Tag: CentOS

Disable IPv6 in centOS

Posted on by admin
  • Edit /etc/sysconfig/network and set “NETWORKING_IPV6” to “no”
  • For 5.4 and later, replace in /etc/modprobe.conf

 

alias ipv6 off

by

options ipv6 disable=1

Alternative (which might be easier and works on any release with /etc/modprobe.d):

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "install ipv6 /bin/true" >> /etc/modprobe.d/disable-ipv6.conf
  • For CentOS 5.3 or older, add the following to /etc/modprobe.conf :

 

alias ipv6 off
alias net-pf-10 off
  • Run /sbin/chkconfig ip6tables off to disable the IPv6 firewall
  • Reboot the system

<!> With the 5.4 update symbol/ipv6 module dependency capabilities have been introduced; therefore, if IPv6 has been previously disabled as above an upgrade to the bonding driver in 5.4 will result in the bonding kernel module failing to load. For the module to load properly use instead:

# touch /etc/modprobe.d/disable-ipv6.conf
# echo "options ipv6 disable=1" >> /etc/modprobe.d/disable-ipv6.conf

<!> <!> Upstream employee Daniel Walsh recommends not disabling the ipv6 module but adding the following to /etc/sysctl.conf:

net.ipv6.conf.all.disable_ipv6 = 1

In a short way this is what I do:

[root@toro.maranello.local ~]#echo "net.ipv6.conf.all.disable_ipv6 = 1" >> /etc/sysctl.conf

While there I would turn off the IPV6Tables service as well

[root@toro.maranello.local ~]# service ip6tables save
[root@toro.maranello.local ~]# service ip6tables stop
[root@toro.maranello.local ~]# chkconfig ip6tables off

NOTE: SSH x11 forwarding may (and probably will) stop working if you disable the IPv6 …just a heads up :)…

nJoy 😉

CENTOS 6 Minimal does not have the Network interfaces up by default

Posted on by admin

So test drove CentOS  6 Minimum install ..

Only real hiccup till now is :

TUV ( the upstream vendor) aka RHEL decided to disable the network interfaces by default. WTF to that.

A glance at the FAQ  will show the solution :

Here’s my version for multiple interfaces.

 

# cd /etc/sysconfig/network-scripts/  

# sed -i -e ‘s@^ONBOOT=”no@ONBOOT=”yes@’ ifcfg-eth*

Vmware tools autoinstall after kickstart

Posted on by admin

kickstart postinstall, you can read how to do this on the internet.

wget http://foo/tools.tar.gz

tar xzvf *.tar.gz

cd directory-where-you-untarred

vmware-tools-install.pl -d

BINGO !
Giggidi Giggidi

Installing SNMP on Centos 6.x

Posted on by admin

Installing SNMP daemon and tools:

As root

yum -y install net-snmp.i686

yum -y install net-snmp-utils

Once these are installed start the snmp daemon:

/etc/init.d/snmpd start

chkconfig snmpd on

 

This is just the basic install but testing it :

snmpwalk -v 1 -c public -O e 127.0.0.1

For production servers it is advisable to at least change the community name.

All configs are in

/etc/snmp/snmpd.conf

and traps are setup here:

/etc/snmp/snmptrapd.conf

No traps are set by default.

Enjoy !!

Installing EPEL Repository on CentOS

Posted on by admin

EPEL stands for Extra Packages for Enterprise Linux. This is a massive collection of packages that are very useful for the building of many modern stacks and include many tools for the running and maintenance of systems.

The homepage of EPEL is here: http://fedoraproject.org/wiki/EPEL.

You can browse the package set using repoview:

Installing on Centos 5.x & 6.x:

For EL5:

su -c 'rpm -Uvh http://mirror.switch.ch/ftp/mirror/epel/5/i386/epel-release-5-4.noarch.rpm'
...
su -c 'yum install puppet'

For EL6:

su -c 'rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm'
...
su -c 'yum install puppet'

For EL7 

sudo yum install epel-release

Setting hostname

Posted on by admin 
#vim /etc/sysconfig/network

Use something like

HOSTNAME=testarossa.maranello.local

to overwrite the default name and domain of the server.

e.g.

NETWORKING=yes
HOSTNAME=testarossa.maranello.local

To avoid rebooting issue the following :

hostname  testarossa.maranello.local

That will set it for the current  session.

 

 

 

Setup default gateway with route command Linux

Posted on by admin

Display default route

The following three commands display the current routing table:

# route

Output:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     *               255.255.255.0   U     0      0        0 ra0
default         dsl-router      0.0.0.0         UG    0      0        0 ra0
# /sbin/route

Output:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
191.255.255.0   *               255.255.255.0   U     0      0        0 eth0
169.254.0.0     *               255.255.0.0     U     0      0        0 eth0
default         191.255.255.1   0.0.0.0         UG    0      0        0 eth0

You can use -n option, to display numerical addresses instead of trying to determine symbolic host names (via dns or /etc/hosts file). This is useful if you are trying to determine why the route to your nameserver has vanished.$ 

#/sbin/route -n

Output:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
191.255.255.0   0.0.0.0         255.255.255.0   U     0      0        0 venet0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 venet0
0.0.0.0         191.255.255.1   0.0.0.0         UG    0      0        0 venet0

 

Please note that a destionation entry 0.0.0.0 (or default) is the default gatway. In above example 191.255.255.1 is a default gatway.

Add / setup a new route

The syntax is as follows:
route add default gw {IP-ADDRESS} {INTERFACE-NAME}

Where,

  • IP-ADDRESS: Specify router IP address
  • INTERFACE-NAME: Specify interface name such as eth0

For example if your router IP address is 192.168.1.254 type the following command as the root user:

# route add default gw 192.168.1.254 eth0

OR use hostname such as dsl-router:

# route add default gw dsl-router eth0

Setting route using GUI tools/command under Linux

If you find above command hard to use, consider using GUI tools. If your are using Red Hat/CentOS/Fedora core Linux type following command:

# redhat-config-network

OR

If you are using other Linux distribution use command:

# network-admin

Installing iostat in CentOS with yum

Posted on by admin

Iostat is a very powerful tool for monitoring the throughput of your storage subsystems. Especially to locate bottle necks and pinpoint possible upgrade scenarios. Not immediately visible here is how to install it on Centos 5.x and 6.x.

We shall use the whatprovides tool in yum to locate the packages that provide iostat

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