Posts Tagged ‘udev’

How to Remove / Add SuSE Linux start service command

Thursday, July 2nd, 2015

opensuse-remove-add-new-service-geeko-suse-linux-mini-logo
If you happen to administer SUSE LINUX Enterprise Server 9 (x86_64) and you need to add or remove already existing /etc/init.d script or custom created Apache / Tomcat .. etc. service and you're already familiar with Fedora's / RHEL chkconfig, then the good news chkconfig is also available on SuSE and you can use in same way chkconfig to start / stop / enable / disable boot time services.

To list all available boot time init.d services use:
 

suse-linux:/etc # chkconfig –list

 

SuSEfirewall2_final       0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_init        0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_setup       0:off  1:off  2:off  3:off  4:off  5:off  6:off
Tivoli_lcfd1.bkp          0:off  1:off  2:off  3:off  4:off  5:off  6:off
activate_web_all          0:off  1:off  2:off  3:on   4:off  5:on   6:off
alsasound                 0:off  1:off  2:on   3:on   4:off  5:on   6:off
apache2                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
apache2-eis               0:off  1:off  2:off  3:on   4:off  5:off  6:off
atd                       0:off  1:off  2:off  3:off  4:off  5:off  6:off
audit                     0:off  1:off  2:off  3:off  4:off  5:off  6:off
autofs                    0:off  1:off  2:off  3:off  4:off  5:off  6:off
autoyast                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.clock                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.crypto               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.device-mapper        0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.evms                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.idedma               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ipconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.isapnp               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.klog                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ldconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.loadmodules          0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localfs              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localnet             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.lvm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.md                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.multipath            0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.proc                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.restore_permissions  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.rootfsck             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sched                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scpm                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scsidev              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.shm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.swap                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sysctl               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.udev                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
coldplug                  0:off  1:on   2:on   3:on   4:off  5:on   6:off

 

To then stop the service:
 

suse-linux:/etc # chkconfig gtiweb off


If you prefer to do it the SuSE way and learn a bit more on SuSE boot time process check out:

 

suse-linux:/etc # man insserv


Removing already existing SuSE start-up script from init.d start up with insserv is done with:

suse-linux:/etc # cd /etc/init.d/
suse-linux:etc/init.d # insserv -r gtiweb
insserv: script ipmi.hp: service ipmidrv already provided!
insserv: script boot.multipath.2008-10-29: service boot.multipath already provided!


To install a new custom written and placed into /etc/inti.d/ on SuSE's server boot time with insserv:

 

suse-linux:/etc/init.d/ # insserv your_custom_script_name

Apache Webserver: No space left on device: Couldn’t create accept lock /var/lock/apache2/accept.lock – Fix

Wednesday, April 8th, 2015

Apache-http-server-no-space-left-on-device-semaphores-quotes-hard-disk-space-resolve-fix-howto
If out of a sudden your Apache webserver crashes and is refusing to start up by manually trying to restart it through its init script on Debian Linux servers – /etc/init.d/apache2 and RPM based ones: /etc/init.d/httpd

Checking in php_error.log there was no shown errors related to loading PHP modules, however apache's error.log show following errors:

[Wed Apr 08 14:20:14 2015] [error] [client 180.76.5.149] client denied by server configuration: /var/www/sploits/info/trojans_info/tr_data/y3190.html
[Wed Apr 08 14:20:39 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:20:39 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.15974) (5)
[Wed Apr 08 14:25:39 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:25:39 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16790) (5)
[Wed Apr 08 14:27:03 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:27:03 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16826) (5)
[Wed Apr 08 14:27:53 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:27:53 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.16852) (5)
[Wed Apr 08 14:30:48 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:30:48 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17710) (5)
[Wed Apr 08 14:31:21 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:31:21 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17727) (5)
[Wed Apr 08 14:32:40 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?
[Wed Apr 08 14:32:40 2015] [emerg] (28)No space left on device: Couldn't create accept lock (/var/lock/apache2/accept.lock.17780) (5)
[Wed Apr 08 14:38:32 2015] [warn] pid file /var/run/apache2.pid overwritten — Unclean shutdown of previous Apache run?

As you can read the most likely reason behind above errors preventing for apache to start is /var/run/apache2.pid  unable to be properly written due to lack of disk space or due to disk quota set for users including for userID with which Apache is running.

First thing I did is of course to see how much free space is on the server:

df -h
Filesystem                     Size  Used Avail Use% Mounted on
/dev/mapper/vg00-rootvol       4.0G  1.7G  2.2G  44% /
udev                           7.8G  204K  7.8G   1% /dev
tmpfs                           24G     0   24G   0% /dev/shm
/dev/sda1                      486M   40M  422M   9% /boot
/dev/mapper/vg00-lv_crashdump 1008M   34M  924M   4% /crashdump
/dev/mapper/vg00-homevol       496M   26M  445M   6% /home
/dev/mapper/vg00-lv_opt         12G  1.4G  9.9G  13% /opt
/dev/mapper/vg00-tmpvol        2.0G   68M  1.9G   4% /tmp
/dev/mapper/vg00-varvol        7.9G  609M  6.9G   8% /var
/dev/mapper/vg00-crashvol      1.9G   35M  1.8G   2% /var/crash
/dev/mapper/vg00-auditvol      124M  5.6M  113M   5% /var/log/audit
/dev/mapper/vg00-webdienste     60G   12G   48G  19% /webservice

 

As visible from above df command output , there is enough disk on HDD, so this is definitely not the issue:

Then I Checked whether there is Quota enabled on the Linux server with repquota command shows there are no quotas enabled:

# repquota / var/
repquota: Mountpoint (or device) / not found or has no quota enabled.
repquota: Mountpoint (or device) /var not found or has no quota enabled.
repquota: Not all specified mountpoints are using quota.

 

So obviously the only few left possible reason for Apache failing to start after invoked via init script is  either due to left tainted semaphores or due to some server hardware  RAM problem / or a dying  hard disk with bad blocks.

So what are Semaphores? Generally speaking Semaphores are apparatus for conveying information by means of visual signals between applications (something like sockets).They're used for communicating between the active processes of a certain application. In the case of Apache, they’re used to communicate between the parent and child processes, hence if Apache can’t properly write and coordinate these things down, then it can’t communicate properly with all of the processes it starts and hence the Main HTTPD process can't spawn probably its childs preventing Webserver to enter "started mode" and write its PID file.

To check general information about system semaphore arrays there is the ipcs -s command, however my experience is that ipcs -a is more useful (because it lists generally all kind of semaphores) including Semaphore Shared Memory Signals which are the most likely to cause you the problem.

ipcs -a

—— Shared Memory Segments ——–
key        shmid      owner      perms      bytes      nattch     status

—— Semaphore Arrays ——–
key        semid      owner      perms      nsems
0x00000000 22970368   www-data   600        1

—— Message Queues ——–
key        msqid      owner      perms      used-bytes   messages

As you see in my case there is a Semaphore Arrays which had to be cleaned to make Apache2 be able to start again.
 

To clean all left semaphores (arrays) preventing Apache from start properly, use below for one liner bash loop:
 

for i in `ipcs -s | awk '/www-data/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


Note that above for loop is specific to Debian on CentOS / Fedora / RHEL and other Linuxes the username with which stucked semaphores might stay will be apache or httpd

Depending on the user with which the Apache Webserver is running, run above loop like so:

For RPM based distros (CentOS / RHEL):

 

for i in `ipcs -s | awk '/apache/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


For other distros such as Slackware or FreeBSD or any custom compiled Apache webserver:

for i in `ipcs -s | awk '/httpd/ {print $2}'`; do (ipcrm -s $i); done
ipcrm -m 0x63637069


If there is also Shared Memory Segments you can remove them with ipcrm i.e.:

ipcrm -m 0x63637069


An alternative way to get rid of left uncleaned semaphores is with xargs:
 

ipcs -s | grep nobody | awk ‘ { print $2 } ‘ | xargs ipcrm


Even though this fixes the issue I understood my problems were due to exceeding semaphores, to check default number of set semaphores on Linux Kernel level as well as few Semaphore related values run below sysctl:

sysctl -a | egrep kernel.sem\|kernel.msgmni
kernel.msgmni = 15904

kernel.sem = 250        32000   32      128


As you can see the number of maximum semaphores is quite large so in my case the failure because of left semaphores was most likely due to some kind of Cracker / Automated bot scanner attack or someone trying malicious against the webserver or simply because of some kind of Apache bug or enormous high load the server faced.

Speed up WordPress / Joomla CMS and MySQL server on Linux with tmpfs ram file system / Decrease Website pageload times with RAM caching

Wednesday, March 4th, 2015

speed-up-accelerate-wordpress-joomla-drupal-cms-and-mysql-server-with-tmpfs_ramfs_decrease-pageload-times-with-ram-caching
As a WordPress blog owner and an sys admin that has to deal with servers running a lot of WordPress / Joomla / Droopal and other custom CMS installed on servers, performoing slow or big enough to put a significant load on servers
and I love efficiency and hardware cost saving is essential for my daily job, I'm constantly trying to find new ways to optimize Customer Website (WordPress) and rest of sites in order to utilize better our servers and improve our clients sites speed (and hence satisfaction). 

There is plenty of little things to do on servers but probably among the most crucial ones which we use nowadays that save us a lot of money is tmpfs, and earlier (ramfs) – previously known as shmfs).
TMPFS is a (Temporary File Storage Facility) Linux kernel technology based on ramfs (used by Linux kernel initrd / initramfs on boot time in order to load and store the Linux kernel in memory, before system hard disk partition file systems are mounted) which is heavily used by virtually all modern popular Linux distributions. 

Using ramfs (cramfs variation – Compressed ROM filesystem) has been used to store different system environment kernel and Desktop components of many Linux environment / applications and used by a lot of the Linux BootCD such as the most famous (Klaus Knopper's) KNOPPIX LiveCD and Trinity Rescue Kit Linux (TRK uses /dev/shm which btw can be seen on most modern Linux distros and is actually just another mounted tmpfs).
If you haven't tried Live Linux yet try it out as me and a lot of sysadmins out there use some kind of LiveLinux at least few times on yearly basis  to Recover Unbootable Linux servers after some applied remote Updates as well as for Rescuing (Save) Data from Linux server failing to properly boot because of hard disk (bad blocks) failures. As I said earlier TMPFS is also used on almost any distribution for the /dev/ filesystem which is kept in memory.

You can see which tmpfs partitions is used on your Linux server with:

 

debian-server:~# mount |grep -i tmpfs
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)

 

Above is an output from a standard Debian Linux server. On CentOS 7 standard mounted tmpfs are as follows:

 

[root@centos ~]# mount |grep -i tmpfs
devtmpfs on /dev type devtmpfs (rw,nosuid,seclabel,size=1016332k,nr_inodes=254083,mode=755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,seclabel)
tmpfs on /run type tmpfs (rw,nosuid,nodev,seclabel,mode=755)
tmpfs on /sys/fs/cgroup type tmpfs (rw,nosuid,nodev,noexec,seclabel,mode=755)

 

[root@centos ~]# df -h|grep -i tmpfs
devtmpfs                 993M     0  993M   0% /dev
tmpfs                   1002M   92K 1002M   1% /dev/shm
tmpfs                   1002M  8.8M  993M   1% /run
tmpfs                   1002M     0 1002M   0% /sys/fs/cgroup

The /run tmpfs mounted directory is also to be seen also on latest Ubuntus and Fedoras and is actually the good old /var/run ( where applications keep there pids and some small app related files) stored in tmpfs filesystem stored in memory.

If you're wondering what is /dev/shm and why it appears mounted on every single Linux Server / Desktop you've ever used this is a special filesystem shared memory which various running programs (processes) can use to transfer data quick and efficient between each other to preven the slow disk swapping. People using Linux for the rest 15 years should remember /dev/shm has been a target of a lot of kernel exploits as historically it had a lot of security issues.

While writting this article I've just checked about KNOPPIX developed amd just for info as of time of writting this distro has already 1000+ programs on CD version and 2600+ packages / application on DVD version.
Nowadays Knoppix is mostly used mostly as USB Live Flash drive as a lot of people are dropping CD / DVD use (many servers doesn't have a CD / DVD Drive) and for USB Live Flash Linux distros tmpfs is also key technology used as this gives the end user an amazing fast experience (Desktop applications run much fasten on Live USBs when tmpfs is used than when the slow 7200 RPM HDDs are used).

Loading big parts of the distribution within RAM (with tmpfs from Linux Kernel 2.4+ onwards) is also heavily used by a lot of Cluster vendors in most of Clustered (Cloud) Linux based environemnts, cause TMPFS gives often speeds up improvements to x30 times and decreases greatly I/O HDD. FreeBSD users will be happy to know that TMPFS is already ported and could be used on from FreeBSD 7.0+ onward.

In this small article I will give you example use on how I use tmpfs to speed up our WordPress Websites which use WP Caching plugins such as W3 Total Cache and WP Super Cache
and Hyper Cache / WP Super Cache disk caching and MySQL server as a Database backend.
Below example is wordpress specific but since it can be easily applied to JoomlaDrupal or any other CMS out there that uses mySQL server to make a lot of CPU expensive memory hungry (LEFT JOIN) queries which end up using a slow 7200 RPM hard disk.


 

1. Preparing tmpfs partitions for WordPress File Cache directory
 

If you want to give tmpfs a test drive, I recommend you try to create / mount a 20 Megabyte partition. To create a tmpfs partition you don't need to use a tool like mkfs.ext3 / mkfs.ext4 as TMPFS is in reality a virtual filesystem that is mapped in the server system physical RAM (volatile memory). TMPFS is very nice because if you run out of free RAM system starts a combination of RAM use + some Hard disk SWAP 
The great thing about TMPFS is it never uses all of the available RAM and SWAP, which would not halt your server if TMPFS partition gets filled, but instead you will start getting the usual "Insufficient Disk Space", just like with a physical HDD parititon. RAMFS cares much less about server compared to TMPFS, because if RAMFS is historically older.

ramfs file systems cannot be limited in size like a disk base file system which is limited by it’s capacity, thus ramfs will continue using memory storage until the system runs out of RAM and likely crashes or becomes unresponsive. This is a problem if the application writing to the file system cannot be limited in total size, so in my opinion you better stay away from RAMFS except you have a good idea what you're doing. Another disadvantage of RAMFS compared to TMPFS is you cannot see the size of the file system in df and it can only be estimated by looking at the cached entry in free.

Note that before proceeding to use TMPFS or RAMFS you should know besides having advantages, there are certain serious disadvantage that if the server using tmpfs (in RAM) to store files crashes the customer might loose his data, therefore using RAM filesystems on Production servers is best to be used just for caching folders which are regularly synchronized with (rsync) to some folder to assure no data will be lost on server reboot or crash.

Memory of fast storage areas are ideally suited for applications which need repetitively small data areas for caching or using as temporary space such as Jira (Issue and Proejct Tracking Software) Indexing  As the data is lost when the machine reboots the tmpfs stored data must not be data of high importance as even scheduling backups cannot guarantee that all the data will be replicated in the even of a system crash.

To test mounting a tmpfs virtual (memory stored) filesystem issue:
 

mount -t tmpfs tmpfs -o size=256m /mnt/tmpfs


If you want to test mount a ramfs instead:

 

 mount -t ramfs -o size=256m ramfs /mnt/ramfs

 

debian-server:~#  mount |grep -i -E "ramfs|tmpfs"
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /mnt/tmpfs type tmpfs (rw,size=256m)
ramfs on /mnt/ramfs type tmpfs (rw,size=256m)

 

Once mounted tmpfs can be used in the same way as any ext4 / reiserfs filesystem. In the same way to make mounts permanent, its necessery to add a line to /etc/fstab

To illustrate better a tmpfs use case on my blog running WordPress with W3TotalCache (W3TC) plugin cache folder in /var/www/blog/wp-content/w3tc to get advantage of tmpfs to store w3tc files.

a) Stop Apache

On Debian
 

debian-server:~# /etc/init.d/apache stop


On CentOS 
 

[root@centos ~]# /etc/init.d/httpd stop


b) Move w3tc dir to w3tc-bak

 

debian-server:~# cd /var/www/blog/wp-content/
debian-server:~# mv w3tc w3tc-bak

 

c) Create w3tc directory
 

debian-server:/var/www/blog/wp-content# mkdir w3tc
debian-server:/var/www/blog/wp-content# chown -R www-data:www-data w3tc


d) Add tmpfs record to /etc/fstab

My W3TC Cache didn't grow bigger than 2Gigabytes so I create a 2Giga directory for it by adding following in /etc/fstab 
 

debian-server:~# vim /etc/fstab

 

tmpfs /var/www/blog/wp-content/w3tc tmpfs defaults,size=2g,noexec,nosuid,uid=33,gid=33,mode=1755 0 0


You might also want to add the nr_inodes (option) to tmpfs while mounting. nr_inodes is the maximum inode for instance. Default is half the number of your physical RAM pages, (on a machine with highmem) the number of lowmem RAM page, some common option that should work is nr_inodes=5k, if you're unsure what this option does you can safely skip it 🙂

e) Mount new added tmpfs folder

Then to mount the newly added filesystem issue:
 

mount -a


Or if you're on a CentOS / RHEL server use httpd Apache user instead and whenever you have docroot and wordpress installed.

 

[root@centos ~]# chown -R apache:apache: w3tc


If you're using Apache SuPHP use whatever the UID / GID is proper.

On CentOS you will need to set proper UID and GID (UserID / GroupID), to find out which ones to to use check in /etc/passwd:
 

[root@centos ~]# grep -i apache /etc/passwd
apache:x:48:48:Apache:/var/www:/sbin/nologin


f) Move old w3tc cache from w3tc-bak to w3tc

 

debian-server:/var/www/blog/wp-content# mv w3tc-bak/* w3tc/

 

g) Start again Apache

On Debian:

 

debian-server:~# /etc/init.d/apache2 start

 


On CentOS:
 

[root@centos~]# /etc/init.d/httpd start

h) Keeping w3tc cache site folder synced

As I said earlier the biggest problem with caching (the reason why many hosting providers) and site admins refuse to use it is they might loose some data, to prevent data loss or at least mitigate the data loss to few minutes intervals it is a good idea to synchronize tmpfs kept folders somewhere to disk with rsync.

To achieve that use a cronjob like this:
 

debian-server:~# crontab -u root -e
*/5 * * * * /usr/bin/ionice -c3 -n7 /usr/bin/nice -n 19 /usr/bin/rsync -ah –stats –delete /var/www/blog/wp-content/w3tc/ /backups/tmpfs/cache/ 1>/dev/null


Note that you will need to have the /backups/tmpfs/cache folder existing, create it with:

 

debian-server:~# mkdir -p /backups/tmpfs/cache


You will also need to add a rsync synchronization from backupped folder to tmpfs (in case if the server gets accidently rebooted because it hanged or power outage), place in

/etc/rc.local

 

ionice -c3 -n7 nice -n 19 rsync -ahv –stats –delete /backups/tmpfs/cache/ /var/www/blog/wp-content/w3tc/ 1>/dev/null


(somewhere before exit 0) line
 

0 05 * * * /usr/bin/ionice -c3 -n7 /bin/nice -n 19 /usr/bin/rsync -ah –stats –delete /var/www/blog/wp-content/w3tc/ /backups/tmpfs/cache/ 1>/dev/null

 

 

2. Preparing tmpfs partitions for MySQL server temp File Cache directory


Its common that MySQL servers had to serve a lot of long and heavy SQL JOIN Queries mostly by related posts WP plugins such as (Zemanta Related Posts) and Contextual Related posts though MySQLs are well optimized  to work as much as efficient using mysql tuner (tuning primer) still often SQL servers get a lot of temp tables created to disk (about 25% to 30%) of all SQL queries use somehow HDD to serve queries and as this is very slow and there is file lock created the overall MySQL performance becomes sluggish at times to fix (resolve) that without playing with SQL code to optimize the slow queries the best way I found is by using TMPFS as MySQL temp folder.

To do so I create a TMPFS usually the size of 256 MB because this is usually enough for us, but other hosting companies might want to add bigger virtual temp disk:

a) Add tmpfs new dir to /etc/fstab

In /etc/fstab add below record with vim editor:
 

debian-server:~# vim /etc/fstab

 

tmpfs /var/mysqltmp tmpfs rw,gid=111,uid=108,size=256M,nr_inodes=10k,mode=0700 0 0

 

Note that the uid / and gid 105 and 114 are taken again from /etc/passwd

On Debian

debian-server:~# grep -i mysql /etc/passwd
mysql:x:108:111:MySQL Server,,,:/var/lib/mysql:/bin/false


On CentOS
 

[root@centos ~]# grep -i mysql /etc/passwd
mysql:x:27:27:MySQL Server:/var/lib/mysql:/bin/bash


b) Create folder /var/mysqltmp or whenever you want to place the tmpfs memory kept SQL folder

 

debian-server:~# mkdir /var/mysqltmp
debian-server:~# chown mysql:mysql /var/mysqltmp

 

debian-server:~# mount|grep -i tmpfs
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /var/www/blog/wp-content/w3tc type tmpfs (rw,noexec,nosuid,size=2g,uid=33,gid=33,mode=1755)
tmpfs on /var/mysqltmp type tmpfs (rw,gid=108,uid=111,size=256M,nr_inodes=10k,mode=0700)


c) Add new path to tmpfs created folder in my.cnf 

Then  edit /etc/mysql/my.cnf

 

debian-server:~# vim /etc/mysql/my.cnf

[mysqld]
#
# * Basic Settings
#
user        = mysql
pid-file    = /var/run/mysqld/mysqld.pid
socket      = /var/run/mysqld/mysqld.sock
port        = 3306
basedir     = /usr
datadir     = /var/lib/mysql
tmpdir      = /var/mysqltmp

 

On CentOS edit and change tmpdir in same way within /etc/my.cnf


d) Finally Restart Apache and MySQL to make mysql start using new set tmpfs memory kept folder

On Debian:
 

debian-server:~# /etc/init.d/apache2 stop; /etc/init.d/mysql restart; /etc/init.d/apache2 start

On CentOS:
 

[root@centos ~]# /etc/init.d/httpd stop; /etc/init.d/mysqld restart; /etc/initd/httpd start


Now monitor your server and check your pagespeed increase for me such an optimization usually improves site performance so site becomes +50% faster, to see the difference you can test your website before applying tmpfs caching for site and after that by using Google PageInsight (PageSpeed) Online Test. Though this example is for MySQL and WordPress you can easily adopt the same for Joomla if you have Joomla Caching enabled to some folder, same goes for any other CMS such as Drupal that can take use of Disk Caching. Actually its a small secret of many Hosting providers that allow clients to create sites via CPanel and Kloxo this tmpfs optimizations are already used for sites and by this the provider is able to offer better website service on lower prices. VPS hosting providers also use heavy caching. A lot of people are using TMPFS also to accelerate Sites that have enabled Google Pagespeed as Cacher and accelerator, as PageSpeed module puts a heavy HDD I/O load that can easily stone the server. Many admins also choose to use TMPFS for  /tmp, /var/run, and /var/lock directories as this leads often to significant overall server services operations improvement.
Once you have tmpfs enabled, It is a good idea to periodically monitor your SWAP used space with (df -h), because if you allocate bigger tmpfs partitions than your physical memory and tmpfs's full size starts to be used your machine will start swapping heavily and this could have a very negative performance affect.
 

debian-server:~# df -h|grep -i tmpfs
tmpfs            3,9G     0   3,9G   0% /lib/init/rw
tmpfs            3,9G     0   3,9G   0% /dev/shm
tmpfs            2,0G  1,4G   712M  66% /var/www/blog/wp-content/w3tc
tmpfs            256M     0   256M   0% /mnt/tmpfs
tmpfs            256M  236K   256M   1% /var/mysqltmp

The applications of tmpfs to accelerate services is up to your imagination, so I will be glad to hear from other admins on any interesting other application or problems faced while using TMPFS.

 Enjoy! 🙂

How to fix Pulseaudio and Skype crappy sound glitches, choppy sound and crackling on Debian GNU / Linux

Tuesday, January 10th, 2012

I've experienced plenty of problems with Pulseaudio and Skype output sound hell crappy. This stupid proprietary program Skype is a total crap … Anyways again thanks to ArchLinux's wiki, I've used the two mentioned steps to fix all this Skype in / out problems …

1. Fix problems with Glitches, voice skips and crackling In file /etc/pulse/default.pa its necessery to substitute the line;

load-module module-udev-detect

with

load-module module-udev-detect tsched=0

2. Resolve Choppy sound in (Pulseaudio) -> Skype

In /etc/pulse/daemon.conf two lines has to be also substituted:

; default-sample-rate = 44100

Should become;

default-sample-rate = 48000

3. Change /etc/default/pulseaudio to allow dynamic module loading

It is a good idea to the default settings from DISALLOW_MODULE_LOADING=1 to DISALLOW_MODULE_LOADING=0 .This step is not required and I'm not sure if it has some influence on solving sound in / out problems with Skype but I believe it can be helpful in some cases..

So in /etc/default/pulseaudio Substitute:

DISALLOW_MODULE_LOADING=1

to;

DISALLOW_MODULE_LOADING=0

4. Restart PulseAudio server

After the line is changed and substituted a restart of PulseAudio is required. For PulseAudio server restart a gnome session logout is necessery. Just LogOff logged Gnome user and issue cmd:

debian:~# pkill pulseaudio

This will kill any left pulseaudio server previous instances.