Ssh – way for setting a shorter timeout in an ssh command

Use GNU Parallel to parallelize your collection:

parallel --slf rhel-nodes --tag --timeout 1000% --onall --retries 3 \
  "rpm -q {}; rpm --queryformat '%{installtime:date} %{name}\n' -q {}" \
  ::: bash bc perl

Put the nodes in ~/.parallel/rhel-nodes.

--tag will prepend the output with the name of the node. --timeout 1000% says that if a command takes 10 times longer than the median to run, it will be killed. --onall will run all commands on all servers. --retries 3 will run a command up to 3 times if it fails. ::: bash bc perl are the packages you want to test for. If you have many packages, use the cat packages | parallel ... syntax instead of the parallel ... ::: packages.

GNU Parallel is a general parallelizer and makes is easy to run jobs in parallel on the same machine or on multiple machines you have ssh access to.

If you have 32 different jobs you want to run on 4 CPUs, a straight forward way to parallelize is to run 8 jobs on each CPU:

GNU Parallel instead spawns a new process when one finishes - keeping the CPUs active and thus saving time:

Installation

If GNU Parallel is not packaged for your distribution, you can do a personal installation, which does not require root access. It can be done in 10 seconds by doing this:

(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash

For other installation options see http://git.savannah.gnu.org/cgit/parallel.git/tree/README

Learn more

See more examples: http://www.gnu.org/software/parallel/man.html

Watch the intro videos: https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Walk through the tutorial: http://www.gnu.org/software/parallel/parallel_tutorial.html

Sign up for the email list to get support: https://lists.gnu.org/mailman/listinfo/parallel

I am able to duplicate this using the command you used, and I am able to resolve it by wrapping the remote command in quotes. Here are my test cases:

#!/bin/bash -x

echo 'Unquoted Test:'
ssh evil sh -x -c exit 5 && echo OK || echo FAIL

echo 'Quoted Test 1:'
ssh evil sh -x -c 'exit 5' && echo OK || echo FAIL

echo 'Quoted Test 2:'
ssh evil 'sh -x -c "exit 5"' && echo OK || echo FAIL

Here are the results:

bash-[540]$ bash -x test.sh
+ echo 'Unquoted Test:'
Unquoted Test:
+ ssh evil sh -x -c exit 5
+ exit
+ echo OK
OK
+ echo 'Quoted Test 1:'
Quoted Test 1:
+ ssh evil sh -x -c 'exit 5'
+ exit
+ echo OK
OK
+ echo 'Quoted Test 2:'
Quoted Test 2:
+ ssh evil 'sh -x -c "exit 5"'
+ exit 5
+ echo FAIL
FAIL

In the first test and second tests, it seems the 5 is not being passed to exit as we would expect it to be. It just seems to be disappearing. It's not going to exit, sh isn't complaining about 5: command not found, and ssh isn't complaining about it.

In the third test, exit 5 is quoted within the larger command to run on the remote host, same as in the second test. This ensures that the 5 is passed to exit, and both are executed as the -c option to sh. The difference between the second and third tests is that the whole set of commands and arguments is sent to the remote host quoted as a single command argument to ssh.