How to copy /etc/hosts to all my machines?

Question

import os, sys, time

servers = ['dev','admin','db1']
for s in servers:
    cmd = 'scp /etc/hosts regular_user@%s:/etc/hosts' % s
    print cmd
    os.system(cmd)

I have written this script to copy my current HOSTS file to all my other servers. However, I would like to do this from a regular user, not ROOT.

Since over-writing /etc/hosts takes root privelages, I would like to do SUDO. How can I put sudo inside that script?

This won't work, because it is permission denied to change /etc/hosts file.

cmd = 'sudo scp /etc/hosts regular_user@%s:/etc/hosts' % s

Solution 1

cat /etc/hosts | ssh otherhost "sudo sh -c 'cat >/etc/hosts'" will do the trick.

Solution 2

This is easily done using Paramiko (the native Python SSH client) rather than calling the ssh command.

• Use Paramiko to scp the file to /tmp on the remoteserver
• Use Paramiko to run 'sudo cp /tmp/hosts /etc/hosts' on the remove server.

There are many examples of Paramiko being used for scp, and to run commands with sudo, available on the web.

Solution 3

You need to do the sudo on the remote host instead of locally. Obviously for this to work, your account on the remote host will need sudo permissions to run the relevant copy command. It would look something like this:

cmd = 'scp /etc/hosts regular_user@%s:/tmp/hosts' % s
os.system(cmd)
cmd = 'ssh regular_user@%s sudo cp /tmp/hosts /etc/hosts' % s
os.system(cmd)

You might find using a framework like fabric or a configuration management system like cfengine or puppet to be a better long term choice...

Comments

[OMG Ponies]

Why not use DNS?

[Alex]

How do I use DNS?

[OMG Ponies]

BIND setup: dalantech.com/fusionbb/showtopic.php?tid/33013

[David Pashley]

you're doing it wrong.

[Spence]

This is definitely one of those "I need to drive a nail-- should I use an egg or fine china?" kind of questions.

[Jim Zajkowski]

This has a race condition on /tmp/hosts.

[user1686]

< /etc/hosts ssh otherhost "sudo tee /etc/hosts > /dev/null" - otherwise you get the "Useless use of sh award"

[Jim Zajkowski]

At least I'll understand my command line when I read it again in six months. Using tee to avoid a call to sh is certainly a candidate for "Obfuscated Command Line" or "Confusing Use of Side Effect." tee was made to watch the output of a command while logging the results, not as a replacement for redirection.