mdadm

1. start raid

mdadm --assemble --scan

2. start raid in case if you do not have /etc/mdadm.conf (should have raid UUID)

mdadm /dev/md0 --assemble -u e6d85d3d:d20ddcfc:c7cxxxxx:6a0xxxx

3. generate /etc/mdadm.conf

 mdadm --detail --scan >> /etc/mdadm.conf

[mdadm] 2 how-tos

1. how to cancel sync:

in order to cancel raid sync its necessary to left only one drive as active (we are talking about raid1):

 mdadm --fail /dev/md2 /dev/sda3

and  we will receive something like that (in my case it was md2 and /dev/sda3):

 mdadm --detail /dev/md2
/dev/md2:
        Version : 0.90
  Creation Time : Fri Feb  4 21:22:50 2011
     Raid Level : raid1
     Array Size : 1462766336 (1395.00 GiB 1497.87 GB)
  Used Dev Size : 1462766336 (1395.00 GiB 1497.87 GB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 2
    Persistence : Superblock is persistent

    Update Time : Tue Jan 10 18:37:27 2012
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 1
  Spare Devices : 0

           UUID : 71b91f85:bdd01b3f:776c2c25:004bd7b2
         Events : 0.28394

    Number   Major   Minor   RaidDevice State
       0       0        0        0      removed
       1       8       19        1      active sync   /dev/sdb3

       2       8        3        -      faulty spare   /dev/sda3

 /dev/sda3 was set as failed.

2. how to re-add failed disk into existing array and restart scan :)

• set disk as failed (we already did that in 1st how-to )
• remove device from array

mdadm --remove /dev/md2 /dev/sda3 

• add device one more time

mdadm --add /dev/md2/ /dev/sda3

We can check the status of the arrays on the system with:

watch -n .1 cat /proc/mdstat

 or

mdadm --detail /dev/md0

Zabbix auto install script

few weeks ago I've noticed that Zabbix team actively developed version 2 of their nice monitoring tool. I decided to install beta version with Postgresql 9.1. Unfortunately Zabbix 1.9.6 does not support Psql 9.1, but with my help :) they fixed that issue. meanwhile I've prepared script which install zabbix from source on clean Centos with Psql 8.4 support.

there is download link to that script https://www.dropbox.com/s/e205kh9vnwyppp8/zabbix_install_centos.sh

this script will be good for testers, sys admins who want to check new features of zabbix :)

reboot hung server

The "magic SysRq key" provides a way to send commands directly to the kernel through the /proc filesystem. It is enabled via a kernel compile time option, CONFIG_MAGIC_SYSRQ, which seems to be standard on most distributions. First you must activate the magic SysRq option:

    echo 1 > /proc/sys/kernel/sysrq

When you are ready to reboot the machine simply run the following:

    echo b > /proc/sysrq-trigger

This does not attempt to unmount or sync filesystems, so it should only be used when absolutely necessary, but if your drive is already failing then that may not be a concern.

How to upgrade Postgres 8.4.x to 9.0.x

I've found a couple of manuals where this procedure is described, but I faced with the problem with postgres-libs which were required for my SVN.

so there is my way how to perfom upgrade

1. service postgresql stop
2. rsync -a -v --progress /var/lib/pgsql/ /var/lib/pgsql.old/ #this will backup everything
3. wget http://yum.pgrpms.org/reporpms/9.0/pgdg-centos-9.0-2.noarch.rpm
4. rpm -i pgdg-centos-9.0-2.noarch.rpm
5. /etc/yum.repos.d/CentOS-Base.repo and add 'exclude=postgresql*' to the [base] and [updates] sections
6. yum remove postgresql84*
7. rpm -e postgresql-libs --nodeps
8. yum install postgresql90 postgresql90-server postgresql90-libs postgresql90-contrib postgresql90-devel
9. service postgresql-9.0 initdb
10. export PATH=/usr/pgsql-9.0/bin:$PATH
11. su - postgres ; export PATH=/usr/pgsql-9.0/bin:$PATH ; pg_upgrade --old-datadir "/var/lib/pgsql.old/data" --new-datadir "/var/lib/pgsql/9.0/data" --old-bindir "/usr/bin" --new-bindir "/usr/pgsql-9.0/bin"
12. cp /var/lib/pgsql.old/data/pg_hba.conf /var/lib/pgsql/9.0/data/pg_hba.conf
13. service postgresql-9.0 start
14. vacuumdb --all --analyze-only

Have fun with new Psql version :)

hackmysql mirror

I've created mirror of hackmysql for personal usage

replace mysql-server with percona server

what is percona-server:

Quote:

Percona Server is an enhanced drop-in replacement for MySQL. With Percona Server,

Your queries will run faster and more consistently.
You will consolidate servers on powerful hardware.
You will delay sharding, or avoid it entirely.
You will save money on hosting fees and power.
You will spend less time tuning and administering.
You will achieve higher uptime.
You will troubleshoot without guesswork.

Does this sound too good to be true? It's not. Percona Server offers breakthrough performance, scalability, features, and instrumentation. Its self-tuning algorithms and support for extremely high-performance hardware make it the clear choice for companies who demand the utmost performance and reliability from their database server

now if you want to have such miracle on your cpanel server you need to do this steps for replacing mysql-server with percona-server:

1. backup VPS.
2. dump all dbs.
3. stop all services on the vps

Code:

/etc/init.d/httpd stop ; /etc/init.d/exim stop ; /etc/init.d/pure-ftpd stop ; /etc/init.d/dovecot stop ; /etc/init.d/cpanel stop ; /etc/init.d/lfd stop ; /etc/init.d/munin-node stop ; /etc/init.d/crond stop ; /etc/init.d/mysql stop ; /etc/init.d/exim stop ;

4. make sure that everything is stopped
5. check what mysql packages are installed

Code:

rpm -qa | grep -i mysql

in my case it was MySQL-client MySQL-devel MySQL-test MySQL-bench MySQL-shared MySQL-server
so I run this command to completely remove mysql from vps

Code:

yum remove MySQL-client MySQL-devel MySQL-test MySQL-bench MySQL-shared MySQL-server

6. add percona repo

Code:

rpm -Uhv http://www.percona.com/downloads/percona-release/percona-release-0.0-1.x86_64.rpm

7. check what packages are available in percona repo

Code:

yum list | grep percona

should be something like

Code:

# yum list | grep percona
percona-release.x86_64                    0.0-1                        installed
Percona-SQL-50-debuginfo.x86_64           5.0.92-b23.85.rhel5          percona
Percona-SQL-client-50.x86_64              5.0.92-b23.85.rhel5          percona
Percona-SQL-devel-50.x86_64               5.0.92-b23.85.rhel5          percona
Percona-SQL-server-50.x86_64              5.0.92-b23.85.rhel5          percona
Percona-SQL-shared-50.x86_64              5.0.92-b23.85.rhel5          percona
Percona-SQL-shared-compat.x86_64          5.1.43-2                     percona
Percona-SQL-test-50.x86_64                5.0.92-b23.85.rhel5          percona
Percona-Server-51-debuginfo.x86_64        5.1.56-rel12.7.224.rhel5     percona
Percona-Server-55-debuginfo.x86_64        5.5.11-rel20.2.115.rhel5     percona
Percona-Server-client-51.x86_64           5.1.56-rel12.7.224.rhel5     percona
Percona-Server-devel-51.x86_64            5.1.56-rel12.7.224.rhel5     percona
Percona-Server-server-51.x86_64           5.1.56-rel12.7.224.rhel5     percona
Percona-Server-shared-51.x86_64           5.1.56-rel12.7.224.rhel5     percona
Percona-Server-test-51.x86_64             5.1.56-rel12.7.224.rhel5     percona
gnuplot.x86_64                            4.2.6-14                     percona
gnuplot-emacs.x86_64                      4.2.6-14                     percona
maatkit.noarch                            7284-1                       percona
xtrabackup.x86_64                         1.6-245.rhel5                percona
xtrabackup-debuginfo.x86_64               1.6-245.rhel5                percona

8. decide what version you need 5.1 or 5.5
in my case I've installed percona 5.5

Code:

# rpm -qa | grep Percona
Percona-Server-client-55-5.5.11-rel20.2.115.rhel5
Percona-Server-server-55-5.5.11-rel20.2.115.rhel5
Percona-Server-shared-55-5.5.11-rel20.2.115.rhel5
Percona-Server-shared-compat-5.5.11-rel20.2.115.rhel5
Percona-Server-devel-55-5.5.11-rel20.2.115.rhel5
Percona-Server-test-55-5.5.11-rel20.2.115.rhel5

9. after Percona-server installation it is necessary to check if it started correctly as some variables in my.cnf are not supported.
10. after successful start it is necessary to run mysql_upgrade.
11. for finishing installation run easyapache and recompile apache/php/etc
12. Go to Server Configuration -> Update Config and set MySQL to "never", save, double check it has been done
13. Test new Apache to be sure server is working

add json support into Flex4

Adobe itself made a JSON library that you can find at https://github.com/mikechambers/as3corelib Follow these steps to add your JSON library to your Flex project:

1. Download the .zip archive and extract it. What you need is the .swc file in the lib folder.
2. In Flex Builder / Flash Builder, go to your project’s properties, and then to the Flex Build Path panel.
3. Click on Add SWC, and select the as3corelib.swc file
4. In your project, add the following line: import com.adobe.serialization.json.JSON;

You should be able now to use JSON functionalities in your Flex project

where is my free disk space :)

To list files larger than 10M:
find / -type f -size +10000k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'

To list files larger than 100M:
find / -type f -size +100000k -exec ls -lh {} \; | awk '{ print $8 ": " $5 }'

how to convert tables to InnoDB

Using nice tool from Maatkit, we can easy convert tables from any storage engine to other. there is example how to convert from myisam to  innodb

mk-find db-name --engine MyISAM --exec "ALTER TABLE %D.%N ENGINE=INNODB" --print