All about Unix groups and access control.

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5
votes
3answers
2k 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 ...
1
vote
1answer
146 views

Is there a whoami to find the current group I'm logged in as?

I'm trying to find my current logged in group without wanting to use newgrp to switch.
1
vote
3answers
46 views

If I delete groups, are users in those groups deleted?

I use ubuntu 14.04 and made 120 users. 115 users are in "student" and 5 users are in "assistant". If I delete groups, then are users in those groups deleted too?
3
votes
1answer
124 views

What is the purpose of the 'ssh' group?

There is a system user named sshd on my system, and a group named ssh: $ cat /etc/passwd | grep ssh sshd:x:120:65534::/var/run/sshd:/usr/sbin/nologin $ cat /etc/group | grep ssh ssh:x:117: My guess ...
-2
votes
2answers
120 views

Delete all users and groups except root in debian

I would like to delete all users present by default on my Debian, but I wonder what can happen if I delete them... I am learning linux so I want to clean everything except root and play around with ...
1
vote
1answer
155 views

logrotate fails to rotate logs: error setting owner

Recently I've noticed that logrotate does not rotate my logs. user1@host:~$ /usr/sbin/logrotate /home/user1/logrotate.conf -v gives me an error: error: error setting owner of /home/logs/mylog.log.1 ...
1
vote
1answer
155 views

share encfs folder within the same group

given an encfs folder mounted under its own user, is it possible to permit read access to someone else (especially a system user), who belongs to the same group? For example user1 owns ...
1
vote
1answer
15 views

Access rights for directory, when you are a part of owner group [duplicate]

Right to the business, here is what I am trying to do foverzar@subsystem /home> ls -aln total 16 drwxr-xr-x 4 0 0 4096 Dec 12 23:07 ./ drwxr-xr-x 17 0 0 4096 Dec 4 13:51 ../ drwx-----...
1
vote
1answer
106 views

How to add users to Linux through a shell script

The shell script that I have to write has to create new users and automatically assign them to groups. This is my code so far: echo -n "Enter the username: " read text useradd $text I was able to ...
1
vote
1answer
263 views

Add multiple user to UNIX group in one line

On Centos 6.5 (and probably any) linux, I can create a group: sudo groupadd mygroup and add several users to it: sudo usermod -a -G mygroup userA sudo usermod -a -G mygroup userB sudo usermod -a -...
1
vote
1answer
106 views

group files into fixed-size chunks

Example: Say I have 20 000 images and I need to group them into folders in order to burn them to a CD (max 700MB / folder). General: I have N files and I need to group them into M groups, so that all ...
0
votes
1answer
53 views

Cannot edit visudo

I have to give my user permission to run sudo. I am using CentOs # uname -a Linux lab-hv1-centos1 3.10.0-229.el7.x86_64 #1 SMP Fri Mar 6 11:36:42 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux and have ...
27
votes
2answers
50k 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
2answers
357 views

Can users in a group access a file that is in another user's home directory?

I have 3 users A,B and C inside a group 'admin'. I have another user 'D' in whose home directory, there is a project folder. I have made D as the owner of that folder and assigned 'admin' as the group ...
1
vote
0answers
39 views

What command should I use to explicitly set list of groups and execute a command?

To execute a command as other uid, one uses su. The list of supplementary groups is not specified on command line, but instead read from configuration files (/etc/passwd, /etc/group), etc. Which tool ...
1
vote
1answer
101 views

How to switch a group without asking for a password?

In linux, there's two files where group definitions are specified. One of them is /etc/group and the other is /etc/gshadow. I want my regular user to be able to switch a group while starting a process ...
8
votes
1answer
11k 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 ...
-1
votes
1answer
65 views

Allowed group can't access a folder [closed]

I've a weird problem on my linux machine, I've multiple users, we can say u1, u2, u3... who all belong to a group G. I have a group folder in /home who belong to one of these user (we'll say u1), and ...
0
votes
6answers
1k views

How can I find out which users are in a group within Linux?

I've recently been creating new users and assigning them to certain groups. I was wondering if there is a command that shows all the users assigned to a certain group? I have tried using the 'groups' ...
1
vote
1answer
37 views

(vsftpd) uploaded file group

I'm creating an ftp server with vsftpd, and I've almost finished, the only thing remaining is when I upload a file (logged as an user U), the file belongs to a group which has the same name (so group ...
2
votes
1answer
84 views

Negative GID in /etc/passwd?

I got following entries in /etc/passwd and /etc/passwd- on one system: userfoo:x:501:-513::/home/userfoo:/bin/false There's no group 513 anywhere on the system. What's this "negative" gid or a gid ...
1
vote
1answer
26 views

Group Directory permission

you have been asked by couple of programmers to make ProjectA a group directory on a UNIX server which allows them to create files under that directory to facilitate collaborative work, but only the ...
3
votes
1answer
137 views

How to specify owner and permissions for an NFS mount?

I have an NFS mount in fstab: 10.0.12.10:/share1 /net/share1 nfs rw 0 0 which defaults to root as owner and group and 777 permissions. How do I specify another owner and different ...
2
votes
1answer
131 views

scp file as another group

I would like to scp a file, however my primary group does not match the permissions of the destination directory so I get a permission denied message when I try to scp. I have the correct group as a ...
3
votes
0answers
129 views

Give a user permission to one folder

I have set up my machine so that my group "sftponly" can access the users home folder. But right now, the users in the group don't have permission to other folders, but they have permission to see ...
3
votes
1answer
106 views

Why there is a group member field in both /etc/group and /etc/gshadow

I am learning more about Linux user and groups in depth and noticed fourth field in both /etc/gshadow/ and /etc/group are exactly same. Do they have any difference or is there any special reason why ...
4
votes
2answers
108 views

Can an AIX user that appears in etc/group but not etc/passwd still log into a server?

Looking at etc/group and etc/passwd files, I see accounts listed in various groups in the etc/group file that do not appear in the etc/passwd files. Can these accounts still log in to the AIX server?
7
votes
4answers
4k views

Reasons behind the default groups and users on Linux

Having a look at the default users & groups management on some usual Linux distributions (respectively ArchLinux and Debian), I'm wondering two things about it and about the consequences of ...
0
votes
1answer
217 views

user exists when trying to add user to systemd-journal group.

I have been wanting to read systemd-journal by running/using journalctl -b . Now if I run it as a user I get the following :- $ journalctl -b Hint: You are currently not seeing messages from other ...
0
votes
2answers
50 views

Can't change group permissions [closed]

I am currently having an issue which is preventing me from editing the group permissions for my '/media/rnetBackup/' directory. I have tried editing the permissions using nautilus and using chgrp -R ...
0
votes
1answer
43 views

Why can't I create directories under /root as a member of root? [duplicate]

I've done the following: sudo usermod -a -G root userA sudo su - root cd / chmod 775 root ls -aln -- drwxrwxr-x. 6 0 0 4096 Sep 13 22:04 root I can cd /root from my userA, but I can't make ...
8
votes
1answer
1k views

File owner must belong to file group?

I have a rather simplistic understanding of file permissions on *nix systems. I understand that there is a file owner and file group, but is there a hard and fast rule on whether the said file owner ...
1
vote
1answer
136 views

Read file permission denied despite sufficient permissions [duplicate]

I'm attempting to cat a file with 770 permissions as a user who is part of the group (but not the owner of the file). This should provide sufficient permissions to my understanding, yet I encounter a ...
1
vote
1answer
476 views

groupadd: group 'terminal' already exists in Linux

I have created a group called "terminal" using groupadd terminal and when I list out the groups using groups command it will not show the newly created group name in the output but if I add the same ...
3
votes
2answers
545 views

Why can't I create a file in a directory where I have group write access? [duplicate]

There's a situation I don't quite understand. I have this directory, where the group 'webadmin' has rwx rights : $ ls -la total 8 drwxrwxr-x 2 root webadmin 4096 Aug 27 12:17 . ⋮ ...
14
votes
1answer
7k 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. ...
67
votes
3answers
86k 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. ...
1
vote
1answer
66 views

directory permissions [closed]

I'm currently working on a PHP server explorer, and I have to determine if a directory is empty or not readable because of insufficient permission. My web application is running under the user apache,...
4
votes
3answers
7k views

How to add group to a user without removing other group in suse linux with usermod?

I have one user, which has one primary group & one secondary group, like: [ testuser Welcome ~ ]$ id uid=2000(testuser) gid=2000(testuser) groups=2000(testuser),27(sudo),2001(testgroup) ...
1
vote
2answers
733 views

Where & How is user group information stored in Ubuntu? [closed]

Two places possible: /etc/group and /etc/passwd. If I use command: adduser [username] [groupname], then the user would be added to the group, and the file /etc/group would then be updated. However, ...
1
vote
1answer
73 views

Unable to execute program without root privileges regardless of group or permissions

avrdude is a simple tool that allows downloading of a program to a target microcontroller. For completeness, the command I am trying to issue is: avrdude -p atmega328p -c usbtiny -P usb -v -U -flash:...
0
votes
1answer
152 views

Configure ssh users under a group [closed]

I created a group called ssh_group and currently have nearly 20 users under AllowUsers in /etc/ssh/sshd_config. After I created the ssh_group, I modified the AllowGroups line like this AllowGroups ...
3
votes
1answer
30 views

give group permissions to specific device

I have a panning web camera I built, (future robot arm). The camera pans via a web interface (cgi scripts and JS interface) which access an arduino. To enable sending of commands via the interface, I ...
-2
votes
2answers
91 views

How to prevent selected users from using “newgrp” with a password [closed]

I'd like to know how can I avoid add some users to a group? I need to avoid some users join to a group --I want to lock a group from some users, not all. Details lgroupmod -L dba ==> This ...
2
votes
1answer
164 views

Udev rule- change group

I would like to change group of /dev/nvidia0. I was write udev rule: KERNEL="nvidia[0-9]", GROUP="video", MODE="0666" But it does't change group, after reboot file is in rootgroup. How do this?
3
votes
1answer
281 views

Two users with different permissions on same directory

Is it possible to give two users different permissions on the same directory? I want to use it for ftp: userFull gets R+W and userLim gets only Read, depending on who logs on. Im getting stuck on the ...
0
votes
1answer
37 views

Directory Permission Order [duplicate]

In Linux, let us assume we have a directory with the following properties: drwx---r-x 29 user1 group1 4096 Jun 22 14:11 dir1 can I, as user2 having group group1, navigate into dir1? Since ...
1
vote
0answers
160 views

groupadd failure: “Cannot open audit interface”

I'm trying to add a group in a chrooted environment: root@my-host:/# /usr/sbin/groupadd -g 101 games Cannot open audit interface - aborting. I'm operating with root permissions. Additional info: ...
3
votes
1answer
383 views

Why does uucp take group 10?

According to YoLinux, group ID 10 typically belongs to wheel. And on my Arch Linux installation, sure enough there in /etc/group is wheel:10. However, on my Ubuntu machine instead I'm greeted with ...
0
votes
1answer
62 views

What is FreeBSD equivalent of Linux /etc/gshadow?

FreeBSD version 9.0 I have here. It has /etc/passwd and /etc/group files as Linux does. I figured that Linux /etc/shadow corresponds to FreeBSD /etc/master.passwd. The open question is what FreeBSD ...