Technology: Learn and Share

Linux: yum options you may not know exist.

Sunny Walia — Mon, 16 Jun 2008 15:18:17 +0000

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. [...]

MySQL: Fix Microsoft Word characters. Shows weird characters on the web page.

Sunny Walia — Thu, 05 Jun 2008 21:03:50 +0000

As a consultant, I do a lot of content migrations for clients. One issue I run into quite often is the encoding of databases, tables, columns differs between source and destination. Most clients do not want me to go and change the way their encoding is to fix issues since they are too [...]

Subversion: What to do when your repository server moves to another ip?

Sunny Walia — Mon, 02 Jun 2008 23:14:42 +0000

This weekend our networking guys decided to change ips for all of our servers. They also changed our subversion server’s ip. This caused some issues in the subversion world with developers who had checkouts pointing to ips instead of hostname, using command similar to: svn co svn+ssh://192.168.1.10/svn/myrepos/ /home/mycheckout/ Now when they do “svn update” inside [...]

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

Sunny Walia — Thu, 29 May 2008 15:54:06 +0000

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 [...]

Amazing Photos from Botanical Garden In Beijing, China

Sunny Walia — Wed, 28 May 2008 07:29:24 +0000

Gardening in BEIJING - ChinaBotanical Garden in BEIJING - Chinabeijing, china30 photos Page: 1 2 3

MySQL: How do you install innotop to monitor innodb in real time?

Sunny Walia — Wed, 21 May 2008 09:06:11 +0000

Innotop is a very useful tool to monitor innodb information in real time. This tool is written by Baron Schwartz who is also an author of “High Performance MySQL, Second edition” book. [Side note: I highly recommend getting this book when it comes out (in June, 08?). Other authors include: Peter Zaitsev, Jeremy [...]

Oh dear MySQL slave, where did you put those rows?

Sunny Walia — Sat, 17 May 2008 10:35:00 +0000

I need help from my fellow mysql users. I know some of the people who read this are alot better then me with mysql so hopefully you can help So today we decided that we are going to migrate one of our master database servers to new hardware. Since we got the hardware this [...]

Forums @ crazytoon.com is up!

Sunny Walia — Fri, 16 May 2008 10:08:13 +0000

I have thought about putting up forums on my blog for LONG time and even thought about writing my own. But after playing with phpBB3 for a while on my other site (http://totalplaystation.com/forum), I have decided to use it instead. Let’s just face it; I don’t have the time or resources to write [...]

MySQL: How do I dump each record from a table to a separate files in csv format?

Sunny Walia — Mon, 12 May 2008 08:45:14 +0000

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 [...]

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

Sunny Walia — Fri, 09 May 2008 11:13:19 +0000

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 [...]

MySQL: How do you use symlinks with MySQL tables?

Sunny Walia — Fri, 02 May 2008 07:48:34 +0000

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 [...]

Linux: How do you display specific information at login prompt in Linux on the console?

Sunny Walia — Wed, 23 Apr 2008 02:00:50 +0000

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 [...]

MySQL Replication Series (tip #1): what should be replicated and what should not be replicated?

Sunny Walia — Tue, 22 Apr 2008 01:26:26 +0000

Welcome to Tip #1 in MySQL Replication Series. In this tip we will go over what to do when you only want to replicate certain data to slave(s). Most general way to tell what is replicated to which slave is to include following configuration directive in my.cnf file depending on your environment and [...]

MySQL Replication Series: How does MySQL replication work?

Sunny Walia — Thu, 17 Apr 2008 16:00:51 +0000

Setting up replication is not hard and can be done by following simple directions. You can learn setting up two type of replication MySQL offers here: master-master replication and master-slave replication. Once you have replication set up, you can start playing with it without doing any more changes to the configuration. But let us [...]

MySQL: Solution for ERROR 1442 (HY000): Can’t update table ‘t1′ in stored function/trigger because it is already used by statement which invoked this stored function/trigger.

Tracy — Tue, 04 Mar 2008 02:42:02 +0000

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 [...]

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

Sunny Walia — Fri, 29 Feb 2008 21:40:02 +0000

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 [...]

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

Sunny Walia — Wed, 30 Jan 2008 03:12:57 +0000

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 [...]

Memcached: How do you install memcached? (CentOS 64 bit, Linux, Redhat, Fedora)

Sunny Walia — Sun, 20 Jan 2008 22:52:32 +0000

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 [...]

PHP: How do I install phpsh, interactive shell prompt for php under CentOS or Fedora?

Sunny Walia — Tue, 11 Dec 2007 08:26:48 +0000

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 [...]

MySQL: How do I import individual table dump files in to MySQL using shell script?

Sunny Walia — Thu, 29 Nov 2007 03:35:49 +0000

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 [...]

MySQL: How do I dump all tables in a database into separate files?

Sunny Walia — Tue, 27 Nov 2007 00:22:53 +0000

There have been numerous occasions where I needed to make backups of individual tables from selected database. Usually I can achieve this by typing: mysqldump database_name table1 > table1.sql mysqldump database_name table2 > table2.sql This could be very painful if you have 10’s or 100’s of tables. Until today, I never ran into a situation where I [...]

MySQL Cluster: Changing datamemory requires node restart with –initial?

Sunny Walia — Wed, 14 Nov 2007 02:52:57 +0000

I ran into something with mysql cluster today which boggles my mind. On http://dev.mysql.com/doc/refman/5.0/en/mysql-cluster-config-params-ndbd.html page, it is documented that if we you change datamemory parameter in the config.ini under mysql-cluster like below, you would have to restart nodes to reread the configuration. [NDBD] id=2 HostName=10.0.0.2 # the IP of the first data node DataMemory=6G IndexMemory=512M But when I tried the: [...]

Linux: How do I mass find and replace text in files under linux using perl?

Sunny Walia — Mon, 29 Oct 2007 07:00:08 +0000

Few friends have asked me how to do mass find and replace text in files under linux. There are quite a bit of options in linux to achieve mass replacing of text in files. If you are doing it file by file, you can achieve that in vi by opening, running replace and [...]

Linux virus scan: How do I check my linux installation for viruses using ClamAV? (CentOS, Linux, Redhat)

Sunny Walia — Sat, 20 Oct 2007 03:50:32 +0000

There are quite a bit of antivirus software exist for Linux nowadays. One of the popular antivirus software is ClamAV. We will install Clam AntiVirus software from source and install it to a custom directory. We will also install gmp-devel package which installs GMP library. GMP library is used to verify [...]

MySQL: Slave lag behind master and data corruption.

Sunny Walia — Tue, 16 Oct 2007 00:09:10 +0000

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 [...]