su and sudo
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In Unix-like operating systems, su (substitute user or switch user) and sudo (superuser do) are two different commands that allow users to run tasks with the security privileges of another user, by default the superuser (root).
su:
The su command is used to switch the current user to another user account. When executed it prompts for the password of the target user.
By default, without any arguments, su switches to the root user.
It does not inherit the environment of the target user which can lead to path issues or other environment-specific problems.
sudo:
The sudo command allows a permitted user to execute a command as the superuser or another user, as specified by the security policy.
sudo is generally considered safer than su because it grants limited administrative rights rather than full root access.
sudo can also be set up to require a password (the user's password, not the root password), but it can also be configured to not require a password.
User Access Control (UAC) security:
UAC is a security component in many Unix-like operating systems. UAC allows users to perform common tasks as non-privileged users and as administrators without having to switch users, log off, or use su.
UAC is designed to prevent unauthorized changes to the operating system.
Sudo user group:
In many systems, users who are allowed to use the sudo command are members of the sudo group.
Being part of this group is often synonymous with having administrative privileges.
sudo -l:
This command lists the allowed (and forbidden) commands for the invoking user on the current host. It's a way to check which commands you can run with sudo.
sudo -s:
This option runs a shell specified by the SHELL environment variable or the shell as specified in the passwd file. It allows a user to start a new shell with root privileges.
sudo -I (capital i):
This initiates a login shell. This means the environment will be similar to that of the target user, with some exceptions like PATH which is specified in the sudoers file.
sudoers permissions:
The sudoers file is where permissions are defined for users and groups. It specifies who can run what commands as which users on which machines and with what privileges.
visudo:
This is the command used to edit the sudoers file. It locks the file against multiple simultaneous edits and provides basic sanity checks and validation for syntactic correctness.
It is recommended to always use visudo to edit the sudoers file to prevent syntax errors that could potentially lock out all sudo users, which can be very problematic especially on systems where root access is not available by default.