Questions tagged [users]

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

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16
votes
4answers
16k 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 user1:...
20
votes
4answers
10k 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 any ...
42
votes
3answers
49k views

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

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
9k 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. Suppose also ...
21
votes
1answer
4k 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 ...
42
votes
3answers
64k 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 ...
53
votes
6answers
111k 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 ...
70
votes
3answers
66k 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 ...
83
votes
6answers
18k views

Why can't Linux usernames begin with numbers?

Is there a technical reason why? Is this an artifact from the early days of Linux or Unix, and if so is there a reason why it persists?
23
votes
1answer
25k views

How do I set a user's default .bashrc file?

On Ubuntu 10.4 I have edited the /etc/bash.bashrc file to set some variables like the command history size (HISTSIZE=5000), however if I create a new users Ubuntu by default gives them a .bashrc file ...
16
votes
10answers
2k 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 ...
106
votes
4answers
46k 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 ...
41
votes
5answers
162k 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 ...
22
votes
3answers
29k 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 ...
471
votes
10answers
2.0m views

How to switch between users on one terminal?

I'd like to log in as a different user without logging out of the current one (on the same terminal). How do I do that?
86
votes
7answers
172k 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 ...
75
votes
8answers
68k views

Does /usr/sbin/nologin as a login shell serve a security purpose?

In my /etc/passwd file, I can see that the www-data user used by Apache, as well as all sorts of system users, have either /usr/sbin/nologin or /bin/false as their login shell. For example, here is a ...
17
votes
2answers
54k 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 folder ...
33
votes
2answers
79k 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 ? ...
14
votes
2answers
27k 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 ...
12
votes
3answers
9k views

How to set permissions in /sys/ permanent?

I'm starting X as a user and need to set my keyboard brightness in /sys/class/leds/asus\:\:kbd_backlight/brightness. The /sys/ directory gets recreated after reboot, so the permissions will reset too. ...
12
votes
4answers
49k views

What is the difference between user and service account?

I would like to know difference between user and service account. I know that e.g. Jenkins installed to ubuntu is not a user, but service account. What is use of service account? When we need them? ...
10
votes
1answer
11k 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 ...
15
votes
7answers
5k 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 ...
0
votes
1answer
74 views

Does a user have to log in to run a process and become its owner?

In general, does a user have to log in to run a process and become its owner (ruid, or euid)? Does this apply to any user or any non-root user? For example: In the boot sequence of Linux, the kernel ...
8
votes
1answer
90k 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 ...
17
votes
1answer
46k views

Difference between sudo user and root user [closed]

The /etc/sudoers file lists which users can do what with the sudo command The root user creates and modifies the /etc/sudoers file. This concept is difficult for me to understand. If all users ...
34
votes
13answers
14k views

Can I create a *super* super-user so that I can actually have a user that can deny permission to root?

I was thinking that it might be advantageous to have a user with permissions higher than the root user. You see, I would like to keep all of the activities and almost all existing root user ...
44
votes
3answers
24k 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 ...
20
votes
3answers
44k 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 ...
11
votes
1answer
2k views

How can you assign one IP per user?

I'm building a headless Steam gameserver which utilises Steam in-home streaming to let two people play at the same time. The multiseat part of the setup is done and functional, but getting it to work ...
20
votes
5answers
2k views

Find files that a user can write, efficiently with minimal process creation

I am root. I would like to know whether a non-root user has write access to some files - thousands of them. How to do it efficiently while avoiding process creation?
9
votes
4answers
46k views

New user with root access in Linux Debian

I've created a new user by using "User Accounts" in "System Settings". How do I grant rights so that this new user can have the same level of access as root?
6
votes
3answers
5k views

How to return the currently active user/session on a graphical Linux desktop session? [closed]

My question is how to get the user name on the shell, who is currently using the Linux desktop (on a "normal" desktop system, where you usually only have one active user, i.e. no server system here, ...
17
votes
1answer
13k 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. As ...
8
votes
1answer
1k 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 ...
6
votes
3answers
21k views

How do I enable auto-login in Mint 18?

Mint 18.2 64b Cinnamon 3.4.3 This is running in a VM on my machine so I'm not worried about login security. I've been looking around on the Mint forums and only found a lot of threads about ...
2
votes
2answers
3k 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 ...
66
votes
10answers
89k 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 ...
50
votes
4answers
77k views

Allow user1 to “su - user2” without password

I need to allow user martin to switch to user martin-test without password su - martin-test I think this can be configured in /etc/pam.d/su. There are already some lines in that file which can be ...
41
votes
2answers
130k 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 ...
122
votes
2answers
79k 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 ...
49
votes
4answers
38k 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 (...
24
votes
1answer
10k views

Why does every user have their own group?

One thing I've noticed in a lot of recent distros is that users all have their own groups with the same name as their user name. What's the purpose of that? Groups are made to group users together in ...
12
votes
1answer
13k 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, ...
9
votes
1answer
20k views

What steps to add a user to a system without using useradd/adduser?

I was browsing through some Linux questions and saw this interesting question. What steps to add a user to a system without using useradd/adduser? The one possible way that comes to my mind is, ...
16
votes
3answers
29k views

How to grant non-root user access to device files

I have device file that appears in /dev when a specific board is plugged in. The read and write operations to it work just fine, but in order to open the device file the program needs to be executed ...
9
votes
1answer
9k views

User systemd PulseAudio service

Not much else to this question: I would like to know what I need to create a PulseAudio systemd service to be run with systemd --user. I've tried a few different things, including various user ...
5
votes
3answers
4k 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 ...
19
votes
3answers
12k views

What is the regex to validate Linux users?

When adding a new user, how is the string validated? I suppose there is a regular expression. What is that regular expression?