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

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4
votes
1answer
815 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 ...
4
votes
1answer
368 views

Is running programs as another user useful?

After watching a talk by Douglas Crockford on security where he talks about how browsers got the right answer to the question "Who's interest does the program represent?", I wondered if it was ...
4
votes
2answers
4k views

/etc/shadow and /etc/passwd format compatibility

Are formats of files /etc/shadow and /etc/passwd same on all unix and unix-like systems same or are there significant differences? I mean syntax of files, not file location or name
4
votes
1answer
1k views

How to clear the last -10 info?

How to clear the last -10 information only for a Linux system? I tried to execute the command > /var/log/wtmp to clear the last info, but it clears the whole login info , but I need to clear only ...
4
votes
3answers
453 views

restrict student account permissions, give faculty access

I have set up two user groups, students and faculty on Ubuntu 12.04 and created a number of students and faculty accounts. The problem is a student can currently see & read all of the files of a ...
4
votes
2answers
113 views

Is it a good practice to have different users for different contexts?

I'm a software developer and I have a new laptop with Ubuntu. I plan to set up this laptop as a development workstation where I'll do my professional work (for my company) and also I'll develop some ...
4
votes
1answer
4k views

file system uid and gid in linux

I came across a linux kernel tutorial and there they talked about 4 pairs of identifiers and one of them was file system uid and gid. Could someone explain me what it is and how it is different from ...
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
1answer
55 views

What's the meaning of a '#' character before owner?

What does the # character preceding the owner name mean? For example: me@server /dir/sub/sub-sub $ ll v* x* -rwxrwxr-x 1 #owner group 1176 Jun 25 2009 vfc.sh -rw-r----- 1 #owner ...
4
votes
1answer
7k views

Expired password and SSH key based login with UsePAM yes

There is a SLES 11 machine. The users logs in via SSH and pubkey (mixed, some user uses password, some use ssh key) The sshd_config has: UsePAM yes PasswordAuthentication yes PubkeyAuthentication ...
4
votes
1answer
1k views

Restricted ssh remote execution with arguments

I need to enable remote execution of a shell script on a server, but deny all other access. The script is a toggle that accepts a single parameter (on/off/status). This comes close to answering my ...
4
votes
2answers
1k views

talkd doesn't print a message

I wanted to use talk with my brother (we both have Debian jessie). So i installed inetutils-inetd, inetutils-talk, and inetutils-talkd. Now i wanted to try wether it works. So i created a testuser ...
4
votes
2answers
515 views

Understanding getlogin()

I think the previous iteration of this question was a little bit like a carpet bomb of questions, so that may have turned people off to it (to the point of almost being flagged for removal) so I'll ...
4
votes
1answer
197 views

Easiest way to manage users for two machines

I'm administrating two ubuntu desktops and one debian server. There are abount ~20 active users on the desktops. A few (5-10) user accounts are added each year and about the same amount become ...
4
votes
1answer
307 views

Can linux use a mix of SHA-1 and CRYPT passwords?

We have an automated sync-routine that uses useradd to create new users on a Ubuntu 10.04 machine. The application launching the routine provided both username and CRYPT-encrypted password. However, ...
4
votes
2answers
181 views

How can I run a program as another user in every way?

Background I'm trying to restart some programs (mail-notification and stalonetray) regularly, as they appear to die frequently. I want to set restart them whenever NetworkManager reconnects. Hence, I ...
4
votes
2answers
287 views

How to update user/group settings of a running process?

Suppose I change some user settings like its initial login group or add it to a new group. I now can do su user and work with these new settings. But all the previously running processes will still ...
4
votes
1answer
2k views

How can a user run a program in kernel mode?

Is it possible for a user to run their own program in kernel mode? How could a user accomplish this? What weakness in the system's protection mechanism would they have to bypass? I'm thinking that a ...
4
votes
4answers
13k views

What type of permissions should a user's home directory and files have?

I'm working with a fresh install of Ubuntu 12.04 and I've just added a new user: useradd -m testuser I thought that the -m flag to create a home directory for users was pretty standard, but now ...
4
votes
2answers
2k views

recommended procedure to create a user/group during RPM install

after trying hard to search for RPM best practices guides and finding virtually none, to my surprise, I resort to the community - I need to ensure that some users and groups exist after the ...
4
votes
1answer
644 views

Force pubkey-auth user to set password at first login

When I create a new user account I ask users to send me a public key, and want to force users to set the password the first time they log in with keypair authentication. If I create an account with an ...
4
votes
2answers
4k views

SSH not landing in the home directory

I have recently installed Raspbian into a Raspberry Pi. As part of the installation process I changed the user name and group from the default (pi) to my own (let's call it user) using usermod and ...
4
votes
2answers
5k views

'mysql' user and group creation, ownership settings

I know what the linux command chown does, I used it to change the ownership or group of a file. If there is a MySQL installation on a Ubuntu machine, I saw some people doing the following thing: ...
4
votes
1answer
227 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 ...
4
votes
1answer
195 views

Where are passwords stored and how are they encrypted in OS X?

I know that on a Linux system passwords are stored in /etc/shadow and are salted and encrypted using a one way hashing algorithm like MD5, SHA-256 or SHA-512. It looks like there is no /etc/shadow ...
4
votes
3answers
1k views

Permanently switching to zsh in a script, without being root and without being asked for the password

Is there any way to run chsh -s /bin/zsh without being root and without being asked for the password? I want to put it into a non-interactive script that isn't called by root.
4
votes
1answer
349 views

What are the default openSUSE 13.1 user groups?

I just installed openSUSE 13.1, and I can't even start X on boot. I have to switch to another tty and type startx (after I set suid for xorg). On top of this, I can barely do anything without root ...
3
votes
1answer
219 views

Enable superuser when logged in with another user

Suppose that the machine has two users: Alice (admin) Bob (standard user) While Bob is logged in, how can Alice modify a root file (Bob does not have this permission even with sudo)? Alice tried: ...
3
votes
2answers
9k views

change root account username

In windows it is possible to change administrator username for security reasons. Is it possible to change root username in Linux too?
3
votes
6answers
4k views

sort ls output by users

On Linux, is there a way to sort ls output by users? What I try to achieve is something like this: user_a   file1 user_a   file2 user_b   another_file user_c   this_file user_c &...
3
votes
5answers
29k views

What is the command for listing all users who are members of the admin group?

I am looking for the name of the superusers list on Fedora. (On Ubuntu is seems to be "sudo".) I want to add one of the users to the superusers list. The groups command only lists the groups of the ...
3
votes
3answers
2k views

Killing other user processes

There are certain user environments in which we have to login during certain performance testing and and kill all the process running in that environment. The environment names are like rswrk01, … up ...
3
votes
3answers
407 views

Why only one active group at a time?

As far as I understand the users in Unix system can belong to multiple groups and one of them will become the primary group for that user. Others will be supplementary groups. All of this User/Group ...
3
votes
4answers
25k 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?
3
votes
4answers
7k views

Allow paswordless user to change to another passwordless user

I have two users dev and tomcat neither of them have a password. How can I allow dev 1 do su - tomcat without having him having to enter any credentials? 1 connects with ssh keyfile
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 ...
3
votes
3answers
9k views

Why is file ownership inconsistent between two systems mounting the same NFS share?

I have one IBM AIX server (serverA) which is connected to the san storage. I have created a volume group and also file system (jfs2) and mounted to directory /profit. After that I created a NFS ...
3
votes
1answer
819 views

basic explanation on NSS , LDAP and PAM

can anyone give me a basic explanation on what are NSS , LDAP and PAM and what they used for and what is their relationship/differences ?
3
votes
3answers
500 views

How to switch back and forth between users quickly on a single terminal?

I'd like to switch to another user without logging out the first user, then log in as a third user without logging out the other two, and so on, then switch between all users quickly. I'd like to ...
3
votes
2answers
6k views

Unable to su into an account: could not open session

in my Linux machine - red-hat I successfully to login to different users as the following su - userC [machine@Linux ~]$ pwd [machine@Linux ~]$ /Users/userC but only in one user I get the ...
3
votes
1answer
5k 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, ...
3
votes
1answer
96 views

Does root not require a password to log in as a user?

Does root not require a password to log in as a user even though a password has been set for that user? When I am logged in as "root", su user logs me in as "user". There is no prompt for a password. ...
3
votes
3answers
11k views

Setting default username and group for files in directory

Using this helpful post I am able to set a default group and file permissions in a folder. I'm having trouble setting a default owner (teamlead uid 1234). setfacl -d -m g::rwx /my/test/folder ...
3
votes
2answers
219 views

Unix command to find files read by specific user

I would like to find files accessed by specific user (even just read) within a folder tree. I thought the find command had this option, but it actually just searches for owner user. Is there any other ...
3
votes
4answers
3k views

How to configure permissions to allow file access?

I'm running Wowza Media Server on my server as "root". The problem is that all files created (recorded) by Wowza are "root:root" and aren't writable, editable, or deletable by any other users. How can ...
3
votes
2answers
3k views

Change file ownership, based on previous owner

I am a moderately new linux user. I changed my PC, and started using CentOS 7 from CentOS 6. So I attached my previous hard disk to my new pc to take backup of my files. Now, copying the files (and ...
3
votes
3answers
45k views

How do I know a specified user's permissions on Linux with root access?

I have root access to my local server. And some days ago my colleague created a user on that server, giving me the uesrname and password. But the user has a minimized permissions. Like the user can't ...
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. ...
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 ...
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 ...