entry, but here's the real problem: ktutil: rkt /etc/ldap/ldap.keytab ktutil: list slot KVNO Principal ---- ---- --------------------------------------------------------------------- 1 2 ldap/[email protected] 2 2 ldap/[email protected] 3 2 ldap/[email protected] 4 2 ldap/[email protected] So, the entry as suggested by the OpenLDAP manual is there allright. Deleting and re-creating both service principal and the keytab on ldap.example.com didn't help, I get the same error. And before I make the keytab file readable by openldap, I get "Permission denied" error instead of the one in the subject. Which implies, that the right keytab file is being accessed, as set in /etc/default/slapd. I have my doubts about the following part of slapd config: root@ldap:~# cat /etc/ldap/slapd.d/cn\=config.ldif | grep -v "^#" dn: cn=config objectClass: olcGlobal cn: config olcArgsFile: /var/run/slapd/slapd.args olcLogLevel: 256 olcPidFile: /var/run/slapd/slapd.pid olcToolThreads: 1 structuralObjectClass: olcGlobal entryUUID: d6737f5c-d321-1030-9dbe-27d2a7751e11 olcSaslHost: kdc.example.com olcSaslRealm: EXAMPLE.COM olcSaslSecProps: noplain,noactive,noanonymous,minssf=56 olcAuthzRegexp: {0}"uid=([^/]*),cn=EXAMPLE.COM,cn=GSSAPI,cn=auth" "uid=$1,ou=People,dc=example,dc=com" olcAuthzRegexp: {1}"uid=host/([^/]*).example.com,cn=example.com,cn=gssapi,cn=auth" "cn=$1,ou=hosts,dc=example,dc=com" A HOWTO at https://help.ubuntu.com/community/OpenLDAPServer#Kerberos_Authentication mentiones vaguely: Also, it is frequently necessary to map the Distinguished Name (DN) of an authorized Kerberos client to an existing entry in the DIT. I fail to understand where in the tree this should be defined, what schema should be used, etc. After hours of googling, it's official: I'm stuck! Please, help. Other things checked: Kerberos as such works fine (I can ssh without using a password to any machine in this setup). That means there should be no DNS-related problems. ldapsearch -b 'dc=example,dc=com' -x works OK. SASL/GSSAPI has been tested using sasl-sample-server -m GSSAPI -s ldap and sasl-sample-client -s ldap -n ldap.example.com -u tom without errors: root@ldap:~# sasl-sample-server -m GSSAPI -s ldap Forcing use of mechanism GSSAPI Sending list of 1 mechanism(s) S: R1NTQVBJ Waiting for client mechanism... C: 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 'GSSAPI' Sending response... S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKicQRvkxggi9pW+yJ1ExbTwLDclqw/VQ98aPq8mt39hkO6PPfcO2cB+t6vJ01xRKBrT9D2qF2XK0SWD4PQNb5UFbH4RM/bKAxDuCfZ1MHKgIWTLu4bK7VGZTbYydcckU2d910jIdvkkHhaRqUEM4cqp/cR Waiting for client reply... C: got '' Sending response... S: BQQF/wAMAAAAAAAAMBOWqQcACAAlCodrXW66ZObsEd4= Waiting for client reply... C: BQQE/wAMAAAAAAAAFUYbXQQACAB0b20VynB4uGH/iIzoRhw=got '?' Negotiation complete Username: tom Realm: (NULL) SSF: 56 sending encrypted message 'srv message 1' S: AAAASgUEB/8AAAAAAAAAADATlqrqrBW0NRfPMXMdMz+zqY32YakrHqFps3o/vO6yDeyPSaSqprrhI+t7owk7iOsbrZ/idJRxCBm8Wazx Waiting for encrypted message... C: AAAATQUEBv8AAAAAAAAAABVGG17WC1+/kIV9xTMUdq6Y4qYmmTahHVCjidgGchTOOOrBLEwA9IqiTCdRFPVbK1EgJ34P/vxMQpV1v4WZpcztgot '' recieved decoded message 'client message 1' root@ldap:~# sasl-sample-client -s ldap -n ldap.example.com -u tom service=ldap Waiting for mechanism list from server... S: R1NTQVBJrecieved 6 byte message Choosing best mechanism from: GSSAPI returning OK: tom Using mechanism GSSAPI Preparing initial. Sending initial response... C: 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 Waiting for server reply... S: YIGZBgkqhkiG9xIBAgICAG+BiTCBhqADAgEFoQMCAQ+iejB4oAMCARKicQRvkxggi9pW+yJ1ExbTwLDclqw/VQ98aPq8mt39hkO6PPfcO2cB+t6vJ01xRKBrT9D2qF2XK0SWD4PQNb5UFbH4RM/bKAxDuCfZ1MHKgIWTLu4bK7VGZTbYydcckU2d910jIdvkkHhaRqUEM4cqp/cRrecieved 156 byte message C: Waiting for server reply... S: BQQF/wAMAAAAAAAAMBOWqQcACAAlCodrXW66ZObsEd4=recieved 32 byte message Sending response... C: BQQE/wAMAAAAAAAAFUYbXQQACAB0b20VynB4uGH/iIzoRhw= Negotiation complete Username: tom SSF: 56 Waiting for encoded message... S: AAAASgUEB/8AAAAAAAAAADATlqrqrBW0NRfPMXMdMz+zqY32YakrHqFps3o/vO6yDeyPSaSqprrhI+t7owk7iOsbrZ/idJRxCBm8Wazxrecieved 78 byte message recieved decoded message 'srv message 1' sending encrypted message 'client message 1' C: AAAATQUEBv8AAAAAAAAAABVGG17WC1+/kIV9xTMUdq6Y4qYmmTahHVCjidgGchTOOOrBLEwA9IqiTCdRFPVbK1EgJ34P/vxMQpV1v4WZpczt

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• Linux not buffering block I/O when the device is not "in use" (i.e. mounted)

  - by Radek Hladík

  I am installing new server and I've found an interesting issue. The server is running Fedora 19 (3.11.7-200.fc19.x86_64 kernel) and is supposed to host a few KVM/Qemu virtual servers (mail server, file server, etc..). The HW is Intel(R) Xeon(R) CPU 5160 @ 3.00GHz with 16GB RAM. One of the most important features will be Samba server and we have decided to make it as virtual machine with almost direct access to the disks. So the real HDD is cached on SSD (via bcache) then raided with md and the final device is exported into the virtual machine via virtio. The virtual machine is again Fedora 19 with the same kernel. One important topic to find out is whether the virtualization layer will not introduce high overload into disk I/Os. So far I've been able to get up to 180MB/s in VM and up to 220MB/s on real HW (on the SSD disk). I am still not sure why the overhead is so big but it is more than the network can handle so I do not care so much. The interesting thing is that I've found that the disk reads are not buffered in the VM unless I create and mount FS on the disk or I use the disks somehow. Simply put: Lets do dd to read disk for the first time (the /dev/vdd is an old Raptor disk 70MB/s is its real speed): [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 36.8038 s, 71.2 MB/s Buffers: 14444 kB Rereading the data shows that they are cached somewhere but not in buffers of the VM. Also the speed increased to "only" 500MB/s. The VM has 4GB of RAM (more that the test file) [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.16016 s, 508 MB/s Buffers: 14444 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.05727 s, 518 MB/s Buffers: 14444 kB Now lets mount the FS on /dev/vdd and try the dd again: [root@localhost ~]# mount /dev/vdd /mnt/tmp [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 4.68578 s, 559 MB/s Buffers: 2574592 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 1.50504 s, 1.7 GB/s Buffers: 2574592 kB While the first read was the same, all 2.6GB got buffered and the next read was at 1.7GB/s. And when I unmount the device: [root@localhost ~]# umount /mnt/tmp [root@localhost ~]# cat /proc/meminfo | grep Buffers Buffers: 14452 kB [root@localhost ~]# dd if=/dev/vdd of=/dev/null bs=256k count=10000 ; cat /proc/meminfo | grep Buffers 2621440000 bytes (2.6 GB) copied, 5.10499 s, 514 MB/s Buffers: 14468 kB The bcache was disabled while testing and the results are same on faster (newer) HDDs and on SSD (except for the initial read speed of course). To sum it up. When I read from the device via dd first time, it gets read from the disk. Next time I reread it gets cached in the host but not in the guest (thats actually the same issue, more on that later). When I mount the filesystem but try to read the device directly it gets cached in VM (via buffers). As soon as I stop "using" it, buffers are discarded and the device is not cached anymore in the VM. When I looked into buffers value on the host I realized that the situation is the same. The block I/O gets buffered only when the disk is in use, in this case it means "exported to a VM". On host, after all the measurement done: 3165552 buffers On the host, after the VM shutdown: 119176 buffers I know it is not important as the disks will be mounted all the time but I am curious and I would like to know why it is working like this.

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• How to setup linux permissions the WWW folder?

  - by Xeoncross

  Updated Summery The /var/www directory is owned by root:root which means that no one can use it and it's entirely useless. Since we all want a web server that actually works (and no-one should be logging in as "root"), then we need to fix this. Only two entities need access. PHP/Perl/Ruby/Python all need access to the folders and files since they create many of them (i.e. /uploads/). These scripting languages should be running under nginx or apache (or even some other thing like FastCGI for PHP). The developers How do they get access? I know that someone, somewhere has done this before. With however-many billions of websites out there you would think that there would be more information on this topic. I know that 777 is full read/write/execute permission for owner/group/other. So this doesn't seem to be needed as it leaves random users full permissions. What permissions are need to be used on /var/www so that... Source control like git or svn Users in a group like "websites" (or even added to "www-data") Servers like apache or lighthttpd And PHP/Perl/Ruby can all read, create, and run files (and directories) there? If I'm correct, Ruby and PHP scripts are not "executed" directly - but passed to an interpreter. So there is no need for execute permission on files in /var/www...? Therefore, it seems like the correct permission would be chmod -R 1660 which would make all files shareable by these four entities all files non-executable by mistake block everyone else from the directory entirely set the permission mode to "sticky" for all future files Is this correct? Update: I just realized that files and directories might need different permissions - I was talking about files above so i'm not sure what the directory permissions would need to be. Update 2: The folder structure of /var/www changes drastically as one of the four entities above are always adding (and sometimes removing) folders and sub folders many levels deep. They also create and remove files that the other 3 entities might need read/write access to. Therefore, the permissions need to do the four things above for both files and directories. Since non of them should need execute permission (see question about ruby/php above) I would assume that rw-rw-r-- permission would be all that is needed and completely safe since these four entities are run by trusted personal (see #2) and all other users on the system only have read access. Update 3: This is for personal development machines and private company servers. No random "web customers" like a shared host. Update 4: This article by slicehost seems to be the best at explaining what is needed to setup permissions for your www folder. However, I'm not sure what user or group apache/nginx with PHP OR svn/git run as and how to change them. Update 5: I have (I think) finally found a way to get this all to work (answer below). However, I don't know if this is the correct and SECURE way to do this. Therefore I have started a bounty. The person that has the best method of securing and managing the www directory wins.

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• Bizarre and very specific Internet connection loss

  - by Synetech

  Yesterday (Friday, September 21, 2012), my Internet connection started acting up. After some testing, I confirmed a very specific and baffling set of symptoms: Internet connection goes away every 25-35 minutes (I did not confirm the exact interval, but it seems to be about 30 mins.) Only some protocols are affected; HTTP*, P2P, etc. stop working; FTP, etc. continue to work When it’s stopped, cannot even ping router or cable-modem IPs or view their firmware pages Domain-names and IPs are irrelevant (for protocols that stop working, neither work, for those that still work, both work) Resetting router fixes it for another 30 minutes Keeping the connection idle or active doesn’t seem to make a difference (nor the bandwidth usage in that period) Connecting directly to cable-modem allows it to work indefinitely Disconnecting the router from the cable-modem works indefinitely (no Internet connection obviously, but can still access router IP and firmware page) Connecting the router to the cable-modem, but putting the modem on standby also works indefinitely Same problem with both a wireless laptop and wired (on any port) desktop (both Windows 7; will try to test Windows XP when possible) Nothing had changed in the days leading up to the issue. No modifications to the networking configuration or the router; there were not even any Windows updates except for an MSSE definition update. Waiting does not fix it, nor does any amount of fiddling with anything; only resetting the router fixes it for 30 minutes (resetting the cable-modem doesn't work either) I tried cleaning the pins in the router’s plugs, but that didn’t help, which was not really a surprise since I was not getting a lost connection error. Obviously my first thought was that the router was having a problem, and this is borne out by some tests. The problem is that when it drops, it is not a full drop since I can still do things like ftp ftp.mcafee.com and such which means that the connection and DNS are still working. Moreover, if it were the router, then why does it stay alive indefinitely when not connected to the cable-modem (i.e., no outside influence)? The problem doesn't seem to be either the cable-modem nor the router, but rather an interaction between the two, like something from the outside (port scan? hacker? ISP?) that is triggering a problem in the router. I see that there have been a couple of vulnerabilities for the DI-524, but those were a while back and should be fixed since I have the last firmware for it. I don’t think it’s my ISP (Rogers) since I have been using the router for several years without problem and can connect indefinitely when bypassing it. But I can’t rule them out since that is one of the only possible things that could have suddenly changed. Does anybody have any ideas of explanations, fixed, or tests? (I note that when I opened the router, I heard a very high-pitched noise from somewhere near the capacitors/ferrite ring which I don’t think I heard the last time I opened it a few years ago, but then if it were that, then why would it affect only a very small, specific set of functions?)

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• Windows 7: How to place SuperFetch cache on an SSD?

  - by Ian Boyd

  I'm thinking of adding a solid state drive (SSD) to my existing Windows 7 installation. I know I can (and should) move my paging file to the SSD: Should the pagefile be placed on SSDs? Yes. Most pagefile operations are small random reads or larger sequential writes, both of which are types of operations that SSDs handle well. In looking at telemetry data from thousands of traces and focusing on pagefile reads and writes, we find that Pagefile.sys reads outnumber pagefile.sys writes by about 40 to 1, Pagefile.sys read sizes are typically quite small, with 67% less than or equal to 4 KB, and 88% less than 16 KB. Pagefile.sys writes are relatively large, with 62% greater than or equal to 128 KB and 45% being exactly 1 MB in size. In fact, given typical pagefile reference patterns and the favorable performance characteristics SSDs have on those patterns, there are few files better than the pagefile to place on an SSD. What I don't know is if I even can put a SuperFetch cache (i.e. ReadyBoost cache) on the solid state drive. I want to get the benefit of Windows being able to cache gigabytes of frequently accessed data on a relativly small (e.g. 30GB) solid state drive. This is exactly what SuperFetch+ReadyBoost (or SuperFetch+ReadyDrive) was designed for. Will Windows offer (or let) me place a ReadyBoost cache on a solid state flash drive connected via SATA? A problem with the ReadyBoost cache over the ReadyDrive cache is that the ReadyBoost cache does not survive between reboots. The cache is encrypted with a per-session key, making its existing contents unusable during boot and SuperFetch pre-fetching during login. Update One I know that Windows Vista limited you to only one ReadyBoost.sfcache file (I do not know if Windows 7 removed that limitation): Q: Can use use multiple devices for EMDs? A: Nope. We've limited Vista to one ReadyBoost per machine Q: Why just one device? A: Time and quality. Since this is the first revision of the feature, we decided to focus on making the single device exceptional, without the difficulties of managing multiple caches. We like the idea, though, and it's under consideration for future versions. I also know that the 4GB limit on the cache file was a limitation of the FAT filesystem used on most USB sticks - an SSD drive would be formatted with NTFS: Q: What's the largest amount of flash that I can use for ReadyBoost? A: You can use up to 4GB of flash for ReadyBoost (which turns out to be 8GB of cache w/ the compression) Q: Why can't I use more than 4GB of flash? A: The FAT32 filesystem limits our ReadyBoost.sfcache file to 4GB Can a ReadyBoost cache on an NTFS volume be larger than 4GB? Update Two The ReadyBoost cache is encrypted with a per-boot session key. This means that the cache has to be re-built after each boot, and cannot be used to help speed boot times, or latency from login to usable. Windows ReadyDrive technology takes advantage of non-volatile (NV) memory (i.e. flash) that is incorporated with some hybrid hard drives. This flash cache can be used to help Windows boot, or resume from hibernate faster. Will Windows 7 use an internal SSD drive as a ReadyBoost/*ReadyDrive*/SuperFetch cache? Is it possible to make Windows store a SuperFetch cache (i.e. ReadyBoost) on a non-removable SSD? Is it possible to not encrypt the ReadyBoost cache, and if so will Windows 7 use the cache at boot time? See also SuperUser.com: ReadyBoost + SSD = ? Windows 7 - ReadyBoost & SSD drives? Support and Q&A for Solid-State Drives Using SDD as a cache for HDD, is there a solution? Performance increase using SSD for paging/fetch/cache or ReadyBoost? (Win7) Windows 7 To Boost SSD Performance How to Disable Nonvolatile Caching

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• IBM Server Config questions

  - by Joel Coel

  I have a few questions on a potential server setup. First, the situation: Last year we bought an IBM x3500 server with 2 Xeon E5410's, 9GB RAM, 6 HDDs. The original intent for this server was to replace the old exchange e-mail server. It was brought in, set up, and then shortly after we switched to gmail. Shortly after that my predecessor left for greener pastures, and finally I was hired. So this nice server is now sitting (mostly) idle. This year I have budget again for one server, and of course I want to put this other server to work. I'm thinking about the best use for the two server, and I think I finally have a plan for what I want to do with them. The idea is to use the two newer servers as a pair of VM hosts. I will set up each server with the same 8 VMs, but divide up the load so that only 4 are active per physical host. That means I've normally got 2GB RAM + 2 cores per host. I've done some load testing to pick out what servers to convert to virtual, and chose them so that each host will be capable of handling the entire set of 8 by itself in a pinch with 1 core and 1GB RAM, but would be very taxed to do so. This should take our data center from 13 total servers down to 7. The "servers" I'm replacing are mostly re-purposed desktops, so I'm more than happy to be able to do this. Now it's time to go shopping for the new server. I'd like my two hosts to match as closely as possible, and so I'm looking at IBM again. It also helps that we have some educational matching grant money from IBM that I need to use to help pay for this system (we're a small private college). So finally, (if you're not bored already), we come to my questions: Am I missing anything big or obvious in this plan? I'm a little worried about network performance since the VM hosts will only have 4 nics total where 8 used to be, but I don't think it will be a problem. Is there anything else like this I might be overlooking? Am I making it even too complicated? IBM no longer has a good analog to last year's server. If I want to match the performance (8 cores, 9GB RAM, 1333mhz front side bus, 6 spindles), I have to spend quite a bit more than we paid last year: $2K+, or nearly a 33% cost increase. This only brings a marginal increase in performance. The alternative to stay in budget is to take a hit on the fsb down to 800mhz or cut the number of cores in half, neither of which is attractive. The main cost culprit is the processor. IBM no longer offers the E5410. It's listed as a part, but not available in any of the server configs I've looked at. I'm considering getting the cheapest 800mhz fsb dual core xeon I can configure and then buying the E5410's separately. That's still an extra $350 I wasn't counting on, but that's better than $2K. I want to know what others think of this - will it work or will I end up with the wrong motherboard or some other issue? Am I missing a simple way to configure the server I really want? I don't really intend to do this, but one option to save some money back is to omit the redundant power supply. Since my redundancy plan for these system is to switch over to a completely different host, the extra power isn't fully necessary. That said, it's still very helpful to avoid even short downtimes while I switch over VMs. Has anyone done this?

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• Cannot Start MySQL Server on Fresh MAMP Install

  - by alexpelan

  I'm using Mac OS X 10.6.2 on my Macbook Pro. I can get the apache server to start, but not the mysql server, on both the default apache and default MAMP ports. When I try to go to my start page, I get the message "Error: Could not connect to MySQL server!" . Here's what's in my mysql error log: 00513 02:00:07 mysqld_safe mysqld from pid file /Applications/MAMP/tmp/mysql/mysql.pid ended 100513 02:00:16 mysqld_safe Starting mysqld daemon with databases from /Applications/MAMP/db/mysql 100513 2:00:16 [Warning] The syntax '--log_slow_queries' is deprecated and will be removed in a future release. Please use '--slow_query_log'/'--slow_query_log_file' instead. 100513 2:00:16 [Warning] You have forced lower_case_table_names to 0 through a command-line option, even though your file system '/Applications/MAMP/db/mysql/' is case insensitive. This means that you can corrupt a MyISAM table by accessing it with different cases. You should consider changing lower_case_table_names to 1 or 2 100513 2:00:16 [Warning] One can only use the --user switch if running as root 100513 2:00:16 [Note] Plugin 'FEDERATED' is disabled. 100513 2:00:16 [Note] Plugin 'ndbcluster' is disabled. InnoDB: Error: log file /usr/local/mysql/data/ib_logfile0 is of different size 0 5242880 bytes InnoDB: than specified in the .cnf file 0 16777216 bytes! 100513 2:00:16 [ERROR] Plugin 'InnoDB' init function returned error. 100513 2:00:16 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed. 100513 2:00:16 [ERROR] /Applications/MAMP/Library/libexec/mysqld: unknown option '--skip-bdb' 100513 2:00:16 [ERROR] Aborting 100513 2:00:16 [Note] /Applications/MAMP/Library/libexec/mysqld: Shutdown complete 100513 02:00:16 mysqld_safe mysqld from pid file /Applications/MAMP/tmp/mysql/mysql.pid ended A couple of things: 1) There are a bunch of different .cnf files that come with MAMP (my-huge, my-medium, etc.)...how can I tell which one is actually being used? 2) I deleted the ib_logfile0 and ib_logfile1 as recommended by another post on serverfault, and then ended up with more errors: 100519 16:01:30 InnoDB: Log file /usr/local/mysql/data/ib_logfile0 did not exist: new to be created InnoDB: Setting log file /usr/local/mysql/data/ib_logfile0 size to 16 MB InnoDB: Database physically writes the file full: wait... 100519 16:01:30 InnoDB: Log file /usr/local/mysql/data/ib_logfile1 did not exist: new to be created InnoDB: Setting log file /usr/local/mysql/data/ib_logfile1 size to 16 MB InnoDB: Database physically writes the file full: wait... InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 100519 16:01:31 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... 100519 16:01:31 InnoDB: Started; log sequence number 0 44556 100519 16:01:31 [ERROR] /Applications/MAMP/Library/libexec/mysqld: unknown option '--skip-bdb' 100519 16:01:31 [ERROR] Aborting And then I got this the next time I tried to run it: InnoDB: Unable to lock /usr/local/mysql/data/ibdata1, error: 35 InnoDB: Check that you do not already have another mysqld process InnoDB: using the same InnoDB data or log files. Sorry that this is a lot of information, but I don't want to leave anything out. Thanks.

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• How to save POST&GET headers of a web page with "Wireshark"?

  - by brilliant

  Hello everybody, I've been trying to find a python code that would log in to my mail box on yahoo.com from "Google App Engine". I was given this code: import urllib, urllib2, cookielib url = "https://login.yahoo.com/config/login?" form_data = {'login' : 'my-login-here', 'passwd' : 'my-password-here'} jar = cookielib.CookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(jar)) form_data = urllib.urlencode(form_data) # data returned from this pages contains redirection resp = opener.open(url, form_data) # yahoo redirects to http://my.yahoo.com, so lets go there instead resp = opener.open('http://mail.yahoo.com') print resp.read() The author of this script looked into HTML script of yahoo log-in form and came up with this script. That log-in form contains two fields, one for users' Yahoo! ID and another one is for users' password. However, when I tried this code out (substituting mu real Yahoo login for 'my-login-here' and my real password for 'my-password-here'), it just return the log-in form back to me, which means that something didn't work right. Another supporter suggested that I should send an MD5 hash of my password, rather than a plain password. He also noted that in that log-in form there are a lot other hidden fields besides login and password fields (he called them "CSRF protections") that I would also have to deal with: <input type="hidden" name=".tries" value="1"> <input type="hidden" name=".src" value="ym"> <input type="hidden" name=".md5" value=""> <input type="hidden" name=".hash" value=""> <input type="hidden" name=".js" value=""> <input type="hidden" name=".last" value=""> <input type="hidden" name="promo" value=""> <input type="hidden" name=".intl" value="us"> <input type="hidden" name=".bypass" value=""> <input type="hidden" name=".partner" value=""> <input type="hidden" name=".u" value="bd5tdpd5rf2pg"> <input type="hidden" name=".v" value="0"> <input type="hidden" name=".challenge" value="5qUiIPGVFzRZ2BHhvtdGXoehfiOj"> <input type="hidden" name=".yplus" value=""> <input type="hidden" name=".emailCode" value=""> <input type="hidden" name="pkg" value=""> <input type="hidden" name="stepid" value=""> <input type="hidden" name=".ev" value=""> <input type="hidden" name="hasMsgr" value="0"> <input type="hidden" name=".chkP" value="Y"> <input type="hidden" name=".done" value="http://mail.yahoo.com"> He said that I should do the following: Simulate normal login and save login page that I get; Save POST&GET headers with "Wireshark"; Compare login page with those headers and see what fields I need to include with my request; I really don't know how to carry out the first two of these three steps. I have just downloaded "Wireshark" and have tried capturing some packets there. However, I don't know how to "simulate normal login and save the login page". Also, I don't how to save POST$GET headers with "Wireshark". Can anyone, please, guide me through these two steps in "Wireshark"? Or at least tell me what I should start with. Thank You.

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• Reuse remote ssh connections and reduce command/session logging verbosity?

  - by ewwhite

  I have a number of systems that rely on application-level mirroring to a secondary server. The secondary server pulls data by means of a series of remote SSH commands executed on the primary. The application is a bit of a black box, and I may not be able to make modifications to the scripts that are used. My issue is that the logging in /var/log/secure is absolutely flooded with requests from the service user, admin. These commands occur many times per second and have a corresponding impact on logs. They rely on passphrase-less key exchange. The OS involved is EL5 and EL6. Example below. Is there any way to reduce the amount of logging from these actions. (By user? By source?) Is there a cleaner way for the developers to perform these ssh executions without spawning so many sessions? Seems inefficient. Can I reuse the existing connections? Example log output: Jul 24 19:08:54 Cantaloupe sshd[46367]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:54 Cantaloupe sshd[46446]: Accepted publickey for admin from 172.30.27.32 port 33526 ssh2 Jul 24 19:08:54 Cantaloupe sshd[46446]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:54 Cantaloupe sshd[46446]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:54 Cantaloupe sshd[46475]: Accepted publickey for admin from 172.30.27.32 port 33527 ssh2 Jul 24 19:08:54 Cantaloupe sshd[46475]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:54 Cantaloupe sshd[46475]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:54 Cantaloupe sshd[46504]: Accepted publickey for admin from 172.30.27.32 port 33528 ssh2 Jul 24 19:08:54 Cantaloupe sshd[46504]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:54 Cantaloupe sshd[46504]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:54 Cantaloupe sshd[46583]: Accepted publickey for admin from 172.30.27.32 port 33529 ssh2 Jul 24 19:08:54 Cantaloupe sshd[46583]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:54 Cantaloupe sshd[46583]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:54 Cantaloupe sshd[46612]: Accepted publickey for admin from 172.30.27.32 port 33530 ssh2 Jul 24 19:08:54 Cantaloupe sshd[46612]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:54 Cantaloupe sshd[46612]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:55 Cantaloupe sshd[46641]: Accepted publickey for admin from 172.30.27.32 port 33531 ssh2 Jul 24 19:08:55 Cantaloupe sshd[46641]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:55 Cantaloupe sshd[46641]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:55 Cantaloupe sshd[46720]: Accepted publickey for admin from 172.30.27.32 port 33532 ssh2 Jul 24 19:08:55 Cantaloupe sshd[46720]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:55 Cantaloupe sshd[46720]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:55 Cantaloupe sshd[46749]: Accepted publickey for admin from 172.30.27.32 port 33533 ssh2 Jul 24 19:08:55 Cantaloupe sshd[46749]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:55 Cantaloupe sshd[46749]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:55 Cantaloupe sshd[46778]: Accepted publickey for admin from 172.30.27.32 port 33534 ssh2 Jul 24 19:08:55 Cantaloupe sshd[46778]: pam_unix(sshd:session): session opened for user admin by (uid=0) Jul 24 19:08:55 Cantaloupe sshd[46778]: pam_unix(sshd:session): session closed for user admin Jul 24 19:08:55 Cantaloupe sshd[46857]: Accepted publickey for admin from 172.30.27.32 port 33535 ssh2

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• Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

  - by vmiazzo

  Hi, Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not good for high availability. When 1 IP goes down clients will continue to use it for minutes. A load balancer is often suggested as a better choice. Both claims are not completely true: When the traffic is HTTP then, most of the HTML browsers are able to automatically try the next A record if the previous is down, without a new DNS look-up. Read here chapter 3.1 and here. When multiple data centers are involved then, DNS RR is the only option to distribute traffic across them. So, is it true that, with multiple data centers and HTTP traffic, the use of DNS RR is the ONLY way to assure instant fail-over when one data center goes down? Thanks, Valentino Edit: Off course each data center has a local Load Balancer with hot spare. It's OK to sacrifice session affinity for an instant fail-over. AFAIK the only way for a DNS to suggest a data center instead of another is to reply with just the IP (or IPs) associated to that data center. If the data center becomes unreachable then all those IP are also unreachables. This means that, even if smart HTML browsers are able to instantly try another A record , all the attempts will fail until the local cache entry expires and a new DNS lookup is done, fetching the new working IPs (I assume DNS automatically suggests to a new data center when one fail). So, "smart DNS" cannot assure instant fail-over. Conversely a DNS round-robin permits it. When one data center fail, the smart HTML browsers (most of them) instantly try the other cached A records jumping to another (working) data center. So, DNS round-robin doesn't assure session affinity or the lowest RTT but seems to be the only way to assure instant fail-over when the clients are "smart" HTML browsers. Edit 2: Some people suggest TCP Anycast as a definitive solution. In this paper (chapter 6) is explained that Anycast fail-over is related to BGP convergence. For this reason Anycast can employ from 15 minutes to 20 seconds to complete. 20 seconds are possible on networks where the topology was optimized for this. Probably just CDN operators can grant such fast fail-overs. Edit 3:* I did some DNS look-ups and traceroutes (maybe some expert can double check) and: The only CDN using TCP Anycast seems to be CacheFly, other operators like CDN networks and BitGravity use CacheFly. Seems that their edges cannot be used as reverse proxies. Therefore, they cannot be used to grant instant failover. Akamai and LimeLight seems to use geo-aware DNS. But! They return multiple A records. From traceroutes seems that the returned IPs are on the same data center. So, I'm puzzled on how they can offer a 100% SLA when one data center goes down.

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• Does this prove a network bandwidth bottleneck?

  - by Yuji Tomita

  I've incorrectly assumed that my internal AB testing means my server can handle 1k concurrency @3k hits per second. My theory at at the moment is that the network is the bottleneck. The server can't send enough data fast enough. External testing from blitz.io at 1k concurrency shows my hits/s capping off at 180, with pages taking longer and longer to respond as the server is only able to return 180 per second. I've served a blank file from nginx and benched it: it scales 1:1 with concurrency. Now to rule out IO / memcached bottlenecks (nginx normally pulls from memcached), I serve up a static version of the cached page from the filesystem. The results are very similar to my original test; I'm capped at around 180 RPS. Splitting the HTML page in half gives me double the RPS, so it's definitely limited by the size of the page. If I internally ApacheBench from the local server, I get consistent results of around 4k RPS on both the Full Page and the Half Page, at high transfer rates. Transfer rate: 62586.14 [Kbytes/sec] received If I AB from an external server, I get around 180RPS - same as the blitz.io results. How do I know it's not intentional throttling? If I benchmark from multiple external servers, all results become poor which leads me to believe the problem is in MY servers outbound traffic, not a download speed issue with my benchmarking servers / blitz.io. So I'm back to my conclusion that my server can't send data fast enough. Am I right? Are there other ways to interpret this data? Is the solution/optimization to set up multiple servers + load balancing that can each serve 180 hits per second? I'm quite new to server optimization, so I'd appreciate any confirmation interpreting this data. Outbound traffic Here's more information about the outbound bandwidth: The network graph shows a maximum output of 16 Mb/s: 16 megabits per second. Doesn't sound like much at all. Due to a suggestion about throttling, I looked into this and found that linode has a 50mbps cap (which I'm not even close to hitting, apparently). I had it raised to 100mbps. Since linode caps my traffic, and I'm not even hitting it, does this mean that my server should indeed be capable of outputting up to 100mbps but is limited by some other internal bottleneck? I just don't understand how networks at this large of a scale work; can they literally send data as fast as they can read from the HDD? Is the network pipe that big? In conclusion 1: Based on the above, I'm thinking I can definitely raise my 180RPS by adding an nginx load balancer on top of a multi nginx server setup at exactly 180RPS per server behind the LB. 2: If linode has a 50/100mbit limit that I'm not hitting at all, there must be something I can do to hit that limit with my single server setup. If I can read / transmit data fast enough locally, and linode even bothers to have a 50mbit/100mbit cap, there must be an internal bottleneck that's not allowing me to hit those caps that I'm not sure how to detect. Correct? I realize the question is huge and vague now, but I'm not sure how to condense it. Any input is appreciated on any conclusion I've made.

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• Nginx and multiple wordpress instances with fastcgi under same domain

  - by damnsweet

  My site is running on apache. two instances of wordpress exist under paths /tr/ and /eng/. I want to move the setup to nginx but could not manage to get it working. My setup consists of nging 0.7.66, php 5.3.2, and php-fpm. /tr/ and /eng/ are two separate wordpress instances located under /home/istci/webapps/wordpress_tr and /home/istci/webapps/wordpress respectively. Below is the server section from nginx.conf containing only configuration for tr, yet could not get it working either. server { listen 80; server_name www.example.com; charset utf-8; location ~ ^/$ { rewrite ^(.+)$ http://www.example.com/tr/ permanent; } location ~ /tr/.*php$ { fastcgi_pass unix:/home/istci/var/run/wptr.sock; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME /home/istci/webapps/wordpress_tr$fastcgi_script_name; fastcgi_param QUERY_STRING $query_string; fastcgi_param REQUEST_METHOD $request_method; fastcgi_param CONTENT_TYPE $content_type; fastcgi_param CONTENT_LENGTH $content_length; fastcgi_param SCRIPT_NAME $fastcgi_script_name; fastcgi_param REQUEST_URI $request_uri; fastcgi_param DOCUMENT_URI $document_uri; fastcgi_param DOCUMENT_ROOT $document_root; fastcgi_param SERVER_PROTOCOL $server_protocol; fastcgi_param GATEWAY_INTERFACE CGI/1.1; fastcgi_param SERVER_SOFTWARE nginx/$nginx_version; fastcgi_param REMOTE_ADDR $remote_addr; fastcgi_param REMOTE_PORT $remote_port; fastcgi_param SERVER_ADDR $server_addr; fastcgi_param SERVER_PORT $server_port; fastcgi_param SERVER_NAME $server_name; # required if PHP was built with --enable-force-cgi-redirect fastcgi_param REDIRECT_STATUS 200; } location /tr/ { root /home/istci/webapps/wordpress_tr/; index index.php index.html index.htm; if (!-e $request_filename) { rewrite ^(.+)$ /tr/index.php?q=$1 last; break; } if (-f $request_filename) { expires 30d; break; } } } php-fpm listens on unix:/home/istci/var/run/wptr.sock. running it in debug-mode shows no active handlers, which means no connection is made to unix socket from nginx. nginx access logs: 127.0.0.1 - - [09/Jun/2010:03:45:11 -0500] "GET /tr/ HTTP/1.0" 404 20 "-" "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.4) Gecko/20100527 Firefox/3.6.4" nginx debug logs : 2010/06/09 03:38:53 [notice] 6922#0: built by gcc 4.1.2 20080704 (Red Hat 4.1.2-48) 2010/06/09 03:38:53 [notice] 6922#0: OS: Linux 2.6.18-164.9.1.el5PAE 2010/06/09 03:38:53 [notice] 6922#0: getrlimit(RLIMIT_NOFILE): 4096:4096 2010/06/09 03:38:53 [notice] 6923#0: start worker processes 2010/06/09 03:38:53 [notice] 6923#0: start worker process 6924 2010/06/09 03:38:53 [notice] 6923#0: start worker process 6925 2010/06/09 03:39:01 [notice] 6925#0: *1 "^(.+)$" matches "/tr/", client: 127.0.0.1, server: www.example.com, request: "GET /tr/ HTTP/1.0", host: "www.example.com" 2010/06/09 03:39:01 [notice] 6925#0: *1 rewritten data: "/tr/index.php", args: "q=/tr/", client: 127.0.0.1, server: www.example.com, request: "GET /tr/ HTTP/1.0", host: "www.example.com" Any clues about what is wrong with my configuration? Thanks.

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• Varnish VCL - Regular Expression Evaluation

  - by Hugues ALARY

  I have been struggling for the past few days with this problem: Basically, I want to send to a client browser a cookie of the form foo[sha1oftheurl]=[randomvalue] if and only if the cookie has not already been set. e.g. If a client browser requests "/page.html", the HTTP response will be like: resp.http.Set-Cookie = "foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=ABCD;" then, if the same client request "/index.html", the HTTP response will contain a header: resp.http.Set-Cookie = "foo14fe4559026d4c5b5eb530ee70300c52d99e70d7=QWERTY;" In the end, the client browser will have 2 cookies: foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=ABCD foo14fe4559026d4c5b5eb530ee70300c52d99e70d7=QWERTY Now, that, is not complicated in itself. The following code does it: import digest; import random; ##This vmod does not exist, it's just for the example. sub vcl_recv() { ## We compute the sha1 of the requested URL and store it in req.http.Url-Sha1 set req.http.Url-Sha1 = digest.hash_sha1(req.url); set req.http.random-value = random.get_rand(); } sub vcl_deliver() { ## We create a cookie on the client browser by creating a "Set-Cookie" header ## In our case the cookie we create is of the form foo[sha1]=[randomvalue] ## e.g for a URL "/page.html" the cookie will be foo4c9ae249e9e061dd6e30893e03dc10a58cc40ee6=[randomvalue] set resp.http.Set-Cookie = {""} + resp.http.Set-Cookie + "foo"+req.http.Url-Sha1+"="+req.http.random-value; } However, this code does not take into account the case where the Cookie already exists. I need to check that the Cookie does not exists before generating a random value. So I thought about this code: import digest; import random; sub vcl_recv() { ## We compute the sha1 of the requested URL and store it in req.http.Url-Sha1 set req.http.Url-Sha1 = digest.hash_sha1(req.url); set req.http.random-value = random.get_rand(); set req.http.regex = "abtest"+req.http.Url-Sha1; if(!req.http.Cookie ~ req.http.regex) { set req.http.random-value = random.get_rand(); } } The problem is that Varnish does not compute Regular expression at run time. Which leads to this error when I try to compile: Message from VCC-compiler: Expected CSTR got 'req.http.regex' (program line 940), at ('input' Line 42 Pos 31) if(req.http.Cookie !~ req.http.regex) { ------------------------------##############--- Running VCC-compiler failed, exit 1 VCL compilation failed One could propose to solve my problem by matching on the "abtest" part of the cookie or even "abtest[a-fA-F0-9]{40}": if(!req.http.Cookie ~ "abtest[a-fA-F0-9]{40}") { set req.http.random-value = random.get_rand(); } But this code matches any cookie starting by 'abtest' and containing an hexadecimal string of 40 characters. Which means that if a client requests "/page.html" first, then "/index.html", the condition will evaluate to true even if the cookie for the "/index.html" has not been set. I found in bug report phk or someone else stating that computing regular expressions was extremely expensive which is why they are evaluated during compilation. Considering this, I believe that there is no way of achieving what I want the way I've been trying to. Is there any way of solving this problem, other than writting a vmod? Thanks for your help! -Hugues

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• How to place SuperFetch cache on an SSD?

  - by Ian Boyd

  I'm thinking of adding a solid state drive (SSD) to my existing Windows 7 installation. I know I can (and should) move my paging file to the SSD: Should the pagefile be placed on SSDs? Yes. Most pagefile operations are small random reads or larger sequential writes, both of which are types of operations that SSDs handle well. In looking at telemetry data from thousands of traces and focusing on pagefile reads and writes, we find that Pagefile.sys reads outnumber pagefile.sys writes by about 40 to 1, Pagefile.sys read sizes are typically quite small, with 67% less than or equal to 4 KB, and 88% less than 16 KB. Pagefile.sys writes are relatively large, with 62% greater than or equal to 128 KB and 45% being exactly 1 MB in size. In fact, given typical pagefile reference patterns and the favorable performance characteristics SSDs have on those patterns, there are few files better than the pagefile to place on an SSD. What I don't know is if I even can put a SuperFetch cache (i.e. ReadyBoost cache) on the solid state drive. I want to get the benefit of Windows being able to cache gigabytes of frequently accessed data on a relativly small (e.g. 30GB) solid state drive. This is exactly what SuperFetch+ReadyBoost (or SuperFetch+ReadyDrive) was designed for. Will Windows offer (or let) me place a ReadyBoost cache on a solid state flash drive connected via SATA? A problem with the ReadyBoost cache over the ReadyDrive cache is that the ReadyBoost cache does not survive between reboots. The cache is encrypted with a per-session key, making its existing contents unusable during boot and SuperFetch pre-fetching during login. Update One I know that Windows Vista limited you to only one ReadyBoost.sfcache file (I do not know if Windows 7 removed that limitation): Q: Can use use multiple devices for EMDs? A: Nope. We've limited Vista to one ReadyBoost per machine Q: Why just one device? A: Time and quality. Since this is the first revision of the feature, we decided to focus on making the single device exceptional, without the difficulties of managing multiple caches. We like the idea, though, and it's under consideration for future versions. I also know that the 4GB limit on the cache file was a limitation of the FAT filesystem used on most USB sticks - an SSD drive would be formatted with NTFS: Q: What's the largest amount of flash that I can use for ReadyBoost? A: You can use up to 4GB of flash for ReadyBoost (which turns out to be 8GB of cache w/ the compression) Q: Why can't I use more than 4GB of flash? A: The FAT32 filesystem limits our ReadyBoost.sfcache file to 4GB Can a ReadyBoost cache on an NTFS volume be larger than 4GB? Update Two The ReadyBoost cache is encrypted with a per-boot session key. This means that the cache has to be re-built after each boot, and cannot be used to help speed boot times, or latency from login to usable. Windows ReadyDrive technology takes advantage of non-volatile (NV) memory (i.e. flash) that is incorporated with some hybrid hard drives. This flash cache can be used to help Windows boot, or resume from hibernate faster. Will Windows 7 use an internal SSD drive as a ReadyBoost/*ReadyDrive*/SuperFetch cache? Is it possible to make Windows store a SuperFetch cache (i.e. ReadyBoost) on a non-removable SSD? Is it possible to not encrypt the ReadyBoost cache, and if so will Windows 7 use the cache at boot time? See also SuperUser.com: ReadyBoost + SSD = ? Windows 7 - ReadyBoost & SSD drives? Support and Q&A for Solid-State Drives Using SDD as a cache for HDD, is there a solution? Performance increase using SSD for paging/fetch/cache or ReadyBoost? (Win7) Windows 7 To Boost SSD Performance How to Disable Nonvolatile Caching

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• Accessing resources on localhost using domain credentials

  - by jas

  I'm trying to set up Team Foundation Server 2010, Sharepoint Server 2010 and Report Server 2008R2. I apologize for how long my question/problem is but I'm really lost on where to even look so am being as descriptive as possible in hopes that I'm making sense. The goal: Since developers can be inside or outside the firewall there needs to be a single http point of entry to TFS that works regardless of which side of the firewall you are and needs to work with external access to SharePoint and Report Server. Meaning we have it set up in DNS so buildserver.mydomain.com: points to the build service box which contains all of the services listed at the top of this post and specific services are defined/located by the port number. This is working great on every machine inside and out except for from the build server itself. All services must be able to work using external URLs. If I use http:// buildserver.mydomain.com:4800/tfs (the external URL) from my notebook which is behind the firewall I'm able to login with my domain credentials as expected. If the other developer points to the same URL from their home which isn't on the domain they are also able to login using their domain credentials. However if I am directly on buildserver and call SharePoint, TFS or Reporting Server from (i.e. http:// buildserver.mydomain.com:4800) itself using the external URL, I am prompted for a username and password. Entering my domain credentials results in another prompt to enter my credentials again. It will prompt three times regardless of which credentials are used (I have rights as a domain admin) and then after the third prompt directs me to a blank white page as though access was denied. There are no errors displayed on the page and nothing ends up in the event viewer. From buildserver if i use just the host name (the internal URL), then I'm prompted a single time for credentials and it works. i.e. http:// buildserver:4800/tfs works from the server itself. The behavior is identical for any service requiring authentication. Meaning from the box itself Sharepoint Central Admin, SharePoint WebApp, TFS, TFS Web Access, Report Server and Report Manager all fail using the external URL but will succeed if called using the interal URL. So the problem comes into play when configuring all of the services to work together. The only way to configure TFS is locally from the server which means I must point to the internal reporting server url (http:// buildserver:4800/reports and reportServer respectively instead of http:// buildserver.domainname.com:4800 like they need to be) since external URLs aren't working from itself. If I configure TFS to use the internal URL for Report Server then creating team projects or working in the SharePoint site for the team project fails for anyone not inside the domain since their machines have no idea who http:// buildserver:/reports even is or how to resolve them. I have configured Sharepoint with Alternate Access Mappings as well as set up Report Server to listen for external URLs. The external URLs simply aren't working when called from the server itself. I hope this makes sense. Thanks for taking the time to read this rather verbose plea for help.

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• Unison synchronization problem. Roots are not identical after synchronization.

  - by binary255

  Hi. When I synchronize two folders using Unison, only one of the roots seems to be affected. Below are all the information I would think is necessary to figure out why it is working like it is. I'm using $ unison -version unison version 2.27.57 From the Ubuntu repositories. My work laptop: $ echo $UNISONLOCALHOSTNAME worklaptop $ pwd /home/userfoo $ ls -lAR .unison* .unison: total 8 drwxr-xr-x 2 userfoo userfoo 4096 2010-04-26 11:39 backups -rw-r--r-- 1 userfoo userfoo 231 2010-04-26 11:38 default.prf .unison/backups: total 0 .unisonroot: total 0 $ cat .unison/default.prf # Roots of the synchronization root = /home/userfoo/.unisonroot root = ssh://devel//home/userbar/.unisonroot path = * backuplocation = central backupdir = /home/.unison/backups backupprefix = $VERSION.bak $ mkdir .unisonroot/aDirectoryFrom-$UNISONLOCALHOSTNAME $ echo something >.unisonroot/aFileFrom-$UNISONLOCALHOSTNAME $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop And the Ubuntu server I want to synchronize with: $ echo $UNISONLOCALHOSTNAME workcmpuserbardevel $ pwd /home/userbar $ ls -lAR .unison* .unison: total 4 drwxr-xr-x 2 userbar userbar 4096 2010-04-26 11:38 .unison .unison/.unison: total 0 .unisonroot: total 0 $ mkdir .unisonroot/aDirectoryFrom-$UNISONLOCALHOSTNAME $ echo something >.unisonroot/aFileFrom-$UNISONLOCALHOSTNAME $ ls .unisonroot/ aDirectoryFrom-workcmpuserbardevel aFileFrom-workcmpuserbardevel I perform the unison synchronization: $ echo $UNISONLOCALHOSTNAME worklaptop $ unison Contacting server... Connected [//worklaptop//home/userfoo/.unisonroot -> //workcmpuserbardevel//home/userbar/.unisonroot] Looking for changes Warning: No archive files were found for these roots, whose canonical names are: /home/userfoo/.unisonroot //workcmpuserbardevel//home/userbar/.unisonroot This can happen either because this is the first time you have synchronized these roots, or because you have upgraded Unison to a new version with a different archive format. Update detection may take a while on this run if the replicas are large. Unison will assume that the 'last synchronized state' of both replicas was completely empty. This means that any files that are different will be reported as conflicts, and any files that exist only on one replica will be judged as new and propagated to the other replica. If the two replicas are identical, then no changes will be reported. If you see this message repeatedly, it may be because one of your machines is getting its address from DHCP, which is causing its host name to change between synchronizations. See the documentation for the UNISONLOCALHOSTNAME environment variable for advice on how to correct this. Donations to the Unison project are gratefully accepted: http://www.cis.upenn.edu/~bcpierce/unison Press return to continue.[<spc>] Waiting for changes from server Reconciling changes local workcmps... dir ----> aDirectoryFrom-worklaptop [f] file ----> aFileFrom-worklaptop [f] Proceed with propagating updates? [] y Propagating updates UNISON 2.27.57 started propagating changes at 11:49:14 on 26 Apr 2010 [BGN] Copying aDirectoryFrom-worklaptop from /home/userfoo/.unisonroot to //workcmpuserbardevel//home/userbar/.unisonroot [BGN] Copying aFileFrom-worklaptop from /home/userfoo/.unisonroot to //workcmpuserbardevel//home/userbar/.unisonroot [END] Copying aDirectoryFrom-worklaptop [END] Copying aFileFrom-worklaptop UNISON 2.27.57 finished propagating changes at 11:49:14 on 26 Apr 2010 Saving synchronizer state Synchronization complete (2 items transferred, 0 skipped, 0 failures) And then check the .unisonroot directory on the computer I started the synchronization from: $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop And on the server: $ echo $UNISONLOCALHOSTNAME workcmpuserbardevel $ ls .unisonroot/ aDirectoryFrom-worklaptop aFileFrom-worklaptop aDirectoryFrom-workcmpuserbardevel aFileFrom-workcmpuserbardevel As can be seen above, the contents of the laptop .unisonroot has not changed while the servers .unisonroot has. The desired result would have been that the two folders would have ended up being identical, holding the union of the contents of the two roots.

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• "Possible SYN flooding" in log despite low number of SYN_RECV connections

  - by al4

  Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a question about this here if you want more background. After enabling syncookies we started seeing the following message in /var/log/messages approximately every 60 seconds: [84440.731929] possible SYN flooding on port 80. Sending cookies. Vinko Vrsalovic informed me that this means the syn backlog is getting full, so I raised tcp_max_syn_backlog to 4096. At some point I also lowered tcp_synack_retries to 3 (down from the default of 5) by issuing sysctl -w net.ipv4.tcp_synack_retries=3. After doing this, the frequency seemed to drop, with the interval of the messages varying between roughly 60 and 180 seconds. Next I issued sysctl -w net.ipv4.tcp_max_syn_backlog=65536, but am still getting the message in the log. Throughout all this I've been watching the number of connections in SYN_RECV state (by running watch --interval=5 'netstat -tuna |grep "SYN_RECV"|wc -l'), and it never goes higher than about 240, much much lower than the size of the backlog. Yet I have a Red Hat server which hovers around 512 (limit on this server is the default of 1024). Are there any other tcp settings which would limit the size of the backlog or am I barking up the wrong tree? Should the number of SYN_RECV connections in netstat -tuna correlate to the size of the backlog? Update As best I can tell I'm dealing with legitimate connections here, netstat -tuna|wc -l hovers around 5000. I've been researching this today and found this post from a last.fm employee, which has been rather useful. I've also discovered that the tcp_max_syn_backlog has no effect when syncookies are enabled (as per this link) So as a next step I set the following in sysctl.conf: net.ipv4.tcp_syn_retries = 3 # default=5 net.ipv4.tcp_synack_retries = 3 # default=5 net.ipv4.tcp_max_syn_backlog = 65536 # default=1024 net.core.wmem_max = 8388608 # default=124928 net.core.rmem_max = 8388608 # default=131071 net.core.somaxconn = 512 # default = 128 net.core.optmem_max = 81920 # default = 20480 I then setup my response time test, ran sysctl -p and disabled syncookies by sysctl -w net.ipv4.tcp_syncookies=0. After doing this the number of connections in the SYN_RECV state still remained around 220-250, but connections were starting to delay again. Once I noticed these delays I re-enabled syncookies and the delays stopped. I believe what I was seeing was still an improvement from the initial state, however some requests were still delayed which is much worse than having syncookies enabled. So it looks like I'm stuck with them enabled until we can get some more servers online to cope with the load. Even then, I'm not sure I see a valid reason to disable them again as they're only sent (apparently) when the server's buffers get full. But the syn backlog doesn't appear to be full with only ~250 connections in the SYN_RECV state! Is it possible that the SYN flooding message is a red herring and it's something other than the syn_backlog that's filling up? If anyone has any other tuning options I haven't tried yet I'd be more than happy to try them out, but I'm starting to wonder if the syn_backlog setting isn't being applied properly for some reason.

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• Unable to remove limit on memory usage for PHP script.

  - by Jess Telford

  The Situation I am having an issue with a PHP script getting the following error message: Fatal error: Out of memory (allocated 359923712) (tried to allocate 72 bytes) in /path/to/piwik/core/DataTable.php on line 969 The script I'm running is: /path/to/piwik/misc/cron/archive.sh I am assuming the numbers are Bytes, which means that total is approximately 360MB. For all intents and purposes, I have increased the memory limits on the server well above 360MB, yet this is the number (give or take a byte) it consistently errors out at. Please note: This question is not about fixing a memory leak in the script, nor about why the script itself is using so much memory. The script is part of the Piwik archiving process, so I cannot just fix any memory leaks, etc. For more info on this script and why I am increasing the memory limit, see "How to setup auto archiving" The question Given that the script is attempting to use over 360MB of memory, which I cannot change, why does it not seem possible for me to increase the amount of memory available to php on my server? What I've tried Increasing PHP's memory_limit Given the php.ini file: php -i | grep php.ini Configuration File (php.ini) Path => /usr/local/lib Loaded Configuration File => /usr/local/lib/php.ini I have edited that file, so the memory_limit directive reads; memory_limit = -1 Restart Apache, and check the new value has stuck; $ php -i | grep memory_limit memory_limit => -1 => -1 Run the script, and get the same error. I've also tried 1G, 768M, etc, all to the same result (ie; no change). Update 22nd June: Based on Vangel's help, I have attempted to set post_max_size to 20M in combination with setting memory_limit. Again, this has no effect. Removing the memory limit on child processes of Apache I have found and edited the httpd.conf file to make sure there is no RLimitMEM directive. I then used WHM's Apache Configuration Memory Usage Restrictions to generate a restriction, which it claimed was at 1000M (and confirmed by checking httpd.conf). Both of these resulted in no change to the script erroring at 360MB. Increasing the per process memory limits of Linux The current limits set on the system: $ ulimit -m 524288 $ ulimit -v 524288 I have attempted to set both of these to unlimited: $ ulimit -m unlimited $ ulimit -v unlimited $ ulimit -m unlimited $ ulimit -v unlimited Once again, this has resulted in absolutely no improvement in my problem. My setup $ cat /etc/redhat-release CentOS release 5.5 (Final) $ uname -a Linux example.com 2.6.18-164.15.1.el5 #1 SMP Wed Mar 17 11:30:06 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux $ php -i | grep "PHP Version" PHP Version => 5.2.9 $ httpd -V Server version: Apache/2.0.63 Server built: Feb 2 2011 01:25:12 Cpanel::Easy::Apache v3.2.0 rev5291 Server's Module Magic Number: 20020903:13 Server loaded: APR 0.9.17, APR-UTIL 0.9.15 Compiled using: APR 0.9.17, APR-UTIL 0.9.15 Architecture: 64-bit Server compiled with.... -D APACHE_MPM_DIR="server/mpm/prefork" -D APR_HAS_SENDFILE -D APR_HAS_MMAP -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled) -D APR_USE_SYSVSEM_SERIALIZE -D APR_USE_PTHREAD_SERIALIZE -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT -D APR_HAS_OTHER_CHILD -D AP_HAVE_RELIABLE_PIPED_LOGS -D HTTPD_ROOT="/usr/local/apache" -D SUEXEC_BIN="/usr/local/apache/bin/suexec" -D DEFAULT_PIDLOG="logs/httpd.pid" -D DEFAULT_SCOREBOARD="logs/apache_runtime_status" -D DEFAULT_LOCKFILE="logs/accept.lock" -D DEFAULT_ERRORLOG="logs/error_log" -D AP_TYPES_CONFIG_FILE="conf/mime.types" -D SERVER_CONFIG_FILE="conf/httpd.conf" Output of $ php -i: http://pastebin.com/EiRut6Nm

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• Wordpress Permissions OS X & MAMP

  - by Matt2020

  I have installed several local versions of Wordpress for development purposes. After the install I can create posts, pages and edit admin options. However as soon as try to upload images which would be saved in wp_content/uploads I get an error: Upload Error: Unable to create directory ...../blog/wp-content/uploads/2011/05. Is its parent directory writable by the server? Looks like MAMP server runs as user _www The blog directory is owned by User1 and the group User1 _www is not in the User1 group, should it be? I do not want to chmod 777 or 765 on the directories just to get it going. Googled up a couple of references: http://codex.wordpress.org/Changing_File_Permissions in "Permission Scheme for WordPress" All files should be owned by your user (ftp) account on your web server, and should be writable by that account. On shared hosts, files should never be owned by the webserver process itself (sometimes this is www, or apache, or nobody user). Any file that needs write access from WordPress should be owned or group-owned by the user account used by the WordPress (which may be different than the server account). For example, you may have a user account that lets you FTP files back and forth to your server, but your server itself may run using a separate user, in a separate usergroup, such as dhapache or nobody. If WordPress is running as the FTP account, that account needs to have write access, i.e., be the owner of the files, or belong to a group that has write access. In the latter case, that would mean permissions are set more permissively than default (for example, 775 rather than 755 for folders, and 664 instead of 644). User and group are User1 (which is admin). Running "ps aux | grep httpd" is running as _www So I think this means Wordpress is running as user _www. So the advice seems contradictory: "files should never be owned by the webserver process" i.e. _www but then later it says "Any file that needs write access from WordPress should be owned or group-owned by the user account used by the WordPress" So isn't this _www again? Another search found this url http://dancingengineer.com/computing/2009/07/how-to-install-wordpress-on-mac-os-x-leopard States Which says: My preferred way to do this is to change the group of the wordpress directory and its contents to _www and give write permissions to the group. Keep the owner as your "username". $ cd /Users/"username"/Sites $ sudo chown -R username:_www wordpress_directory $ sudo chmod -R g+w wordpress_directory However, when I tried this, it did not work for automatic upgrades to newer versions of WordPress although it worked for automatically updating the .htaccess file for pretty permalinks. It is not entirely clear to me what should be done. This last suggestion seems to be saying change the group from User1 to _www and give the group write access, but Wordpress upgrades won't work. Is this the right solution? I would have thought there would be a clear way to set this up on OS X 10.6? Be great if there was a plugin that could run a script for each of the main OS's that Wordpress runs on.

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• mysqld service crashes on restart, after importing mysqldump #innodb

  - by ubunut

  I have 2 mysql servers. Let's call them server01 & server02. Both have the same configuration: mysqladmin Ver 8.42 Distrib 5.1.61, for redhat-linux-gnu on x86_64 [client] default-character-set=utf8 [mysqld] datadir=/var/lib/mysql socket=/var/lib/mysql/mysql.sock user=mysql # Disabling symbolic-links is recommended to prevent assorted security risks symbolic-links=0 max_allowed_packet = 16M default-character-set=utf8 default-collation=utf8_unicode_ci character-set-server=utf8 collation-server=utf8_unicode_ci default-storage-engine = InnoDB innodb_data_home_dir = /var/lib/mysql innodb_log_group_home_dir = /var/lib/mysql innodb_data_file_path = ibdata1:10M:autoextend innodb_additional_mem_pool_size = 2M innodb_log_file_size = 5M innodb_log_buffer_size = 8M innodb_lock_wait_timeout = 50 innodb_flush_log_at_trx_commit = 1 innodb_buffer_pool_size = 700M table_cache = 300 thread_cache_size = 4 query_cache_size = 200m query_cache_limit = 10m [mysqld_safe] log-error=/var/log/mysqld.log pid-file=/var/run/mysqld/mysqld.pid I make a mysqldump on server01: mysqldump -uuser -ppassword --all-databases testservers.sql (most tables in these databases are innodb, some of the mysql.* tables are Innodb too) Then I import the testservers.sql on server02: mysql -uuser < testservers.sql (mysqld has been started with --skip-network). So far so good, I can login into mysql & everything seems to be ok. BUT when I exit to the shell and execute service mysqld restart, The service fails to start. stack-trace in /var/log/mysqld.log: 121022 14:53:19 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql 121022 14:53:19 [Warning] '--default-character-set' is deprecated and will be removed in a future release. Please use '--character-set-server' instead. 121022 14:53:19 [Warning] '--default-collation' is deprecated and will be removed in a future release. Please use '--collation-server' instead. 12:53:19 UTC - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=8384512 read_buffer_size=131072 max_used_connections=0 max_threads=151 thread_count=0 connection_count=0 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 338324 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. Thread pointer: 0x267e630 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 7fff3efe0be0 thread_stack 0x40000 /usr/libexec/mysqld(my_print_stacktrace+0x29) [0x84bd89] /usr/libexec/mysqld(handle_fatal_signal+0x483) [0x6a0be3] /lib64/libpthread.so.0() [0x338d60f500] /usr/libexec/mysqld(ha_resolve_by_name(THD*, st_mysql_lex_string const*)+0x81) [0x6956e1] /usr/libexec/mysqld(open_table_def(THD*, st_table_share*, unsigned int)+0xe0a) [0x60e5ba] /usr/libexec/mysqld(get_table_share(THD*, TABLE_LIST*, char*, unsigned int, unsigned int, int*)+0x20b) [0x602b0b] /usr/libexec/mysqld() [0x603597] /usr/libexec/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x7a1) [0x6079a1] /usr/libexec/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5d0) [0x608570] /usr/libexec/mysqld(open_and_lock_tables_derived(THD*, TABLE_LIST*, bool)+0x6a) [0x60877a] /usr/libexec/mysqld(plugin_init(int*, char**, int)+0x622) [0x715af2] /usr/libexec/mysqld() [0x5bd3b2] /usr/libexec/mysqld(main+0x1b3) [0x5bfc93] /lib64/libc.so.6(__libc_start_main+0xfd) [0x338d21ecdd] /usr/libexec/mysqld() [0x5087b9] Trying to get some variables. Some pointers may be invalid and cause the dump to abort. Query (0): is an invalid pointer Connection ID (thread ID): 0 Status: NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 121022 14:53:19 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended A typical mysqdump entry looks like this: DROP TABLE IF EXISTS `adodb_logsql`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `adodb_logsql` ( `id` bigint(10) unsigned NOT NULL AUTO_INCREMENT, `created` datetime NOT NULL, `sql0` varchar(250) NOT NULL DEFAULT '', `sql1` text, `params` text, `tracer` text, `timer` decimal(16,6) NOT NULL DEFAULT '0.000000', PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='to save some logs from ADOdb'; /*!40101 SET character_set_client = @saved_cs_client */; IF I change all occurrences of "ENGINE=InnoDB" to "ENGINE=MyISAM" before import, then the service has no problem restarting. I'm quite puzzled as to what's happening, maybe I'm just an idiot, then by all means tell me so. Any help would be greatly appreciated!

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• Can not access network computers anymore

  - by Johny Skovdal

  Last Thursday (03/05/12) I got a new computer to be able to work from home. I plugged it, by cable, into the company network and installed most of the software needed for me to do so, by accessing a share on my stationary computer at work. I had no issues here what so ever, and everything just worked. Yesterday evening I tried accessing the company network trough Windows VPN, and while I was able to connect to the network, I was unable to connect to any computers on the network. I did, however, get an error when connecting, but I can't seem to get the error again, to get the details of the error message. Today I am sitting on the company network again, and now I can not access anything on the network like I could last Thursday, though I can ping all the computers I am attempting to access. Here is a list of details that might help in troubleshooting this issue (updated): List of observations / actions My computer is identical to another computer that has no issues. It is not on the domain but rather on the default workgroup, but this was not an issue last Thursday, so I am assuming it still is not. I am able to access my e-mail on the exchange server. I can connect to our TFS server from Visual Studio but not from Explorer. I can also connect to Database Servers and Remote Desktop. I can see several computers when browsing network computers, but I am unable to connect to any of them. When trying to connect to a computer I am consistently met with the error code "0x80070035" (network path not found). I also get the 0x80070035 error when double clicking the target computer from the Network UI. I am not met with a login dialog when trying to access a computer, as I should, since I am not on the domain. (I did login to both Exchange, Remote Desktop and TFS though) Between Thursday where it worked and Sunday evening where it did not, I have installed quite a few security updates, plus various tools etc. that I need for programming. I have tried accessing by computer name and ip and neither of them work. I can ping by computer name. I have deleted all (1 entry) stored network credentials. I am able to access my computer from the target computer. Client and Server can see each other on the network = Network Discovery is enabled. I am using the network profile "Work". When accessing the network through VPN, I am unable to get anything to work using computernames, but all of the above applies when using IP adresses instead of computername. I run Windows 7 Home Premium on my computer. Using powershell attempting to access a share I get the following error (ComputerName and ShareName being correct values of course): PS C:\Users\MyUser> cd \\ComputerName\ShareName Set-Location : Cannot find path '\\ComputerName\ShareName' because it does not exist. At line:1 char:3 + cd <<<< \\ComputerName\ShareName + CategoryInfo : ObjectNotFound: (\\ComputerName\ShareName:String) [Set-Location], ItemNotFoundException + FullyQualifiedErrorId : PathNotFound,Microsoft.PowerShell.Commands.SetLocationCommand However, ping'ing the same machine (ping ComputerName) from powershell I get response immediately. (As mentioned in the list of observations/actions, I tried the above with the IP address again on VPN, to get the same result) Conclusion So to sum up, pretty much the only thing I can not do, is access the other computers through browsing (explorer.exe, powershell, map networkdrive, etc.), which means that I am pretty much down to, that it is unable to resolve the path somehow, when trying to connect to other computers trough browsing, though the path gets resolved perfectly using all kinds of other services. Any recommendations as to what I can try next to resolve the issue? :)

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• Hour-long shutdown duration "shutting down hyper-v virtual machine management service"

  - by icelava

  I have a Windows 2008 R2 server that is a Hyper-V host (Dell PowerEdge T300). Today for the first time I encountered an odd situation; i lost connection with one of the guest machines but logging on physically it seems the guest OS is still running but no longer contactable via the network. I tried to shut down the guest machine (Windows XP) but it would not shut down, getting stuck in a "Not responding" dialog box that cannot be dismissed. I used the Hyper-V management console to reset the machine and it could not get out of resetting state. I tried to save another Windows 2003 guest machine, and it would be progress with its Saving state (0%). The other running Windows 2003 guest was stuck in the logon dialog. My first suspicion is perhaps one of the Windows update patches this week (10 Nov 2011) may something to do with it, which was still pending a system restart. Well, since I could not do anything with Hyper-V i proceeded with the Windows Update restart, and now it is stuck half an hour at "Shutting down hyper-v virtual machine management service" Prior to restarting I did not observe any hard disk errors reported in the system event log; doubt it is a disk-related condition. Shall I force a hard reboot? UPDATE Ok so i left it hanging over an hour while attending to other matters, and thankfully the host cleanly restarted. I can operate the guest machines fine now. Phew. Hyper-V must have been crawling for some reason. The VMs have been observed to become slow in the past when the host has been up for a long duration (two weeks to a month), but never this slow. Would love to know what types of performance monitoring items i can observe to give a hint why this can happen. UPDATE 2012-02-13 In the months ever since, Hyper-V has stalled into this state another two times. It appears so randomly and without any error event logs to hint what is causing it enter this "drunkard" state. Just an Hyper-V management service timeout. Log Name: System Source: Service Control Manager Date: 13/2/2012 9:16:48 AM Event ID: 7043 Task Category: None Level: Error Keywords: Classic User: N/A Computer: elune Description: The Hyper-V Virtual Machine Management service did not shut down properly after receiving a preshutdown control. Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Service Control Manager" Guid="{555908d1-a6d7-4695-8e1e-26931d2012f4}" EventSourceName="Service Control Manager" /> <EventID Qualifiers="49152">7043</EventID> <Version>0</Version> <Level>2</Level> <Task>0</Task> <Opcode>0</Opcode> <Keywords>0x8080000000000000</Keywords> <TimeCreated SystemTime="2012-02-13T01:16:48.882901900Z" /> <EventRecordID>567844</EventRecordID> <Correlation /> <Execution ProcessID="764" ThreadID="8484" /> <Channel>System</Channel> <Computer>elune</Computer> <Security /> </System> <EventData> <Data Name="param1">Hyper-V Virtual Machine Management</Data> </EventData> </Event> The only means out of it is to restart the system.

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