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73
votes
6answers
21k 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 ...
55
votes
5answers
75k views

How do I remove a user from a group?

Which command should I use to remove a user from a group in Debian? When adding a user to a group, it can be done with: usermod -a -G group user However, I could not find a similar command ...
31
votes
3answers
29k 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. ...
16
votes
2answers
217 views

Typical use case for a group password

I checked more than half a century worth Unix experience and neither my colleagues, nor myself has ever set a password on a group (sg and gpasswd). What would be a typical use case for a group ...
15
votes
2answers
32k 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 ...
12
votes
2answers
6k 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 ...
11
votes
2answers
288 views

Why is root in wheel and operator? Can root being in a group ever make a difference?

I just noticed on my FreeBSD machine that root is in wheel and operator. I'm trying to think of a situation where UID 0 being in a group would have any effect on... well... anything, and I'm coming up ...
11
votes
3answers
584 views

Groups differ from the local ones when logging in remotely

We store our users in LDAP, alongside some groups that have meaning across different systems (organizational roles including wheel). There are also groups local to workstations, e.g. audio or video ...
10
votes
3answers
26k views

Change gid of a specific group

I'd like to change group id of a specific group. There are so may solution for changing the gid of a file or directories. But that's not what I want. Is there a way to do that?
10
votes
1answer
6k views

Meaning of root:wheel

What does root:wheel mean in the following? chown root:wheel myfile
9
votes
2answers
7k 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 ...
8
votes
1answer
2k views

In /etc/group what is the meaning of the second field?

A sample /etc/group file contains the following entries: root:*:0: adm:!:4:logcheck antoine:x:1000: The man pages I've read (Debian & OSX) says the second field is to store a group password. ...
7
votes
2answers
3k 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': ...
7
votes
4answers
170 views

Groupwise uniq command?

I am searching for a command to get from a file in this format: hello 32 hello 67 hi 2 ho 1212 ho 1390 ho 3000 To this format (deduplicate by taking the last row of a "group"): hello ...
7
votes
1answer
518 views

What is the purpose of `/etc/group-`

On a standard Linux distribution (e.g. Ubuntu) there is usually /etc/group and /etc/group-, where the second one is only readable by root. man group only describes /etc/group. Thus my question: What ...
7
votes
2answers
6k 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 ...
7
votes
1answer
375 views

Why cannot a user change group ownership of his own files? [duplicate]

Why cannot a user change the group permissions of files which he owns. Let's suppose I have user martin: $ ls -lAd /home/martin/ drwx------ 8 martin martin 4096 Apr 20 01:06 /home/martin/ For some ...
7
votes
2answers
3k views

linux permission, 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: ...
6
votes
2answers
5k 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 ...
6
votes
5answers
230 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 ...
6
votes
2answers
3k views

What are the allowed group names for groupadd?

I followed these instructions to build Shadow, which provides the groupadd command. I am now getting an error when trying this: $ groupadd automake1.10 groupadd: 'automake1.10' is not a valid group ...
6
votes
3answers
2k 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 ...
6
votes
1answer
4k 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 ...
6
votes
1answer
3k views

addgroup vs groupadd

I happen to know there is a slight difference between adduser and useradd. (i.e., adduser has additional features to useradd, such as creating a home directory.) Then what is the relation between ...
6
votes
1answer
6k views

what is 'nogroup' group's purpose

When I list al groups I see one called 'nogroup'. What is this for? Is it supposed to be least privileged one or something? I'm using ubuntu 11.04.
5
votes
2answers
5k 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 ...
5
votes
2answers
261 views

Group memberships and setuid/setgid processes

Processes which de-escalate privileges via setuid() and setgid() do not seem to inherit the group memberships of the uid/gid they set. I have a server process that must be executed as root in order ...
5
votes
1answer
96 views

How to run a process with a specific group?

I have to start an application with my own user rights, but the group must be different. So, instead of: $ ps -eo "user,group,args" | grep qbittorrent morfik morfik /usr/bin/qbittorrent it ...
5
votes
1answer
158 views

Can I add to my groups in the current (shell) process? [duplicate]

If I add myself to a group, it applies only to newly launched processes. Actually it's more restricted than that; it seems to apply only to new logins. I'm not sure what the exact mechanism is, but ...
5
votes
3answers
883 views

Can't read a file although it's in my group and permissions for group read are set

I encounter a strange problem on a unix/linux machine: I'm member of a group, let's call it group A and a certain file (which has a different owner) belongs to group A as well. The permissions of ...
5
votes
1answer
88 views

assigning files of a group to another one

I want to delete a group using groupdel command, but before doing this I want to assign all files belonging to this group to another one is there a way to do this? I know that I can use find / -gid ...
5
votes
1answer
149 views

Apache, Group Permissions and User Uploads

I have a folder named "digitalgoods" with the following ownership -- apache:apache residing outside of the htdocs folder and is therefore not accessible to the public. However I need the same folder ...
5
votes
2answers
71 views

Nested POSIX groups in Linux [duplicate]

If I want to add all of the members who belong to the supplemental group web_users to the apache group (as an additional supplemental group) can I just add web_users group to the apache group? Or do ...
4
votes
2answers
919 views

Why don't /etc/group and /etc/password match?

OK this is a basic question showing my ignorance of sysadmin matters... Looking at the UNIX system I work on, my /etc/passwd entry says my_name:x:uid:gid:comments:home directory:login shell Then ...
4
votes
1answer
463 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 ...
4
votes
2answers
390 views

Group ID 501 cannot be found

A file in a directory has a Group ID "501" After checking /etc/group, Group ID "501" was not found how is that possible ?
4
votes
5answers
1k views

Why is it recommended to create a group and user for some applications?

Most of the time, when installing a program from source it is recommended to create a new user and a new group and give /usr/local/<myapp> the recently created user and group ownership. Why is ...
4
votes
3answers
237 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 ...
4
votes
2answers
754 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 ...
4
votes
3answers
610 views

how to login as a member of specific group

i want to login as a member of non primary group to create files whose owner as a member of non primary group of current user. -rwxr-xr-x 2 gowtham gowtham 4096 Sep 5 14:48 defaultNewFile ...
4
votes
2answers
2k views

Problem while running “newgrp” command in script

I want to change the working group in my script. So I wrote a line newgrp test_grp1 in my script. But my script is automatically exited after running this line. Are there any solution to overcome this ...
4
votes
1answer
119 views

View List of Sudoers with No Sudo Priviledges

If I'm not a sudoer, is it possible to view the list sudoers? Does /etc/group show this information?
4
votes
1answer
50 views

When a member of multiple groups, how do I set the default group for newly created files?

With umask, I can determine the permissions for newly created files. But if I am a member of multiple groups, how do I set the default group for newly created files? This question seems relevant, ...
4
votes
3answers
172 views

restrict student account permissions, give faculty access

I have set up two user groups, students and faculty on Ubuntu 12.04 and created a number of students and faculty accounts. The problem is a student can currently see & read all of the files of a ...
4
votes
2answers
1k views

How do i extend a partition with a LVM and the contained physical volume and logical volume?

On my 240 GB SSD i had at first two partitions, one containing the Logical Volume with Linux Mint and the other had contained a NTFS partition to share with Windows. Now i removed the NTFS partition ...
4
votes
1answer
48 views

How do you give a developer group access to apache, MySQL, php and the webroot?

We have 3 web designers that are currently logging in to our server via root to configure apache and setup websites. I have very basic linux knowledge (I'm a web designer) and have created users and ...
4
votes
2answers
151 views

How to run script with the privileges expected of the script's general “intended user”?

During the development of a script, some bugs remain "latent" until the script is run by a different user. (For example, the script may access a file that only the person developing the script has ...
3
votes
3answers
5k views

What does GID mean?

What does GID actually mean? I have Googled it and this is what linux.about.com said: Group identification number for the process. Valid group numbers are given in /etc/group, and in the GID field ...
3
votes
3answers
491 views

Escaping argument in bash script?

I'm writing a bash script wherein I want to check that one of the arguments passed to it is a valid group. I have the line if [ `grep -c -e '\b$2\b' /etc/group` -eq 0 ]; then echo "Error: $2 is ...
3
votes
2answers
229 views

Seems that chown is allowed to non root user

We are using LDAP authentication and probably another things that I did not understand well, in our company so maybe the following questions are result of this. I have found strange behavior of chown ...