Python IP V4 validation

def validIP(address):
    parts = address.split(".")
    if len(parts) != 4:
        return False
    for item in parts:
        if not 0 <= int(item) <= 255:
            return False
    return True

Password less login's between servers ( ssh , scp , rsync)

For a particular user

/home/username/.ssh   ( go to this directory if that directory does not exists create one with name .ssh )

The key generated for password less login is user specific. So create separate keys for each user.

Goto .ssh directory

ssh-keygen -t rsa  (give that command and click next next as usual :) )

It will generate id_rsa and two files

one is private key and another is public key

now append the contents of to file authorized_keys in the system you want to connect

the file authorized_keys will be in .ssh directory of the other system if that file is not there create it.

cat >> ~/.ssh/authorized_keys

now try user@ ( if is the system you want to connect without password)