Unix permissions: how groups work on Unix

Question

This is probably a duplicate (but did not find it ..)

When you type ls -lin unix, you get output like this:

% ls -l
total 48
-rwxr--r--   ... change*
-rwxrwxrwx   ... checkVersion*
-rwx------   ... info*

I know that the first group rwx sets the rights of users, and the last group sets "everyone else". I think the second rwx group sets the group permissions.

How can I tell people who are in a group? Which group do I belong to? Can I create new groups? Where are the groups defined on my machine?

---

Edit: Can I change groups by modifying the / etc / groups file or do I need to do this with a command?

Answer 1

,

groups

.

/etc/group

Answer 2

/etc/group, , :

• groupadd
• usermod

, yoda jedi:

• usermod -A jedi yoda

. :

• man groupadd
• man usermod

Answer 3

/etc/group. , .

unix groups , .

Hubble:~ $ groups
staff _developer _lpoperator _lpadmin admin localaccounts everyone

Answer 4

/etc/passwd. . /etc/group. id

group-name:x:group-number:user1,user2