So recently I've been helping other teams that have a lot of EC2 instances and find my self ssh into them and running common and similar commands a lot!
On my personal machine I have my terminal using oh-my-zsh and Spaceship-prompt. My .zshrc is public here: https://github.com/ChrisTowles/dotfiles.
And I take for granted all the useful behavior and commands that I use on my personal machine. Autocomplete previous commands, better syntax highlighting, and more.
When I ssh into a server I find my self grepping the history and looking for commands that I use all the time. On top of that the default prompt doesn't have the server name. So its SOOOO easy to be on the wrong server. Are you in production or nonprod.
I'm wasting time it's only a matter of time I make a change to the wrong and impact users by mistake.
After many weeks of helping out with this I decided to try and make it easier for myself. I've started setting up oh-my-zsh on the servers for my profiles I'm in constantly.
The Setup
In my case these machines are Amazon Linux 2 and I found a great starting place at here
# Installing ZSH
sudo yum -y install zsh
# Check ZSH has been installed
zsh --version
# Install "util-linux-user" because "chsh" is not available by default - https://superuser.com/a/1389273/599050
sudo yum -y install util-linux-user
# Change default shell for current user
chsh -s "$(which zsh)" $(whoami)
# Install oh-my-zsh from https://github.com/ohmyzsh/ohmyzsh#basic-installation
# using unattended means not trying to change the default shell, and it also won't run zsh when the installation has finished.
sh -c "$(curl -fsSL https://raw.githubusercontent.com/ohmyzsh/ohmyzsh/master/tools/install.sh)" "" --unattended
# some of the most useful oh my zsh plugins
git clone https://github.com/zsh-users/zsh-syntax-highlighting.git ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-syntax-highlighting
git clone https://github.com/zsh-users/zsh-autosuggestions ${ZSH_CUSTOM:-~/.oh-my-zsh/custom}/plugins/zsh-autosuggestions
# open new shell
sudo su - $(whoami)
Now modify the ~/.zshrc to update the plugins
plugins=(git zsh-autosuggestions zsh-syntax-highlighting)
Update the prompt to include server name
So I want to quickly know what server I'm on you can modify the prompt in ~/.zshrc by adding this line:
SERVER_FRIENDLY_NAME=REPLACE_WITH_FRIENDLY_SERVER_NAME
# add user and host to ohmyzsh terminal prompt - https://stackoverflow.com/questions/30199068/zsh-prompt-and-hostnameE
autoload -U colors && colors
PS1="%{$fg[green]%}%n%{$reset_color%}@%{$fg[cyan]%}%m %{$fg[yellow]%}%~ %{$reset_color%}%% "
But if the default hostname is the ec2 IP? Here is AWS advice on changing prompt without changing the DNS or hostname.
https://docs.aws.amazon.com/linux/al2/ug/set-hostname.html#set-hostname-shell
Here we'll append this to the ~/.zshrc file.
SERVER_FRIENDLY_NAME=REPLACE_WITH_FRIENDLY_SERVER_NAME
# add user and host to ohmyzsh terminal prompt - https://stackoverflow.com/questions/30199068/zsh-prompt-and-hostnameE
autoload -U colors && colors
PS1="%{$fg[green]%}%n%{$reset_color%}@%{$fg[cyan]%}$SERVER_FRIENDLY_NAME %{$fg[yellow]%}%~ %{$reset_color%}%% "
Here is a screenshot of what this looks like.
Security
So the reasons for not doing this are mainly security. Any additional piece of code on the machine is another attack vector. So this is a judgment call. What is the impact of oh-my-zsh is compromised against the benefits. Based on the popularity of oh-my-zsh and I'm leaning towards this being safe enough to do in some environments.