I'll try to talk about groups and rights. The comment did not fit ...
No, in * nix the group itself (as well as the user) does not have any rights. Rights are in the file .
A user and group are assigned to the file. And the user, in turn, is assigned to one or more groups.
Look at
avp@avp-xub11:~$ ls -l /var/log/syslog -rw-r----- 1 syslog adm 83972 Mar 19 14:39 /var/log/syslog avp@avp-xub11:~$
These -rw-r ----- are the rights (if briefly and not fully complete - r - read, w - write, x - launch the file for execution) user (in this case, syslog - rw-), group (adm r--) and all others (---) on actions with the file /var/log/syslog .
Id command
avp@avp-xub11:~$ id uid=1000(avp) gid=1000(avp) groups=1000(avp),4(adm),20(dialout),24(cdrom),46(plugdev),117(lpadmin),119(admin),124(sambashare),1001(vboxsf) avp@avp-xub11:~$
Shows information about the current user and the groups in which he belongs.
For example, tail reads the last few lines of a file. If it is started by syslog or avp (it belongs to the adm group), the command will work, and if someone else is not in the adm group (as you can see this is the group assigned to the file. When creating the file, the primary group of the user who creates file, but then you can change it), then we will see /var/log/syslog: Permission denied .
Here is a brief and all. If you have specific questions - ask.