Accounts and their lifecycle

Articles

• bash — the command shell — A command interpreter for interactive input, builtins, and shell scripts.
• SSH keys and ssh-agent — Key pairs for passwordless login; sshd rejects ~/.ssh if it is writable by the group or by others.
• chage — password and account expiry — Reads and changes local password aging settings and an account expiration date.
• nologin — a shell that refuses login — A login-shell replacement that reports refusal and exits instead of opening an interactive shell.
• Users and groups — Linux accounts and groups; usermod -G without -a replaces all of a user's supplementary groups instead of adding one.
• useradd — create a user — The useradd command creates a user account with a home directory, shell, groups and UID; passwd sets the password.
• passwd — change or lock a password — The passwd command changes your own password; as root it sets, locks and shows the passwords of other users.
• usermod — change an account and its groups — The usermod command changes an existing account — groups, login shell, home directory, name and locking.
• Processes — Viewing processes, signals and priorities; finding the processes that hog CPU or memory.
• sudo — running commands as another user — Grants temporary root rights via sudoers; edit the file only through visudo, or a mistake locks everyone out of sudo.
• systemd — System and service manager that manages units and their dependencies.