diff --git a/2024-03-10_Shell-Customizations.md b/2024-03-10_Shell-Customizations.md new file mode 100644 index 0000000..e250785 --- /dev/null +++ b/2024-03-10_Shell-Customizations.md @@ -0,0 +1,151 @@ +--- +date: 2024-03-27 +title: Shell Customizations and SSH +tags: + - homelab + - linux + - bash + - development +--- + +Taking a detour from actual deployments, I recently started experimenting with different shell customizations. +Until now, I've just used whatever default shell I have available on a given system, but a recent live stream +from [Lawrence Systems](https://www.youtube.com/@LAWRENCESYSTEMS) mentioned shell customizations and tmux and +lead me down this rabbithole. I'll also mention SSH configuration as its something that greatly helps my daily +productivity and is tangentially related to some of my customizations. + +## tmux +I only recently tried using tmux and I don't know why I went so long without it! The +[tmux wiki](https://github.com/tmux/tmux/wiki) offers a complete explanation of what tmux is and all of the +things it can do; in short, it manages processes and terminals. `tmux` has a pretty steep learning curve, but +it only took me a day to get the hang of a few basic shortcuts; `ctrl`+`b`, or the "prefix key" enables +interacting with `tmux` and then a command can be issued. Some of the commands I find most useful are: +- `?` - Shows a list of tmux key bindings +- `"` - Splits the window vertically and adds a pane +- `up`/`down` - Navigates between vertical panes; if you hold `ctrl`+`b` then it moves the split up and down +- `d` - Detaches the temux session; easy to remember since `ctrl`+`d` is how you detach an SSH session + +I'm not (yet) using tmux by default for local sessions, but I do have it enabled to run when I SSH into some +systems; this is the primary reason I really like `tmux`. I can ssh into my server from my laptop and start a + command (i.e.a very long rsync process) without worrying about disowning the process before my laptop goes + to sleep; when I ssh back in, perhaps from another computer, I have the same terminal history and the same + process attached. I will go into more detail in the "ssh" section of this post, but all I had to do is run + `tmux new -A -s ssh_tmux` when I connect to attach a tmux session named `ssh_tmux`, creating it if it doesn't + exist. + +## ssh +For SSH keys, I have one key pair I use for personal systems and another for work. I won't go into detail about +key management or key rotation and instead will focus on SSH configuration. My SSH config simply contains global +config options and includes other configuration files for specific hosts. I find this makes it easier to manage +hosts since I can group hosts in different files. My `~/.ssh/config` looks like: +``` +Include config.d/* +Host * + AddKeysToAgent yes + IdentitiesOnly yes +``` +- `AddKeysToAgent` adds keys to my ssh agent so I don't need to enter a passcode after the first time I use a key +- `IdentitiesOnly` prevents SSH from trying to infer an identity file to use if it isn't specified in SSH config + or explicitly supplied as an argument. + +> You can find descriptions of all the SSH config options in the [BSD manpages](https://man.openbsd.org/ssh_config). + +A couple example hosts look like: +``` +Host work.server + HostName + User ┌──[22:27]─[d_mcknight@MCKNIGHT-FW13]─(~) +└$ + + +And a snippet from .bashrc related to that: +```shell + color_off="\[\033[0m\]" # Text Reset + + # Regular Colors + black="\[\033[0;30m\]" + red="\[\033[0;31m\]" + green="\[\033[0;32m\]" + yellow="\[\033[0;33m\]" + blue="\[\033[0;34m\]" + purple="\[\033[0;35m\]" + cyan="\[\033[0;36m\]" + white="\[\033[0;37m\]" + + path_color=$blue + chrome_color=$purple + context_color=$cyan + prompt_symbol=@ # 🚀💲 + prompt='\$' + if [ "$EUID" -eq 0 ]; then # Change prompt colors for root user + context_color=$red + prompt_symbol=💀 + fi + PROMPT_COMMAND='if [[ $? != 0 && $? != 130 ]];then echo "⚠️";fi' + PS1="$chrome_color┌──[${context_color}\A${chrome_color}]─"'${debian_chroot:+('${path_color}'$debian_chroot'${chrome_color}')─}${VIRTUAL_ENV:+('${path_color}'$(realpath $VIRTUAL_ENV --relative-to $PWD --relative-base /home)'${chrome_color}')─}'"[${context_color}\u${chrome_color}${prompt_symbol}${context_color}\h${chrome_color}]─(${path_color}\w${chrome_color})\n${chrome_color}└${context_color}${prompt}${color_off} " + PS2=$chrome_color'└>$color_off ' + + export VIRTUAL_ENV_DISABLE_PROMPT=1 +``` +There's a lot going on in the prompt, but I will highlight pieces of it; keep in mind that the snippets below may +not be valid on their own and that some of the color formatting may be lost as I cut up the long prompt string. + +- `PROMPT_COMMAND='if [[ $? != 0 && $? != 130 ]];then echo "⚠️";fi'` isn't part of the prompt string, but rather an +expression evaluated before the prompt string. This renders a ⚠️ if the previous command fails and isn't just an +empty command. + +- `[${context_color}\A${chrome_color}]` prints the current time in 24H format. Helpful if you open a terminal and +want to quickly reference when you ran the last command and when it completed. + +- `${debian_chroot:+('${path_color}'$debian_chroot'${chrome_color}')─}` +and `${VIRTUAL_ENV:+('${path_color}'$(realpath $VIRTUAL_ENV --relative-to $PWD --relative-base /home'${chrome_color}')─})` +print an active chroot or Python venv path, if active. I print the venv path relative to the current directory +if within `home`; I find this helpful when I have multiple projects to make sure I know which one I'm looking at. +Note that I also specify `export VIRTUAL_ENV_DISABLE_PROMPT=1` to suppress the default `(venv)` prompt prefix. + +- `[${context_color}\u${chrome_color}${prompt_symbol}${context_color}\h${chrome_color}]` looks like the default shell, +`user@hostname` except when root the `@` is replaced with `💀` as an extra visual reminder that its a root shell. + +- `(${path_color}\w${chrome_color})` shows the current shell path like the default shell + +- `\n${chrome_color}└${context_color}${prompt}${color_off} ` continues to the next line and inserts the `$` or `#` +prompt, followed by a space. + +- `PS2=$chrome_color'└>$color_off '` updates the prefix used when there's a newline in a command. I like that this +makes each line start vertically aligned and it keeps the chrome colored differently from the inputs. + +## Further Reading +SSH, BASH, and tmux are all over a decade old with plenty of good documentation and write-ups that I've referenced. +My current `.bashrc` is in [this gist](https://gist.github.com/d-mcknight/176899ca924b5b4cfdf7692e36ca568e) and +I will try to keep that updated as I make changes; maybe one day I'll promote it to an actual repository with other +config files.