All about Unix groups and access control.

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Where does Linux track who is a group admin through the gpasswd command?

If I modify group membership and admins using the gpasswd command and add a user as a group admin Linux will allow that user to perform tasks otherwise reserved by root. Ex. [test1@centos ~]$ ...
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3answers
29k 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 ...
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2answers
65 views

Meaning of the colon and x in getent group

I'm new to Linux and I came across the command getent group sudo to list sudoers in sudo group and I got the output sudo:x:27:lion now I wounder what is the meaning of :x:, colon and 27 ... also I see ...
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1answer
220 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 ...
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1answer
2k 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 ...
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2answers
56 views

Why do you have to be a member of a group to make that group the group owner of your file?

In unix, I know that you have to be a member of a group to change the group owner of a file to that group even if you own it, but can someone please tell me why. I don't understand why you shouldn't ...
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3answers
35 views

Is group priority available?

[tjm@ArchPad bin]$ LANG=en [tjm@ArchPad bin]$ pwd /usr/bin [tjm@ArchPad bin]$ ll | grep wireshark -rwxr-x--- 1 root wireshark 88K Apr 25 00:22 dumpcap -rwxr-xr-x 1 root wireshark 2.0M Apr 25 00:23 ...
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1answer
54 views

Cannot Bash chgrp GROUP /home/*/SOMEFILE/ How to do it?

So am setting a code that will change group owner of the file to a specific group. PS there are more than 10 users, with same folder and file structure, and i want change the ownership of a specific ...
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1answer
9 views

Significance of groups assigned to user by Debian installer (only)?

I want to remove my default user from the sudo group. IOW I want to change it to an unprivileged account. However it also seems to be a member of ten other system groups. What is the overall ...
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2answers
11k views

What is nobody user and group?

On my server (Synology DS212) some files and folders have nobody nobody users and groups. What are the characteristics of this user and group? Who can write of read this file? How can I change it ? ...
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1answer
25 views

usermod -a -G group user not work [duplicate]

I use Ubuntu 12.04. I am trying to add the user gefalko to the www-data group. I use root@xxx~# usermod -a -G www-data gefalko If I understand correctly, I should now see www-data in the output of ...
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957 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 ...
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1answer
26 views

Linux, having trouble adding user to second group

Redhat Linux 5.10 (Tikanga) I'm trying to add an existing user to a second group. The user is already part of the primary group called "prim" and the secondary group I want to add him to is "sec". ...
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0answers
17 views

useradd failing [duplicate]

Debian 8, I'm trying to allow a user to run Wireshark. user1@system:~$ sudo useradd -G wireshark user11 useradd: user 'user11' already exists However: user11@system:~$ groups user11 cdrom floppy ...
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2answers
55 views

Primary and secondary groups

So I've got the basics of primary and secondary groups down, but still have some questions I can't seem to find solid answers to: Can many users belong to the same primary group? Can one user's ...
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3answers
64 views

Predefined group ids across Linux distros?

In order to successfully implement w/r access via ACL for external storage with ext4 fs I need to assign default group id for files on storage. LSB_5.0.0 say: This specification makes no attempt to ...
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5answers
50 views

Show a user exists command

Is there a command that shows a user exists and is assigned to a group? I have just used the command usermod -a -G [GROUP] [NAME OF USER] and assigned a user to a group but, I was wondering if there ...
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1answer
34 views

How to avoid that Geany editor changes owner of file when it's edited?

I use Geany to edit files in a web app that resides in /var/www. The owner and group of /var/www and all sub directories and files are www-data:www-data. My user account is a member of that group and ...
147
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9answers
230k 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 ...
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1answer
45 views

trouble understanding GID and chmod g+s

I am having trouble understanding the GID and the command chmod g+s I read this as setting the permissions of the passed file or directory, for the group, as +s (sticky im assuming?) Does the +s mean ...
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1answer
4k views

id command doesn't show all user's groups [duplicate]

I did a usermod to add the current user user in a group, but when I run id -Gn it only shows the main user's group: [user@computer ~]$ id -Gn user But when I specify the user, it works normally: ...
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2answers
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Files are created with old group ownership even though the creator doesn't belong to old group anymore

I am currently preparing for LPIC Level 1 exam and I have been practicing management of user accounts on CentOS 7 system installed on VirtualBox. Firstly, as root, I created a user 'foo' with group ...
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2answers
54 views

How can I create a sub-directory where my group has no write permissions?

I am working in my Tomcat deployment directory. The files in the directory have the permission: drwxrwsr-x. 10 tomcat www 4.0K Mar 15 15:14 webapps A sample sub-directory within webapps looks ...
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4answers
260 views

Can a Linux user have multiple primary user groups?

How many primary groups can an individual Linux user have? If they can have more than one, how does one go about assigning multiple primary groups to a user? If it's just one, what's the cause?
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File System Permissions: User who can backup all files

I am setting up an automated backup job for some computers on my network. There is a server that will, daily, run an rsync command to backup each of the other computers. I'd like the user that the ...
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1answer
27 views

What is each group's permissions, and what is the “ranking” of each group (most privileged to least)?

My question is basically the title, but for further clarification with the ranking part, I'm asking about who inherits permissions from who, along with any additional permissions for the group as ...
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0answers
35 views

How to set correct user group rights to application running with java?

How to set correct user group rights to application using java? There is this scenario: 1) I have created user group and user (the same) - call it "groupgroup" 2) When I create a file with this ...
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2answers
55 views

Why are privs required to setgid() to supplementary groups

The various set*gid() system calls require privileges to change groups except in a very few cases. Changing primary group to one of the processes' supplementary groups does not appear to be one of ...
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3answers
17k 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 ...
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1answer
633 views

Implications creating System Accounts “useradd -r” Linux Fedora/RHEL/CentOS

I want to know what are the implications of create an account using -r option? # useradd -r ... The help says: -r, --system Create a system account. System users will be created with no aging ...
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1answer
63 views

Access from multiple users to same directory but can't change directory group to a common one

I need to give full access to user1 and user2 to this directory: drwxr-xr-- 3 oracle dba 4096 feb 9 23:16 scripts I can't change directoy group because probably that group is needed for other ...
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6answers
40k 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 ...
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1answer
60 views

How can I add all my groups to a different user in bash?

I've got a user named foo. I'd like foo to have all the same group memberships that I do. I thought I was close, with this: sudo usermod -a -G $(id -Gn | tr " " ",") node4 The id piped to tr is ...
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2answers
45 views

How to count how many files belong to each user/group combination?

How to count how many files belong to each user/group combination? I need to do this for each user/group combination that exists, in each of the directory trees /etc, /usr, and /var.
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2answers
3k views

Allow all group members to create directories and files

There are 2 users sftp_user apache Both users belong to the updaters group as well as other groups. New directories and files are created in the /updates/ directory. drwxrwsr-x 8 sftp ...
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5answers
11k views

Setting multiple groups as directory owners

On my server I have directory /srv/svn. Is it possible to set this directory to have multiple group ownerships, for instance devFirmA, devFirmB and devFirmC? The point is, I want to subversion ...
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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 ...
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1answer
126 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.
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3answers
45 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?
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1answer
109 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 ...
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2answers
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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 ...
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1answer
118 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 ...
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1answer
115 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 ...
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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 ../ ...
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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 ...
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1answer
147 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 ...
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1answer
93 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 ...
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1answer
49 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 ...
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2answers
46k 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 ...
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2answers
253 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 ...