Nishant - My Linux Guide (Page 2)

Mounting Open stack Cloud Object Storage in Linux

Prerequisites: libcurl and libcurl-devel fuse, fuse-devel, and fuse-libs libxml2 and libxml2-devel Download the cloudfuse : This version doesnot support mounting at container level : wget https://github.com/redbo/cloudfuse/tarball/master This supports mounting at container level: https://github.com/vfloz/cloudfuse/tarball/master tar -zxvf master cd <extracted dir&

Perl Issues and Solutions

Display The Include paths for perl : perl -e 'print join("\n", @INC);' View Cpan Configuration: cpan>o conf Find perl module’s Path: perl -MList::Util -e'print $_ . " => " . $INC{$_} . "\n" for keys %INC'

IPtables

Delete Rules in Iptables

iptables -D (Chain Name) ( RuleNum) eg. iptables -D FORWARD 1 You can delete all rules from filter chain by typing : iptables -F or from nat table iptables -F -t nat

Apache

Creating SSL Certificates

Create a Self Signed Certificate : 1. Generate A Server Key : #openssl genrsa -des3 -out server.key 4096 2. Generate the Signing Request using the key above #openssl req -new -key server.key -out server.csr 3.Sign the certificate signing request. #openssl x509 -req -days 365 -in server.csr -signkey

Network

Installing Vnc Server on Linux Machine without monitor

Vnc Installation Without Monitor Packages Required : 1.vnc 2.vnc-server 3.Desktop Environment KDE or GNOME Configuring VNC : 1. Add users like normal users. 2. login to each users 3. create password by running vncpasswd 4. It creates .vnc folder 5. Edit /etc/sysconfig/vncservers, and add the following to

HA & Synchronization

Using Rsync to Syncronise files between servers

Rsync is a nice utility to synchronize files and folders between two servers securely and efficiently. It only copies the difference so making the process much faster and efficient. Ok, here i will show you how to setup rsync. 1. Download the rsync package. Click Here 2. Untar the package

Web Snipetts

Combobox On change

If you need to get a value for the selected item in a combo box you can use the following function : onchange=”alert(this.options[this.selectedIndex].text) if you need the value then just replace text with value . For example, if you want to redirect the page based on

Systems Administrator

Force Install CPAN Module in Linux from CLI

Force Install CPAN Module perl -MCPAN -e “CPAN::Shell->force(qw(install HTTP::Cookies));”

Systems Administrator

Changing the password hashing algorithm to sha-512

change password hashing algorithm to sha-512 # authconfig –test | grep hashing # authconfig –passalgo=sha512 –update

IPtables

Redirecting Ports in Iptables

Redirect ports in iptables iptables -t nat -A PREROUTING -i eth0 -p tcp –dport $srcPortNumber -j REDIRECT –to-port $dstPortNumbe

Systems Administrator

Installing Perl Modules

Its convenient to install perl modules from command line. #perl -MCPAN -e shell cpan> install PACKAGE NAME eg. cpan> install HTML::Template

Network

Adding Multiple IP Address to A NIC Card

It is possible to bind more than one ip address on a single network interface card in linux. copy your existing network card configuration file as shown: #cd /etc/sysconfig/network-scripts #cp ifcfg-eth0 ifcfg-eth0:1 >>ifcfg-eth0 looks like this : # File: ifcfg-eth0 DEVICE=eth0 ONBOOT=yes BOOTPROTO=static IPADDR=

DNS

How to retrieve named.ca file

You can retrieve named.ca file by issuing the following command dig @a.root-servers.net . ns > named.ca or download from this location : ftp://ftp.internic.net/domain/named.root

Systems Administrator

Grub reinstall in rescue mode

You can re-install grub boot loader in rescue mode by issuing the following command : #grub-install /dev/sda1 or hda1 ( based on your boot partition) if it is scsi drive it would be sda and hda if it is ide drive. If you get something like this : ” Error /dev/hdx or

Vi & String Processing

Save File as in VI Editor

You can save file as another file in vi editor after you make changes to the current file, so that you can quit without saving and still retain the changes in another file. :w! newfile.txt or :w! /var/newfile.txt Thanks

Vi & String Processing

Introduction to String Processing

Introduction to string Processing Head/Tail Head and tail command are used to view the first and last few lines of a file respectively. By default these commands generate 10 number of lines. # head /etc/passwd (shows first 10 lines) # tail /etc/passwd (shows last 10 lines) One very handful

Systems Administrator

Managing Partitions

*Mounting filesystem #mount (fs-type> -o <options> <partition_name> <mount_point> fs_type=vfat,ext2,ext3,iso9660 etc options=rw ro exec noexec dev nodev auto noauto suid nosuid user nouser or (owner, noowner) async sync the above options are default keywords additional options

Systems Administrator

Linux Filesystem Management

Linux Filesystem management –>File system Ids ext2/ext3 –>83 linux swap ->82 RAID –>fd LVM –>83 above id no. are based on hex system #fdisk -l -> Disk partitioning tools .fdisk -> post-installaton disk partitioning tool (other disk partition tools sfdiks – can

Systems Administrator

Linux Hardware and Kernel

* Hardware Resources –>Kudzu – .It is hardware detection program that typically runs during boot time to detect any added or removed h/w. .It refers the file/etc/sysconfig/hwconf to deletct any added/removed h/w. #hwbrowser . Graphical tool that displays the list of detected h/w. #cd /usr/

Systems Administrator

Controlling Services in Linux

–> Controlling services service management tools: 1 .chkconfig .it is noninteractive tool that can be used in shell scripts. .xinetd-based services comes into immediate effect if actived/de-activated with this tool. .Stand-Alone service comes into effect only on next rebootif activated/de-activated using this tool. [to avoid reboot, use ‘service

Systems Administrator

Linux Daemons

Deamons (what is deamons) ——————————- .Background process are called deamons and sometimes called services) Types ——- Two types: 1. Stand-alone deamon .Location: /etc/rc.d/init.d/* .Keeps running all the time 2. Transient deamon (service) .Controled by super-deamon ‘xinetd’ .Location: /etc/xinetd.d/* .Also called xniedtd-based deamons (or services)

Systems Administrator

Linux Init Initialization

-init initialization #vi /etc/inittab format id:runlevel:action:process id –> it is 1-4 char. long identification char. runlvele–> It represents the runlevel for which the action has to be taken. If omitted, action will be taken for all the runlevels. Action–> Represents the action to be

Systems Administrator

Linux Kernel Initialization

Kernel initialization ————————- .kernel detects the attached devices in the system & loads thier drivers into RAM. .mounts root filesystem into read-only memory mode. .Then initializes the ‘init’ process for further processing init=it is the first process that is started at the boot time. –init initialization /etc/inittab – main

Systems Administrator

Linux Boot process, system initialization

System Initialization & Services –> Boot sequence i. BIOS initialization ii. Boot Loader initialization iii. Kernel initailization iv. init initialization Power on –> BIOS —-> BOOT LOADER(MBR) –> KERNEL–>init Kernel- Monolithik kernel -Boot Loader i. Grub (Grand Unified Boot loader) (latest) ii. LILO (Linux Loader) (old)

Linux Installation Guide

Hardware: redhat.com/HCL (information about redhat supported hardware) http://www.xfree86.org (to check graphics compatibility e.g. VGA card, monitor) http://www.redhat.com/support/errata /bug-fixes Redhat supported architechre * RHEL supports the following cpu architechures .intel’s x86 arch. . interl’s Itanium ,, . AMD64 . IBM’s s/390,