I wish I could bring my aliases and scripts with me when I ssh...

4 min read

I can though, and you can too if you don’t mind a tiny wrapper function around your ssh command.

The way it works is:

  • Have a .serc file with your favorite aliases and scripts
  • Before ssh, base64 encode it to get rid of any formatting issues.
  • Pass the b64 decoded config to bash via --rcfile, using process substitution <(…) so bash reads it as a path that only exists in memory, making sure no file gets left behind on the remote.
  • You’re in.

It needs to have bash installed on the remote but the login shell can be anything.

This comes about because I was looking at this QoL improvement and wasn’t finding anything to my liking on the web. My hard requirement was:

  • Not bring any files whatsoever and have almost no overhead.

There is xxh but that brings your whole shell to whatever remote machine you ssh into. I didn’t want that compromise, even though the only cost is the very first connection, it felt like a bad crutch to move and install a custom shell on remote environments. sshrc is abandoned (though one could argue feature-complete) and it requires also bringing files around permanently; however, sshrc is a good alternative and a fair compromise all things considered and I might try it more thoroughly in the future.

Wrapper

Really simple as you can see. Throw it in your .zshrc or .bashrc and then just se HOST.

# Your portable shell config lives in ~/.serc (aliases, exports, functions).
# Requires bash to exist on the remote; the remote's login shell can be anything.
se() {
  local b64
  b64=$( {
    cat ~/.serc 2>/dev/null
  } | base64 | tr -d '\n' )
  ssh -t "$@" "bash -c 'exec bash --rcfile <(echo $b64 | base64 -d) -i'"
}
 
compdef se=ssh   # reuse ssh's host completion (needs compinit loaded; put this after it)

The last line (compdef) is zsh specific and is there so that we have the same tab completion as we’d have by using standalone ssh.

Be mindful to add the following two source lines to the .serc file:

source /etc/profile
source ~/.bashrc
# Your personal aliases and others
export EDITOR='vi'
alias k=kubectl
alias 'p'="python3"
alias 'v'="vim"
alias 'de'="deactivate"
alias 'c'="clear"
alias 'lh'="ls -ahl"
alias df='df -h'
alias diff="diff --color -u"
alias sr="source .venv/bin/activate"
alias sht="history | grep "
alias rr='sudo $(fc -ln -1)' #rerun last command as sudo
alias 'dc'='docker-compose'
alias 'dk'='docker'
alias nd='vim -d' # start a vim diff session
alias ss='ss -nltup' #
...

The first two lines are what make sure we don’t completely override the host’s .bashrc and run into PATH and other problems.

Test results

TL;DR: There’s a ~14ms of added overhead which is negligible and not noticeable. In fact, it’s almost the same value as the standard deviation (σ).

Since I wanted to make sure I wasn’t adding any meaningful overhead, I used hyperfine to measure my wrapper against the default ssh connection.

Both scripts were tested in a “warm” state, that is, the ssh connection control path was reused for every subsequent connection to avoid the key exchange and authentication.

.ssh/config:

ControlMaster     auto
ControlPath       ~/.ssh/control-%C
ControlPersist    yes

Helper script for the wrapper. It’s basically the wrapper we use anyway, we just add the -ic exit so that the connection terminates and doesn’t hang.

#!/usr/bin/env bash
b64=$(cat ~/.serc 2>/dev/null | base64 | tr -d '\n')
ssh -t "$1" "bash -c 'exec bash --rcfile <(echo $b64 | base64 -d) -ic exit'"
Testing:
hyperfine --warmup 3 --runs 100 --shell=none \
  'ssh -t muttley exit' \
  '/tmp/se-bench muttley'

The --warmup 3 makes sure we’ve setup the connection before the timing of the tests so that the session we created is being reused on the actual tests, resulting in a “warm” state.

The muttley host is one that is on my job’s infra and I’m connecting to it via my home network and through an OpenVPN connection; fairly standard.

Results:

Results

You can see that it’s barely noticeable. The extra System time is the cost of the extra process and pipe the wrapper sets up Very small price to pay in my opinion.

Graph View