linux admin

DHCP client overwriting resolv.conf how to stop it on linux

2013-11-25T22:35:00.000-08:00

prevent resolv.conf updates only, the fastest way is to redefine the function to do nothing:
create flowing file

# cat /etc/dhclient-enter-hooks
make_resolv_conf() {
exit 0
}

Then save the file and ensure it is executable:

# chmod a+x /etc/dhclient-enter-hooks

Note that, as explained in the man page, the dhclient-script is not standard so if this configuration doesn’t work, please read the man page.

backup zenoss monittoring server in linux

2013-10-17T23:18:00.000-07:00

It is important to back your Zenoss data up. The default location it wants to dump the backup to is /tmp when you kick off a backup from the GUI. Most times this is fine, but every now and then you will run into /tmp filling up during a Zenoss backup. Here is how to use zenbackup from the command line and specify a specific backup directory.

Procedure 1. SSH into the server and su to the zenoss user.
2. Make a backup directory under $ZENHOME/backup/tmp if it doesn't exist already.

   zenoss@servername$ mkdir -p $ZENHOME/backup/tmp

3. Change directory into the $ZENHOME/backup/ and kick off the backup:

   zenoss@servername$ cd $ZENHOME/backup 
   zenoss@servername$ zenbackup --temp-dir=./tmp --file=Zenoss.Backup.July.12.2012
      INFO:zenbackup:Getting MySQL dbname, user, password from ZODB.
      2012-07-12 14:31:15,045 INFO zenbackup: Backing up events database.

zenoss-4 installation steps on linux server

2013-10-17T23:13:00.000-07:00

Here is getting Zenoss 4 up and running on CentOS 6 server. This guide was originally tested on a freshly patched CentOS 6.3 on August 12, 2012. Zenoss 4.2 was the current version of Zenoss.

two types of installation.
1.Auto Deploy

There is a nice auto install script available now - it is recommended you use this method on a new install. Example is for Zenoss 4.2.4 - always check the Zenoss site for new versions before starting.

# wget --no-check-certificate https://github.com/zenoss/core-autodeploy/tarball/4.2.4 -O auto.tar.gz
# tar xvf auto.tar.gz
# cd zenoss-core-autodeploy-*
# ./core-autodeploy.sh

Navigate to your server using a web browser:
http://server-ip:8080

2.Manual Way

Install EPEL repos.

rpm -ivh http://fedora.mirror.nexicom.net/epel/6/i386/epel-release-6-8.noarch.rpm
yum check-update

Disable SELinux (or configure it properly)
Disable iptables (or configure it - see Firewall Ports)

Procedure

1. Setup /home/zenoss directory.

useradd -m -d /home/zenoss -c "Zenoss User" zenoss 
chown zenoss:zenoss /home/zenoss

2. Remove conflicting packages

rpm -qa | grep -i matahari
rpm -qa | grep -i qpid
rpm -e --nodeps <package>

3. Remove Old Mysql - if any:

service mysql stop
rpm -qa | grep -i mysql 
rpm -e --nodeps <package>

4. Install / Update prerequisites:

Oracle Java → 1.6 Update 31 or later. 1.7 is NOT supported. The one in yum is 1.5.x. DO NOT use this version. Get 1.6.

wget http://javadl.sun.com/webapps/download/AutoDL?BundleId=65508
chmod +x jre-6u33-linux.x64-rpm.bin*
./jre-6u33-linux.x64-rpm.bin

Test with:

java -version
 java version "1.6.0_33"
 Java(TM) SE Runtime Environment (build 1.6.0_33-b04)
 Java HotSpot(TM) 64-Bit Server VM (build 20.8-b03, mixed mode)

RRDtool → 1.4.7 or later.

wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
yum -y --nogpgcheck localinstall rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm
vi /etc/yum.repos.d/rpmforge.repo and set enabled to 0. 
yum -y --enablerepo=rpmforge-extras install rrdtool-1.4.7

MySQL Community Server → 5.5.25 or later. Go to: http://dev.mysql.com/downloads/mysql → Select Oracle & Red Hat Linux 6
Download the following:

MySQL Client Utilities (currently MySQL-client-5.5.25a-1.el6.x86_64.rpm)
MySQL Server (currently MySQL-server-5.5.25a-1.el6.x86_64.rpm)
MySQL Shared (currently MySQL-shared-5.5.25a-1.el6.x86_64.rpm)

SCP them to your server.

yum -y --nogpgcheck localinstall MySQL*

DO NOT set mysql password.
Add the following to /etc/my.cnf (create if not already existing)

[mysqld]
max_allowed_packet=16M
innodb_buffer_pool_size=256M
innodb_additional_mem_pool_size=20M

Start up MySQL:

service mysql start
chkconfig --add mysql
chkconfig --level 2345 mysql on

If you see the following message when you start mysql:
A RANDOM PASSWORD HAS BEEN SET FOR THE MySQL root USER ! You will find that password in '/root/.mysql_secret'.
Then you will need to check the /root/.mysql_secret file for the current password. This appears to be fairly new behaviour (MySQL-server.x86_64 0:5.6.11-1.el6 )

Configure blank root password for the Zenoss installer (add the -p option to be prompted for password if you find that a password was generated for you during first mysql start):

mysqladmin -u root password ''
mysqladmin -u root -h localhost password ''

RabbitMQ → 2.8.4 or later.

wget http://www.rabbitmq.com/releases/rabbitmq-server/v2.8.4/rabbitmq-server-2.8.4-1.noarch.rpm
yum -y --nogpgcheck --enablerepo=epel localinstall rabbitmq-server-2.8.4-1.noarch.rpm
service rabbitmq-server start
chkconfig rabbitmq-server on

Nagios Plugins → 1.4.15 or later.

yum --enablerepo=epel install nagios-plugins

Erlang → (was installed during rabbitmq install if you didnt notice)

6. Download the latest version of ZenOSS to your server. Current in example is 4.2.

wget http://sourceforge.net/projects/zenoss/files/zenoss-4.2/zenoss-4.2.0/zenoss-4.2.0.el6.x86_64.rpm/download
yum -y --enablerepo=epel --nogpgcheck localinstall zenoss-4.2.0.el6.x86_64.rpm

7. Fire up the last few services:

service memcached start
chkconfig memcached on
service snmpd start
chkconfig snmpd on

8. Start up Zenoss - watch for errors or complaints.

service zenoss start

9. Hit the Zenoss WebGUI at <serverip>:8080 and finish walking through the wizard to complete the install.
10. Install Zenpacks:

wget http://sourceforge.net/projects/zenoss/files/zenpacks-4.2/zenpacks-4.2.0/zenoss-core-zenpacks-4.2.0.el6.x86_64.rpm
yum -y --nogpgcheck localinstall zenoss-core-zenpacks-4.2.0.el6.x86_64.rpm

11. Next fine tune your Zenoss installation. See Performance Tuning section.

Errors

Symlinking /usr to /local/usr or something of that nature breaks zenoss startup script.

service zenoss start
env: /etc/init.d/zenoss: No such file or directory

No skip to dashboard button off install.

Rebooted server. Fixed it - there were no errors during install when this happened.

How to install Cisco VPN client on ubuntu 13.04

2013-09-20T20:16:00.003-07:00

This tutorial explain how to install Cisco VPN client on ubuntu 13.04.On Ubuntu, you don't need to install the Cisco VPN Client: NetworkManager includes support for Cisco IPSec VPNs.
Procedure to follow
Install network-manager-vpnc using the following command from your terminal

sudo apt-get install network-manager-vpnc

This will install vpnc, network-manager-vpnc and network-manager-vpnc-gnome.
Now you need to left click on your network manager applet (Located in your notification area) And choose "Configure VPN..."

Now you need to click on Add

Choose VPN connection type as "Cisco Compatible VPN(VPNC)" and click on create

Enater your cisco VPN details under VPN tab

Now you need to select IPV4 Settings tab click on routes

Here you need to select "Use this connection only for resources on its network" click ok otherwise your traffic significantly slowed down

To start your new VPN, just follow the steps again, but instead of "Configure VPN", you'll click on the entry you created.

How to install bacula on centos6 step by step

2013-08-21T02:30:00.002-07:00

Bacula is an open source, network backup software, used to allow the System Administrators to manage backup, recovery and send the verification of data’s from any systems in any location across the network.

Install Bacula

In this how-to i am using MySQL for database, you can use either PostgreSQL or MySQL. My Backup server hostname and IP Address are “server.unixmen.local” and “192.168.1.101/24″ respectively. Change the values as per your scenario. This how-to was tested on CentOS 6.5, although it should work with RHEL, Scientific Linux 6.x versions too.

First let us install Bacual and mysql server using command:

# yum install bacula-director-mysql bacula-console bacula-client bacula-storage-mysql mysql-server mysql-devel -y

Start MySQL service and create root password for mysql.

Note: In this tutorial, i am using password as “centos” wherever i need to setup password . Define your own.

# service mysqld start
# chkconfig mysqld on
# mysqladmin -u root password centos

Next run the following commands one by one to create database and necessary tables for Bacula. Here “-u root” means that login with root account and “-p” means prompt for mysql root password i.e “centos” in my case.

# /usr/libexec/bacula/grant_mysql_privileges -u root -p
# /usr/libexec/bacula/create_mysql_database -u root -p
# /usr/libexec/bacula/make_mysql_tables -u root -p
# /usr/libexec/bacula/grant_bacula_privileges -u root -p

Now set bacula user password on MySQL. To do that, log in to your MySQL server with command:

# mysql -u root -p

And set password as shown below:

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 67
Server version: 5.5.35 MySQL Community Server (GPL) by Remi

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> UPDATE mysql.user SET password=PASSWORD("centos") WHERE user='bacula';
Query OK, 2 rows affected (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> FLUSH PRIVILEGES;
Query OK, 0 rows affected (0.01 sec)

mysql> exit
Bye

Now update all Bacula configuration files with new password and addresses as shown below.

Update Bacula Director

Edit file /etc/bacula/bacula-dir.conf,

# vi /etc/bacula/bacula-dir.conf

Update Bacula server hostname, bacula mysql user password, Bacula console password, Bacula file daemon password etc. Be mindful that you should use a fully qualified domain name for adding clients or simply use the IP address instead.

[...]
Director {                            # define myself
  Name = bacula-dir
  DIRport = 9101                # where we listen for UA connections
  QueryFile = "/usr/libexec/bacula/query.sql"
  WorkingDirectory = "/var/spool/bacula"
  PidDirectory = "/var/run"
  Maximum Concurrent Jobs = 1
  Password = "centos"         # Console password
  Messages = Daemon

[...]

# Client (File Services) to backup
Client {
  Name = bacula-fd
  Address = 192.168.1.101
  FDPort = 9102
  Catalog = MyCatalog
  Password = "centos"          # password for FileDaemon
  File Retention = 30 days            # 30 days
  Job Retention = 6 months            # six months
  AutoPrune = yes                     # Prune expired Jobs/Files
}

[...]
# Definition of file storage device
Storage {
  Name = File
# Do not use "localhost" here
  Address = 192.168.1.101                # N.B. Use a fully qualified name here
  SDPort = 9103
  Password = "centos"
  Device = FileStorage
  Media Type = File
}

[...]
# Generic catalog service
Catalog {
  Name = MyCatalog
# Uncomment the following line if you want the dbi driver
# dbdriver = "dbi:sqlite3"; dbaddress = 127.0.0.1; dbport =
  dbname = "bacula"; dbuser = "bacula"; dbpassword = "centos"
}

[...]

Console {
  Name = bacula-mon
  Password = "centos"
  CommandACL = status, .status
}

Update Bacula Console

Edit file /etc/bacula/bconsole.conf,

# vi /etc/bacula/bconsole.conf

Change the console password:

Director {
  Name = bacula-dir
  DIRport = 9101
  address = localhost
  Password = "centos"
}

Update Storage Daemon

Edit file /etc/bacula/bacula-sd.conf,

# vi /etc/bacula/bacula-sd.conf

Update the password, Find the red lines and delete them, do not uncomment them. Also set your Archive device path.

[...]
Director {
  Name = bacula-dir
  Password = "centos"
}

##Delete the following lines (Do not uncomment). As i installed centos minimal server, i don't have a GUI mode, so that i deleted the following section##

# Restricted Director, used by tray-monitor to get the
#   status of the storage daemon
#
Director {
  Name = bacula-mon
  Password = "@@MON_SD_PASSWORD@@"
  Monitor = yes
}

[...]

Device {
  Name = FileStorage
  Media Type = File
  Archive Device = /mybackup
  LabelMedia = yes;                   # lets Bacula label unlabeled media
  Random Access = Yes;
  AutomaticMount = yes;               # when device opened, read it
  RemovableMedia = no;
  AlwaysOpen = no;
}
[...]

Update file daemon

Edit file /etc/bacula/bacula-fd.conf,

# vi /etc/bacula/bacula-fd.conf

Update the password and delete the lines shown in red colour.

# List Directors who are permitted to contact this File daemon
#
Director {
Name = bacula-dir
Password = "centos"
}

##Delete (do not uncomment) these lines if you only using CUI mode in Backup server ##

# Restricted Director, used by tray-monitor to get the
#   status of the storage daemon
#
Director {
Name = bacula-mon
Password = "@@MON_SD_PASSWORD@@"
Monitor = yes
}

As i mentioned in the above configuration, my archive device path is “/mybackup”. So let me create a directory called “mybackup”.

# mkdir /mybackup
# chown bacula /mybackup

Now we finished all passwords and address modifications. Next restart all bacula daemons and make them to start automatically on every reboot.

# service bacula-dir start
# service bacula-fd start
# service bacula-sd start
# chkconfig bacula-dir on
# chkconfig bacula-fd on
# chkconfig bacula-sd on

Bacula has been successfully installed and configured. You can now add clients, jobs and volumes by updating the bacula config files. Alternatively you can use webmin to make the work more simple. It is quite easier then updating the config files manually.

Manage Bacula With Webmin

Webmin is a web-based interface for system administration for Unix. Using any modern web browser, you can setup user accounts, Apache, DNS, file sharing and much more.

# wget http://sourceforge.net/projects/webadmin/files/webmin/1.660/webmin-1.660-1.noarch.rpm
# rpm -Uvh webmin-1.660-1.noarch.rpm
# service webmin start
# chkconfig webmin on

Adjust Firewall/Router

If you want to access the bacula server through from a remote system, allow the webmin port “10000″ and bacula ports “9101″, “9102″, “9103″ through your firewall or router.

Edit file /etc/sysconfig/iptables,

# vi /etc/sysconfig/iptables

Add these following lines in your iptables config file.

[...]
-A INPUT -m state --state NEW -m tcp -p tcp --dport 10000 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 9101 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 9102 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 9103 -j ACCEPT
[...]

Restart iptables:

# service iptables restart

Access Webmin

Now you can login through webmin by “//http://server-ip-address:10000″ or “http://domain-name:10000/”.

You will find the Bacula Backup System in the left pane of webmin console under System -> Bacula Backup System. If not is found there, try in the “unused modules” section.

Click on the “Bacula Backup System” link. Initially the Bacula server won’t start automatically. To start Bacula server click on “Module Configuration” link on the right of the “Bacula Backup System” page.

Select the database i.e “MySQL” in this case and enter the bacula database user password. Then click save.

Now you will get the window like shown below.

That’s it. From here you can add Backup clients, Volumes and schedule jobs etc.

install RHEL EPEL repository on Centos 5.x or 6.x

2013-08-20T23:38:00.000-07:00

The following article will describe how to configure a CentOS 5.x-based or Centos 6.x-based system to use Fedora Epel repos and third party remi package repos. These package repositories are not officially supported by CentOS, but they provide much more current versions of popular applications like PHP or MYSQL.

Install the extra repositories

The first step requires downloading some RPM files that contain the additional YUM repository definitions. The instructions below point to the 64-bit versions that work with our Cloud Server instances.

Centos 5.x

wget http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-5.rpm
sudo rpm -Uvh remi-release-5*.rpm epel-release-5*.rpm

Centos 6.x

wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
wget http://rpms.famillecollet.com/enterprise/remi-release-6.rpm
sudo rpm -Uvh remi-release-6*.rpm epel-release-6*.rpm

Once installed you should see some additional repo definitions under the /etc/yum.repos.d directory.

$ ls -1 /etc/yum.repos.d/epel* /etc/yum.repos.d/remi.repo
/etc/yum.repos.d/epel.repo
/etc/yum.repos.d/epel-testing.repo
/etc/yum.repos.d/remi.repo

Enable the remi repository

The remi repository provides a variety of up-to-date packages that are useful or are a requirement for many popular web-based services. That means it generally is not a bad idea to enable the remi repositories by default.
First, open the /etc/yum.repos.d/remi.repo repository file using a text editor of your choice:

sudo vim /etc/yum.repos.d/remi.repo

Edit the [remi] portion of the file so that the enabled option is set to 1. This will enable the remi repository.

name=Les RPM de remi pour Enterprise Linux $releasever - $basearch
#baseurl=http://rpms.famillecollet.com/enterprise/$releasever/remi/$basearch/
mirrorlist=http://rpms.famillecollet.com/enterprise/$releasever/remi/mirror
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-remi
failovermethod=priority

You will now have a larger array of yum repositories from which to install.

Configure linux dns server step by step guide (Master Slave DNS Server)

2013-08-18T23:45:00.002-07:00

The DNS ( Domain Name System ) is a distributed system, used for transalate domain names to IP and vice a versa. This article will help you to How to Setup Master Slave DNS Server on CentOS 6 and RHEL Systems.

Network Scenario for this Setup:

Master DNS Server IP: 10.3.150.14 ( ns1.linuxadmin.net )
Slave DNS Server IP: 10.3.150.15 ( ns2.linuxadmin.net )
Domain Name : demolinuxadmin.net ( For Testing Purpose )
Domain IP : 10.3.150.16 ( For Testing Purpose )

Step 1: Install Required RPMS ( at Master and Slave Both )

Install bind packages at both Master and Slave dns servers using following commands.

# yum install bind bind-chroot

Step 2: Setup Master (NS1) DNS Server

There are two types of configuration files in DNS.

One is main dns configuration files named “named.conf”
Another type of configuration file are called zone file. Which is individually created for all domains. named.conf keeps an entry for all zone files.

2.1 Configure named.conf using below configuration

# vim /var/named/chroot/etc/named.conf

Content of named.conf:

// /var/named/chroot/etc/named.conf
options {
        listen-on port 53 { 127.0.0.1; 192.168.1.0/24; };
        listen-on-v6 port 53 { ::1; };
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { localhost; 192.168.1.0/24; };
        recursion yes;

        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};

zone "demolinuxadmin.net" IN {
        type master;
        file "/var/named/demolinuxadmin.net.db";
        allow-update { none; };
};

include "/etc/named.rfc1912.zones";

2.2 Create a zone file for you domain “demolinuxadmin.net”

# vim /var/named/chroot/var/named/demolinuxadmin.net.db

Content of zone file:

; Zone file for demolinuxadmin.net
$TTL 14400
@      86400    IN      SOA     ns1.linuxadmin.net. webmaster.linuxadmin.net. (
                3215040200      ; serial, todays date+todays
                86400           ; refresh, seconds
                7200            ; retry, seconds
                3600000         ; expire, seconds
                86400 )         ; minimum, seconds

demolinuxadmin.net. 86400 IN NS ns1.linuxadmin.net.
demolinuxadmin.net. 86400 IN NS ns2.linuxadmin.net.
demolinuxadmin.net. IN A 10.3.150.16
demolinuxadmin.net. IN MX 0 demolinuxadmin.net.
mail IN CNAME demolinuxadmin.net.
www IN CNAME demolinuxadmin.net.

2.3 Add more domains in dns server.
To add more domains in dns, create zone files individually for all domain as above. After that add any entry for all zones in named.conf like below. Change demolinuxadmin.net with your domain name.

zone "demolinuxadmin.net" IN {
        type master;
        file "/var/named/demolinuxadmin.net.db";
        allow-update { none; };
};

Step 2.4: Start named service .
Start named (bind) service using following command and setup auto start on system boot.

# /etc/init.d/named restart
# chkconfig named on

Step 3: Setup Slave (NS2) DNS Server

At slave dns server you need to update named.conf file only. All zone files will automatically synced from master dns server. Any changes done on Master will reflect on slave after a specified time interval.

3.1 Configure named.conf using below configuration

# vim /var/named/chroot/etc/named.conf

Content of named.conf:

// /var/named/chroot/etc/named.conf
options {
        listen-on port 53 { 127.0.0.1; 192.168.1.0/24; };
        listen-on-v6 port 53 { ::1; };
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { localhost; 192.168.1.0/24; };
        recursion yes;

        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";
};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};

zone "demolinuxadmin.net" IN {
        type slave;
        file "slaves/demolinuxadmin.net.db";
        masters { 10.3.150.14; };
};

include "/etc/named.rfc1912.zones";

Step 3.2: Start named Service
Start named (bind) service using below command.

# /etc/init.d/named restart
# chkconfig named on

After restarting named service, Check zone files on slave dns server at /var/named/chroot/var/named/slaves/.

Step 4: Finally Test Your DNS Setup.

Query to your Master and Slave DNS Server directly using following commands, You will get the same resonse from both servers.
Syntax: nslookup <domainname.com> <dns server name/ip>

Query to Master DNS Server:

# nslookup demolinuxadmin.net 10.3.150.14

Server:         10.3.150.14
Address:        10.3.150.14#53

Name:   demolinuxadmin.net
Address: 10.3.150.16

Query to Slave DNS Server:

# nslookup demolinuxadmin.net 10.3.150.15

Server:         10.3.150.15
Address:        10.3.150.15#53

Name:   demolinuxadmin.net
Address: 10.3.150.16

Above outputs is showing that dns server has successfully resolved domain demolinuxadmin.net from master and slave dns servers.

Configration of SVN Server on CentOS/RHEL 5/6, Fedora (Subversion)

2013-08-18T23:26:00.001-07:00

Subversion (SVN) is an open source version control system. It helps you keep track of a collection of files and folders. Any time you change, add or delete a file or folder that you manage with Subversion, you commit these changes to your Subversion repository, which creates a new revision in your repository reflecting these changes. You can always go back, look at and get the contents of previous revisions.

This article will help you for step by step installing SVN server.

Step 1: Install Apache/PHP Packages

You need to install apache web server to access svn server using http urls.

# yum install httpd php php-devel php-cli php-pear

Start Apache web server and setup to auto start on system boot

# service httpd restart
# chkconfig httpd on

Step 2: Install Subversion Using Yum

Use following command to install subversion and mod_dav_svn packages.

# yum install mod_dav_svn subversion

Step 3: Configure Subversion with Apache

Subversion creates an apache configuration file, we just need to make necessary changes to it.

# vim /etc/httpd/conf.d/subversion.conf
LoadModule dav_svn_module     modules/mod_dav_svn.so
LoadModule authz_svn_module   modules/mod_authz_svn.so

<Location /svn>
   DAV svn
   SVNParentPath /var/www/svn
   AuthType Basic
   AuthName "Subversion User Authentication "
   AuthUserFile /etc/svn-users
   Require valid-user
</Location>

Step 4: Create First SVN Repository

Use following command to create your fist svn repository.

# cd /var/www/svn
# svnadmin create svnrepo
# chown -R apache.apache svnrepo

Step 5: Add SVN Users

Following commands will add two users for svn. It will prompt for users password to be assigned.

# htpasswd -cm /etc/svn-users user1
# htpasswd -m /etc/svn-users user2

Step 6: Access Your Repository in Browser

Use http urls to access your repository in browser. It will prompt for authentication. Use login credentials created in Step 5.

http://svn.linuxadmin.in/svn/svnrepo/

enter user name and password in brower.

Step 5: Adding Files to Your Repository

This step is for testing that repository is working properly. Use following commands to add few files to your svn repository.

# svn co http://svn.linuxadmin.in/svn/svnrepo/
# cd svnrepo
# touch file1.txt file2.txt
# svn add file1.txt file2.txt
# svn ci file1.txt file2.txt -m "initial commit"

Again checkhttp://svn.linuxadmin.in/svn/svnrepo/ url in browser. You will see your new files there.

BusyBox v1.18.5 (Ubuntu 1:1.18.5-1ubuntu4) built-in shell (ash) Enter 'help' for a list of built-in commands. (initramfs)

2013-07-31T02:25:00.003-07:00

1. Boot from Ubuntu Alternate

As ext3 and ext4 are quite robust, it should be repaired quite easily with a tool like fsck run from a live CD. The main constraint is that the live CD should allow not to mount the root filesystem of the host computer.
After a quick search, I realised that Ubuntu Alternate allows to do that.
So, first step is to download Ubuntu Precise PC (Intel x86) alternate install CD and to :

either write the ISO file to a CD-ROM
or generate a USB key with unetbootin or startup disk boot creator under Ubuntu

Next step is to boot from your CD-ROM or USB Key on your computer with a corrupted filesystem.
From the main menu, select the last choice Rescue a broken system.

After selecting your keyboard, follow all the steps till the Filesystem Mount menu.
Select the last menu Do not use root file system.
Next, select the menu Execute a shell in the installer environment.
You will get a busybox prompt.

2. Repair Corrupted Root Filesystem

From the prompt, type :

# fdisk -l
Périphérique Amorce Début Fin Blocs Id Système
/dev/sda1 * 1 3647 29294496 83 Linux
/dev/sda2 3648 121601 947465505 5 Etendue
/dev/sdb3 120582 121601 8193150 82 Linux swap / Solaris

Here, the root filesystem is the first one : /dev/sda1. It is of Linux type.
To repair it, we just need to run fsck with the force option :

# fsck.ext3 -f /dev/sda1

At the end of the fdisk command, your filesystem should be repaired.
At this stage, you should already be able to succesfully reboot your computer.

3. Search your Hard Disk for Bad Sectors

Please note that this step is not compulsory at all.
In case you feel that your hard disk may be in an unhealty condition, you may want to search for bad sectors.
To search for bad sectors on your hard disk, you can need to run fdisk with the check option.

# fsck.ext3 -c /dev/sda1

This action may take a very long time to complete.

Once you root filesystem has been repaired, you just need to reboot ... and your Ubuntu system should be back to life !

Error when installing rabbitMQ server on centos5.6

2013-07-04T21:14:00.002-07:00

Best way is to tell rabbitmq to not to look for hostname.
You can do that using rabbitmq config file.
edit config, create it if it does not exist

vim /etc/rabbitmq/rabbitmq.conf
vim /etc/rabbitmq/rabbitmq-env.conf (in later versions of RabbitMQ)

Add following entries:

NODENAME=rabbit@localhost 
NODE_IP_ADDRESS=127.0.0.1

Remove Control M' Characters (^M) with Unix and Linux commands

2013-06-19T22:34:00.005-07:00

Using dos2unix command
dos2unix ORIG_FILENAME TEMP_FILENAME
mv TEMP_FILENAME ORIG_FILENAME
IMP NOTE: use dos2ux command if you are using HPUX
use dos2unix command if you are using LINUX
Using sed command
sed ‘s/^M//g’ ORIG_FILENAME > TEMP_FILENAME
mv TEMP_FILENAME ORIG_FILENAME
IMP NOTE: To get ^M in UNIX (Hold control key and then press v and m character).
Using vi Editor
ESCAPE :%s/^M//g ENTER
IMP NOTE: To get ^M in UNIX (Hold control key and then press v and m character).

EXP-00008: ORACLE error 904 encountered ORA-00904: "IFREEPOOL": invalid identifier

2013-06-14T22:21:00.003-07:00

Applies to:

Oracle Server - Enterprise Edition - Version: 10.2.0.3 to 10.2.0.4
This problem can occur on any platform.

Symptoms

Export reports ORA-00904 "IFREEPOOL": invalid identifier while using a version 10.2.0.4.0 export client to export from a 10.2.0.3.0 database.

Export Log File 
--------------- 
. . Export der Tabelle CALCULATEDFIELDS 
EXP-00008: ORACLE-Fehler 904 aufgetreten 
ORA-00904: "IFREEPOOL": invalid identifier

Cause

This is an expected behaviour.
The version of the Export utility must be equal to the earliest version of the source or target database. Here, the source database is based on release 10.2.0.3.0 and hence the export client has to be a version 10.2.0.3.0.
An export client of a later release cannot be used for the following reasons:

The export utility is continuously accessing dictionary objects such as SYS.EXU9LOB.
Starting with release 10.2.0.4.0 we introduced additional columns such as 'IFREEPOOL'. This column is not available in 10.2.0.3.0 and hence the client cannot handle this and ORA-00904/EXP-00008 appears.

Client 10.2.0.4.0 is not supported to export from 10.2.0.3.0 database.

Solution

The version of the Export utility must be equal to the earliest version of the source or target database.

RCS Basics ( Building a Simple Local RCS Repository)

2013-06-10T21:12:00.003-07:00

Create a subdirectory named RCS in your private working directory:

$ mkdir RCS

Check in files you want to add to the repository (this moves them into the RCS repository):

$ ci foo.c
$ ci blah.c

Check out file you want to work on (-l locks the file so only you can check it out to modify it):

$ co -l foo.c
$ co -l blah.c

Subsequent check-ins create a new version of the file, and you can revert to older versions by using the -r flag with co (see the man pages for co and ci for more details).
Some other commands (and see man page for rcsintro):

$ rcsdiff foo.c    ( diff between foo.c and latest version in repository)
$ rlog  foo.c      ( see the log messages associated with commits to foo.c)

Run Multiple Apache On Single Host

2013-06-06T22:14:00.001-07:00

In this blog post we are going to discuss on how to run two Apache instances on single Linux host.

We already have one Apache installed and serving the static content. The Apache is installed at the following location:

/etc/httpd

Let`s copy the directory /etc/httpd to /etc/avon_httpd

  cp -pr /etc/httpd  /etc/avon_httpd

Now, as we have copied the old Apache web-server to a new location /etc/avon_httpd. We need to make the changes to the configuration file.

cd /etc/avon_httpd and open the httpd.conf file in a vi editor and make changes to the following values:

ServerRoot “/etc/httpd” TO ServerRoot “/etc/avon_httpd”

Listen 80 TO Listen 82

PidFile run/httpd.pid TO PidFile run/avon_httpd.pid

Save and close the file.

In the next step we are going to copy the RHEL httpd configuration file.

 cp -pr /etc/sysconfig/httpd  /etc/sysconfig/avon_httpd

In the next step, let`s copy the script /etc/init.d/httpd TO /etc/init.d/avon_httpd

 cp -pr  /etc/init.d/httpd   /etc/init.d/avon_httpd

In this step, Link the /usr/sbin/httpd TO /usr/sbin/avon_httpd

 ln -s  /usr/sbin/httpd   /usr/sbin/avon_httpd

Open the file avon_httpd under /etc/sysconfig/ and enter the following lines:

## CUSTOM SETTINGS ##
HTTPD=/usr/sbin/avon_httpd
OPTIONS="-f /etc/avon_httpd/conf/httpd.conf"
LOCKFILE=/var/lock/subsys/avon_httpd
PIDFILE=/var/run/avon_httpd.pid

Open the avon_httpd file under /etc/init.d and replace httpd to avon_httpd.

The command used to start/stop httpd and avon_httpd service could be:

/etc/init.d/httpd {start|stop|restart|condrestart|reload|status|fullstatus|graceful|help|configtest}
/etc/init.d/avon_httpd {start|stop|restart|condrestart|reload|status|fullstatus|graceful|help|configtest}

Ubuntu 12.10- No Unity GUI(missing sidebar in ubuntu 12.10)

2013-06-05T21:43:00.001-07:00

Install unity Package first

sudo apt-get install unity

To see what will happen.

For now, it might be easier for you to use some other DE, such as Gnome-shell.

sudo apt-get install gnome-shell

Then restart Your system .

SQLite3 SQL Commands Explained with Examples

2013-05-19T22:23:00.001-07:00

SQLite3 is very lightweight SQL database which focuses on simplicity more than anything else. This is a self-contained serverless database engine, which is very simple to install and use.

While most of the commands in the SQLite are similar to SQL commands of other datbases like MySQL and ORACLE, there are some SQLite SQL commands that are different.

This article explains all the basic SQL commands that you need to know to use the SQLite database effectively.

If you don’t have sqlite installed, execute “yum install sqlite” to install it. You can also install SQLite database from source to get the latest version.

1. Create a SQLite Database (and a Table)

First, let us understand how create a SQLite database with couple of tables, populate some data, and view those records.

The following example creates a database called company.db. This also creates an employee table with 3 columns (id, name and title), and a department table in the company.db database. We’ve purposefully missed the deptid column in the employee table. We’ll see how to add that later.

# sqlite3 company.db
sqlite> create table employee(empid integer,name varchar(20),title varchar(10));
sqlite> create table department(deptid integer,name varchar(20),location varchar(10));
sqlite> .quit

Note: To exit from the SQLite commandline “sqlite>” prompt, type “.quit” as shown above.

A SQLite database is nothing but a file that gets created under your current directory as shown below.

# ls -l company.db
-rw-r--r--. 1 root root 3072 Sep 19 11:21 company.db

2. Insert Records

The following example populates both employee and department table with some sample records.

You can execute all the insert statements from the sqlite command line, or you can add those commands into a file and execute the file as shown below.

First, create a insert-data.sql file as shown below.

# vi insert-data.sql
insert into employee values(101,'John Smith','CEO');
insert into employee values(102,'Raj Reddy','Sysadmin');
insert into employee values(103,'Jason Bourne','Developer');
insert into employee values(104,'Jane Smith','Sale Manager');
insert into employee values(105,'Rita Patel','DBA');

insert into department values(1,'Sales','Los Angeles');
insert into department values(2,'Technology','San Jose');
insert into department values(3,'Marketing','Los Angeles');

The following will execute all the commands from the insert-data.sql in the company.db database

# sqlite3 company.db < insert-data.sql

3. View Records

Once you’ve inserted the records, view it using select command as shown below.

# sqlite3 company.db
sqlite> select * from employee;
101|John Smith|CEO
102|Raj Reddy|Sysadmin
103|Jason Bourne|Developer
104|Jane Smith|Sale Manager
105|Rita Patel|DBA

sqlite> select * from department;
1|Sales|Los Angeles
2|Technology|San Jose
3|Marketing|Los Angeles

4. Rename a Table

The following example renames department table to deptusing the alter table command.

sqlite> alter table department rename to dept;

5. Add a Column to an Existing Table

The following examples adds deptid column to the existing employee table;

sqlite> alter table employee add column deptid integer;

Update the department id for the employees using update command as shown below.

update employee set deptid=3 where empid=101;
update employee set deptid=2 where empid=102;
update employee set deptid=2 where empid=103;
update employee set deptid=1 where empid=104;
update employee set deptid=2 where empid=105;

Verify that the deptid is updated properly in the employee table.

sqlite> select * from employee;
101|John Smith|CEO|3
102|Raj Reddy|Sysadmin|2
103|Jason Bourne|Developer|2
104|Jane Smith|Sale Manager|1
105|Rita Patel|DBA|2

6. View all Tables in a Database

Execute the following command to view all the tables in the current database. The folowing example shows that there are two tables in the current database.

sqlite> .tables
dept      employee

7. Create an Index

The following example creates an unique index called empidx on the empid field of employee table.

sqlite> create unique index empidx on employee(empid);

Once an unique index is created, if you try to add another record with an empid that already exists, you’ll get an error as shown below.

sqlite> insert into employee values (101,'James Bond','Secret Agent',1);
Error: constraint failed

8. Create a Trigger

For this example, first add a datecolumn called “updatedon” on employee table.

sqlite> alter table employee add column updatedon date;

Next, create a file that has the trigger definition. The following trigger will update the “updatedon” date column with the current timestamp whenever you perform an update on this table.

# vi employee_update_trg.sql
create trigger employee_update_trg after update on employee
begin
  update employee set updatedon = datetime('NOW') where rowid = new.rowid;
end;

Create the trigger on the company.db database as shown below.

# sqlite3 company.db < employee_update_trg.sql

Now anytime you update any record in the employee table, the “updatedon” date column will be updated with the current timestamp as shown below. The following example updates the “updatedon” timestamp for empid 104 through trigger.

# sqlite3 company.db
sqlite> update employee set title='Sales Manager' where empid=104;

sqlite> select * from employee;
101|John Smith|CEO|3|
102|Raj Reddy|Sysadmin|2|
103|Jason Bourne|Developer|2|
104|Jane Smith|Sales Manager|1|2012-09-15 18:29:28
105|Rita Patel|DBA|2|

9. Create a View

The following example creates a view called “empdept”, which combines fields from both employee and dept table.

sqlite> create view empdept as select empid, e.name, title, d.name, location from employee e, dept d where e.deptid = d.deptid;

Now you can execute select command on this view just like a regular table.

sqlite> select * from empdept;
101|John Smith|CEO|Marketing|Los Angeles
102|Raj Reddy|Sysadmin|Technology|San Jose
103|Jason Bourne|Developer|Technology|San Jose
104|Jane Smith|Sales Manager|Sales|Los Angeles
105|Rita Patel|DBA|Technology|San Jose

After creating a view, if you execute .tables, you’ll also see the view name along with the tables.

sqlite> .tables
dept      empdept   employee

10. SQLite Savepoint, Rollback, Commit

Currently dept table has the following 3 records.

sqlite> select * from dept;
1|Sales|Los Angeles
2|Technology|San Jose
3|Marketing|Los Angeles

Now, create a savepoint called “major”, and perform some transactions on the dept table. As you see below, we’ve added two records, deleted one record, after creating a savepoint called “major”.

sqlite> savepoint major;
sqlite> insert into dept values(4,'HR','Los Angeles');
sqlite> insert into dept values(5,'Finance','San Jose');
sqlite> delete from dept where deptid=1;
sqlite> select * from dept;
2|Technology|San Jose
3|Marketing|Los Angeles
4|HR|Los Angeles
5|Finance|San Jose

Now for some reason, if we don’t want the above transactions, we can rollback the changes to a particular savepoint. In this example, we are rolling back all the changes we’ve made after the “major” savepoint.

sqlite> rollback to savepoint major;
sqlite> select * from dept;
1|Sales|Los Angeles
2|Technology|San Jose
3|Marketing|Los Angeles

If you don’t want your savepoints anymore, you can erase it using release command.

sqlite> release savepoint major;

11. Additional Date Functions

By default, the date columns values displayed in UTC time. To display in the local time, use the datetime command on the date column as shown below.

sqlite> select empid,datetime(updatedon,'localtime') from employee;
104|2012-09-15 11:29:28

You can also use strftime to display the date column in various output.

sqlite> select empid,strftime('%d-%m-%Y %w %W',updatedon) from employee;
104|19-09-2012 3 38

The following are the possible modifers you can use in the strftime function.

%d day of month: 00
%f fractional seconds: SS.SSS
%H hour: 00-24
%j day of year: 001-366
%J Julian day number
%m month: 01-12
%M minute: 00-59
%s seconds since 1970-01-01
%S seconds: 00-59
%w day of week 0-6 with Sunday==0
%W week of year: 00-53
%Y year: 0000-9999
%% %

12. Dropping Objects

You can drop all the above created objects using the appropriate drop command as shown below.

Since we are dropping objects for testing purpose, copy the company.db to a test.db and try these commands on the test.db

# cp company.db test.db

# sqlite3 test.db
sqlite> .tables
dept      empdept   employee

sqlite> drop index empidx;
sqlite> drop trigger employee_update_trg;
sqlite> drop view empdept;
sqlite> drop table employee;
sqlite> drop table dept;

All the tables and views from the test.db are now deleted.

sqlite> .tables
sqlite>

Note: When you drop a table all the indexes and triggers for that table are also dropped.

13. Operators

The following are the possible operators you can use in SQL statements.

||
* / %
+ -
<< >> & |
< >=
= == != <> IS IS NOT IN LIKE GLOB MATCH REGEXP
AND OR

For example:

sqlite> select * from employee where empid >= 102 and empid  select * from dept where location like 'Los%';
1|Sales|Los Angeles
3|Marketing|Los Angeles

14. Explain Query Plan

Execute “explain query plan”, to get information about the table that is getting used in a query or view. This is very helpful when you are debugging a complex query with multiple joins on several tables.

sqlite> explain query plan select * from empdept;
0|0|TABLE employee AS e
1|1|TABLE dept AS d

For a detailed trace, just execute “explain” followed by the query to get more performance data on the query. This is helpful for debugging purpose when the query is slow.

sqlite> explain select empid,strftime('%d-%m-%Y %w %W',updatedon) from employee;
0|Trace|0|0|0||00|
1|Goto|0|12|0||00|
2|OpenRead|0|2|0|4|00|
3|Rewind|0|10|0||00|
4|Column|0|0|1||00|
5|String8|0|3|0|%d-%m-%Y %w %W|00|
6|Column|0|3|4||00|
7|Function|1|3|2|strftime(-1)|02|
8|ResultRow|1|2|0||00|
9|Next|0|4|0||01|
10|Close|0|0|0||00|
11|Halt|0|0|0||00|
12|Transaction|0|0|0||00|
13|VerifyCookie|0|19|0||00|
14|TableLock|0|2|0|employee|00|
15|Goto|0|2|0||00|

15. Attach and Detach Database

When you have multiple database, you can use attach command to execute queries across database.

For example, if you have two database that has the same table name with different data, you can create a union query across the database to view the combined records as explained below.

In this example, we have two company database (company1.db and company2.db). From the sqlite prompt, attach both these database by giving alias as c1 and c2 as shown below.

# sqlite3
sqlite> attach database 'company1.db' as c1;
sqlite> attach database 'company2.db' as c2;

Execute “.database” command which will display all the attached databases.

sqlite> .database
seq  name             file
---  ---------------  ------------------
0    main
2    c1               /root/company1.db
3    c2               /root/company2.db

Now, you can execute a union query across these databases to combine the results.

sqlite> select empid, name, title from c1.employee union select empid, name, title from c2.employee;
101|John Smith|CEO
102|Raj Reddy|Sysadmin
103|Jason Bourne|Developer
104|Jane Smith|Sales Manager
105|Rita Patel|DBA
201|James Bond|Secret Agent
202|Spider Man|Action Hero

After attaching a database, from the current sqlite session, if you want to detach it, use detach command as shown below.

sqlite> detach c1;

sqlite> .database
seq  name             file
---  ---------------  -----------------
0    main
2    c2               /root/company2.db

RAID 1+0 Configuration in HP Servers

2013-04-29T06:26:00.001-07:00

Let’s see what is RAID1+0 and how can we configure RAID1+0 in a HP Server. RAID 1+0 is mixture of RAID 0 (Stripping) and RAID 1 (Mirroring). It also delivers the benefits of both in a single system. As you can see in the picture, it stripes the mirrored drives. Thus, it will have the security of mirroring all data on another set of drives while striping of each set of drives to increases the data transfer speed. RAID 1+0 is the perfect solution for the servers running databases and high availability applications which demands data read/write efficiency and high fault tolerance. RAID 1+0 requires minimum four drives.
Power on the server and wait for the Array Controller ROM utility to prompt you to press F8 to run RAID configuration.
Press F8 to enter the utility then you will get the Array controller utility to create logical drives. Select Create logical drive and press Enter
Press Enter to create the logical drive.

Press F8 to Save the configuration. This will create the RAID 0 Logical Drive.
Press Enter to continue. That will take you to the main menu again. It is good to verify the Logical drive we created. For that select View Logical Drive and press Enter

That will show you the logical drive you have just created. Since I have selected all eight Physical disks (146GB each disk) available, for this logical drive we have got 546 TB capacity. Since it will mirror you will get only the half size of the total capacity of the drives. You can select the Logical Drive and press Enter to see the physical disk array(total number of disk used in this RAID 1+0 local drive.When you quit from the utility server will continue the boot process.

Setup a logon banner for ssh clients to see when they login

2013-04-29T03:55:00.005-07:00

SSH (Secure Shell) is a protocol for creating a secure connection between two computers. The secure SSH connection provides authentication and encryption. In the SSH server, it is possible to configure logon or welcome banner with the use of the Banner directive in /etc/ssh/sshd_config file.The Banner directive is only available for ssh protocol version 2 and by default there are no banner configured.

Configutration

1. Create a banner file. (e.g. /etc/banner) using vi editor.

# vi /etc/banner

**********************************

******** WELCOME TO REDHAT *******

**********************************

Configure the ssh configuration file /etc/ssh/sshd_config file and add the line Banner /etc/banner to it.

# vi /etc/ssh/sshd_config

Banner /etc/banner

Restart sshd daemon for the changes to take effect

# service sshd restart

Example

If we are accessing server using ssh , message will appear as follows:

[root@mail ~]# ssh 10.30.32.206

**********************************

*********WELCOME TO REDHAT********

**********************************

root@10.30.32.206's password:

Monitor user activity using sudo and sudosh2

2013-04-28T23:10:00.003-07:00

Note: I used UBUNTU 12.04TLS 64Bit machine to test this.

1. Change the password of ALEXANDER and do not share with anyone.

2. Now download sudosh2-1.0.4.tgz and install as instructed below

# tar zxvf sudosh2-1.0.4.tgz

# cd sudosh2-1.0.4

# CFLAGS="-D_GNU_SOURCE" ./configure

# make

# sudo make install

3. Create four users SURESH,NARESH,YOGESH and NAGESH

# sudo adduser SURESH
# sudo adduser NARESH
# sudo adduser YOGESH
# sudo adduser NAGESH

4. Create one GROUP say DEVELOPERS

# sudo groupadd DEVELOPERS

5. Add users SURESH,NARESH,YOGESH and NAGESH to Secondary Group DEVELOPERS

#sudo usermod -a -G DEVELOPERS SURESH
#sudo usermod -a -G DEVELOPERS NARESH
#sudo usermod -a -G DEVELOPERS YOGESH
#sudo usermod -a -G DEVELOPERS NAGESH

6. Open /etc/sudoers file and make below changes

Defaults env_reset
Defaults syslog=auth
Defaults>root !set_logname
Defaults log_year, logfile=/var/log/sudo.log
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

Cmnd_Alias SUDOSH = /usr/local/bin/sudosh

root ALL=(ALL:ALL) ALL

%DEVELOPERS ALL=(ALEXANDER) SUDOSH

%sudo ALL=(ALL:ALL) ALL

This will enable the sudo log which can be found at /var/log/sudo.log
Allowing users /usr/local/bin/sudosh command only to use with ALEXANDER user.

Note: Be very careful with this file especially when you are in UBUNTU system. If you mess up with this file, there is no other option than rebooting the system and booting it in recovery mode to fix the file if you dont have policykit-1 installed.For safer side please install...

# sudo apt-get install policykit-1

7. That's it done! We are good to test this...

Once you get the prompt Enter..

# sudo -u ALEXANDER sudosh

will be asked for the SURESH passwd. provide it and you are in.

check with id command you should see ALEXANDER details.

# id

uid=1000(ALEXANDER) gid=1000(ALEXANDER) groups=1000(ALEXANDER),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),111(lpadmin),112(sambashare)

You will find the logs at below location

Open a new session and login as ALEXANDER or a user who belongs to sudo group.

# cd /var/log/sudosh

# sudo ls -ltrh

-rw------- 1 ALEXANDER ALEXANDER 81 Oct 12 10:33 SURESH-ALEXANDER-time-1350063234-YTvv0lB4sLtImfI3

-rw------- 1 ALEXANDER ALEXANDER 196 Oct 12 10:33 SURESH-ALEXANDER-script-1350063234-YTvv0lB4sLtImfI3

Now you got two options to see this file either you use

# tail -f SURESH-ALEXANDER-script-1350063234-YTvv0lB4sLtImfI3

you will get all details that to live if SURESH is still logged into ALEXANDER.

or use

# sudo sudosh-replay SURESH-ALEXANDER-script-1350063234-YTvv0lB4sLtImfI3 1 2

You will see Action Replay!

Httpd Status Codes

2013-04-28T21:54:00.003-07:00

Informational 1xx

Successful 2xx

Redirection 3xx

Client Error 4xx

Server Error 5xx

100 Continue

101 Switching Protocols

102 Processing (WebDAV) (RFC 2518)

103 Checkpoint

122 Request-URI too long (Microsoft/IE7)

--------------------------------------------

200 OK

201 Created (+ etag)

202 Accepted

203 Non-Authoritative Information

204 No Content (no body)

205 Reset Content (reset view)

206 Partial Content (+ range header)

207 Multi-Status (WebDAV) (RFC 4918)

226 IM Used (RFC 3229)

--------------------------------------------

300 Multiple Choices

301 Moved Permanently

302 Found

303 See Other (since HTTP/1.1)

304 Not Modified

305 Use Proxy (since HTTP/1.1)

306 Switch Proxy (no longer used)

307 Temporary Redirect (since HTTP/1.1)

308 Resume Incomplete

--------------------------------------------

400 Bad Request

401 Unauthorized

402 Payment Required (future)

403 Forbidden

404 Not Found

405 Method Not Allowed

406 Not Acceptable

407 Proxy Authentication Required

408 Request Timeout

409 Conflict (with the resource)

410 Gone

411 Length Required

412 Precondition Failed

413 Request Entity Too Large

414 Request-URI Too Long

415 Unsupported Media Type

416 Requested Range Not Satisfiable

417 Expectation Failed

418 I'm a teapot (RFC 2324)

420 Enhance Your Calm (Twitter API)

422 Unprocessable Entity (WebDAV) (RFC 4918)

423 Locked (WebDAV) (RFC 4918)

424 Failed Dependency (WebDAV) (RFC 4918)

425 Unordered Collection (RFC 3648)

426 Upgrade Required (RFC 2817)

428 Precondition Required (RFC 2616 pending)

429 Too Many Requests (RFC 2616 pending)

431 Request Header Fields Too Large

444 No Response (Nginx)

449 Retry With (Microsoft)

450 Blocked by Windows Parental Controls (Microsoft)

499 Client Closed Request (Nginx)

--------------------------------------------

500 Internal Server Error

501 Not Implemented

502 Bad Gateway

503 Service Unavailable

504 Gateway Timeout

505 HTTP Version Not Supported

506 Variant Also Negotiates (RFC 2295)

507 Insufficient Storage (WebDAV)(RFC 4918)

509 Bandwidth Limit Exceeded (Apache)

510 Not Extended (RFC 2774)

511 Network Authentication Required (RFC 2616 pending)

598 Network read timeout error (Informal convention)

599 Network connect timeout error (Informal convention)

Send mail when cron fails in Linux server

2013-04-26T02:01:00.004-07:00

$ crontab -e

At the top of the file, enter:

MAILTO=”support@urmail.com”

Setting Root login email alert on a Linux server

2013-04-26T00:50:00.002-07:00

How to set up a root login alert

vi /root/.bashrc
echo ‘ALERT – Root Shell Access MY SERVER on:’ `date` `who` | mail -s “Alert: Root Access from `who | cut -d”(” -f2 | cut -d”)” -f1`” email@gmail.com

Find Apache last restart time

2013-04-26T00:44:00.001-07:00

[root@devel]# /etc/init.d/httpd status | grep Restart
Restart Time: Fri Apr 26 01:43:23 MDT 2013
[root@devel]#

Killing Oracle Sessions

2013-03-18T02:59:00.004-07:00

Killing Oracle Sessions

There are a number of ways to kill rogue sessions both within Oracle and externally.

Identify the Session to be Killed

Killing sessions can be very destructive if you kill the wrong session, so be very careful when identifying the session to be killed. If you kill a session belonging to a background process you will cause an instance crash.

Identify the offending session using the [G]V$SESSION and [G]V$PROCESS views as follows.

SET LINESIZE 100
COLUMN spid FORMAT A10
COLUMN username FORMAT A10
COLUMN program FORMAT A45

SELECT s.inst_id,
       s.sid,
       s.serial#,
       p.spid,
       s.username,
       s.program
FROM   gv$session s
       JOIN gv$process p ON p.addr = s.paddr AND p.inst_id = s.inst_id
WHERE  s.type != 'BACKGROUND';

   INST_ID        SID    SERIAL# SPID       USERNAME   PROGRAM
---------- ---------- ---------- ---------- ---------- ---------------------------------------------
         1         30         15 3859       TEST       sqlplus@oel5-11gr2.localdomain (TNS V1-V3)
         1         23        287 3834       SYS        sqlplus@oel5-11gr2.localdomain (TNS V1-V3)
         1         40        387 4663                  oracle@oel5-11gr2.localdomain (J000)
         1         38        125 4665                  oracle@oel5-11gr2.localdomain (J001)

SQL>

The SID and SERIAL# values of the relevant session can then be substituted into the commands in the following sections.

ALTER SYSTEM KILL SESSION

The basic syntax for killing a session is shown below.

SQL> ALTER SYSTEM KILL SESSION 'sid,serial#';

In a RAC environment, you optionally specify the INST_ID, shown when querying the GV$SESSION view. This allows you to kill a session on different RAC node.

SQL> ALTER SYSTEM KILL SESSION 'sid,serial#,@inst_id';

The KILL SESSION command doesn't actually kill the session. It merely asks the session to kill itself. In some situations, like waiting for a reply from a remote database or rolling back transactions, the session will not kill itself immediately and will wait for the current operation to complete. In these cases the session will have a status of "marked for kill". It will then be killed as soon as possible.

In addition to the syntax described above, you can add the IMMEDIATE clause.

SQL> ALTER SYSTEM KILL SESSION 'sid,serial#' IMMEDIATE;

This does not affect the work performed by the command, but it returns control back to the current session immediately, rather than waiting for confirmation of the kill.

If the marked session persists for some time you may consider killing the process at the operating system level. Before doing this it's worth checking to see if it is performing a rollback. You can do this by running this script (session_undo.sql). If the USED_UREC value is decreasing for the session in question you should leave it to complete the rollback rather than killing the session at the operating system level.

ALTER SYSTEM DISCONNECT SESSION

The ALTER SYSTEM DISCONNECT SESSION syntax is an alternative method for killing Oracle sessions. Unlike the KILL SESSION command which asks the session to kill itself, the DISCONNECT SESSION command kills the dedicated server process (or virtual circuit when using Shared Sever), which is equivalent to killing the server process from the operating system. The basic syntax is similar to the KILL SESSION command with the addition of the POST_TRANSACTION clause. The SID and SERIAL# values of the relevant session can be substituted into one of the following statements.

SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' POST_TRANSACTION;
SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' IMMEDIATE;

The POST_TRANSACTION clause waits for ongoing transactions to complete before disconnecting the session, while the IMMEDIATE clause disconnects the session and ongoing transactions are recovered immediately.

The POST_TRANSACTION and IMMEDIATE clauses can be used together, but the documentation states that in this case the IMMEDIATE clause is ignored. In addition, the syntax diagram suggests both clauses are optional, but in reality, one or both must be specified or you receive an error.

SQL> alter system disconnect session '30,7';
alter system disconnect session '30,7'
                                     *
ERROR at line 1:
ORA-02000: missing POST_TRANSACTION or IMMEDIATE keyword

SQL>

This command means you should never need to switch to the operating system to kill sessions, which reduces the chances of killing the wrong process.

The Windows Approach

To kill the session on the Windows operating system, first identify the session, then substitute the relevant SID and SPID values into the following command issued from the command line.

C:> orakill ORACLE_SID spid

The session thread should be killed immediately and all resources released.

The UNIX Approach

To kill the session on UNIX or Linux operating systems, first identify the session, then substitute the relevant SPID into the following command.

% kill spid

If after a few minutes the process hasn't stopped, terminate the session using the following.

% kill -9 spid

If in doubt check that the SPID matches the UNIX PROCESSID shown using.

% ps -ef | grep ora

The session thread should be killed immediately and all resources released.

Easy Way to Checking Hard Drive for Bad Sectors and Errors in Ubuntu

2013-03-10T21:30:00.003-07:00

How to know if you have bad sectors on your hard drive in Ubuntu Desktop and how to fix them. You can use badblock program to fix this problem. The badblocks is program command line based allow to test your harddrive for, you guessed it, bad blocks. The badblocks program is part of the e2fsprogs package, which is installed by default in ubuntu based distro.
To check your harddrive for bad blocks, open the terminal type following command:

sudo badblocks -v /dev/sda1 > bad-blocks-result

After executing the above command it will generate the file bad-blocks-result in the current directory where you are execute this command. Now, you can pass this file to the fsck command to record these bad blocks.

sudo fsck -t ext4 -l bad-blocks-result /dev/sda1

If badblocks reports a block that was already used, e2fsck will try to move the block to another place. If the block was really bad, not just marginal, the contents of the file may be corrupted.