Category Archives: System admin

MySQL: How do you enable sphinxse (Sphinx Storage Engine) in your mysql installation?

As you may know mysql fulltext search is not highly scalable.  One of the options to get around this scalability limitation, which I prefer, is to use Sphinx.  You can use Sphinx with out having to alter your mysql installation.  But, if you would like to use from within mysql and not have to worry about how to pass data between Sphinx and MySQL, you can enable sphinxse (sphinx storage engine).  It is not included with mysql by default so you will have to compile it yourself.

Here are the instructions on how to get sphinxse compiled with your mysql installation on CentOS x64.  I am sure same instructions will work for other flavors but I have not tested it.  I will be compiling the most current version of sphinx (0.9.8) with most current stable version of mysql (5.0.51b) at the time of the writing.  Let’s get the appropriate packages first:

wget http://www.sphinxsearch.com/downloads/sphinx-0.9.8.tar.gz
wget http://dev.mysql.com/get/Downloads/MySQL-5.0/mysql-5.0.51b.tar.gz/from/http://mysql.he.net/
tar zxpf sphinx*
tar zxpf mysql*

You will also need “bison”, “patch”, “automake” and “libtool” installed.  Let us just do a yum install for it.

yum -y install bison patch automake libtool

NOTE:  if you don’t install bison, you will get the following error:
sed '/^#/ s|y\.tab\.c|sql_yacc.cc|' y.tab.c >sql_yacc.cct && mv sql_yacc.cct sql_yacc.cc
sed: can't read y.tab.c: No such file or directory
make[2]: *** [sql_yacc.cc] Error 2

Let us continue with patching mysql source with sphinx storage engine (sphinxse) code and compile/install our new binaries.

cd mysql*
patch -p1 < ../sphinx-0.9.8/mysqlse/sphinx.5.0.37.diff #Make sure everything succeeded.
BUILD/autorun.sh
mkdir sql/sphinx
cp ../sphinx-0.9.8/mysqlse/* sql/sphinx
./configure --prefix=/usr/local/mysql --with-sphinx-storage-engine
make
make install

Now start your mysql installtion and check if engine support is compiled in:

mysql> show engines\G
Engine: SPHINX
Support: YES
Comment: Sphinx storage engine 0.9.8

To read more about how to use Sphinx storage engine, please refer to:  Sphinx documentation for using sphinx storage engine

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DISCLAIMER: Please be smart and use code found on internet carefully. Make backups often. And yeah.. last but not least.. I am not responsible for any damage caused by this posting. Use at your own risk.

Linux: yum options you may not know exist.

Most of the users who work with distributions such as: centos, fedora, redhat, etc use yum as a package update/installer. Most of them know how to do “yum update [packagename]” (to update all or [certain packages]) or they do “yum install packagename” to install certain package(s). But yum can do so much more. Here are some options you may find useful:

Following command will search for the string you specified. Generally this will give you all of the packages which has specified string in title or description. Most of the time you will have to look through a lot of output to find what you are looking for.

yum search string

Probably one of the most important options for yum is provides/whatprovides. If you know what command you need, you can find out what package you have to install in order to have that command available to you.

yum provides (or whatprovides) command

Following command is same as above but with less output.

yum -d 1 provides command

So for example if you are trying to figure out what you need to install to use bunzip2, type:

yum -d 1 provides bunzip2

you will get a similar output as below.

# yum -d 1 provides bunzip2
bzip2.x86_64 1.0.2-13.EL4.3 base
bzip2.x86_64 1.0.2-13.EL4.3 base
man-pages-fr.noarch 0.9.7-13.el4 base
man-pages-ja.noarch 20050215-2.EL4.3 base
man-pages-pl.noarch 0.23-5 base

As you can see bunzip2 is part of bzip2 package. So now you can you just install bzip2.x86_64 to get bunzip2.

To learn more about what else is available, read man yum.

Apache2 gzip compression: How do I speed up my website download time?

One of the things people tend to forget is the ability for web servers to compress content before sending it back to client. Client’s browser then uncompresses the data and displays it to the user. Pretty much all of the recent browsers support gzip compression. In this post, I will go over how to setup apache2 to use compression. First let’s see if your Apache installation has “deflate” enabled. You can check to see if you have deflate by typing:

# /usr/local/apache2/bin/apachectl -t -D DUMP_MODULES
Loaded Modules:
...
deflate_module (static)
...
Syntax OK

If you don’t have have deflate_module, you would have to recompile your apache with “–enable-deflate” option.

Going forward, I am going to assume you have deflate_module. Add the following to your apache conf file:

<Location />
SetOutputFilter DEFLATE
BrowserMatch ^Mozilla/4\.0[678] no-gzip\
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html
# Don't compress images
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png)$ no-gzip dont-vary
</Location>

The main thing you need to configure is the line which says “no-gzip dont-vary” also in bold above. This tells apache to not compress certain type of files. I have noticed on some of my sites that swf (flash) files do not work as expected if they are compressed. So if you have swf files in your site, you may want to add |swf right after png.

This is all what it takes for you to enable gzip compression in Apache2. Once you restart your apache so it reads the conf file, you can test if your site is getting compressed or not by using this tool: http://www.gidnetwork.com/tools/gzip-test.php

Here are the results for my blog:

Results for: http://crazytoon.com
Web page compressed? Yes
Compression type? gzip
Size, Markup (bytes) 57,337
Size, Compressed (bytes) 11,666
Compression % 79.7

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DISCLAIMER: Please be smart and use code found on internet carefully. Make backups often. And yeah.. last but not least.. I am not responsible for any damage caused by this posting. Use at your own risk.

Linux: How do you rename a user account in linux?

In Linux, there is no command which will rename a user account. If you make a mistake creating a user account, user changes their name or if user does not like his user name, there is no real easy way of going and making the change. Only thing I know you can do is to go through some files and rename user manually. Let us say that we have a user who is named joe and we want to rename him to john.

Note: you must be logged in as root to do following.

vi /etc/passwd
find joe and change it to john, save/exit

vi /etc/group
find joe and change it to john, save/exit

vi /etc/shadow
find joe and change it to john. This file is read only and you have to force overwrite it. In vi it is :w! once saved, quit.

cd /home
mv joe john

And that should do the trick.

[Edited] Right after I posted this post, I was contacted and was told to look at utility called usermod. Read more about it man usermod. Got to love the quick responses.

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DISCLAIMER: Please be smart and use code found on internet carefully. Make backups often. And yeah.. last but not least.. I am not responsible for any damage caused by this posting. Use at your own risk.

MySQL: How do you set up master-master replication in MySQL? (CentOS, RHEL, Fedora)

Setting up master-master replication in MySQL is very similar to how we set up master/slave replication. You can read up about how to setup master/slave replication in my previous post: How to set up master/slave replication in MySQL. There is obviously pros and cons about using master/master replication. But this is not a post which discuses advantages and disadvantages for using master/master replication. One of the differences between master/master set up and master/slave is that in master/master set up, you have true redundancy. If one server dies, second server can take all the inserts/selects. In master/slave setup, if master dies, you will have to go through steps to make slave become the master. Master/master set up we are going to set up is essentially master/slave and slave/master. Meaning, if you had two servers, db0 and db1, your setup will be db0(master)/db1(slave) and also db0(slave)/db1(master). Here are some assumptions:

Master1 server ip: 10.0.0.1
Master2 server ip: 10.0.0.2
Slave username: slaveuser
Slave pw: slavepw
Your data directory is: /usr/local/mysql/var/

Let us go through the steps you must take on Master1 to enable it to act as master and slave by using following configuration which goes under [mysqld] section:

# let's make it so auto increment columns behave by having different increments on both servers
auto_increment_increment=2
auto_increment_offset=1
# Replication Master Server
# binary logging is required for replication
log-bin=master1-bin
binlog-ignore-db=mysql
binlog-ignore-db=test
# required unique id between 1 and 2^32 - 1
server-id = 1
#following is the slave settings so this server can connect to master2
master-host = 10.0.0.2
master-user = slaveuser
master-password = slavepw
master-port = 3306

Following is the configuration which goes on master2 under [mysqld] section:

# let's make it so auto increment columns behave by having different increments on both servers
auto_increment_increment=2
auto_increment_offset=2
# Replication Master Server
# binary logging is required for replication
log-bin=master2-bin
binlog-ignore-db=mysql
binlog-ignore-db=test
# required unique id between 1 and 2^32 - 1
server-id = 2
#following is the slave settings so this server can connect to master2
master-host = 10.0.0.1
master-user = slaveuser
master-password = slavepw
master-port = 3306

On master1 server, go to mysql> prompt and add the appropriate user:

mysql> grant replication slave on *.* to [email protected]'10.0.0.2' identified by 'slavepw';

On master2 server do the same but allow right ip:

mysql> grant replication slave on *.* to [email protected]'10.0.0.1' identified by 'slavepw';

Restart both of the master servers and check slave status:

mysql> show slave status\G

That is all you have to do to set up the replication. Of course there are a lot more configuration options but this should get your replication going and you can tweak from here on.

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DISCLAIMER: Please be smart and use code found on internet carefully. Make backups often. And yeah.. last but not least.. I am not responsible for any damage caused by this posting. Use at your own risk.