rex (remote execute)

rex executes given command(s) on multiple remote hosts, ssh-connecting to them in parallel.

You're expected to have passwordless access to hosts, rex authenticates itself with the help of ssh-agent that is expected to be running.

Setup

go install github.com/artyom/rex@latest

Binary will be placed either to directory set with ${GOBIN} environment or to ${GOPATH}/bin which defaults to ${HOME}/go/bin.

Usage examples

Execute uptime command on multiple hosts:

rex -l root -cmd 'uptime' host1.example.com host2.example.com

Default username may be overridden on a per-host basis:

rex -l root -cmd 'uptime' host1.example.com [email protected]

Default username can be set as environment variable:

export REX_USER=admin

If output should be saved to files, not printed to console, use -logs flag:

rex -logs -l root -cmd '/etc/init.d/mysql restart' db1.example.com db2.example.com

By default output would be saved to /tmp/db1.example.com.stdout, /tmp/db1.example.com.stderr, etc. Empty files would be automatically removed. Override filename templates with -logs.stderr and -logs.stdout flags.

When complex processing is required on remote hosts, it can be easier to write separate script and pass it via -stdin flag:

rex -stdin my-script.sh -cmd '/bin/sh' host1.example.com host2.example.com

Note, -stdin argument should be a regular file, since it is read multiple times — one time per remote host, so giving something pipe-like here won't work.

The same mechanism can be used to copy arbitrary data:

rex -stdin archive.tar.gz -cmd 'tar xz -C /tmp && cp -v /tmp/file-from-archive /dst' host1 host2

Since in most workflows multiple hosts are used together over and over again, it's easier to group them together. rex treats hostname starting with @ symbol as group name; groups are read from yaml file specified by -g flag which defaults to $HOME/.rex-groups.yaml. Consider the file with following content:

alpha:
  - alpha1.example.com
  - alpha2.example.com
  - alpha3.example.com
beta:
  - beta1.example.com
  - beta2.example.com
  - beta3.example.com
  - beta4.example.com

Now rex can use groups:

rex -cmd 'uptime' @alpha @beta

Both groups and arbitrary hosts can be used together.

License

MIT