Linux (redhat) configuration

SSH Login without password

Source: http://linuxproblem.org/art_9.html

First log in on A as user a and generate a pair of authentication keys. Do not enter a passphrase:

a@A:~> ssh-keygen -t rsa 

Generating public/private rsa key pair. Enter file in which to save the key (/home/a/.ssh/id_rsa):  Created directory '/home/a/.ssh'. Enter passphrase (empty for no passphrase):  Enter same passphrase again:  Your identification has been saved in /home/a/.ssh/id_rsa. Your public key has been saved in /home/a/.ssh/id_rsa.pub. The key fingerprint is: 3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A 

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh 

b@B's password:  

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys' 

b@B's password:  

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B hostname B 

A note from one of our readers: Depending on your version of SSH you might also have to do the following changes:

• Put the public key in .ssh/authorized_keys2
• Change the permissions of .ssh to 700
• Change the permissions of .ssh/authorized_keys2 to 640

Chang host name

1. Change the hostname on a running system

hostname NEW_NAME
will set the hostname of the system to NEW_NAME. This is active right away and will remain like that until the system will be rebooted

• Permanent hostname change

RedHat based system use the file /etc/sysconfig/network to read the saved hostname at system boot. This is set using the init script /etc/rc.d/rc.sysinit
/etc/sysconfig/network
NETWORKING=yes
HOSTNAME="plain.domainname.com"
GATEWAY="192.168.0.1"
GATEWAYDEV="eth0"
FORWARD_IPV4="yes"

Also need to change the /etc/hosts if the host name is there.

Archive tool example command

tar -xvzf apache-ant-1.7.1-bin.tar.gz -C /opt/sce

//unzip file to a specific folder, note: gunzip does not support this.

unzip package.zip -d /opt

rpm example command:

rpm -ivh downloads/oracle-xe-univ-10.2.0.1-1.0.i386.rpm