Friday, March 2, 2012

Notes on Sharing a Unix Account

After accidentally breaking an ec2 instance while trying to set up a separate user account with admin rights, I decided to keep using ec2-user and set it up to coexist with any other people who logged in on the account.  I don't expect my boss wants all my shell/vim/etc. customizations.

To achieve this, I took advantage of openssh's environment support (which required enabling PermitUserEnvironment yes in /etc/ssh/sshd_config) to set a variable when I log into the server with my key pair:

environment="VUSER=sapphirepaw" ssh-rsa ...

Next, a one-line change to ~/.bashrc:

[ -n "$VUSER" -a -r "$HOME/.$VUSER/bashrc" ] && . "$HOME/.$VUSER/bashrc"

That newly-sourced bashrc then takes care of setting up the rest of the world, with code like:

export SCREENRC="$mydir/screenrc"
export VIMINIT="source $mydir/ec2init.vim"
alias st="svn status -q"

Notice that vim doesn't support any sort of "find the vimrc here" environment variable, but it does allow for arbitrary Ex commands to run, so I used that instead.  (Hat tip to this helpful message.)  ec2init.vim then reads:

let s:rdir="/home/ec2-user/.sapphirepaw"
let &rtp=s:rdir . "/vimfiles," . &rtp . "," . s:rdir . "/vimfiles/after"
exec "source " . s:rdir . "/vimrc"

This expands all the variables soon enough to be useful, and also means that if I ever move/reconfigure the root directory name, I will have only one place to change it in vim.  And from there, all my settings are loaded.  Life is good again.

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