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

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5
votes
3answers
531 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?
2
votes
1answer
7k views

Changing my default primary GID for every login session

I read the following about newgrp: The newgrp command is used to change the current group ID during a login session. This made me think, how can I change my default's primary group ...
2
votes
2answers
852 views

su user fails with “grep: /var/cpanel/users/user: Permission denied”

I just did something pretty simple. Given a user user, I modified his user id, primary group's id, and added him to a new group in order to make my server use the same uid and gid as another server ...
2
votes
2answers
2k views

Directory/files owned by a non-existent user

A user has created a directory with files, but the user does not exist in /etc/passwd or /etc/group. The system is a Fedora server with an FTP server and proxy which redirects to a CentOS server with ...
2
votes
1answer
85 views

skill on your own session

So I kind of (read: did) run skill -STOP -u <username> on my own session... and I don't have root privileges on the machine. Short of getting the sysadmin to restore things (he's away), is ...
10
votes
2answers
4k 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 ...
14
votes
2answers
15k 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 ...
4
votes
1answer
807 views

How to disable certain system calls for a given user?

I am creating a web app similar to codepad and for each run-action my app copies a directory (/home/radeks/voidptr/private/chroot-root) to /tmp/voidptr/[random-id]/chroot-root. This chroot directory ...
2
votes
1answer
1k views

NFS to clients with different uid:s than on the server, where the client uid:s shall not show up in the server

I have a problem with a embedded Linux device that is mounting its root filesystem over NFS. But for different reason the embedded device is a single user device running as root (and later it will ...
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, ...
6
votes
1answer
722 views

Backing up and restoring a system user account

How would I go about completely backing up a user account and restoring it on a new system? The Home directory is just 'copy-and-paste'. But then what about things like the account password; and its ...
3
votes
1answer
3k 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
3answers
680 views

Group information reported wrong for a specific user

I have a problem on a server I manage. An account (specifically, my account) does not seem to have the correct groups. I think the problem is most easily demonstrated by looking at the following ...
2
votes
1answer
136 views

Suddenly changing users [closed]

Has anyone ever encountered a scenario where you are logged into a system going about your standard business, cat, ls, tail, grep, vim, find etc. and suddenly permissions to regular things stop ...
9
votes
3answers
15k views

Correct permissions for /var/www/html?

I'm able to write changes in the home directory, but when it comes to the /var/www/html folder, it's not allowing me to make any changes or create new files or folders. I'm able to view the files in ...
3
votes
2answers
8k views

How can I have a separate umask for directory or user?

I want a separate umask for a directory or a user. How can I do this? Edit: I am using Debian 6. The reason why I want to do this is, I want all my SFTP users to create files with write on group. ...
5
votes
4answers
1k views

How sudo/root-ness detection works

Programs that make changes system-wide require sudo unless I am already the root user. Now, the question is: how exactly does the system figure out that I am (not) root? Does it: Check to see if I'...
3
votes
1answer
284 views

Duplicate a user, or at least the password

I have some application that needs to create users that have the same password as others. Is there a way to do this without having to edit the /etc/shadow manually? Some sort of command?
2
votes
1answer
370 views

Verify that /etc/passwd has correct number of fields on each line?

I'm looking for an easy, portable way to validate the number of fields in /etc/passwd, /etc/shadow, /etc/group and /etc/master.passwd. This would run on FreeBSD, Linux and other Un*xes. pwck does this,...
4
votes
1answer
648 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 ...
9
votes
1answer
11k 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, ...
3
votes
3answers
4k views

Reset all groups to default

I recently set up some groups and users on my machine, and now I want to remove all those users and all those groups. Somewhat stupidly, I read on an Ubuntu forum or something like that that it was ...
2
votes
2answers
307 views

using chown in linux

I want to assign www-data user full rights in folder /var/www/ and all of the files inside this folder. I have tried chown www-data /var/www/
11
votes
3answers
5k views

What is the point of the 'operator' user?

Many un*x systems ship with a user account named 'operator'. What is the purpose of this account? Do some systems actually make use of this account, or is this more of a historical legacy? Have you ...
3
votes
4answers
2k views

different shell for root and non-root user

When I ssh as root, my shell is bash, but when it's a non-root user it is sh. How can I make them both to use bash? This actually goes against the logic in this question: Why root's default shell is ...
1
vote
1answer
68 views

Equivalent of newusers for groups

The newusers command is useful for adding or modifying users in bulk. Is there an equivalent command for managing groups?
8
votes
2answers
8k 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
1answer
2k views

How to get the name of the user that launched `sudo`

My problem: I have a Python program, and the user launch it using sudo. Sometimes I have to get the user's home, and I can do this only knowing its name: import pwd pwd.getpwnam(username) So: how ...
3
votes
2answers
8k views

How can I switch one user to another in Freebsd?

How can I switch one user to another in Freebsd? For examples, I am user david now and I want to change to user Bob. This is a personal OS for my study. not a server. I searched it, but only got ...
5
votes
1answer
7k views

What is hvc0? (appearing in “who” list)

I have an Ubuntu Server, and when I type who, to see who's connected, I can see that there's a user connected, and instead of being logged to a pts/x, he's connected to hvc0. Is there something to ...
10
votes
7answers
3k 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 ...
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 ...
7
votes
1answer
1k views

Why root's default shell is configured differently with other normal user account's default shell?

As I know, root's default shell is configured csh and normal user's default shell is sh in FreeBSD. And in Ubuntu, root is dash, normal user is bash. (refer: What's the Ubuntu's default shell?) Why ...
2
votes
1answer
5k views

How do I add a new user to an embedded Linux system by hand?

I have a system which was designed for use by root only and I want to run an FTP server on it. The software I use handles authentication by using same username and password as OS itself. To me it ...
3
votes
2answers
1k views

How to trace a process to original user?

Say, on a Solaris server, user1 logs in, switches to someother user, say sruser, using su - and then starts a process of id X. And then another user user2 logs in, switches to sruser the same way and ...
2
votes
2answers
2k views

How to get hashed password in /etc/shadow using getpwnam()?

Apparently there is a function (getpwnam) that given a username, will return the appropriate entry in /etc/passwd with the other details for that user (shell, uid, gid, etc.). However, I have no idea ...
6
votes
2answers
9k 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 ...
2
votes
1answer
124 views

rc control user

I am playing around with rc scripts. I am starting a daemon from rc.local. I would like to know how I start the process under a specific user instead of root?
8
votes
4answers
3k views

Multiple Users on a Desktop Environment [closed]

This is probably a REALLY stupid question. But anyways, lets pretend we had a *nix rather powerful system... Now Obviously I know you can set up multiple users to login to a system.......but how ...
2
votes
3answers
948 views

su and aliases confusion

I create an alias as my current user in the bash shell, which I can see using the alias command. When I switch user without the -, i.e. su testuser, the alias is not carried into the new user's ...
2
votes
3answers
319 views

How to make files created by a specific user to have specific permissions by default

Here's a sequence of commands and the resulting output: $ touch testfile $ stat -c'%a %A' testfile 644 -rw-r--r-- What must I do so that when a user follows that sequence, I get this output instead:...
3
votes
2answers
1k views

In new users's home directory create sub-directory with a specific group and permissions

Linux will copy the the contents of /etc/skel when a new user is created. I want to have a sub-directory in each user's home directory, MyStevedore. I want this directory to have the owner be the new ...
3
votes
1answer
819 views

Set visible directories for SFTP access?

I am setting up SFTP access to one of my machines running Linux with the Dropbear SSH server. When I SFTP onto the machine remotely, I can see the entire filesystem on it, even if I might not have ...
4
votes
4answers
276 views

How do I check what 'normal' users are there on the system?

I want to find out what 'normal' users are available on a system. By normal, I mean those who are manually created, not those like sshd or gdm.
6
votes
3answers
8k 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?
3
votes
2answers
1k views

PHP interface to manage linux user accounts

I have a linux web & samba server. I need to give administrators access to manage minor accounts & groups. Is there a secure php web interface that can do this? I don't want to give them shell ...
1
vote
2answers
135 views

How would you create a user with the HOME_DIR field in /etc/passwd completely blank?

Closest I can come is: useradd --home / -r --shell /sbin/nologin someuser But this creates an entry into /etc/htpasswd that looks something like this: someuser:x:100:100::/:/sbin/nologin I want ...
5
votes
5answers
526 views

Setting up a family server

I'm very new to Unix, but after having become comfortable with bash over the past year and after having played with Ubuntu recently, I've decided to make my next computer run Ubuntu, and I think my ...