Changing the primary IP address of a CentOS Server

ssh to the server.

#nano /etc/sysconfig/network-scripts/ifcfg-eth0

You will find…

# =============================================================
# Network Interface Script generated by BareMetal
# =============================================================
DEVICE=eth0
BOOTPROTO=STATIC
ONBOOT=yes
IPADDR=216.55.xx.xx
NETMASK=255.255.255.0
HWADDR=6C:62:xx:xx:xx:C3

Change this line only to the new IP

IPADDR=216.55.xx.xx

Note: If you are changing to an IP on a different subnet and need to change your default gateway, this can be configured under /etc/sysconfig/network

Save the file and restart

# service network restart

Date/Timezone for CentOS 6.5 server

My Server time Zone was +00:00 GMT and today I found the time showing +1:00 GMT . Would you please tell how it has been changed ? Is that because of Daylight Saving issue ?

The server currently is set to British Summer Time, which is UTC +1 currently, you can change the time zone to UTC/GMT which does not adjust for Daylight Saving Time, you can run the following commands to set the time zone to UTC:


mv /etc/localtime /etc/localtime.bak
ln -s /usr/share/zoneinfo/UTC /etc/localtime

You can prevent this from being changed by updates by running:


chattr +i /etc/localtime

Install Groups of Packages in Centos

[root@localhost Downloads]# yum grouplist
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Group Process
Loading mirror speeds from cached hostfile
 * base: yum.tamu.edu
 * extras: mirror.raystedman.net
 * rpmforge: repoforge.spinellicreations.com
 * updates: mirrors.centarra.com
google-talkplugin                                                                                                                                                                                                     |  951 B     00:00     
google-talkplugin/primary                                                                                                                                                                                             | 1.4 kB     00:00     
Installed Groups:
   Additional Development
   Base
   Console internet tools
   Desktop
   Desktop Platform
   Dial-up Networking Support
   Directory Client
   E-mail server
   FCoE Storage Client
   Fonts
   General Purpose Desktop
   Graphical Administration Tools
   Hardware monitoring utilities
   Internet Applications
   Internet Browser
   Legacy UNIX compatibility
   Legacy X Window System compatibility
   Network Infrastructure Server
   Networking Tools
   Office Suite and Productivity
   Performance Tools
   Perl Support
   Remote Desktop Clients
   Security Tools
   Storage Availability Tools
   X Window System
   iSCSI Storage Client
Installed Language Groups:
   Arabic Support [ar]
   Armenian Support [hy]
   Bhutanese Support [dz]
   Chinese Support [zh]
   Georgian Support [ka]
   Hebrew Support [he]
   Inuktitut Support [iu]
   Japanese Support [ja]
   Khmer Support [km]
   Konkani Support [kok]
   Korean Support [ko]
   Kurdish Support [ku]
   Lao Support [lo]
   Myanmar (Burmese) Support [my]
   Tajik Support [tg]
   Venda Support [ve]
Available Groups:
   Backup Client
   Backup Server
   CIFS file server
   Client management tools
   Compatibility libraries
   Debugging Tools
   Desktop Debugging and Performance Tools
   Desktop Platform Development
   Development tools
   Directory Server
   Eclipse
   Emacs
   FTP server
   Graphics Creation Tools
   High Availability
   High Availability Management
   Identity Management Server
   Infiniband Support
   Input Methods
   Java Platform
   KDE Desktop
   Large Systems Performance
   Load Balancer
   Mainframe Access
   Messaging Client Support
   MySQL Database client
   MySQL Database server
   NFS file server
   Network Storage Server
   Network file system client
   PHP Support
   PostgreSQL Database client
   PostgreSQL Database server
   Print Server
   Printing client
   Resilient Storage
   Ruby Support
   SNMP Support
   Scientific support
   Server Platform
   Server Platform Development
   Smart card support
   System Management
   System administration tools
   TeX support
   Technical Writing
   TurboGears application framework
   Virtualization
   Virtualization Client
   Virtualization Platform
   Virtualization Tools
   Web Server
   Web Servlet Engine
   Web-Based Enterprise Management
Available Language Groups:
   Afrikaans Support [af]
   Albanian Support [sq]
   Amazigh Support [ber]
   Assamese Support [as]
   Azerbaijani Support [az]
   Basque Support [eu]
   Belarusian Support [be]
   Bengali Support [bn]
   Brazilian Portuguese Support [pt_BR]
   Breton Support [br]
   Bulgarian Support [bg]
   Catalan Support [ca]
   Chhattisgarhi Support [hne]
   Chichewa Support [ny]
   Coptic Support [cop]
   Croatian Support [hr]
   Czech Support [cs]
   Danish Support [da]
   Dutch Support [nl]
   English (UK) Support [en_GB]
   Esperanto Support [eo]
   Estonian Support [et]
   Ethiopic Support [am]
   Faroese Support [fo]
   Fijian Support [fj]
   Filipino Support [fil]
   Finnish Support [fi]
   French Support [fr]
   Frisian Support [fy]
   Friulian Support [fur]
   Gaelic Support [gd]
   Galician Support [gl]
   German Support [de]
   Greek Support [el]
   Gujarati Support [gu]
   Hiligaynon Support [hil]
   Hindi Support [hi]
   Hungarian Support [hu]
   Icelandic Support [is]
   Indonesian Support [id]
   Interlingua Support [ia]
   Irish Support [ga]
   Italian Support [it]
   Kannada Support [kn]
   Kashmiri Support [ks]
   Kashubian Support [csb]
   Kazakh Support [kk]
   Kinyarwanda Support [rw]
   Latin Support [la]
   Latvian Support [lv]
   Lithuanian Support [lt]
   Low Saxon Support [nds]
   Luxembourgish Support [lb]
   Macedonian Support [mk]
   Maithili Support [mai]
   Malagasy Support [mg]
   Malay Support [ms]
   Malayalam Support [ml]
   Maltese Support [mt]
   Manx Support [gv]
   Maori Support [mi]
   Marathi Support [mr]
   Mongolian Support [mn]
   Nepali Support [ne]
   Northern Sotho Support [nso]
   Norwegian Support [nb]
   Occitan Support [oc]
   Oriya Support [or]
   Persian Support [fa]
   Polish Support [pl]
   Portuguese Support [pt]
   Punjabi Support [pa]
   Romanian Support [ro]
   Russian Support [ru]
   Sanskrit Support [sa]
   Sardinian Support [sc]
   Serbian Support [sr]
   Sindhi Support [sd]
   Sinhala Support [si]
   Slovak Support [sk]
   Slovenian Support [sl]
   Somali Support [so]
   Southern Ndebele Support [nr]
   Southern Sotho Support [st]
   Spanish Support [es]
   Swahili Support [sw]
   Swati Support [ss]
   Swedish Support [sv]
   Tagalog Support [tl]
   Tamil Support [ta]
   Telugu Support [te]
   Tetum Support [tet]
   Thai Support [th]
   Tibetan Support [bo]
   Tsonga Support [ts]
   Tswana Support [tn]
   Turkish Support [tr]
   Turkmen Support [tk]
   Ukrainian Support [uk]
   Upper Sorbian Support [hsb]
   Urdu Support [ur]
   Uzbek Support [uz]
   Vietnamese Support [vi]
   Walloon Support [wa]
   Welsh Support [cy]
   Xhosa Support [xh]
   Zulu Support [zu]

# yum groupinstall "Development Tools"

Adding Additional IP Addresses CentOS

ssh to the server

# cd /etc/sysconfig/network-scripts
# ls -l | grep ifcfg-eth
-rw-r--r-- 1 root root   119 Jan 11 19:16 ifcfg-eth0
-rw-r--r-- 1 root root   119 Jan  3 08:45 ifcfg-eth0.bak
-rw-r--r-- 1 root root   119 Feb 24 04:34 ifcfg-eth1
-rw-r--r-- 1 root root   128 Jan 19 18:20 ifcfg-eth1.bak

If the main adapter is called “eth0” you have to call the next (virtual) adapter in a sequential order like so:

ifcfg-eth0 (primary adapter, physical)
ifcfg-eth0:1 (first virtual adapter to the physical primary adapter)
ifcfg-eth0:2 (second virtual adapter to the physical primary adapter)

Copy our primary adapter configuration file and name it to be the first virtual adapter:


# cp ifcfg-eth0 ifcfg-eth0:1
# ls -l | grep ifcfg-eth
-rw-r--r-- 1 root root   119 Jan 11 19:16 ifcfg-eth0
-rw-r--r-- 1 root root   119 Feb 24 08:53 ifcfg-eth0:1
-rw-r--r-- 1 root root   119 Jan  3 08:45 ifcfg-eth0.bak
-rw-r--r-- 1 root root   119 Feb 24 04:34 ifcfg-eth1
-rw-r--r-- 1 root root   128 Jan 19 18:20 ifcfg-eth1.bak

Configure this virtual adapter to be a static IP, no hardware address (MAC), configure netmask and of course rename the device.


# vim ifcfg-eth0:1
DEVICE=eth0:1
BOOTPROTO=static
ONBOOT=yes
IPADDR=10.1.1.2
NETMASK=255.255.255.0

There is no need to specify a MAC address – it is a virtual adapter and there is also no need to specify a default gateway as it is already routed through the primary adapter. Basically there are only four things that you will need to change:

File name for the adapter itself
DEVICE= (should correspond with the file name)
IPADDR=
NETMASK=

Restart the networking service:


# service network restart

That’s it; lets check ifconfig to make sure the virtual adapter is there and working:


# ifconfig eth0:1
eth0:1    Link encap:Ethernet  HWaddr 08:00:27:ED:05:B7
inet addr:10.1.1.2  Bcast:10.1.1.255  Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1


# ping 10.1.1.2
PING 10.1.1.2 (10.1.1.2) 56(84) bytes of data.
64 bytes from 10.1.1.2: icmp_seq=1 ttl=64 time=0.073 ms
64 bytes from 10.1.1.2: icmp_seq=2 ttl=64 time=0.042 ms
64 bytes from 10.1.1.2: icmp_seq=3 ttl=64 time=0.029 ms
64 bytes from 10.1.1.2: icmp_seq=4 ttl=64 time=0.029 ms
--- 10.1.1.2 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.029/0.043/0.073/0.018 ms

Cisco VPN on CentOS 6

Install eplel repo


# rpm -ivh http://mirror.vcu.edu/pub/gnu+linux/epel/6/i386/epel-release-6-8.noarch.rpm


# yum -y install vpnc
# chmod 700 /etc/vpnc/vpnc-script
# cp /etc/vpnc/default.conf /etc/vpnc/default.conf.orig

Save your .pnc file from Networking to /etc/vpnc/ folder

Install the VPN .pnc file as a default.conf file

Get the pcf to vpnc configuration file converter


# wget http://svn.unix-ag.uni-kl.de/vpnc/trunk/pcf2vpnc

Make it executable


# chmod +x pcf2vpnc

Move it to a place in our path


# mv pcf2vpnc /usr/local/bin/


# cd /etc
# pcf2vpnc /path/username.pcf default.conf
# chown root:root default.conf
# chmod 600 default.conf

Edit the config file to either use your username and password, or to manually enter


# nano default.conf
# Uncomment for auto login
# Xauth username myusername
# Xauth password userpass
# Uncomment for manual login
Xauth interactive

Backup resolv.conf

As a final configuration step, it is a good idea to make a backup of your resolv.conf file. The vpnc program will replace the resolv.conf upon connection and will restore it when you disconnect.

Connect and Disconnect

You must be logged in as Root for this to work

# vpnc
# vpnc-disconnect