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85 lines
2.0 KiB
Markdown
85 lines
2.0 KiB
Markdown
# Sudo
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> Avoid modifying the `sudoers` files manually and execute `visudo` instead; it will check the syntax on save, preventing you from screwing up the file.
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## TL;DR
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```sh
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# Make changes to a sudoers file.
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visudo
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visudo -f path/to/file
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# Check the syntax of a sudoers file.
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visudo -c path/to/file
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```
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## Drop privileges
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```sh
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# Invalidate the user's cached credentials.
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sudo -k
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# Ignore the user's cached credentials for the given command only.
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sudo -k ls
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```
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## Restrict permissions a little
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```sh
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# file /etc/sudoers.d/user
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Cmnd_Alias UPGRADE_CMND = /usr/bin/apt update, /usr/bin/apt list --upgradable, /usr/bin/apt upgrade
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Cmnd_Alias SHUTDOWN_CMND = /sbin/shutdown
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user ALL=(ALL:ALL) NOPASSWD: SHUTDOWN_CMND, UPGRADE_CMND
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```
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## Avoid providing a password
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```sh
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# file /etc/sudoers.d/user
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user ALL=(ALL:ALL) NOPASSWD: ALL
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```
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## Execute commands as a specific user
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Invoke a login shell using the `-i, --login` option. When one does not specify a command a login shell prompt is returned, otherwise the output of the command is returned:
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```sh
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% whoami
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root
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% sudo -i -u user
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$ whoami
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user
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% sudo -i -u user whoami
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user
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```
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## Troubleshooting
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### I modified a sudoers file manually, messed it up, and now I cannot use sudo anymore
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Should you see something similar to this when using `sudo`:
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```sh
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$ sudo visudo
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>>> /etc/sudoers: syntax error near line 28 <<<
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sudo: parse error in /etc/sudoers near line 28
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sudo: no valid sudoers sources found, quitting
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```
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try using another access method like `PolicyKit` and fix the file up:
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```sh
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pkexec visudo -f /etc/sudoers.d/user
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```
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## Sources
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- [How to modify an invalid sudoers file]
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- [sudo as another user with their environment]
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- [sudo: Drop root privileges]
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[how to modify an invalid sudoers file]: https://askubuntu.com/questions/73864/how-to-modify-an-invalid-etc-sudoers-file
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[sudo as another user with their environment]: https://unix.stackexchange.com/questions/176997/sudo-as-another-user-with-their-environment
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[sudo: drop root privileges]: https://coderwall.com/p/x2oica/sudo-drop-root-privileges
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