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

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Update: Karanbir says “Just one thing to keep in mind is that we dont want too many people using it from the Testing repository - we only need enough feedback to move it from testing to stable ( and to be honest, there are already 8 people who have said yes it works - so move to stable should happen within the next 24 - 48 hrs ). Once the package is in stable, users on CentOS4 and 5 wont need to do anything more than just ‘yum install maatkit’ and it will install for them.”

At least one person (Karanbir Singh) is working to get Maatkit into the CentOS repositories, and I believe there might be movement towards RHEL also. From an email to the Maatkit discussion list a little while ago,

I am in

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I honestly do not know why somebody would want to export each record from a table in to its’ own files in a csv format. I am sure people have their own reasons. But since I got request from couple people, I figure I would post a solution here. Same script can be used to dump the whole table in to one csv file as well, with little tweaking. I will start with creating database with a table. I then insert three rows with test data into the table just to show three separate files creation.

mysql> CREATE DATABASE testdump;
mysql> USE testdump
mysql> CREATE TABLE `testtable` (
`id` TINYINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY ,
`testfield` VARCHAR( 15 ) NOT NULL ,
`testfield2` VARCHAR( 15 ) NOT NULL
) ENGINE = innodb COMMENT = 'test table for dumping each row to file';
mysql> INSERT INTO `testtable` values








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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

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Creating table symlinks in MySQL is very easy and it is probably one of the features a lot of MySQL users overlook or never think about. You may ask, why would I want to use symlinks? Some of the reasons you would want symlinks is if you are running low on disk space on the partition where your data generally is and/or you want to move one (or more) table(s) on to a different disk/partition for performance reasons.

One of the things worth mentioning is that MySQL documentation states: “Symlinks are fully supported only for MyISAM tables. For files used by tables for other storage engines, you may get strange problems if you try to use symbolic links.” Keeping that in mind, if you have a innodb table and would like to create symlinks for, you should change the engine type to myisam before symlinking. Although, I have heard and personally used symlinks for innodb

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Buddy of mine asked me a question over chat today: “how do I show my machines’ IP at login prompt with out logging in?” He is referring to his Virtual Machine in this case. He does not want to have to log in to the server to see what ip it has (since its on dhcp) for him to ssh in or hit it from the browser. I could have answered him with a simple how to but what is the fun in that? So I decided to give some background on how login prompts are done and show what can be done.

When Linux server boots up, it calls a program called mingetty. This program creates that infamous login prompt as show in a screenshot:

You can see how server calls the mingetty program by looking at /etc/inittab. You will see a block like below:

# Run

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I prefer to install mySQL using the pre-compiled binaries. Depending on the environment, these usually go in either /opt or /usr/local. When you choose this type of install, chances are you are going to need to ensure that you somehow configure your system so that the mysql binaries end up in your PATH. If you are [...]

Here is a sample table you can create to test following problem/solution on: CREATE TABLE `t1` ( `a` char(1) default NULL, `b` smallint(6) default NULL ); insert into t1 values ('y','1'); I have a table t1 which has column a and b, I want column a to be updated to ‘n’ when column b = 0. Here is the first version [...]

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 [...]   [Read more...]

This February I`ll be heading to my 8th Fosdem in row.

I went to every single Fosdem so far, some years only one day because of other obligations but I was a round most of the time
During the first couple of years I was pretty active in the FIT team, helping out people to find the right rooms , keeping the fosdem contributions safe with Sven, funding different social events and devroom dinners ,
Later I was in charge of the HPC and Cluster devroom in which we also held the openMosix summits.
And back in 2004 I replaced Moshe at the openMosix Summit standing in front of a great audience at the Janson room.

As Wim just pointed out the Drupal Devroom schedule is out
and it seems like 2008 will be the

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Before we go into how to set up master-slave replication in MySQL, let us talk about some of the reasons I have set up master-slave replication using MySQL. 1) Offload some of the queries from one server to another and spread the load: One of the biggest advantages to have master-slave set [...]   [Read more...]

Memcached is a very popular open source object caching server. It was developed to speed up livejournal.com by Danga Interactive.  We use memcached for a lot of our sites.  We use it for different purposes but one main purpose is to cache query results so we don’t have to keep hitting database.  As most [...]   [Read more...]

Peter posted that CentOS comes with a build of MySQL Enterprise. It should really be clarified that CentOS itself, comes with MySQL Community, as does Red Hat Enterprise Linux. On RHEL5/CentOS5, you’ll see:

mysql-5.0.22-2.2.el5_1.1
mysql-server-5.0.22-2.2.el5_1.1

The above are the default packages that CentOS provides. However, what Peter really is referring to is the CentOSPlus Repository, which by their own admittance is “not part of the upstream distribution and extend CentOS’s functionality at the expense of upstream compatibility. Enabling this repository makes CentOS different from upstream.”

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Peter notes that you indeed can find pretty recent Enterprise level MySQL rebuilds over at the CentOSPlus repository.

Good things come to those who wait :)

I took the opportunity today evening to get myself upgraded (from 4.5.3_GA_733) to the latest (5.0.0_GA_1869) open source version of Zimbra - ZCS 5.0 GA. The database migration took about the longest, mainly due to some schema changes. Lots of starts and stops to the database. Its now running MySQL 5.0.45 Community.

What prompted the upgrade? A few days ago, I got a bunch of new packages, and rebooted the server (new kernel). To my dismay, Zimbra started to have issues - amavisd wouldn’t start. This meant that there was a large amount of mail, sitting in the queue, not being delivered. Things you don’t normally check for, immediately, anyway.

Turns out Compress::Zlib was too old. Well, not the system provided

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phpsh requires readline support built into python. It also requires python version 2.4+. You can check which version of python you have installed by typing: python -V Let us download and install readline: wget ftp://ftp.cwru.edu/pub/bash/readline-5.2.tar.gz tar zxf readline-5.2.tar.gz cd readline-5.2 ./configure make install Now let us install python with readline support: wget http://www.python.org/ftp/python/2.5.1/Python-2.5.1.tgz tar zxf Python-2.5.1.tgz cd Python-2.5.1 I had some problems on one of the [...]   [Read more...]

Over at ITToolbox Tarry has another blog . He posted an article where he tried to debunk some myths about open source. I feel he needs some help there :)

Let's start with his second Myth , Open Source is Free. Off course it isn't , you need to invest your own time to get familiar with it or pay other people to use it. Compare it to building a house ... you can build one if you have the skills and the time , but you still need to pay for the bricks and the mortar, or you can pay someone who has the skills to build one for you. With software there used to be a similar thing. You could buy software, then install and configure it yourselve, or you could hire someone more skilled than you to install and support it when you run into

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After I wrote the post: How do I dump all tables in a database into separate files? I got emails from couple people asking how to import the individual table files back in to MySQL. First way to import each sql file created by the post is to import each file individually by [...]   [Read more...]

I am reaching out to mysql experts out there! We just inherited a site which uses MySQL master/slave replication. We set up the master and slaves per MySQL documents and did some of our own tweaking in my.cnf to get things working. Things were great when we were testing the site but [...]   [Read more...]

One of my clients asked me today to make their MySQL installation go back to default database install. Basically they wanted me to get rid of all their databases (in this case test databases) so they can start fresh and go live with only the databases they needed. So here are the steps [...]   [Read more...]

One of the mysql database servers I manage started to have issues with doing backups yesterday. mysqldump was running but nothing was happening on the backup side. I started to investigate to see why our full backups were failing. I opened up the mysql error log file (mine is at: /usr/local/mysql/var/hostname.err) [...]   [Read more...]