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Questions tagged [login]

the process of logging in: from the login prompt, through user authentication, to session startup

445
votes
9answers
1.9m 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?
281
votes
4answers
153k views

Difference between Login Shell and Non-Login Shell?

I understand the basic difference between an interactive shell and a non-interactive shell. But what exactly differentiates a login shell from a non-login shell? Can you give examples for uses of a ...
155
votes
8answers
187k views

What's the difference between /sbin/nologin and /bin/false

Technically, unless pam is set up to check your shell with pam_shells neither of these can actually prevent your login, if you're not on the shell. On my system they are even different sizes, so I ...
119
votes
8answers
27k views

Which is the safest way to get root privileges: sudo, su or login?

I would like to have the root account in safety even if my unprivileged user is compromised. On Ubuntu you can only use sudo for "security reasons" by default. However I am not sure it is any safer ...
86
votes
3answers
370k views

SSH login with clear text password as a parameter? [duplicate]

I need to login to a user that I've created on a remote host running Ubuntu. I can't use an ssh key because the ssh login will happen from a bash script ran within a server that I won't have access to ...
83
votes
7answers
166k 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 ...
74
votes
2answers
9k views

I accidentally typed my password into the login field, is it still secure?

I was looking down at my keyboard and typed my password in because I thought I had already typed my login name. I pressed Enter, then when it asked for the password I pressed Ctrl+c. Should I take ...
72
votes
8answers
64k 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 ...
58
votes
4answers
71k views

What is “.xsession” for?

What is the purpose of the .xsession file in the home folder? What should be put in there? The desktop environments don't use that file and for the X startup from the tty there is .xinitrc.
51
votes
6answers
106k 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 ...
49
votes
6answers
65k views

Making zsh default shell without root access

I am using my school's computers and would like to use zsh instead of bash. I'd like to make it the default shell, but I cannot run a command such as $ chsh -s $(which zsh) because I don't have admin ...
43
votes
2answers
29k views

Difference between .xinitrc, .xsession and .xsessionrc

I found three configuration files. .xinitrc .xsession .xsessionrc I know that the first one is for using startx and the second and third are used when using a display manager. But what is the ...
37
votes
5answers
35k views

how can I use bash as my login shell when my sysadmin refuses to let me change it

The unix sysadmin where I'm working is reluctant to give me access to change my login shell from ksh to bash. He has given various excuses, the funniest being that since they write all their scripts ...
37
votes
4answers
33k views

How to remove “You have mail” welcome message

When I open up my terminal it says "you have mail", anyone has any idea of why? I am running OS X, but since it too is based on Unix and relies on files such as bashrc, bash_profile etc. I thought ...
33
votes
3answers
49k views

How to change default shell to ZSH - chsh says “invalid shell”

I installed ZSH on a VM of mine, where I compiled it from source. The location of ZSH is /usr/local/bin/zsh when I run chsh -s /usr/local/bin/zsh it outputs chsh: /usr/local/bin/zsh is an invalid ...
32
votes
2answers
19k views

Do you need a shell for SCP?

I'm allowing a friend a local account on my machine, exclusively for SCP. Can I specify his account's shell as /bin/true, or in any other way limit the account, while still allowing SCP?
32
votes
2answers
14k views

How does one change the delay that occurs after entering an incorrect password?

After entering an incorrect password at a login prompt, there s an approximately 3-second delay. How can I change that on a Linux system with PAM?
31
votes
5answers
66k views

Why doesn't my ~/.bash_profile work?

I'm using Linux Mint. My login shell (cat /etc/passwd | grep myUserName) is bash. After I start my graphical desktop environment and run a terminal emulator from it, I can see that .bash_profile is ...
30
votes
3answers
5k views

What's the best distro/shell-agnostic way to set environment variables?

The question says it all. I currently use Arch Linux and the zsh, but I'd like a solution that (at minimum) works both on VTs and in xterms and also (hopefully, preferably) will continue to work if I ...
28
votes
6answers
23k views

Is there any reason why I get ^[[A when I press up arrow at the console login screen?

Whenever I'm at the console login, I press up arrow intentionally to see the previously typed commands. But I see this ^[[A. But when I press Ctrl Alt Print Screen Scroll Lock Pause Break Page Up ...
26
votes
2answers
53k views

How do I force a user to change a password at the first time login using ssh?

I'm trying to force a newly created user to change a password at the first time login using ssh. For security reasons I want to give him a secure password until he logs in for the first time. I did ...
23
votes
5answers
4k views

Recovering from setting root's shell to a bad file

Let's say I've gone and done a silly thing, such as using 'chsh' to change the root user's shell to a bad file path. Future logins to the root account will abruptly fail, citing /bin/whatever not ...
23
votes
2answers
75k views

User's Login date and login time

I want to fetch user's login time and login date, is there any command in Unix providing User's login date and User's login time ? this problem i want to perform in Shell-script where username is ...
23
votes
3answers
60k views

Execute a command on user logon

In Linux desktop system, I want to execute a command when the user logs in. After reading some other posts, I tried to insert the command in ~/.bashrc but unsuccessfully. Moreover, the system uses a ...
22
votes
8answers
31k 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. What'...
21
votes
7answers
29k views

How can I change what's displayed at a login shell?

I'm getting more familiar with tweaking the way things look in a shell via the prompt (.bashrc), but I'm now trying to change the initial stuff displayed when I first log in. On my EC2 instance, this ...
19
votes
1answer
2k views

WHY a **login** shell over a **non-login** shell?

I have a basic understanding of dotfiles in *nix system. But I am still quite confused about this Difference between Login Shell and Non-Login Shell? A bunch of different answers (including multiple ...
18
votes
3answers
49k views

Which users are allowed to log in via SSH by default?

When I set up my Debian 6, I was wondering, which users apart from root whose password I know can log into my system via SSH? When I install Apache 2 a user called www-data gets created. Does this ...
18
votes
2answers
46k views

Effect of entries in /etc/securetty

By default on RHEL 5.5 I have [deuberger@saleen trunk]$ sudo cat /etc/securetty console vc/1 vc/2 vc/3 vc/4 vc/5 vc/6 vc/7 vc/8 vc/9 vc/10 vc/11 tty1 tty2 tty3 tty4 tty5 tty6 tty7 tty8 tty9 tty10 ...
18
votes
4answers
4k views

Why is root in wheel and operator? Can root being in a group ever make a difference?

I just noticed on my FreeBSD machine that root is in wheel and operator. I'm trying to think of a situation where UID 0 being in a group would have any effect on... well... anything, and I'm coming up ...
17
votes
3answers
74k views

I Can't login as root with su command, but I can with SSH

How is it possible that I cannot log in as root by su root or su (I get incorrect password error), but I can log in by ssh root@localhost or ssh root@my_local_IP with the same password? I'm using ...
17
votes
2answers
6k views

Bash .hushlogin, keep last login time and host

At my company, when I log into some servers, my last login and a huge banner are displayed: me@my-laptop$ ssh the-server Last login: Mon Feb 8 18:54:36 2016 from my-laptop.company.com **************...
17
votes
5answers
15k views

Is the username in Unix case sensitive?

Is ssh abc@servername different from ssh Abc@servername? Does the case of the username matter in Unix? My user authenticates via LDAP.
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 ...
16
votes
5answers
136k views

How to display welcome message in unix? [duplicate]

How can I display the welcome message "welcome panni" every time I log into unix?
16
votes
3answers
11k views

How can I make a user able to log in with ssh keys but not with a password?

I would like to create a user and have no password. As in you can't log in with a password. I want to add keys to its authorized_keys by using root. This is for my automated backup system.
15
votes
3answers
25k views

How to open Fedora without a user password?

How do I open Fedora 19 without a user password? My user name is mz2, and I want to login without a password.
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 ...
15
votes
2answers
80k views

How to know when and which user logged into the system under Mac OS X? Last is not enough!

In Mac OS X, if I don't touch it for a while, it will lock the screen and one must use password to unlock it, but this kind of log in is not recorded by last command. I want to know if anybody tried ...
14
votes
2answers
60k views

Error message id: cannot find name for group ID after logging in

BACKGROUND Trevor logs into his account on ssh://foobar.university.edu as one of the developers on the box, and he gets the message: id: cannot find name for group ID 131 Trevor then checks this ...
14
votes
2answers
1k views

How does X11 interact with the kernel / perform login

As I understand for text-based interaction with the Linux kernel, a program called init starts getty (or agetty) which connects to one of the TTY devices under /dev and prompts for a username. After ...
14
votes
2answers
11k views

Escape hash mark (#) in /etc/environment

I am adding an env variable to /etc/environment but because the variable value contains # sign, string is striped. MYSQL_PWD="something#no" Now if I do env above code yields MYSQL_PWD=something. How ...
13
votes
5answers
985 views

How to tell if console login is genuine?

On Windows one can enforce pressing Ctrl+Alt+Del to fire an interrupt that brings up the login window. When logging onto a console of a Linux computer: How can I tell if this login is a real one or a ...
13
votes
4answers
30k views

How do I configure the GNOME gdm login screen?

I recently installed Arch Linux and have it mostly set up. With many other Linux distributions, there is a tool that is used to configure the look and feel of the login screen. I would like to change ...
12
votes
4answers
23k views

What are the different ways that a message can be displayed to a bash shell after a user logs in?

I have a CentOS 5.7 VPS using bash as its shell that displays a branded greeting immediately after logging in via SSH. I've been trying to modify it, but can't seem to find where it is in the usual ...
12
votes
3answers
16k views

Is “/etc/issue” common for all Linux distributions?

I'm trying to Create OS detect portable function in bash script, So I just want to know, the file "/etc/issue" is common for all Linux Flavors ?
12
votes
1answer
3k views

Relationship of keyboard layout and xmodmap

I'm using Xubuntu. Before login I can choose a keyboard layout. I'm using xmodmap for remapping some keys. I'm interested in two things: How the state of keyboard mapping changes (a) when I turn the ...
12
votes
3answers
7k views

Creating a UNIX account which only executes one command

Is there a way to create a user account in Solaris which allows the users to run one command only? No login shell or anything else. I could possibly do it with /usr/bin/false in /etc/passwd and just ...
12
votes
3answers
33k views

Ubuntu 16.04 - GUI freezes on login start page

I am unable to enter anything at the login screen; it just freezes directly after the page shows. The cursor inside the login form blinks about 10 times, then it stops. I can't move the mouse or use ...
12
votes
2answers
21k views

How to change tty login prompt?

To be clear, I am not referring to /etc/issue (shown before the prompt) or /etc/motd (shown after login), but the prompt itself, which is currently hostname login: For good measure, I am running ...