Password free ssh logging to remote computer

1. Create rsa id
> cd
> ssh-keygen -t rsa

2. Copy rsa id to remote computer as user me
> ssh-copy-id -i ~/.ssh/id_rsa.pub me@10.19.169.5

3. Test by
> ssh me@10.19.169.5

The computer at 10.19.169.5 shall NOT ask you for password

Shell script to execute command on the list of computers

The list of computers is given as a text list of IP adresses named "all.list". Each IP in saparate line

To execute commands on each computer create file all.sh with following text
for i in `cat all.list | awk '{ print $i}'` ; do echo $i; ssh $i $1 ; done

Execute commands by
> source ./all.sh "ls -la"

To execute command as root on remote computer with ip 10.19.148.65 using ssh

To execute command as root on remote computer with ip 10.19.168.65
> ssh root@10.19.148.65 "ls -la"

To execute text replacement on remote computer using perl script
> ssh root@10.19.148.65 "perl -p -e 's/oldtext/newtext/g' oldfile >newfile"

How to replace text in many files using single perl command

To replace text "localhost" to "localnet" in all files with extension text execute following
> perl -p -e "s/localhost/localnet/g" *.txt

To add new line after new text "localnet" use new line code \x0a
> perl -p -e "s/localhost/localnet\x0anew line/g" *.txt

To insert TAB in replaced text use code \x09
> perl -p -e "s/localhost/localnet\x0anew line\x09rest of line after tab/g" *.txt