Anything related with user accounts and user management on Unix-like systems.

learn more… | top users | synonyms

6
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 ...
9
votes
2answers
3k views

How to restrict internet access for a particular user on the lan using iptables in Linux

Let's say there are two users on the LAN, A and B. How do I restrict user A from internet access using iptables rules and saving the rules so that after reboot, they are still effective. And suppose I ...
12
votes
1answer
2k views

Can one PC be used by two users at the same time via dual-monitor?

Since modern PCs can use two screens at the same time I wonder if it is possible to plug in two keyboards and mouses as well to have the two screens run two (more or less) independent X-sessions at ...
24
votes
1answer
13k views

What does adduser do that useradd doesn't?

In addition to the more widespread useradd, Debian based systems also contain an additional adduser command which provides a higher level interface for adding users and some related tasks. There are ...
19
votes
2answers
10k 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 ...
16
votes
2answers
19k views

How to create a user with limited RAM usage?

So I have 4 GB RAM + 4GB swap. I want to create a user with limited ram and swap: 3 GB RAM and 1 GB swap. Is such thing possible? Is it possible to start applications with limited RAM and swap ...
4
votes
2answers
374 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 ...
34
votes
5answers
44k views

Disable a user's login without disabling the account

Let's say I create a user named "bogus" using the adduser command. How can I make sure this user will NOT be a viable login option, without disabling the account. In short, I want the account to be ...
13
votes
11answers
1k views

Concern about logging in as root overrated?

For personal linux on my personal notebooks, I've usually set my environment to autologin as root even under X or lower runlevels. I've found my workflow is very pleasant and fast, without any ...
31
votes
4answers
14k views

Is it possible to rename a Unix user account?

I installed Ubuntu on a computer that is now used by somebody else. I renamed the account with her name, but it only changes the fullname, not the user name, which is still displayed in the top right ...
20
votes
2answers
53k 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 ...
17
votes
3answers
8k views

How can I determine if someone's SSH key contains an empty passphrase?

Some of my Linux & FreeBSD systems have dozens of users. Staff will use these "ssh gateway" nodes to SSH into other internal servers. We're concerned that some of these people use an unencrypted ...
8
votes
2answers
26k views

How to add a ssh user who only has permissions to access specific folder?

How to add an ssh user who only has permissions to access specific folder? useradd -d /var/www/xyz.com.tr/musteri -s /bin/bash -g sshd musteri I created a user called musteri. I set its home ...
6
votes
5answers
17k views

Disable user shell for security reasons

We have several user accounts that we create for automated tasks that require fine-grained permissions, such as file transfer across systems, monitoring, etc. How do we lock down these user accounts ...
6
votes
7answers
2k views

Is it bad practice to set root's shell to something other than the default?

Once a friend of mine (who is an experienced Unix/Linux user) told me that setting root's shell to something other than sh (i.e bash or zsh) might create problems, because some script might assume ...
3
votes
3answers
1k views

What mechanism prevents any user from accessing any other user's files via root?

On a multi-user system, what protects against any user accessing any other users files via root? As context, the question is based on my understanding as follows: There are two commands related to ...
2
votes
2answers
674 views

What does the `who` command result `root :0` mean?

The return value of command who will always include root :0 in X Window pts. I guess it actually means the GNOME login. Am I right? Another question is where to get this knowledge, as I don't see it ...
0
votes
1answer
353 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 ...
56
votes
4answers
14k views

What are other ways to share a tmux session between two users?

I'm looking for a clean and easy way to share a tmux session with another user on the same machine. I've tried the -S socket-path option, but it requires opening up all permissions of the socket-path ...
34
votes
7answers
25k views

How do you kick a benign user off your system?

I was googling this a bit ago and noticed a couple of ways, but I'm guessing that google doesn't know all. So how do you kick users off your Linux box? also how do you go about seeing they are logged ...
25
votes
2answers
61k views

What user should apache and PHP be running as? What permissions should /var/www files have?

I just spun up an Ubuntu 11.10 box and then ran apt-get install apache2 php5 to install apache2 and PHP 5 on the box. Now it is functioning as a "web server" and it loads the "It Works!" page. Now I'm ...
2
votes
1answer
31k views

How can I create an SFTP user in CentOS?

I'd like to give temporary SFTP access to a support guy. How do I create an SFTP user? And how can I delete it once the job is done? Also, how do I specify a home directory for them? Can I prevent ...
20
votes
2answers
10k views

What's the difference between a normal user and a system user?

Some documentation I'm going through has a boolean switch on whether or not a user is a 'system' user or a 'normal' user defaulting to 'normal'). What is the difference between these two modes of ...
10
votes
5answers
17k views

Can a linux user change their password without knowing the current password?

I'm setting up a few ubuntu boxes, and using opscode's chef as a configuration tool. It would be fairly easy to install public keys for each user on each of these servers, and disable password ...
10
votes
1answer
9k 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 ...
11
votes
2answers
2k views

Why is /etc/passwd open to public for reading?

Is there any reason that /etc/passwd should be world-wide readable ? It's not like password hashes that shouldn't be exposed, I just want to know why.
8
votes
1answer
717 views

Lightweight virtualization on Linux with user isolation

What Linux-on-Linux virtualization technologies provide user isolation? Specifically, I want root in the virtual machine not to have any privilege on the host. This was not the case for LXC, but was ...
7
votes
3answers
824 views

Does character 'ä' in usernames cause bugs in linux systems?

I want to use my first name as an username but it contains character 'ä'. I found this thread. Now I understand, why some some characters are disabled, but what about 'ä'? Can this character cause ...
6
votes
3answers
4k views

How can I create automatically expiring user accounts?

This is what I'd like to be able to do: After a user's account is created, they should be able to ssh-tunnel, but their account is automatically removed after 30 days unless the countdown is reset by ...
5
votes
3answers
496 views

Unix users, groups, and permissions

I don't understand unix users, groups, permissions, etc. For example, things managed by the chmod, chgrp, usermod, groupadd, etc. commands. How do all these things work?
4
votes
3answers
4k views

How to find the machine from which a user logged into current machine using ssh?

In a multi server architecture, is it possible to find out from which machine a user logged into current machine using ssh? For example, user1 logged into host1. From there, the user logged into ...
4
votes
2answers
2k views

Local Account Creation Date

For compliance purposes there is the need to fetch information regarding local (user and non-user) accounts creation date on UNIX machines. Is there any way (even if it's not the most reliable or ...
4
votes
4answers
180 views

“Who” prints duplicated usernames

This is result of who -uH: NAME LINE TIME IDLE PID COMMENT me :0 2013-08-29 01:29 ? 1686 (:0) me pts/0 2013-08-29 01:42 old ...
3
votes
1answer
147 views

Ubuntu user disappeared from machine

Unsolved mystery - I was given a coworker's Ubuntu 12.04.1 LTS machine and set up my own (sudo/admin) user on there from the command line. I switched to my user (from his sudo/admin user) and ...
3
votes
1answer
2k views

User logged in by sftp does not show up in `w`

My server is Centos 5. I have a chroot environment set up with the following in my sshd_config Match group sftponly ForceCommand internal-sftp ChrootDirectory %h AllowTcpForwarding no ...
2
votes
2answers
52 views

Find files created by a particular user

How would I go about discovering all of the files created by a particular user and display them to the screen? I've started a script that prompts the current user to enter the username of whom they ...
2
votes
3answers
233 views

How to create a user account with specific permissions?

I want to create a unix user account with specific permissions: this user must be able to install software, but can't remove software. Furthermore, when the user logs in, root must receive a ...
2
votes
1answer
183 views

Where can I find a reference to the format of the comment field (field 5) of the /etc/passwd file?

In the /etc/passwd file on my system, the "comment" field, field 5, is inconsistent in its contents. I thought that I could extract it to get the full name of the user. fullname=`awk -F: '$1 == name ...
1
vote
1answer
1k views

Disable operations outside user's home directory with chroot jail?

I'm trying to restrict a user to a specific directory called gclegal using a chroot jail. I've uncommented the line in the /etc/vsftpd.conf file chroot_local_user=YES Created a new user called kg: ...
13
votes
5answers
21k views

User-friendly command to list all users on Ubuntu system?

Is there a user-friendly command I can use to list users in a console on an Ubuntu system? When I cat /etc/passwd I get a hard-to-read list of users. It would be nice to see an alphabetized list, ...
11
votes
4answers
38k views

How can I look up a username by id in linux?

The command id can be used to look up a user's uid, for example: $ id -u ubuntu 1000 Is there a command to lookup up a username from a uid? I realize this can be done by looking at the /etc/passwd ...
9
votes
2answers
9k 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 ...
13
votes
3answers
1k views

Can I limit a user (and their apps) to one network interface?

As the title really. I've actually got two scenarios to apply this: Multiseat Desktop: two network connections both with internet gateways and two accounts doing bandwidth-intensive tasks on each. I ...
20
votes
6answers
16k views

How do you create a user with no password?

In os X it's possible to have users without passwords. If you inspect them with dscl their password show up as *. This is used for system users such as users for databases like mysql, pgsql etc. ...
7
votes
1answer
9k views

Mounting an ext3 fs with user privledges

I'm trying to mount an ext3 file system from another linux installation so that the user, not root, will have full access to all the files. (I really do need user to have access to those files, ...
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 ...
6
votes
3answers
6k views

Why are underscores not allowed in usernames in some distros (Debian for example)

So why has the underscore been considered a bad character for user names in Debian (and possibly other distributions) while it has been removed from adduser's NAME_REGEX in Ubuntu?
5
votes
2answers
924 views

Deleting users with nologin shell

On a security audit performed on our production Linux servers , we were asked to remove nobody user if no application are using it. I checked and could see that there are no files owned by 'nobody' ...
4
votes
2answers
1k views

How to see who is logged on to many workstations?

Before I go to work creating my own I would like to find an existing system to do the following: Provide a concise list of users logged on to any of the workstations Show workstation host name, IP, ...
4
votes
1answer
560 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 ...