All about Unix groups and access control.

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7
votes
2answers
7k views

I added a user to a group, but group permissions on files still have no effect

I changed permissions of a file (chmod g+w testfile) and running ls -l testfile gives: -rwxrwxr-x 1 user1 user1 0 2011-01-24 20:36 testfile I then added a user to that group ("/etc/group" has ...
50
votes
3answers
63k views

Make all new files in a directory accessible to a group

Suppose I have two users A and B and a group G and a folder foo, both users are members of G (using linux and ext3). If I save as user A a file under foo, the permissions are: -rw-r--r-- A A. ...
19
votes
2answers
11k views

How to apply changes of newly added user groups without needing to reboot?

Assume I'm logged in with user takpar: takpar@skyspace:/$ As root, I've added takpar as a member of group webdev using: # usermod -a -G webdev takpar But it seems it has not been applied. because ...
4
votes
2answers
487 views

Precedence of user and group owner in file permissions

I just ran into something unexpected (for me) regarding file permissions on Linux (Arch Linux). Basically I have: userX in groupX fileX userX:groupX ---rwx---- What puzzles me: I cannot perform ...
16
votes
2answers
19k views

Getting new files to inherit group permissions on Linux

I am having a problem with permissions on a Linux server. I am used to BSD. When a directory is owned by a group the user who owns it isn't in such as www-data, files created in it will be owned by ...
97
votes
6answers
31k views

Where did the “wheel” group get its name?

The wheel group on *nix computers typically refers to the group with some sort of root-like access. I've heard that on some *nixes it's the group of users with the right to run su, but on Linux that ...
20
votes
2answers
59k views

How can I change a user's default group in Linux?

Being new to Linux administration, I'm a little confused about the following commands: useradd usermod groupadd groupmod I've just finished reading the user administration book in the Linux/Unix ...
6
votes
3answers
4k views

What does it mean to be in group 0?

Several users in a system I inherited have their group set to 0 in /etc/passwd. What does that mean? Do they essentially get full root privileges? The system is running CentOS 5, and the users ...
0
votes
1answer
388 views

Added user supplementary group, but 'groups(1)' not showing change [duplicate]

I'm trying to add myself to the fuse user group but it doesn't look like the change is taking effect even though /etc/group looks correct after invoking addgroup or usermod. I've tried both ... sudo ...
12
votes
2answers
10k views

Why is Debian not creating the 'wheel' group by default?

It appears to be Unix tradition that a wheel group is created automatically, but Debian (and children, naturally) doesn't do so. Is there a rationale somewhere? Where else have you seen this tradition ...
10
votes
1answer
10k views

Group within group file permissions

I tried finding this on here, but couldn't so sorry if it's a duplicate. Say I have 2 groups and a user: group1, group2, user1 with the following structure: group1 is a member of group 2, user1 is a ...
8
votes
2answers
5k views

Group member cannot write even with write permission

The logged in user is a member of a group that has a write permission on a folder. But when this user is trying to write something, "permission is denied". The log below summarizes the question: ...
5
votes
3answers
14k views

granting write permissions to a group to a folder

How can I grant write permission to 1 group ? I have 2 users (alex and ben). alex is member of group alex and of group consult. ben is member of group ben and of group consult. I want to grant read ...
2
votes
2answers
58 views

Who should own files shared by a group and where should they go

I am configuring a Linux work station that will be used by a small number of users (20-30). These users will belong to a small set of groups (5-10) with each user belonging to at least one group and ...
1
vote
2answers
1k views

newgrp and groups assigned via pam_group.so

For convenience reasons I tend to assign special group memberships like floppy, audio, plugdev, video etc. via /etc/security/group.conf (pam_group.so) mechanism instead of adding all users to this ...
10
votes
2answers
10k views

GID, current, primary, supplementary, effective and real group IDs?

The following links discuss these concepts in different contexts. I have read their definitions, but I still can't tell how they are related, or if some of them are just the same. Current group ID ...
6
votes
2answers
7k views

Add all users in one group to another group?

I have some users in a group called aa and I need to give them the rights to write to a folder which is currently tomcat:tomcatdeploy. The straightforward way to do this is to add all the users to ...
4
votes
1answer
576 views

Why do I need to use newgrp or su (or logout and login again) to have new group memberships applied?

What is it that makes new group membership require a new login (or new login shell as started by su or newgrp) to be visible? Just running another bash (or whatever other shell) instance with --login ...
11
votes
2answers
5k views

I can't delete a file that I have write permissions for as a group member

$ touch testfile $ chmod g+w testfile $ sudo adduser user2 user1 $ stat -c'%a %A' testfile 664 -rw-rw-r-- $ su user2 Password: $ groups user2 user1 $ rm testfile rm: cannot remove `testfile': ...
3
votes
2answers
170 views

how to initialize `/etc/group`?

After editing /etc/group, How this update starts functioning without restarting the system in Unix? Is there any command we need to run?
6
votes
5answers
267 views

Changing Unix group for files

I have a file that a colleague and I are editing together, on a Unix system. We are using Unix group permissions to edit it. We have one Unix group that we are both members of. Whenever I save the ...
4
votes
2answers
224 views

Why are newly created users assigned to primary groups of their usernames?

I've noticed that on a number of linux distributions that whenever a new user is created, it is assigned to a primary group of its own name. eg. If i create a user called "testuser", by default it is ...
3
votes
3answers
218 views

Is there way to stop random software packages from remotely transferring your files?

I am running a bitcoin client on my archlinux computer. If somebody can get ahold of the wallet.dat file, located in the ~/.bitcoin/ directory they can steal my coins. I have minimal software ...
3
votes
3answers
3k views

Reset all groups to default

I recently set up some groups and users on my machine, and now I want to remove all those users and all those groups. Somewhat stupidly, I read on an Ubuntu forum or something like that that it was ...
2
votes
1answer
73 views

Different write behavior for owner and member of group despite 775 permissions

I have mounted a remote share via my fstab using the line: //path/to/target /media/f cifs gid=<mygroup's id>,dir_mode=0775,file_mode=0775 0 0 As a result, everything under /media/f winds up ...
2
votes
1answer
76 views

Do root's supplementary groups behave differently than regular account ones for NFS shares?

OS: Linux CentOS 7, NFSv4 On one machine I exported an NFS share group-owned by the nfsgroup with 2770 privileges for group collaboration: groupadd -g 5000 nfsgroup chown nobody:nfsgroup ...
2
votes
1answer
10k views

Changing user and group ID system wide (including file system attributes)?

(this question possibly related to Linux: simulating/masking user ownership upon mount of 'external' partitions? - Stack Overflow) I typically use Ubuntu (currently 11.04) as my desktop OS; let's say ...
1
vote
1answer
2k views

Accessing another user's files

I have a file "abc" with permissions 440 .The owner of this file is "root" and the group of this file is "groupabc" . I have a user "user1" .Is their anyway I can see the contents of files "abc" using ...