Handy Linux Blog.

awk basic

2012-01-12T17:08:00.003+07:00

awk is very useful tool for linux user.
For example, you have output from ps aux like this :

#ps aux

root 2213 0.0 0.4 6596 2428 pts/2 S 12:08 0:00 bash
root 2235 0.0 0.1 4848 952 pts/2 S+ 12:08 0:00 /bin/bash xxx
root 2236 0.0 0.6 7132 3236 pts/2 S+ 12:08 0:04 ssh xxx

The second column is PID, and 8th is process state.
To find the zombie process you just execute the following command :

# ps aux | awk '{ print $8 " " $2 }' | grep -w Z

See just use $th of the column, you will get the value of that column. Also, you can apply even you have comma separated field with -F option.

For more usage of this command please consult
#man awk

:)

Ubuntu ramdisk

2011-12-13T10:58:00.002+07:00

Mounting ram as a working space which help I/O faster.

#mkdir -p /tmp/ram#sudo mount -t tmpfs -o size=512M tmpfs /tmp/ram/

However, be careful to not exceed the memory you have in the system.

http://www.ubuntuka.com/ubuntu-ramdisk-ramdrive-easy-way/

ubuntu installing mongodb- part II : install php driver

2011-12-08T14:29:00.001+07:00

After finishing this part, your php will be able to use mongodb function.

To install mongodb php driver, first of all we need pecl to install from PHP repository.

#sudo apt-get install php5-dev php5-cli php-pear

Running pecl to get and install php driver.

#sudo pecl install mongo

Turn your back to the screen and have a coffee while system compiling the mongo extension. After finishing installation, you will see this :

Build process completed successfully
Installing '/usr/lib/php5/20090626+lfs/mongo.so'
install ok: channel://pecl.php.net/mongo-1.2.6
configuration option "php_ini" is not set to php.ini location
You should add "extension=mongo.so" to php.ini

Then, edit php.ini (/etc/php5/cli/php.ini, ubuntu) and add this line extension=mongo.so.

Reference : http://www.mongodb.org/display/DOCS/PHP+Language+Center

ubuntu installing mongodb- part I : install server

2011-11-30T16:07:00.001+07:00

The newest version of mongodb is not in repository of ubuntu. To install newest 2.0, custom repository 10gen is needed.

Add key :

#sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10

Add repository by creating file name '/etc/apt/sources.list.d/10gen.list'
with this line :
(using upstart)

deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen

You're ready to install :

#apt-get update#apt-get install mongodb-10gen

The mongodb is running in the system. The configuration for mongodb is /etc/mongodb.conf and in /etc/init/mongodb.conf (for startup script)

Reference:
http://www.mongodb.org/display/DOCS/Ubuntu+and+Debian+packages

(link) Nginx "how to" - Fast and Secure webserver

2011-10-14T16:33:00.001+07:00

This might be a informative link worth to visit if you are experiencing performance issue with web server. Nginx is an option.
https://calomel.org/nginx.html

mysql commonly use statement

2011-09-30T10:14:00.000+07:00

Create table

mysql> CREATE table if not exists tblname like old_tblname;

INSERT ... SELECT

mysql> INSERT INTO tblname1 SELECT * from tblname2 where ...;

Empty table

mysql> TRUNCATE table story_longcon_40;

Delete/Drop table

mysql> DROP TABLE tblname;

Delete/Drop database

mysql> DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

Optimize Table

mysql> OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE tbl_name [, tbl_nam

[MySQL] Backing up data

2011-09-29T17:38:00.001+07:00

There are several ways to backing up data
1) Logical backup

* SQL dumps

#mysqldump dbname tblname

Not suitable for huge backup. Both table structure and the data are stored together.(option available)

* Delimited file backups
backing up :

mysql> SELECT * INTO OUTFILE '/tmp/t1.txt'
-> FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
-> LINES TERMINATED BY '\n'
-> FROM test.t1

restore :

mysql> LOAD DATA INFILE '/tmp/t1.txt'
-> INTO TABLE test1.t1
-> FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
-> LINES TERMINATED BY '\n';

*parallel dump: maatkit(mk-parallel-dump)

2) File system snapshot (LVM)
not covered here.

mysql backup/dump/export table schema, definition

2011-09-29T17:15:00.000+07:00

1) use mysqldump

server# mysqldump -uroot -p dbname tblname -d

with this method you will get sql statement. You can use this for backing up table definition as well.

2) create table from another table

mysql> create table if not exists tblname like old_tblname;

with this method you get a copy of table. It is useful if you want to have a another table with the same structure for backing up, testing.

Postfix วิธีการ pipe mail ที่ได้รับ ไปยัง command ต่างๆ

2011-08-05T18:03:00.002+07:00

Environment ที่ใช้ทดสอบนะครับ ใช้ Ubuntu 10.04.3, Postfix, Dovecot เป็นหลัก สิ่งที่ต้องการคือ เมื่อมีคนส่ง e-mail มาที่ test@example.com แล้ว ให้ postfix ทำการ pipe email นั้นเข้าสู่โปรแกรม /home/myuser/testperl ซึ่งเป็น perl script ที่ผมเขียนรอไว้ก่อนหน้านี้แล้ว

ทั้งนี้ ตัว postfix ผม config ตัว virtual domains, virtual mailbox ที่ติดต่อกับ mysql server เอาไว้ด้วยนะครับ

เริ่มจาก

เข้าไปแก้ไข /etc/postfix/main.cf

ที่บรรทัด smtpd_recipient_restrictions เพิ่มคำสั่ง check_recipient_access เข้าไป

smtpd_recipient_restrictions =

# bypass checks on outgoing mail

permit_mynetworks

# reject if not full email address

reject_non_fqdn_recipient

# next line rejects if the account/domain does not exist

# ALSO prevents OPEN RELAY - if missing RELAY is OPEN!!

# MUST appear before the check_recipient_access

reject_unauth_destination

# perform filter access by recipient name

check_recipient_access hash:/usr/local/etc/postfix/script_filter

เพิ่ม /etc/postfixscript_filter

test@example.com FILTER support:dummy

# postmap script_filter จะมีไฟล์ script_filter.db เพิ่มขึ้นมา
เข้าไปแก้ master.cf

support  unix - n n - - pipe  flags=Rq user=www    argv=/home/myuser/testperl $(sender)$(recipient)

โดยใน perl script จะได้ argument 1 = sender และ argument 2 = receiver

แค่นี้ ระบบก็เรียบร้อยพร้อมใช้งานแล้ว

How to Setup Canon MX350 Series on Ubuntu 11.04 Natty

2011-06-16T13:39:00.003+07:00

sudo add-apt-repository ppa:michael-gruz/canon
sudo apt-get update

apt-get install cnijfilter-mx350series

and now you can add printer by
1. Go to search -> printing
2. Add -> Network Printer
3. Canon MX350 Series will appear in left panel
4. Follow the instruction
5. Finish installation

Ubuntu apt-get history

2011-06-09T13:58:00.002+07:00

for Ubuntu admin you can track apt-get history at

/var/log/apt/history.log

for a brief

and

for more detail at

/var/log/apt/term.log

mdadm cheat sheet

2011-06-09T11:42:00.002+07:00

Mdadm Cheat Sheet

1. Create a new RAID array

Create (mdadm –create) is used to create a new array:

mdadm --create --verbose /dev/md0 --level=1 /dev/sda1 /dev/sdb2

or using the compact notation:

mdadm -Cv /dev/md0 -l1 -n2 /dev/sd[ab]1

2. /etc/mdadm.conf

/etc/mdadm.conf or /etc/mdadm/mdadm.conf (on debian) is the main configuration file for mdadm. After we create our RAID arrays we add them to this file using:

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

or on debian

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

3. Remove a disk from an array

We can’t remove a disk directly from the array, unless it is failed, so we first have to fail it (if the drive it is failed this is normally already in failed state and this step is not needed):

mdadm --fail /dev/md0 /dev/sda1

and now we can remove it:

mdadm --remove /dev/md0 /dev/sda1

This can be done in a single step using:

mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1

4. Add a disk to an existing array

We can add a new disk to an array (replacing a failed one probably):

mdadm --add /dev/md0 /dev/sdb1

5. Verifying the status of the RAID arrays

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

cat /proc/mdstat

mdadm --detail /dev/md0

The output of this command will look like:

cat /proc/mdstat

Personalities : [raid1]

md0 : active raid1 sdb1[1] sda1[0]

104320 blocks [2/2] [UU]

md1 : active raid1 sdb3[1] sda3[0]

19542976 blocks [2/2] [UU]

md2 : active raid1 sdb4[1] sda4[0]

223504192 blocks [2/2] [UU]

here we can see both drives are used and working fine – U. A failed drive will show as F, while a degraded array will miss the second disk -

Note: while monitoring the status of a RAID rebuild operation using watch can be useful:

watch cat /proc/mdstat

6. Stop and delete a RAID array

If we want to completely remove a raid array we have to stop if first and then remove it:

mdadm --stop /dev/md0

mdadm --remove /dev/md0

and finally we can even delete the superblock from the individual drives:

mdadm --zero-superblock /dev/sda

#Clone partition table

sfdisk -d /dev/sda | sfdisk /dev/sdb

(this will dump the partition table of sda, removing completely the existing partitions on sdb, so be sure you want this before running this command, as it will not warn you at all).

There are many other usages of mdadm particular for each type of RAID level, and I would recommend to use the manual page (man mdadm) or the help (mdadm –help) if you need more details on its usage. Hopefully these quick examples will put you on the fast track with how mdadm works.

Reference :

http://www.ducea.com/2009/03/08/mdadm-cheat-sheet/

ubuntu snmp

2011-06-03T15:33:00.002+07:00

I've install cacti to a server which will poll the data from linux box, installed snmp.

To test polling data from cacti to linux box,

#snmpwalk -c public -v 2c [ip-address]

In ubuntu if you want to allow other host to view this data you need to modified

"/etc/default/snmp "

SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -g snmp -I -smux -p /var/run/snmpd.pid [ip-address]'

apache http auth with cgi

2011-05-31T12:53:00.001+07:00

If you are using apache http auth with cgi, you have a few more things to do.

You need to enable .htaccess

RewriteEngine On

RewriteRule .* - [E=REMOTE_USER:%{HTTP:Authorization},L]

mysql open query log without changing my.cnf and restart

2011-05-15T14:33:00.000+07:00

Use mysql client connect to server

#show variables like 'general%';

+------------------+----------------------------+

| Variable_name | Value |

+------------------+----------------------------+

| general_log | OFF |

| general_log_file | /var/run/mysqld/mysqld.log |

+------------------+----------------------------+

This 2 vaiables control mysql query logging.

To turn query log on :

SET GLOBAL general_log_file = '/var/log/mysql/sql-log.log' ;

SET GLOBAL general_log = 1

To turn query log off :

SET GLOBAL general_log = 0 ;

SET GLOBAL general_log_file = '/var/run/mysqld/mysqld.log';

Notice: This is for mysql 5.1 only. For mysql 5.0, those variable is not available. you need editing my.cnf and restart.

Page cache and pdflush: Theory of operation and tuning for write-heavy loads

2011-02-24T14:16:00.000+07:00

For write-heavy option in system, some kernel option must be adjusted. Here are link to article about some kernel options that might help.

Please refer to : http://www.westnet.com/~gsmith/content/linux-pdflush.htm

perc H200 hardware raid utility in linux

2011-02-22T11:02:00.000+07:00

I just bought server coming with hardware raid PERC H200 (Dell).

By the time of this blog, I understand that it use chipset from LSI here are out put from

#lspci --n

LSI Logic / Symbios Logic SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] [1000:0072] (rev 03)

Unfortunately, the monitoring software for this h/w raid is not open. You have to download sas2ircu bin code. The program will display raid status.

I've downloaded from this link :

http://www.natecarlson.com/2010/08/23/lsi-command-line-utility-for-sas2-non-raid-controllers/#comments

Please visit for usage:

http://hwraid.le-vert.net/wiki/LSIFusionMPTSAS2#a2.Linuxkerneldrivers

find command for deleting empty folder

2011-01-12T15:57:00.000+07:00

find ./ -type d -exec rmdir 2>/dev/null {} \;

protecting web access with mod_auth

2011-01-04T10:23:00.000+07:00

You can limit web access by password. Apache has module mod_auth* for you. It's easy.

1. create password file

# htpasswd -c /usr/local/apache/passwd/passwords rbowen

New password: mypassword

Re-type new password: mypassword

Adding password for user rbowen

for additional user just remove "-c"

2. add directive to apache (.httaccess or )

AuthType Basic

AuthName "Restricted Files"

# (Following line optional)

AuthBasicProvider file

AuthUserFile /usr/local/apache/passwd/passwords

Require user rbowen

3. Restart apache and have fun!

If you have a problem, please investigate the error_log first.

More information :

http://httpd.apache.org/docs/trunk/howto/auth.html

split /var/log/message log

2010-10-27T15:45:00.001+07:00

I'm using gentoo and vixie-cron as a system cron. After using it for a while, I found that gentoo store cron log in to /var/log/message. And, I just kind of like to split this for monitoring easily. Here is what I have done.

edit this :

/etc/syslog-ng/syslog-ng.conf

add the following lines :

filter f_cron { facility (cron); };

destination cron { file("/var/log/cron.log"); };

log { source(src); filter(f_cron); destination(cron); };

reload syslog-ng :

/etc/init.d/syslog-ng reload

you may need to setting the logrotate. Please see the example in /etc/logrotate.d/ for example

terminal key map

2010-10-19T14:58:00.000+07:00

Some ssh client need config for special button.

You can use this value to map the keyboard button to this value perform function properly.

Home \033[1~

Delete \033[3~

End \033[4~

Page Up \033[5~

Page Down \033[6~

find command with -exec options

2010-10-06T11:48:00.000+07:00

find command is quite a handy tool for file searching. It can also include an command to execute for matched file with

1) -exec command ;

2) -exec command {} +

Both are different.

Let say you have 3 files, a b c in the directory.

#find . -exec echo '{}' >> tmp1 \;

output in tmp1 will be :

./b

./a

./c

./tmp1

#find . -exec echo '{}' >> tmp2 \+;

output in tmp2 will be :

a b c

with + all matched file will be append and execute once.

with ; all matched file will be execute for each matching.

Gentoo prebuilt package installation

2010-09-10T13:59:00.000+07:00

With gentoo, you can customize every packages you want because gentoo give that choices to you. Emerge, package manager, will built package for you from source code. However, compiling package in gentoo can be very time-consuming task, Especially, when you have more gentoo system. I have found option of emerge that can build package and you can use this prebuilt package to other system.

(1) build package

#quickpkg mysql

- This will build package from files on your system. If the package you wanna built are on the system already.

#emerge -b mysql

-the -b(--buildpkg) option tell emerge to do additional task when installing package to the system.

*In this case(mysql), the prebuilt package will be available in /usr/portage/packages/dev-db/ directory.

(2) use prebuilt package

Place the prebuilt package in appropriate directory, in this case : /usr/portage/packages/dev-db/

#emerge --usepkgonly mysql

For more information please consult the man page :

#man emerge

#man quickpkg

#man make.conf

Install windows font in linux(ubuntu)

2010-09-07T16:55:00.000+07:00

Linux user cannot avoid living with windows user. That make linux users to adjust ourselves to read file from windows including fonts they using. 

(1) using font package
#sudo apt-get install msttcorefonts

#sudo fc-cache -fv

(2) copying font files from windows

copy *.ttf font to /usr/share/fonts/truetype/thai

#fc-cache -fv

reference

1. ms-font package installation [here]

mtime, ctime, and atime timestamp Linux

2010-08-30T14:05:00.000+07:00

Recently, I've implemented a caching system. This involve removing old file from the cache. One important factor for making a decision is a file timestamp. There are many timestamp implemented in the file system here are method for viewing timestamp info.

mtime, ctime, and atime

atime - access time
mtime - if modify time
ctime - of change time

To view atime

ls -lu

To view ctime

ls -lc

To view mtime

ls -lt

Access time is when last time data from the file was access.

Modify time is when last change was done to the file.

Change time id when you change owner.

Use stat command

stat filename

stat newname2.txt

File: `newname2.txt'

Size: 13 Blocks: 8 IO Block: 4096 regular file

Device: 805h/2053d Inode: 2338058 Links: 1

Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)

Access: 2011-01-28 16:01:10.000000000 +0700

Modify: 2011-01-28 16:02:35.000000000 +0700

Change: 2011-01-28 16:06:26.000000000 +0700

to verify with ls command

References :

http://baliyansandeep.blogspot.com

Gentoo migration to raid

2010-08-04T13:46:00.000+07:00

At some point, high availability become more essential to your server. Raid1(mirror) can help server to be able to continue even the disk go wrong. This blog is intend to be a complete just-type-guide for system admin. I hope that you guy succeeded in this migration

Background my system is gentoo on sda. The new disk will be sdb. After finishing copying data to sdb. The another new disk will be replace as sda. sda and sdb will be raid1 mirroring each other.

#0 move running service to another system

- make sure that the system can be down for maintainance

#1 shutdown system

shutdown -h now

#2 install new hdd as sdb

some vendor disable port B (for sdb) please make sure that it is enable so it can be visible from linux.

#3 boot system with live cd

modprobe raid1

#4 format disk and create raid on sdb

available 500GB

-> sdb1 boot 1GB ext2

-> sdb5 root entire ext3

-> sdb6 swap 4GB swap

cfdisk /dev/sdb

cd /dev && MAKEDEV md

mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb1

mdadm --create /dev/md5 --level=1 --raid-devices=2 missing /dev/sdb5

mke2fs /dev/md1

mke2fs -j /dev/md5

mkswap /dev/sdb6

swapon /dev/sdb6

#5 copy data from sda to raid

mkdir /mnt/gentoo1

mount /dev/sda5 /mnt/gentoo1

mount /dev/md5 /mnt/gentoo

mount /dev/sda1 /mnt/gentoo1/boot

mkdir /mnt/gentoo/boot

mount /dev/md1 /mnt/gentoo/boot

cp -dpRx /mnt/gentoo1/* /mnt/gentoo/

#6 install boot loader to raid

mount -t proc none /mnt/gentoo/proc

mount -o bind /dev /mnt/gentoo/dev

chroot /mnt/gentoo /bin/bash

env-update

source /etc/profile

export PS1=”(chroot) $PS1”

#Edit grub.conf change root=/dev/sdaxx to mdxx

nano /boot/grub/grub.conf

#install boot loader to the disk

grub –no-floppy

- device (hd0) /dev/sdb

- root (hd0,0)

- setup (hd0)

#7 edit fstab to mount disk on raid instead // or just copy from preedit @ /home/username/fstab

nano /etc/fstab

#8 shutdown & replace sda with new disk

exit

cd /

umount /mnt/gentoo/boot /mnt/gentoo/proc /mnt/gentoo/dev /mnt/gentoo

umount /mnt/gentoo1/boot /mnt/gentoo1

shutdown -h now

-replace new disk

#9 sync disk and install boot loader

-change bios priority to start boot from sdb

sfdisk -d /dev/sdb | sfdisk /dev/sda

mdadm --add /dev/md1 /dev/sda1

mdadm --add /dev/md5 /dev/sda5

#edit fstab add sda as swap

nano /etc/fstab

mkswap /dev/sda6

swapon /dev/sda6

grub –no-floppy

- device (hd0) /dev/sda

- root (hd0,0)

- setup (hd0)

#wait until sync finish

- reboot test

- restore bios boot priority

- restore sevice back to the server.

Mounting file as filesystem

2010-04-23T09:41:00.000+07:00

Linux provide various and flexible file system for user to choose.

Here are an example

Create empty 10 Mb file.

#dd if=/dev/zero of=file.img bs=1k count=10000

Attach the file to loopback file system

#losetup /dev/loop0 file.img

Create file system on loopback device

#mke2fs -c /dev/loop0 10000

Mount loopback device

#mount -t ext2 /dev/loop0 /mnt/point1

So you can have any file system on any file system.

To find out more detail about file system please visit the following links :

-Anatomy of file system

http://www.ibm.com/developerworks/linux/library/l-linux-filesystem/

-Cryptographic File Systems Performance

http://www.fsl.cs.sunysb.edu/docs/nc-perf/index.html

-Loopback Tricks

http://nst.sourceforge.net/nst/docs/user/ch04s04.html#filesystem.loopback

The linux documentation project

2010-03-12T13:03:00.000+07:00

Linux newbie might be looking for reliable document for linux.
Here is a good link that worth a look.

Link:
http://tldp.org/guides.html

Configuring gentoo apache with fcgi

2010-03-10T12:59:00.000+07:00

mod php and worker are not stable as PHP official page.

Gentoo user might not aware this because we can compile PHP with threads use flag without realizing the warning.

Before get start with apache-worker fcgid and php. You need the following :

1) installed PHP with cgi use flag.

2) installed mod_fcgid (emerge mod_fcgid)

PHP configuration :

- modify /etc/php/cgi-php5/php.ini to suite your need.

apache configuration :

- modify /etc/apache2/modules.d/20_mod_fcgid.conf adding the following in

AddHandler fcgid-script .php .fcgi
DefaultInitEnv PHPRC "/etc/php/cgi-php5"

IdleTimeout 60
BusyTimeout 120
ProcessLifeTime 360
SpawnScoreUpLimit 2100
MaxProcessCount 2100
DefaultMaxClassProcessCount 2100
IPCConnectTimeout 120
IPCCommTimeout 120

FCGIWrapper /usr/bin/php-cgi .php

Please change the /usr/bin/cgi/ to your path. And don't forget to add +ExecCGI to option directive.

- edit /etc/conf.d/apache2 add -D FCGID to APACHE2_OPTS

restarting apache.

Monit : debuging monit process

2010-03-09T17:37:00.000+07:00

Misconfiguration on apache can lead monit false alet and do wrong action. I found that some monit process in one of my servers always complaining about apache cannot connect port 80. which is not right cause I can still access the pages.

Here are tip for debugging what goes wrong:

1) stop monit as a daemon
2) smart monit in foreground
#monit -Iv
3) see the message

From my experience, the server response with 403 http code cause monit alert cannot connect host port 80.
So, I change apache config to get 200 code and everything back to work :)

Monit : server monitoring tools

2010-03-09T17:26:00.000+07:00

If you have a web server, have you ever experience apache process not responding to http request?

or

How to make sure that apache are running? and If server load go too high please restart it for me.

Monit can help you monitoring common for system admin.

It can monitoring server process, file size, memory server load. And, you can set the appropriate action to those events: sending email, restart process etc.

To install monit
for gentoo :
#emerge -av monit
for debian:
#apt-get install monit

Configuring monit
Locate configuration file : /etc/monitrc or /etc/monit/monitrc
Here is the example configuration for apache with these condition
1) check whether apache is running : if not restart
2) check http:80 is working : if not restart
3) if server go to high : restart apache process

set daemon 120

set mailserver smtp.localhost

set mail-format { from: admin@localhost.com }

set alert systemadmin@localhost.com

check process apache with pidfile /var/run/apache2.pid
start program = "/etc/init.d/apache2 start"
stop program = "/etc/init.d/apache2 stop"
if failed port 80 protocol http then restart
if loadavg(5min) greater than 100 for 2 cycles then restart
alert extrapeople@localhost.com

If you are interested in monit for advance feature please visit monit official site.
check out monit document

Advance php error handling

2010-03-05T17:20:00.000+07:00

PHP server need different configuration for production and development server.

This article help you understanding php.ini configuration better and applicable to your server.

- display_errors
echo error to the browser this should be turn off for production but should be enable for test server.

- log_errors
instead of displaying error to stderr, you can choose to enable error logging to the file instead for production.

More option can be study here :
http://perishablepress.com/press/2008/01/30/advanced-php-error-handling-via-php/

apache with fcgid

2010-03-05T16:37:00.000+07:00

Once, I used gentoo with apache(worker) + phpmod as a webserver. After switching to ubuntu, I've found that phpmod is not stable with apache(worker), this is not a problem with gentoo b'coz u can customize everything by yourself.

Up to this point ,there are 2 choice for ubuntu apache works with php
1) use apache prefork + phpmod
2) use apache worker + cgi + php

More description about fcgid/fastcgi http://www.seaoffire.net/fcgi-faq.html

I found the following study show that fcgid might be a good choice. And, it is.
http://2bits.com/articles/apache-fcgid-acceptable-performance-and-better-resource-utilization.html

For fcgid reference for apache :
http://httpd.apache.org/mod_fcgid/mod/mod_fcgid.html

monitoring mysql with cacti

2010-03-04T15:15:00.000+07:00

By default, cacti don't come with mysql graphing template. Here is the plugin that help you graphing mysql important data.

The installation is like the other plugins.
1) copy php script to cacti host /script directory
2) import template using web interface
3) add mysql user to mysql host
4) have fun :)

plugin document/download :
http://code.google.com/p/mysql-cacti-templates/wiki/InstallingTemplates

author blog:
http://www.xaprb.com/blog/2009/10/25/version-1-1-4-of-improved-cacti-templates-released/

Apache Mod setenvif

2010-02-17T09:22:00.000+07:00

Some software/browser didn't follow the standard or have some bugs. I found that MSIE 6 have problem with richtext editor -javascript. Mod setenvif can be used to set special variable to correct the problem.

In file: /etc/apache2/mods-enabled/setenvif.conf
BrowserMatch "MSIE 4\.0b2;" gzip-only-text/html
BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0

With this line apache the user with MSIE6 will be:
-send gzip format for text/html only
-disable keepalive
-downgraded request to HTTP 1.0
-response with HTTP 1.0

To find our more directive of this mod.
http://httpd.apache.org/docs/2.2/mod/mod_setenvif.html

There are more interesting variable that can be set.
http://httpd.apache.org/docs/2.2/env.html

Ubuntu package management & package installed for web server

2010-02-12T17:55:00.000+07:00

Update list of package
#apt-get update

Upgrade all package in system
#apt-get upgrade

To install package
#apt-get install foo

To remove package
#apt-get remove foo
-remove configuration on the system
#apt-get --purge remove for

To upgrade all packages on the system
#apt-get dist-upgrade

apt-cache : query package list tool

To ﬁnd packages whose description contain word:
#apt-cache search word

To print the detailed information of a package:
#apt-cache show package

To print the packages a given package depends on:
#apt-cache depends package

#To print detailed information of the versions available for a package and the packages
that reverse-depends on it:
apt-cache showpkg package

PHP package
php5
php5-cgi
php5-cli
php5-curl
php4-common
php5-gd
php5-imagick
php5-memcache
php5-mysql
php5-xcache
libapache2-mod-fcgid
nfs-kernel-server

Apache package
apache2
apache2-mpm-worker
apache2-utils
apache2.2-bin
apache2.2-common
libapache2-mod-fcgid

Apache Ubuntu vs Apache gentoo
add user apache with uid81 (gentoo)
#useradd -r -u 81 apache

edit /etc/apache2/envvars to run apache with user apache

Reference :

A Debian Package Primer: Part One

http://www.linux-mag.com/cache/7747/1.html

Aptitude :part two

http://www.linux-mag.com/cache/7752/1.html

Ubuntu Community Doc.

https://help.ubuntu.com/community/SoftwareManagement

Understanding apache config order in debian/ubuntu

2010-02-11T16:09:00.000+07:00

In ubuntu, i've found a lot of config file for apache. To identify the problem, you need to know which config loading sequence which might overwrite another one.

/etc/apache2

1) apache2.conf - define #process, timeout etc...
2) mods-enabled/*.conf - module configuration
3) httpd.conf (user configuration)
4) ports.conf - port listening
5) conf.d/*- generic snippet statement - charset localized-error-pages, security
6) sites-enable/* -all vhost

xcache opcode/optimizer for php tunning

2010-02-11T13:42:00.001+07:00

Installing xcache can help php-apache app responding faster.

1) installing xcache
gentoo :
#emerge cache
ubuntu/debian
#apt-get install php5-xcache

after installing you will see path for xcache admin
2) set xcache config and admin password
#echo -n "yourpassword" | md5sum
edit xcache.ini this line :
xcache.admin.pass="" (from previous command)
http://xcache.lighttpd.net/wiki/XcacheIni

3) point apache to xcache admin path

4) browse xcache admin with browser

use this admin page to see what variable need to be adjusted.

I'll point some importtatn config

xcache.size
- set just fit, not too low or too high. see OOM(out of memory column) from admin page. If there are lots of OOM, please consider increasing.

xcache.count
- set to number of your cpu : cat /proc/cpuinfo | grep -c processor

xcache.slots
- the more slot, the faster PHP code accessing

More reading here :

introduction to xcache http://www.ibm.com/developerworks/opensource/library/os-php-fastapps1/
set xcache adminpage http://www.linuxtuts.net/ubuntu-webserver-tutorials/228-how-install-xcache-administration-page-ubuntu-linux.html
xcaching tunning http://serveradmins.net/tuning-xcache-for-fun-and-profit/
xcache ini document http://xcache.lighttpd.net/wiki/XcacheIni

rrdtool tune rra file

2010-02-09T13:48:00.000+07:00

Using SNMP and cacti, you need to adjust rrd file manually for displaying graph correctly.

/cacti/rra
show file info to see the limitation of value
#rrdtool info filename.rrd

tunning it
#rrdtool tune filename.rrd --maximum cpu_user:800

gentoo SNMP

2010-02-08T11:46:00.000+07:00

Installing SNMP in gentoo for system monitoring.

#emerge net-snmp

edit /etc/snmp/snmpd.conf add the following
com2sec Mybox localhost public
com2sec cacti 192.168.1.0/24 public

group RWGroup v2c Mybox
group ROGroup v1 cacti
group ROGroup v2c cacti

view all included .1 80
view system included system fe

access ROGroup "" any noauth exact all none none
access RWGroup "" v2c noauth exact all all all

#rc-update add snmpd default

timer shell script

2010-01-21T14:20:00.000+07:00

To measure performance, you might want to know how much does it take to complete the task.
Here are shell script to help you.

The following measure hard disk performance by creating 10 GB file.
#!/bin/bash
START=$(date +%s)
# do something
# start your script work here

dd if=/dev/zero of=/home/user/hd2/file.img bs=1M count=1000

# your logic ends here
END=$(date +%s)
DIFF=$(( $END - $START ))

echo "It took $DIFF seconds"

Nginx / lighttpd light weight web server.

2010-01-21T09:41:00.000+07:00

Apache is a standard for web server. But, you can help apache and utilize computing resource by using lighttpd and nginx as a helper for static content/load balancer for your website.

nginx :
http://wiki.nginx.org/NginxModules
lighttpd
http://redmine.lighttpd.net/wiki/lighttpd

webserver http-caching header

2010-01-20T10:25:00.000+07:00

Here are link to speed up your http server :

http://www.mnot.net/cache_docs/
http://www.web-caching.com/

User & group management : uid, gid user

2010-01-20T09:10:00.001+07:00

If you share file about variety distro of linux, you might experience with permission error.

The following command help to change uid, gid of user apache group apache to 81 :
#usermod -u 81 apache
#groupmod -g 81 apache
#id apache

user & group management : http://www.linux-mag.com/cache/7759/1.html

How to monitor harddisk with smartmontools

2010-01-12T11:50:00.000+07:00

Now let's install the smartmontools package:

# emerge -av smartmontools

Finally, you have to check if your hard disk(s) support SMART:

# smartctl -i /dev/hda

For SATA drives:

# smartctl -i -d ata /dev/sda

Using smartctl

[edit]

SMART Health Status

Let's check the SMART Health Status:

# smartctl -H /dev/hda

If you read PASSED it's ok, but if you read FAILED you have to backup your data now: the disk has already failed or it's predicted to fail within 24 hours!

To recover from bad block :

http://smartmontools.sourceforge.net/badblockhowto.html

smartmontool document:

http://sourceforge.net/apps/trac/smartmontools/wiki/TocDoc

swappiness tuning linux

2010-01-08T15:54:00.000+07:00

vm.swappiness is a tunable kernel parameter that controls how much the kernel favors swap over RAM. At the source code level, it’s also defined as the tendency to steal mapped memory. A high swappiness value means that the kernel will be more apt to unmap mapped pages. A low swappiness value means the opposite, the kernel will be less apt to unmap mapped pages. In other words, the higher the vm.swappiness value, the more the system will swap.

More to read : http://www.linuxvox.com/2009/10/what-is-the-linux-kernel-parameter-vm-swappiness/

The following is the test. It seems that the higher swapiness the slower i/o rate. More to read : http://lwn.net/Articles/100978/

linux memory management

2010-01-08T10:59:00.000+07:00

Overview of memory management

Traditional Unix tools like 'top' often report a surprisingly small amount of free memory after a system has been running for a while. For instance, after about 3 hours of uptime, the machine I'm writing this on reports under 60 MB of free memory, even though I have 512 MB of RAM on the system. Where does it all go?

The biggest place it's being used is in the disk cache, which is currently over 290 MB. This is reported by top as "cached". Cached memory is essentially free, in that it can be replaced quickly if a running (or newly starting) program needs the memory.

The reason Linux uses so much memory for disk cache is because the RAM is wasted if it isn't used. Keeping the cache means that if something needs the same data again, there's a good chance it will still be in the cache in memory. Fetching the information from there is around 1,000 times quicker than getting it from the hard disk. If it's not found in the cache, the hard disk needs to be read anyway, but in that case nothing has been lost in time.

To see a better estimation of how much memory is really free for applications to use, run the command free -m:

Code: free -m

             total       used       free     shared    buffers     cached
Mem:           503        451         52          0         14        293
-/+ buffers/cache:        143        360
Swap:         1027          0       1027

The -/+ buffers/cache line shows how much memory is used and free from the perspective of the applications. Generally speaking, if little swap is being used, memory usage isn't impacting performance at all.

Notice that I have 512 MB of memory in my machine, but only 52 is listed as available by free. This is mainly because the kernel can't be swapped out, so the memory it occupies could never be freed. There may also be regions of memory reserved for/by the hardware for other purposes as well, depending on the system architecture. However, 360M are free for application consumption.

The difference among VIRT, RES, and SHR in top output

VIRT stands for the virtual size of a process, which is the sum of memory it is actually using, memory it has mapped into itself (for instance the video card's RAM for the X server), files on disk that have been mapped into it (most notably shared libraries), and memory shared with other processes. VIRT represents how much memory the program is able to access at the present moment.

RES stands for the resident size, which is an accurate representation of how much actual physical memory a process is consuming. (This also corresponds directly to the %MEM column.) This will virtually always be less than the VIRT size (there are only very rare cases that they will be equal, and RES will never be more than VIRT).

SHR indicates how much of the VIRT size is actually sharable (memory or libraries). In the case of libraries, it does not necessarily mean that the entire library is resident. For example, if a program only uses a few functions in a library, the whole library is mapped and will be counted in VIRT and SHR, but only the parts of the library file containing the functions being used will actually be loaded in and be counted under RES.

The difference between buffers and cache

Buffers are allocated by various processes to use as input queues, etc. Most of the time, buffers are some processes' output, and they are file buffers. A simplistic explanation of buffers is that they allow processes to temporarily store input in memory until the process can deal with it.

Cache is typically frequently requested disk I/O. If multiple processes are accessing the same files, much of those files will be cached to improve performance (RAM being so much faster than hard drives), it's disk cache.

More to read : http://www.gentoo-wiki.info/FAQ_Linux_Memory_Management

http://forums.gentoo.org/viewtopic-t-175419-postdays-0-postorder-asc-start-0.html

optimize Tortoise SVN cache

2010-01-08T09:11:00.000+07:00

From : http://www.paraesthesia.com/archive/2007/09/26/optimize-tortoise-svn-cache-tsvncache.exe-disk-io.aspx

To optimize the disk usage...

Right-click on your desktop and select "TortoiseSVN -> Settings..."
In the tree view, find the "Look and Feel/Icon Overlays" branch.
In the "Exclude Paths" box, put C:\* to exclude the entire C drive. If you have more drives than that, exclude them all at the top level. Separate the values by newlines.
In the "Include Paths" box, list all of the locations you have working copies, separated by newlines. Again, this is easier if you keep all of your working copies in a specific folder or set of folders. Using my example, this is what I put in the "Include Paths" box:
C:\dev\* C:\Documents and Settings\tillig\My Documents\Visual Studio 2005\* C:\Documents and Settings\tillig\My Documents\Visual Studio Projects\*

And here's a screen shot:
Click OK to apply the changes.
Either reboot or open Task Manager and kill "TSVNCache.exe" so it restarts when needed. You have to restart it for these options to take effect.

After I did this, the icon overlays still worked great but the disk I/O went down to nearly nothing. YMMV.

Apache Segmentation fault

2010-01-06T16:24:00.000+07:00

Recently, I've found the message in
#/var/log/apache2/error_log
[notice] child pid 20295 exit signal Segmentation fault (11)

Getting core dump file : http://www.question-defense.com/2009/07/15/apache-notice-child-pid-27609-exit-signal-segmentation-fault-11

debugin apache : http://httpd.apache.org/dev/debugging.html

Apache document directive for coredump : http://httpd.apache.org/docs/2.0/mod/mpm_common.html

CoreDumpDirectory Directive

Description:	Directory where Apache attempts to switch before dumping core
Syntax:	`CoreDumpDirectory directory`
Default:	`See usage for the default setting`
Context:	server config
Status:	MPM
Module:	`beos`, `leader`, `mpm_winnt`, `perchild`, `prefork`, `threadpool`, `worker`

This controls the directory to which Apache attempts to switch before dumping core. The default is in the ServerRoot directory, however since this should not be writable by the user the server runs as, core dumps won't normally get written. If you want a core dump for debugging, you can use this directive to place it in a different location.

TCP/networking tunning

2010-01-05T10:16:00.000+07:00

Kernel TCP Networking tunning .
You can achieve a high network performance by adjusting some value to to the kernel
From http://www.gentoo-wiki.info/HOWTO_TCP_Tuning
http://blogs.techrepublic.com.com/opensource/?p=62
http://www.freebsd.org/doc/en/books/handbook/index.html

Variables to Change, and suggested Values

net.core.rmem_max="16777216": This setting changes the maximum network receive buffer size to 16777216 bytes.

net.core.wmem_max="16777216": The same thing for the send buffer

net.ipv4.tcp_rmem="4096 87380 16777216": This sets the kernel's minimum, default, and maximum TCP receive buffer sizes. You might be surprised, seeing the maximum of 16M, that many Unix-like operating systems still have a maximum of 256K!

net.ipv4.tcp_wmem="4096 65536 16777216": A similar setting for the TCP send buffer. Note that the default value is a little lower. Don't worry about this, the send buffer size is less important than the receive buffer.

net.ipv4.tcp_no_metrics_save=1

Moreover, There are a couple of kernel value you should adjust
tcp_max_syn_backlog
somaxconn

Hardisk upgrade/Replace

2010-01-04T17:29:00.001+07:00

เปลี่ยน ฮาร์ดดิส ให้ลิกนุกซ์
http://www.losurs.org/docs/LDP/HOWTO/Hard-Disk-Upgrade/index.html

Ubuntu handy configuration and command after installation + apache PHP

2009-12-08T13:37:00.000+07:00

Ubuntu

configuration after setup.

startup interface/fix ip on startup
> /etc/network/interfaces.
iface eth1 inet static
address 192.168.0.2
netmask 255.255.255.0
gateway 192.168.0.1

set name server
> /etc/resolv.conf
nameserver 204.11.126.131

install ssh for remote login
> openssh
sudo apt-get install openssh-client openssh-server

>adduser
sudo adduser username

>user / add/ super user (group admin) sodoer
sudo adduser xeon
sudo adduser xeon admin

>php5 + mysql
sudo apt-get install

php5
php5-cgi
php5-cli
php5-mysql
php5-memcache
php5-gd
php5-imagick

>apache
sudo apt-get install apache2-mpm-worker

>remove service from startup
update-rc.d -f apache2 remove

>add service
update-rc.d apache2 defaults

>more reading on services
http://www.debuntu.org/how-to-manage-services-with-update-rc.d

>NFS server
sudo apt-get install nfs-kernel-server
sudo /etc/init.d/nfs-kernel-server start

>/etc/exports
/ubuntu *(ro,sync,no_root_squash)
/home *(rw,sync,no_root_squash)

>package management
-install
#apt-get install packagename
-see update current version

# apt-cache policy apache2
apache2:
Installed: 2.2.8-1ubuntu0.3
Candidate: 2.2.8-1ubuntu0.14
Version table:
2.2.8-1ubuntu0.14 0
500 http://th.archive.ubuntu.com hardy-updates/main Packages
500 http://security.ubuntu.com hardy-security/main Packages
*** 2.2.8-1ubuntu0.3 0
100 /var/lib/dpkg/status
2.2.8-1 0
500 http://th.archive.ubuntu.com hardy/main Packages

Remark
*apache worker mpm not work with libapach2-php
using fcgid mod and php cgi

*NFS add host to /etc/hosts.allow
*snmpd change init opt /etc/default/snmpd
*all rp_filter need to be disable

How to Monitor/manager software raid

2009-12-08T13:02:00.000+07:00

# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sdb5[2] sda5[0]
9767424 blocks [2/1] [U_]
[=====>...............] recovery = 25.8% (2528512/9767424) finish=4.4min speed=27019K/sec

md2 : active raid1 sdb6[1]
19534912 blocks [2/1] [_U]

md3 : active raid1 sdb8[1] sda8[0]
44756992 blocks [2/2] [UU]

md0 : active raid1 sdb1[1] sda1[0]
64128 blocks [2/2] [UU]

# mdadm --detail /dev/md1
/dev/md1:
Version : 0.90
Creation Time : Sat Jul 9 21:46:05 2005
Raid Level : raid1
Array Size : 9767424 (9.31 GiB 10.00 GB)
Used Dev Size : 9767424 (9.31 GiB 10.00 GB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Tue Dec 8 12:59:37 2009
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

UUID : 5757d121:b65d61e8:0f50c7af:cbb83343
Events : 0.367292852

Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
1 0 0 1 removed

Rebuild raid :
# mdadm --add /dev/md1 /dev/sdb5
mdadm: re-added /dev/sdb5

Mark device as faulty
#mdadm --manage /dev/md0 --fail /dev/sda2

Remove device from array
#mdadm --remove /dev/md3 /dev/sb3

Stop & remove raid

*please unmount all file system before stop / remove raid.

#mdadm --stop /dev/md2

#mdadm --zero-superblock /dev/sda2

----

Reference :
http://tldp.org/HOWTO/Software-RAID-0.4x-HOWTO.html#toc4
http://tldp.org/HOWTO/Software-RAID-HOWTO-6.html
http://www.sanitarium.net/golug/Linux_Software_RAID.html

http://blogama.org/node/1825

How to : Software Raid migration

2009-12-08T12:42:00.000+07:00

Now use sfdisk to duplicate partitions from old drive to new drive:

#sfdisk -d /dev/sda | sfdisk /dev/sdb

Now use mdadm to create the raid arrays. We mark the first drive (sda) as "missing" so it doesn't wipe out our existing data:

#mdadm --create /dev/md0 --level 1 --raid-devices=2 missing /dev/sdb1

Now copy the remaining partitions. Be careful to match your md devices with your filesystem layout. This example is for my particular setup

mount /dev/md1 /mnt/var
cp -dpRx /var /mnt
... repeat for remaining folder.

Setting fstab, grub to boot from mdX

Reboot

At this point, you have all of your original data on the new drive, so we can safely add the original drive to the raid volume.

mdadm --add /dev/md0 /dev/sda1
mdadm --add /dev/md1 /dev/sda2
... repeat for remaining partitions.

Thanks to :
http://www.debian-administration.org/articles/238

How to : software raid GRUB + RAID

2009-12-08T12:30:00.000+07:00

How to : software raid GRUB + RAID

In the Software RAID howto it is mentioned that it is not known how
to set up GRUB to boot off RAID. Here is how I did it:
**Follow at your own risk. If you break something it's your fault.**
==================================================================
Configuration:
- /dev/hda (Pri. Master) 60 GB Seagate HDD (blank)
- /dev/hdc (Sec. Master) 60 GB Seagate HDD (blank)
- /dev/hdd (Sec. Slave) CDROM Drive

Setup Goals:
- /boot as /dev/md0: RAID1 of /dev/hda1 & /dev/hdc1 for redundancy
- / as /dev/md1: RAID1 of /dev/hda2 & /dev/hdc2 for redundancy
- swap*2 with equal priority: /dev/hda3 & /dev/hdc3 for more speed
- GRUB installed in boot records of /dev/hda and /dev/hdc so either
drive can fail but system still boot.

Tools:
- mdadm (http://www.cse.unsw.edu.au/~neilb/source/mdadm/)
(I used 1.2.0, but notice that as of 20030729 1.3.0 is available)

1. Boot up off rescue/installation CD/disk/HDD/whatever with mdadm
tools installed.

2. Partitioning of hard drives:
(I won't show you how to do this. See: # man fdisk ; man sfdisk )
But here's how stuff was arranged:

# sfdisk -l /dev/hda

Disk /dev/hda: 7297 cylinders, 255 heads, 63 sectors/track
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting
from 0

Device Boot Start End #cyls #blocks Id System
/dev/hda1 * 0+ 16 17- 136521 fd Linux raid autodetect
/dev/hda2 17 7219 7203 57858097+ fd Linux raid autodetect
/dev/hda3 7220 7296 77 618502+ 82 Linux swap
/dev/hda4 0 - 0 0 0 Empty
------------------------------------------------------------------
To make /dev/hdc the same:
------------------------------------------------------------------
# sfdisk -d /dev/hda | sfdisk /dev/hdc
------------------------------------------------------------------
/dev/hd[ac]1 for /dev/md0 for /boot
/dev/hd[ac]2 for /dev/md1 for /
/dev/hd[ac]3 for 2*swap
It is important to make md-to-be partitions with ID 0xFD, not 0x83.

3. Set up md devices: (both are RAID1 [mirrors])
------------------------------------------------------------------
# mdadm --create /dev/md0 --level=1 \
--raid-devices=2 /dev/hda1 /dev/hdc1
# mdadm --create /dev/md1 --level=1 \
--raid-devices=2 /dev/hda2 /dev/hdc2
------------------------------------------------------------------

• สร้าง metadevice ด้วยคำสั่ง cd /dev && MAKEDEV md
(หรือทำเอง mknod /dev/md1 b 9 1 )
• กำหนด raid ด้วยคำสั่ง
◦ mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
◦ mdadm --create --verbose /dev/md5 --level=1 --raid-devices=2 /dev/sda5 /dev/sdb5
◦ mdadm --create --verbose /dev/md6 --level=1 --raid-devices=2 /dev/sda6 /dev/sdb6

รอให้สร้าง raid เสร็จก่อนด้วย คำสั่ง cat /proc/mdstat

หมายเหตุ ถ้ามีการ create แล้วให้ใช้ mdadm --assemble /dev/md1 /dev/sda1 /dev/sdb1

4. Make filesystems:
------------------------------------------------------------------
# mke2fs /dev/md0
# mkreiserfs /dev/md1
# mkswap /dev/hda3
# mkswap /dev/hdc3
------------------------------------------------------------------

5. Install Your distribution:
Simply treat /dev/md0 and /dev/md1 as the partitions to install on,
and install the way your normally do.

Here're the relevant entries /etc/fstab for the newly created
partitions:
------------------------------------------------------------------
/dev/md0 /boot ext2 noauto,noatime 1 1
/dev/md1 / reiserfs noatime 1 1
/dev/hda3 none swap sw,pri=1 0 0
/dev/hdc3 none swap sw,pri=1 0 0
------------------------------------------------------------------
The "pri=1" for each of the swap partitions makes them the same
priority so the kernel does striping and that speeds up vm. Of
course, this means that if a disk dies then the system may crash,
needing a reboot. Perhaps it would be wiser to make hd[ac]3 a RAID1
array too, and just use /dev/md2 as swap.

6. Setting up GRUB: (assuming you've already installed it)
------------------------------------------------------------------
# grub
grub> root (hd0,0)
Filesystem type is ext2fs, partition type 0xfd

grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 16 sectors are
embedded.
succeeded
Running "install /boot/grub/stage1 (hd0) (hd0)1+16 p
(hd0,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded
Done.

grub> root (hd1,0)
Filesystem type is ext2fs, partition type 0xfd

grub> setup (hd1)
Checking if "/boot/grub/stage1" exists... yes
Checking if "/boot/grub/stage2" exists... yes
Checking if "/boot/grub/e2fs_stage1_5" exists... yes
Running "embed /boot/grub/e2fs_stage1_5 (hd1)"... 16 sectors are
embedded.
succeeded
Running "install /boot/grub/stage1 (hd1) (hd1)1+16 p
(hd1,0)/boot/grub/stage2 /boot/grub/grub.conf"... succeeded
Done.

grub> quit
------------------------------------------------------------------
Here is how /boot/grub/grub.conf is: (/dev/md0 mounted as /boot)
(Assuming kernel is installed as /boot/bzImage, and RAID1 support
compiled into the kernel).
------------------------------------------------------------------
# Boot automatically after 30 secs.
timeout 30

# By default, boot the first entry.
default 0

# Fallback to the second entry.
fallback 1

# For booting with disc 0 kernel
title GNU/Linux (hd0,0)
kernel (hd0,0)/bzImage root=/dev/md1

# For booting with disc 1 kernel, if (hd0,0)/bzImage is unreadable
title GNU/Linux (hd1,0)
kernel (hd1,0)/bzImage root=/dev/md1

http://www.linuxsa.org.au/mailing-list/2003-07/1270.html
http://en.gentoo-wiki.com/wiki/RAID/Software
http://www.geisterstunde.org/drupal/?q=raid1
http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml