Can't start mysql server

Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock

If you get the above error on Ubuntu and you have tried all the things suggested by others (permissions, recreating the socket file, reboot, bind address change) you may want to try stopping apparmor and starting again mysql.

service apparmor stop
service mysql start

later edit
to do: instructions for correct configuration of apparmor, since stopping the service is a bit barbarian(but efficient).

ISPConfig3: Updating to myDNS-ng

If you have followed the tutorials "the perfect setup" for installing ISPConfig 3 chances are that you have an older myDNS version (1.1.0 or so). Since I had a few problems with that version I decided to update to myDNS-ng, the latest version.

In this article I will refer to rpmbuilder user, a user I create to compile and/or make RPMs. For more information on how to set it up check this link.

Also the instructions are for CentOs 5.4(but will probably work for any other 5.x version).

su - rpmbuilder
cd /tmp
wget http://downloads.sourceforge.net/project/mydns-ng/mydns/1.2.8.27/mydns-1.2.8.27.tar.gz?use_mirror=garr
tar zxvf mydns-1.2.8.27.tar.gz
cd mydns-1.2.8
./configure
make

Everything should be ok untill now. I had no problems to compile it. Then I decided to use checkinstall.
sudo yum install checkinstall
checkinstall
It will ask you a few questions, answer them and you should have a rpm package in /usr/src/redhat/RPMS. It will tell you anyway where he created the rpm.
After that I removed the old mydns packages and installed the new one as root:
service mydns stop
yum remove mydns mydns-mysql
yum install /usr/src/redhat/RPMS/i386/mydns-1.2.8-1.i386.rpm --nogpgcheck
After that I needed to create mydns start script:
vi /etc/init.d/mydns
chmod +x /etc/init.d/mydns
I used the script posted by rukus77 on howtoforge. Make sure you read all the comments on that forum (especially the one containing [ -f /usr/sbin/mydns ] || exit 1).
The last step is to run ISPConfig 3 setup:
cd ispconfig3_install/
cd install
php -q update.php
When asked if to reconfigure services answer yes, the rest you can answer no.

That would be all, thanks for reading.

Install Postfix, Courier-IMAP on CentOS 5

Platform: CentOS 5.4 i386
Extra repositories used: utterramblings and rpmforge
You will end up with Postfix 2.6.5, Courier IMAP 4.6.0, authlib 0.62.4 and maildrop 2.2.0

First of all you will need to install gcc++:
yum install gcc-c++ redhat-rpm-config
Create a user to compile packages if you don't have one already. I used rpmbuilder for the account name.
useradd -m -s /bin/bash rpmbuilder
passwd rpmbuilder
It will need some privileges so type visudo and add this line somewhere (I added it after root):
rpmbuilder ALL=(ALL) ALL
Create the directory structure:
su - rpmbuilder
mkdir $HOME/rpm
mkdir $HOME/rpm/SOURCES
mkdir $HOME/rpm/SPECS
mkdir $HOME/rpm/BUILD
mkdir $HOME/rpm/SRPMS
mkdir $HOME/rpm/RPMS
mkdir $HOME/rpm/RPMS/i386
echo "%_topdir $HOME/rpm" >> $HOME/.rpmmacros
Start downloading the needed courier packages(under the user rpmbuilder):
cd /tmp
wget http://sourceforge.net/projects/courier/files/maildrop/2.2.0/maildrop-2.2.0.tar.bz2/download
wget http://sourceforge.net/projects/courier/files/imap/4.6.0/courier-imap-4.6.0.tar.bz2/download
wget http://sourceforge.net/projects/courier/files/authlib/0.62.4/courier-authlib-0.62.4.tar.bz2/download
These were the latest versions when I wrote the article, feel free to browse sourceforge and get what version you want.
Start building and installing the RPMs:
sudo rpmbuild -ta courier-authlib-0.62.4.tar.bz2
cd $HOME/rpm/RPMS/i386
sudo rpm -ivh courier-authlib-0.62.4-1.i386.rpm courier-authlib-mysql-0.62.4-1.i386.rpm courier-authlib-devel-0.62.4-1.i386.rpm
cd /tmp
rpmbuild -ta courier-imap-4.6.0.tar.bz2
cd $HOME/rpm/RPMS/i386
sudo rpm -ivh courier-imap-4.6.0-1.i386.rpm
cd /tmp
sudo rpmbuild -ta maildrop-2.2.0.tar.bz2
cd $HOME/rpm/RPMS/i386
sudo rpm -ivh maildrop-2.2.0-1.i386.rpm

Done with Courier. Moving to postfix...

Download source RPM from this location:
cd /tmp
wget http://ftp.wl0.org/official/2.6/SRPMS/postfix-2.6.5-1.src.rpm
rpm -ivh postfix-2.6.5-1.src.rpm
I've made a few changes to the postfix.spec file (enabled mysql_redhat, vda patch) and also installed the required dependencies:
sudo yum install db4-devel mysql-shared mysql-devel
Building the postfix-2.6.5 rpm:
cd $HOME/rpm/SPECS
rpmbuild -ba postfix.spec
You should have the rpm in $HOME/rpm/BUILD so cd there and type:
sudo rpm -ivh postfix-2.6.5-1.rhel5.i386.rpm

In the end enable required services as root user:
chkconfig --levels 235 courier-authlib on
chkconfig --levels 235 sendmail off
chkconfig --levels 235 postfix on
chkconfig --levels 235 saslauthd on
chkconfig --levels 235 courier-imap on
service sendmail stop
service postfix start
service saslauthd start
service courier-authlib start
service courier-imap start

If everything went ok when telneting on port 25 of localhost you should get something similar to this:
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 lightbringer.inno-solutions.ro ESMTP Postfix (2.6.5)
ehlo localhost
250-lightbringer.inno-solutions.ro
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN

NOTE 1:
If you already have any of the packages install use rpm -Uvh instead of rpm -ivh.

MySQL benchmarks using Amazon EC2 instances

Here are some tests I've run on Amazon using AMIs provided by scalr for the mysql role. I've used the benchmark scripts supplied by MySQL located in /usr/share/mysql/sql-bench. I had to install a package before running the tests:
apt-get install libdbd-pg-perl

After that everything was simple:
root@ec2# mysql
mysql> create database test;
mysql> quit;
root@ec2# cd /usr/share/mysql/sql-bench
root@ec2# perl run-all-tests --dir='/root/'


For EBS tests I've done the following:
-created 1GB EBS volume in scalr
-attached it to the instance I was testing
-notice the device name (/dev/sdb for example)
root@ec2# apt-get install xfsprogs
root@ec2# mkfs.xfs /dev/sdb
root@ec2# mkdir /mnt/storage
root@ec2# cp -R /var/lib/mysql /mnt/storage/
root@ec2# chown mysql:mysql -R /mnt/storage/mysql

-edit /etc/mysql/my.cnf and change datadir from "/var/lib/mysql" to "/mnt/storage/mysql"
-restart mysql server and start the tests:

root@ec2# /etc/init.d/mysql restart
root@ec2# mysql
mysql> drop database test;
mysql> create database test;
mysql> quit;
root@ec2# cd /usr/share/mysql/sql-bench
root@ec2# perl run-all-tests --dir='/root/'


Instances types used and their codes:

m1.small(0.10$/hour) - Small Instance (Default) 1.7 GB of memory, 1 EC2 Compute Unit (1 virtual core with 1 EC2 Compute Unit), 160 GB of instance storage, 32-bit platform

m1.large(0.40$/hour) - Large Instance 7.5 GB of memory, 4 EC2 Compute Units (2 virtual cores with 2 EC2 Compute Units each), 850 GB of instance storage, 64-bit platform

c1.medium(0.20$/hour) - High-CPU Medium Instance 1.7 GB of memory, 5 EC2 Compute Units (2 virtual cores with 2.5 EC2 Compute Units each), 350 GB of instance storage, 32-bit platform

c1.xlarge(0.80$/hour) - High-CPU Extra Large Instance 7 GB of memory, 20 EC2 Compute Units (8 virtual cores with 2.5 EC2 Compute Units each), 1690 GB of instance storage, 64-bit platform

EC2 Compute Unit (ECU) – One EC2 Compute Unit (ECU) provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor.


seconds usr sys cpu tests
m1.small 1823 196.54 28.66 225.2 3425950
m1.small+ebs 1646 197.18 29.61 226.79 3425950
m1.large 1072 157.06 26.97 184.03 3425950
m1.large+ebs 1088 154.23 25.23 179.46 3425950
c1.medium 902 131.18 25.63 156.81 3425950
c1.medium+ebs 901 130.76 28.84 159.6 3425950
c1.xlarge 704 123.31 32.8 156.11 3425950
c1.xlarge+ebs 781 121.02 29.52 150.54 3425950

Bellow you can see a nice chart with how much time it took for each instance to finish the benchmark tests. Either I did something terribly wrong or EBS doesn't improve MySQL performance.