Lesson 4: Users, Groups, Permissions¶
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Warning
This lesson is under construction. Learn from it at your own risk. If you have any feedback, please fill out our General Feedback Survey.
The User¶
You... ish.
$ whoami # your username
$ who # who is logged in?
$ w # who is here and what are they doing?
$ id # user ID, group ID, and groups you're in
Sometimes robots are users too: Apache, Mailman, ntp.
What a User has¶
/etc/passwd:
root:x:0:0:root:/root:/bin/bash
username:password:uid:gid:uid info:home directory:shell
What Users Can Do¶
- Change Passwords with the passwd command.
- Act as Another user with su.
$ su $USER # become user, with THEIR password
$ su # become root, with root's password
$ sudo su - # use your password instead of root's
$ sudo su $USER # become $USER with your password
Act as themselves.
- ls -l to see file permissions.
- Check the file’s group and user.
- Check the file’s read, write, and execute bits.
Managing Groups and Users¶
$ cat /etc/passwd
# username:x:UID:GID:GECOS:homedir:shell
$ useradd <user_name> # vs adduser, the friendly Ubuntu version
$ userdel <user_name>
$ passwd
$ groupadd
$ usermod
$ groupmod
$ cat /etc/group
root:x:0:
Examples of Non-Human Users¶
- mailman: For the mailing list program.
- apache: For the HTTP Server.
- postfix: For the other mail program.
Root and Sudo¶
- Root:
- Basically god on Linux.
[foo@compe ~]$ yum install httpd # Runs command as `foo` user
Loaded plugins: fastestmirror, ovl
ovl: Error while doing RPMdb copy-up:
[Errno 13] Permission denied: '/var/lib/rpm/__db.002'
You need to be root to perform this command.
[foo@compe ~]$ sudo yum install httpd # Runs command as `root` user.
password:
Loaded plugins: fastestmirror, ovl
[... installs correctly ...]
Warning
Acting as root is dangerous! You can accidentally delete your filesystem, forcing you to completley re-install your OS! Type carefully.
TODO¶
- Create a user on your system for yourself, with your preferred username.
- Give your user sudo powers.
- Use su to get into your user account.
- Change your password.
- Create a directory called bootcamp in your home directory.
- Create a group called devops.