Archive for November, 2011


Quicktip: BASH (Shell) script – show duration/time taken to execute script

Simple BASH script example for showing the elapsed time for a script to execute:


start_time=`date +%s`

end_time=`date +%s`

echo "Script execution took $time_elapsed seconds."


Passwordless SSH (Public Key Authentication) for CentOS 5, CentOS 6, Ubuntu, Debian, Linux in General


You have two servers, ServerA and ServerB – you would like ServerA to be able to SSH in to ServerB without a password. Use this simple tutorial to achieve this:


Step 1: Generate public key on ServerA

SSH in to ServerA and enter the following command. Keep pressing enter (accept the defaults) – do not enter a passphrase.
ssh-keygen -t dsa

This should have generated a file, /root/.ssh/

Copy the contents of the file above:
cat /root/.ssh/

Step2: Copy ServerA’s public key to ServerB

SSH in to ServerB and paste the contents from /root/.ssh/ from ServerA (above) in to /root/.ssh/authorized_keys on ServerB:

If the /root/.ssh directory does not exist, create it first:
mkdir /root/.ssh
vim /root/.ssh/authorized_keys

Set the required permissions on the authorized_keys file:
chmod 0600 /root/.ssh/authorized_keys

Now try and SSH to ServerA from ServerB – you should not be prompted for a password. The same process can be used for other users, apart from root. If you want ServerB to have passwordless SSH access to ServerA, perform the same steps as above, but swap ServerA for ServerB the next time you do it.

Random Posts Recent Comments

  • Tony Says:

    Thanks it works! Just close the cmd windows and open a new one...

  • greenhart Says:

    I found another way around it. For the /format switch I used: /format:"%WINDIR%\system32\wbem\en-...

  • Jari Aalto Says:

    To determine OS, you can also use command lsb_release(1). See the options how to extract only part o...

  • shadovice Says:

    thanks! it worked like a charm, although there is still minor typo remained: rpm -Uvh http://downlo...

  • Joh Says:

    Great, thank you. Also works with the new version and Centos 6.3 without test repo, just install ...

  • sierprinsky Says:

    Muchas gracias por tu aporte :)...

  • kilby Says:

    The listed solution worked fine for me under Win7 64bit Though I had to run the copy as Asministr...

  • Viper5112 Says:

    The files are already in the C:\Windows\SysWOW64\wbem\en-US and they need to be in the system32 fold...

  • slowmOoh Says:


  • Jørgen Says:

    @Jordan, I had the same problem also on Windows 7 64 bits. It worked for my user account and Admini...

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