Users, groups, permissions

Linux is multi-user from the ground up. Every process runs as some user, every file belongs to a user and a group, and the kernel decides who may do what based on exactly those two things. In Part II you step out of the role of the machine's only owner and start managing accounts and access.

To find out who you are right now and which groups you belong to:

$ id
uid=1000(student) gid=1000(student) groups=1000(student),27(sudo)
$ groups
student sudo

uid is the numeric user identifier, gid is that of your primary group. Names are for humans, but inside the system works with numbers. Membership in the sudo group decides whether you can raise your privileges; more on that below. On Debian and Ubuntu this group is calle