Linux Find FC ID WWNN of a disk/LUN

If your server is connected to more than two SANs of the same type it is really hard to find what disk is on what SAN and how it is connected to your server. You can get the Fiber Channel addresses of the HBAs by typing the following commands:
# systool -c fc_host -v
Type the following command to determine the fibre channel target WWN:
# systool -c fc_transport -v

How to Set Up Master Slave Replication in MySQL

The following tutorial aims to provide you a simple step-by-step guide for setting up MySQL(Master-Slave) Replication in RHEL 6.x/5.x, CentOS 6.x/5.x and Fedora 17,16,15,14,13,12 using latest MySQL version. This guide is specially written for CentOS 6.3 Operating System, but also work with older version of Linux distributions with MySQL 5.x.

MySQL replication is a process that allows you to easily maintain multiple copies of a MySQL data by having them copied automatically from a master to a slave database. This can helpful for many reasons including facilating a backup for the data,a way to analyze it without using the main database, or simply as a means to scale out.

The MySQL Replication is very useful in terms of Data Security, Fail-over Solution, Database Backup from Slave, Analytics etc. We use the following things to carry the replication process. In your scenario it would be different.

This tutorial will cover a very simple example of mysql replication—one master will send information to a single slave. For the process to work you will need two IP addresses: one of the master server and and one of the slave. 


Master IP Address is: 172.24.0.1. - Master Database 

Slave IP Address is: 122.24.0.2. - Slave Database

Master and Slave are on the same LAN network.

Master allow remote MySQL connections on port 3306.

Step 1 —Configure the Master Database Server

Install a MySQL in Master Server

First, proceed with MySQL installation using YUM command. If you already have MySQL installation, you can skip this step.

#  yum install mysql-server mysql

Open up the mysql configuration file on the master server.

#  vi /etc/my.cnf

Add the following entries under [mysqld] section and don’t forget to replace  prakash  with database name that you would like to replicate on  Slave.

server-id = 1
binlog-do-db=prakash
relay-log = /var/lib/mysql/mysql-relay-bin
relay-log-index = /var/lib/mysql/mysql-relay-bin.index
log-error = /var/lib/mysql/mysql.err
master-info-file = /var/lib/mysql/mysql-master.info
relay-log-info-file = /var/lib/mysql/mysql-relay-log.info
log-bin = /var/lib/mysql/mysql-bin

Restart the MySQL service.

# /etc/init.d/mysqld restart

Login into MySQL as root user and create the slave user and grant privileges for replication. Replace slave_user with user and your_password with password.

#  mysql -u root -p

Please write down the File (mysql-bin.000001) and Position (107) numbers, we required these numbers later on Slave server. Next apply READ LOCK to databases to export all the database and master database information with mysqldump command.

#  mysqldump -u root -p --all-databases --master-data > /root/dbdump.db

Once you’ve dump all the databases, now again connect to mysql as root user and unlcok tables.

mysql> UNLOCK TABLES;

mysql> quit;

Upload the database dump file on Slave Server (172.24.0.2) using SCP command.

#  scp /root/dbdump.db root@172.24.0.2:/root/

That’s it we have successfully configured Master server

Step 2 —Configure the Slave Database Server

Configure Slave Server (172.24.0.2) for Replication.

#  yum install mysql-server mysql

Configure a MySQL in Slave Server

Open my.cnf configuration file with VI editor.

# vi /etc/my.cnf

Add the following entries under [mysqld] section and don’t forget to replace IP address of Master server, prakash with database name etc, that you would like to replicate with Master.

server-id = 2
master-host=172.24.0.1
master-connect-retry=60
master-user=slave_user
master-password=yourpassword
replicate-do-db=prakash
relay-log = /var/lib/mysql/mysql-relay-bin
relay-log-index = /var/lib/mysql/mysql-relay-bin.index
log-error = /var/lib/mysql/mysql.err
master-info-file = /var/lib/mysql/mysql-master.info
relay-log-info-file = /var/lib/mysql/mysql-relay-log.info
log-bin = /var/lib/mysql/mysql-bin

Restart the MySQL service.

#  /etc/init.d/mysqld restart

Login into MySQL as root user and stop the slave. Then tell the slave to where to look for Master log file, that we have write down on master with SHOW MASTER STATUS; command as File (mysql-bin.000001) and Position (107) numbers. You must change 172.24.0.1 to the IP address of the Master Server, and change the user and password accordingly.

#  mysql -u root -p

mysql> slave stop;
mysql> CHANGE MASTER TO MASTER_HOST='172.24.0.1', MASTER_USER='slave_user', MASTER_PASSWORD='yourpassword', MASTER_LOG_FILE='mysql-bin.000001', MASTER_LOG_POS=107;
mysql> slave start;
mysql> show slave status\G

If there is an issue in connecting, you can try starting slave with a command to skip over it:

SET GLOBAL SQL_SLAVE_SKIP_COUNTER = 1; SLAVE START;

Verifying MySQL Replication on Master and Slave Server

It’s really very important to know that the replication is working perfectly. On Master server create table and insert some values in it.

On Master Server

mysql> create database prakash;
Query OK, 1 row affected (0.00 sec)

mysql> use prakash;
Database changed

mysql> CREATE TABLE employee (c int);
Query OK, 0 rows affected (0.12 sec)

mysql> INSERT INTO employee (c) VALUES (1);
Query OK, 1 row affected (0.07 sec)

mysql> SELECT * FROM employee;
+------+
| c    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

mysql>

On Slave Server
mysql> use prakash;
Database changed
mysql> SELECT * FROM employee;
+------+
| c    |
+------+
|    1 |
+------+
1 row in set (0.00 sec)

mysql>

That’s it, finally you’ve configured MySQL Replication in a few simple steps.

If you have any further questions about the specific capabilities of MySQL, feel free to post your questions and I’ll be happy to answer them .

Memory use by which process Centos/RHEL/Fedora

# ps aux | awk '{if ($5 != 0 ) print $2,$5,$6,$11}' | sort -k2n

[root@microair ~]# ps aux | awk '{if ($5 != 0 ) print $2,$5,$6,$11}' | sort -k2n

PID VSZ RSS COMMAND

1960 4128 640 /usr/sbin/acpid

1706 6208 600 /sbin/portreserve

1781 6820 280 /usr/sbin/mcelog

1828 8404 368 /usr/sbin/fcoemon

396 11372 1408 /sbin/udevd

1815 12420 2636 /sbin/udevd

1816 12420 2408 /sbin/udevd

1803 13600 652 lldpad

2067 14912 596 tgtd

2068 14912 384 tgtd

2015 17856 1028 hald-addon-acpi:

1970 18156 1144 hald-runner

1767 19024 932 rpcbind

1 19408 1508 /sbin/init

2264 20088 408 dbus-launch

2014 20272 888 hald-addon-input:

2212 21544 392 /usr/sbin/atd

1941 23140 392 rpc.idmapd

1871 23396 1352 rpc.statd

1969 26524 5148 hald

2265 29648 912 /bin/dbus-daemon

1841 30080 1488 dbus-daemon

2158 32304 444 /usr/sbin/htcacheclean

144 36016 1352 /bin/plymouthd

1901 45020 488 /usr/sbin/wpa_supplicant

6667 49992 3956 /usr/libexec/polkit-1/polkitd

1856 55880 2320 /usr/sbin/modem-manager

2237 62312 416 /usr/sbin/certmonger

2082 66584 1228 /usr/sbin/sshd

2557 68876 1748 /usr/sbin/saslauthd

2559 68876 1664 /usr/sbin/saslauthd

2560 68876 1664 /usr/sbin/saslauthd

2561 68876 1732 /usr/sbin/saslauthd

2562 68876 1664 /usr/sbin/saslauthd

1852 80188 4416 NetworkManager

2108 93572 1688 /usr/sbin/exim

24965 100328 3984 sshd:

25145 106008 788 awk

2146 108116 804 abrt-dump-oops

2242 108516 1680 /bin/bash

1519 108520 1744 /bin/bash

24969 108520 1888 -bash

2134 110228 996 /usr/sbin/abrtd

25144 110244 1120 ps

2189 117256 1384 crond

2248 127460 16140 /usr/bin/Xorg

2268 131916 4084 /usr/libexec/gconfd-2

25146 155488 836 sort

2173 186424 5252 /usr/sbin/httpd

16817 186556 3684 /usr/sbin/httpd

631 186556 3684 /usr/sbin/httpd

632 186556 3804 /usr/sbin/httpd

633 186556 3756 /usr/sbin/httpd

634 186556 3684 /usr/sbin/httpd

635 186556 3784 /usr/sbin/httpd

636 186556 3684 /usr/sbin/httpd

637 186556 3684 /usr/sbin/httpd

638 186556 3848 /usr/sbin/httpd

1713 242988 1904 /sbin/rsyslogd

2253 251264 8452 /usr/bin/metacity

2251 270292 16956 /usr/bin/python2

2090 289524 196316 clamd

2047 381604 1652 automount

2246 412056 36420 /usr/bin/python2

6669 1031644 2480 /usr/sbin/console-kit-daemon

682 1106792 58480 /usr/bin/python

[root@microair ~]#

GPT(GUID Partition Table) problem during the linux installation on CentOS5.6

During the installation process of CentOS 5.6 one can face following error

Error: - "Your boot partition is on a disk using the GPT partitioning scheme but this machine cannot boot using GPT".

Reason:- This error mainly arises in the event where the total disk size is more than 2TB, irrespective of the primary partition disk.

Solution:-Enter the rescue mode and delete the MBR on the disk as below:-

#  dd if=/dev/zero of=/dev/sda bs=512 count=1

Reinstall the system again and it should work right.

How To Enable EPEL Repository in RHEL/CentOS 6/5

Why we use EPEL (Extra Packages for Enterprise Linux) repository ?
Provides lots of open source packages to install via Yum.
Epel repo is 100% open source and free to use.
It does not provide any core duplicate packages and no compatibility issues.
All epel packages are maintained by Fedora repo.

First, you need to download the file using Wget and then install it using RPM on your system to enable the EPEL repository. Use below links based on your Linux OS versions. (Make sure you must be root user).

For RHEL/CentOS 6 32-64 Bit
## RHEL/CentOS 6 32-Bit ##
# wget http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
# rpm -ivh epel-release-6-8.noarch.rpm
## RHEL/CentOS 6 64-Bit ##
# wget http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
# rpm -ivh epel-release-6-8.noarch.rpm
For RHEL/CentOS 5 32-64 Bit
## RHEL/CentOS 5 32-Bit ##
# wget http://download.fedoraproject.org/pub/epel/5/i386/epel-release-5-4.noarch.rpm
# rpm -ivh epel-release-5-4.noarch.rpm
## RHEL/CentOS 5 64-Bit ##
# wget http://download.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
# rpm -ivh epel-release-5-4.noarch.rpm
For RHEL/CentOS 4 32-64 Bit
## RHEL/CentOS 4 32-Bit ##
# wget http://download.fedoraproject.org/pub/epel/4/i386/epel-release-4-10.noarch.rpm
# rpm -ivh epel-release-4-10.noarch.rpm
## RHEL/CentOS 4 64-Bit ##
# wget http://download.fedoraproject.org/pub/epel/4/x86_64/epel-release-4-10.noarch.rpm
# rpm -ivh epel-release-4-10.noarch.rpm
How Do I Verify EPEL Repo?
# yum repolist
Loaded plugins: fastestmirror, priorities, refresh-packagekit, security
Loading mirror speeds from cached hostfile
epel/metalink                                            | 5.6 kB     00:00
 * base: centos.aol.in
 * epel: mirror.neu.edu.cn
 * extras: mirrors.digipower.vn
 * remi: fr2.rpmfind.net
 * rpmforge: mir01.syntis.net
 * updates: centos.aol.in
base                                                     | 3.7 kB     00:00
epel                                                     | 4.2 kB     00:03
epel/primary_db                                          | 5.8 MB     01:13
extras                                                   | 3.4 kB     00:00
rpmforge                                                 | 1.9 kB     00:00
updates                                                  | 3.4 kB     00:00
updates/primary_db                                       | 1.3 MB     00:29
repo id        repo name                                               status
base           CentOS-6 - Base                                          6,327+40
epel           Extra Packages for Enterprise Linux 6 - x86_64          9,712+518
extras         CentOS-6 - Extras                                              14
remi           Les RPM de remi pour Enterprise Linux 6 - x86_64        200+1,174
rpmforge       RHEL 6 - RPMforge.net - dag                              4,627+23
updates        CentOS-6 - Updates                                         254+43
repolist: 21,134
How Do I Use EPEL Repo?
You need to use YUM command for searching and installing packages. For example we search for Zabbix package using epel repo, lets see it is available or not under epel.
# yum --enablerepo=epel info zabbix
Sample Output
Available Packages
Name       : zabbix
Arch       : i386
Version    : 1.4.7
Release    : 1.el5
Size       : 1.7 M
Repo : epel
Summary    : Open-source monitoring solution for your IT infrastructure
URL        : http://www.zabbix.com/
License    : GPL
Description: ZABBIX is software that monitors numerous parameters of a network
Let’s install Zabbix package using epel repo option –enablerepo=epel switch.
# yum --enablerepo=epel install zabbix
Note: The epel configuration file is located under /etc/yum.repos.d/epel.repo.
This way you can install as many as high standard open source packages using EPEL repo