Run multiple commands on multiple machines asynchronously

mssh is a small, cross-platform, multi-threaded SSH client designed to run a series of commands in order across any number of hosts. It's entirely key-based, and does not support non-PKI authentication.

This was a weekend project for me. While it's a fairly simple little app, there aren't any tests beyond my functional testing (PRs welcome :)). I wouldn't rely on mssh for highly risky operations.

NAME:
   mssh - Run SSH commands on multiple machines

USAGE:
   mssh [global options] command [command options] [arguments...]

VERSION:
   0.0.3

COMMANDS:
   help, h	Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --user, -u 						SSH user (defaults to current user) [$MSSH_USER]
   --server, -s [--server option --server option]	Remote server [$MSSH_HOSTS]
   --key, -k 						SSH key (defaults to ~/.ssh/id_rsa) [$MSSH_KEY]
   --fail, -f						Fail immediately if an error is encountered
   --lines, -n "0"					Only show last n lines of output for each cmd
   --color						Print cmd output in color (use --color=false to disable)
   --help, -h						show help

# Get the number of running Docker containers
# and % used of /dev/xvdb
# Since no --key is defined, mssh will try
# to use the local ssh-agent
mssh \
  --user core \
  --server dev-01.lab.dev \
  --server dev-02.lab.dev \
  --server dev-03.lab.dev \
  'docker ps -q | wc -l' \
  'df -h | grep /dev/xvdb | awk "{print \$5}"'

mssh does not provide its own ssh-agent server, but it will fall back to an existing agent specified by SSH_AUTH_SOCK if no explicit --key is defined.

mssh runs each command in a detached shell. This means that there is no interactivity, so things like answering prompts are not possible. IO redirection and piping within a command work though, most interactivity needs can be accomodated that way.

The combined stderr and stdout streams are printed on completion. You can grab the last n lines with the --lines flag, similar to tail.

There are 2 ways to specify target servers: via the --server flag, or the $MSSH_HOSTS environment variable. Using both flags and the environment variable is allowed (i.e. flags do not override the env). The lists are combined but not deduplicated, that's a todo item. Ports can be specified by appending :<number> to the server name.

Env:

# comma separated list of hosts
export MSSH_HOSTS=test1.dev.lab,test2.dev.lab,test3.dev.lab:2222

Flag:

# Ports can be specified by appending ":<number>"
mssh --server test4.dev.lab --server 10.0.99.9:2022 ...

I've tested mssh primarily on OSX and 64 bit Linux. The changes for v0.0.3 were to accomodate the Windows command prompt, but I've only lightly tested functionality. mssh does not display color on Windows prompts, and commands need to be double-quoted (not single).

The default RSA key paths are ~/.ssh/id_rsa or ~/ssh/id_rsa on Linux and OSX, and %PROFILEDIR%\ssh\id_rsa on Windows.

Here are some alternatives in various other languages. The difference between those and this? This one's in Go, that's probably about it but I don't have much experience with other multi-ssh clients.

• pssh: Python
• pussh: Python
• mssh Python
• pdsh: C
• clusterit: C
• mussh: Bash
• GNU parallel: C
• parallel-ssh: Python
• multi-ssh: NodeJS