SSH

ssh into a machine

ssh <user>@<host>

About .bashrc

When you ssh into a machine with bash, /.bashrc will be sourded.

However, when you do it in another shell, e.g. zsh, only ~/.bash_profile will be sourced. So if you want to make ~/.bashrc sourced automatically in this case, source it in the machine's ~/.bash_profile.

if [ -f ~/.bashrc ]; then
  . ~/.bashrcvi
fi

See https://stackoverflow.com/a/820533/15493213 for discussion, and http://mywiki.wooledge.org/DotFiles for how it works under the hood.

Now, since bash is being invoked as a login shell, it reads /etc/profile first. On Linux systems, this will typically also source some or all files in /etc/profile.d (as suggested by the Linux Standard Base -- generally /etc/profile should include code for this). Then, bash looks in your home directory for .bash_profile, and if it finds it, it reads that. If it doesn't find .bash_profile, it looks for .bash_login, and if it doesn't find that, it looks for .profile (the standard Bourne/POSIX/Korn shell configuration file). Otherwise, it stops looking for dot files, and gives you a prompt.

Now let's take the second-simplest example: an ssh login. This is extremely similar to the text console login, except that instead of using getty and login to handle the initial greeting and password authentication, sshd(8) handles it. sshd in Debian is also linked with PAM, and it will read the /etc/pam.d/ssh file (instead of /etc/pam.d/login). Otherwise, the handling is the same. Once sshd has run through the PAM steps (if applicable to your system), it "execs" bash as a login shell, which causes it to read /etc/profile and then one of .bash_profile or .bash_login or.profile.

ssh with password in one line

sshpass -p <password> ssh <user>@<host>

but then your password will be visible for other processes or in the shell history

ssh without password

if you don't have ssh key on your machine yet

ssh-keygen -t rsa -f ~/.ssh/id_rsa

copy your ssh key to the target machine

ssh-copy-id -i ~/.ssh/id_rsa <user>@<host>

https://apple.stackexchange.com/a/285806
https://www.ssh.com/academy/ssh/copy-id

Install ssh server

install

sudo apt install openssh-server

enable & start

sudo systemctl enable ssh
sudo systemctl start ssh

open port 22

sudo ufw allow 22

ssh session

SSH sessions will be on a pseudo-terminal slave (pts). But keep in mind that not all pts connections are necessarily SSH connections.

keep ssh session from freezing

https://unix.stackexchange.com/a/200256

generate ssh key

1. ssh-keygen -t ed25519 -C [username]
2. press ok til the end (or type something to set password or change saving location)
3. private key & public key would be in ~/.ssh