Shell Programming and Scripting

Hey Gurus,

I have this requirement to change the password for other servers remotely from one server. So, I installed public keys on all servers and wrote the following script to do the job. Something appears to be wrong with my loop, as it only changes one server and ignores the rest. I'm testing the script with a test data file with about 5 servers in it. The data file is the command-line argument to the script. Can you please tell me what's wrong and how to fix it?

As always, I truly appreciate this community effort. You guys are truly awesome; thank you very much.

Code:

#!/bin/bash
##data file name is passed in as argument to .sh script
filename="$1"
while  read -r line
do
        ##newPassword and username are placeholders
        ssh $line 'echo -e "TestPW\nTestPW" | passwd SomeUser'
done < "$filename"

Hi,

I think that this behaviour is being caused by the use of a 'while read' loop to drive the 'ssh' command. The way input is read in and processed in this particular script may not actually be what you'd expect. Instead of it looping nicely around, the entirety of your arguments end up being passed to 'ssh' in one glob, and it's just doing the first one.

Maybe try a 'for' loop instead ? So something like:

Code:

##data file name is passed in as argument to .sh script
filename="$1"
for server in `cat $1`
do
        ##newPassword and username are placeholders
        ssh $server 'echo -e "TestPW\nTestPW" | passwd SomeUser'
done

See if that works, and let us know how you get on.

maybe -n option for ssh is missing as its a script... Otherwise ssh is tempted to read StdIN which here is void...

@drysdalk, I copied and pasted your version, it just hangs, I never get the prompt back.

@vbe, it does work just the way it is, but it only processes one server and not all in the list.

Thanks guys.

Hi,

(Edit)

Just checking, but are you running it with the filename as an argument ? e.g. ./script.sh serverlist.txt or something like that ? The script takes the first argument ($1) as the filename to be read and processed.

I ask becasue if you were just running ./script.sh on its own will never return a prompt, which is what you describe. In that usage case it would be sitting waiting for you to type in the input yourself, and would only proceed with execution after you did a Ctrl-D or otherwise indicated the end of input.

It's also possible of course that the issue is with the ssh or passwd parts of the script now as well. You may need different flags to passwd, something like passwd --stdin on a Red Hat-style system.

Yeah, I'm running it exactly like that,

root@testserver1# ./pwchange.sh pwchange.dat

and my pwchange.dat is formatted as follows:

Code:

server1
server2
server3
server4
server5

With the while loop, it did read the pwchange.dat file, but it only changed the password for one server. And I got the prompt back.
With the for loop, ctrl-D does nothing, but ctrl-C breaks out of the script and give me the prompt back w/o doing anything.

Also, my environment is a mix of Solaris 10 and Linux (RHEL & SUSE). My script with the while loop does change one password, it changes either Solaris or Linux server. So, looks like the ssh & passwd commands are both OK.

So you havent tried ssh -n ... as I said ssh will read the first line but then it will expect things to coem from standard input unless you specify -n option