Linux User Management - Revision history

Kevin: /* Add User to sudo List */

2022-03-13T06:38:13Z

Add User to sudo List

← Older revision		Revision as of 06:38, 13 March 2022
Line 190:		Line 190:
	Defaults env_keep += "HOME"		Defaults env_keep += "HOME"
	</pre>		</pre>
		+	<div style="background: #ffd; border: 1px solid">
	<b>WARNING</b>: This can be dangerous so please read https://askubuntu.com/a/1187000 first.		<b>WARNING</b>: This can be dangerous so please read https://askubuntu.com/a/1187000 first.
		+	</div>

	=== Disable root User ID ===		=== Disable root User ID ===

Kevin: /* Add User to sudo List */

2022-03-13T06:37:39Z

Add User to sudo List

← Older revision		Revision as of 06:37, 13 March 2022
Line 184:		Line 184:
	<code>i -> edit -> ESC -> : -> wq</code>		<code>i -> edit -> ESC -> : -> wq</code>

		+
		+	***
		+	If <code>sudo -s</code> in new Ubuntu doesn't add user's <code>HOME</code> to the environment, add the following line to <code>/etc/sudoers</code>.
		+	<pre>
		+	Defaults env_keep += "HOME"
		+	</pre>
		+	<b>WARNING</b>: This can be dangerous so please read https://askubuntu.com/a/1187000 first.

	=== Disable root User ID ===		=== Disable root User ID ===

Kevin at 06:32, 12 July 2015

2015-07-12T06:32:32Z

← Older revision		Revision as of 06:32, 12 July 2015
Line 1:		Line 1:
	[[Category:Linux]]		[[Category:Linux]]
	== Add a new user on Linux ==		== Add a new user on Linux ==
		+
		+	=== Use THIS!!! ===
		+	Details:
		+	https://www.linode.com/docs/security/securing-your-server
		+
		+	<pre>
		+	$ adduser yourusername
		+	$ usermod -a -G sudo yourusername
		+	</pre>
		+	Now, use the new username to log in.
		+
		+
	=== Essential ===		=== Essential ===
	One way to add a new user on Linux is using ''useradd'' command.		One way to add a new user on Linux is using ''useradd'' command.

Kevin at 12:09, 28 March 2013

2013-03-28T12:09:29Z

← Older revision		Revision as of 12:09, 28 March 2013
Line 174:		Line 174:

	=== Disable root User ID ===		=== Disable root User ID ===
-	-Do not forget to have at least one sudoer user before running this.	+	<div style="background: #ffd; border: 1px solid">
		+	* '''Do not forget to have at least one sudoer user before running this.'''
		+	</div>
	<pre>		<pre>
	$ passwd -l root		$ passwd -l root

Kevin at 12:22, 22 June 2011

2011-06-22T12:22:50Z

← Older revision		Revision as of 12:22, 22 June 2011
Line 30:		Line 30:
	</pre>		</pre>

		+	=== Set User Password ===
		+	<pre>
		+	$ passwd USERNAME
		+	Enter new UNIX password:
		+	Retype new UNIX password:
		+	passwd: password updated successfully
		+	</pre>

	To get valid login shell list, check out ''/etc/shells'' file.		To get valid login shell list, check out ''/etc/shells'' file.

Kevin at 16:53, 28 April 2009

2009-04-28T16:53:26Z

← Older revision		Revision as of 16:53, 28 April 2009
Line 53:		Line 53:


-	=== ~~'''~~useradd~~'''~~ Help Result ===	+	=== <code>useradd</code> Help Result ===
	<pre>		<pre>
	$ useradd --help		$ useradd --help
Line 84:		Line 84:
	-u, --uid UID force use the UID for the new user account		-u, --uid UID force use the UID for the new user account
	</pre>		</pre>
		+
		+
		+	== Modify User ==
		+	=== Change Home Directory ===
		+	<pre>
		+	$ sudo usermod -d /userhome/path/ <username>
		+	</pre>
		+
		+	=== <code>usermod</code> Help Result ===
		+	<pre>
		+	$ usermod --help
		+	Usage: usermod [options] LOGIN
		+
		+	Options:
		+	-c, --comment COMMENT new value of the GECOS field
		+	-d, --home HOME_DIR new home directory for the user account
		+	-e, --expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE
		+	-f, --inactive INACTIVE set password inactive after expiration
		+	to INACTIVE
		+	-g, --gid GROUP force use GROUP as new primary group
		+	-G, --groups GROUPS new list of supplementary GROUPS
		+	-a, --append append the user to the supplemental GROUPS
		+	mentioned by the -G option without removing
		+	him/her from other groups
		+	-h, --help display this help message and exit
		+	-l, --login NEW_LOGIN new value of the login name
		+	-L, --lock lock the user account
		+	-m, --move-home move contents of the home directory to the
		+	new location (use only with -d)
		+	-o, --non-unique allow using duplicate (non-unique) UID
		+	-p, --password PASSWORD use encrypted password for the new password
		+	-s, --shell SHELL new login shell for the user account
		+	-u, --uid UID new UID for the user account
		+	-U, --unlock unlock the user account
		+	</pre>
		+

	== Remove User ==		== Remove User ==
Line 102:		Line 138:
	</pre>		</pre>

-	=== Help Result ===	+	=== <code>userdel</code> Help Result ===
	<pre>		<pre>
	$ userdel --help		$ userdel --help
Line 136:		Line 172:
	</pre>		</pre>

-	=== Help Result ===	+	=== <code>passwd</code> Help Result ===
	<pre>		<pre>
	$ passwd --help		$ passwd --help

Kevin at 05:50, 29 March 2009

2009-03-29T05:50:20Z

← Older revision		Revision as of 05:50, 29 March 2009
Line 5:		Line 5:

	<pre>		<pre>
-	$ useradd <username>	+	$ useradd <username>
	</pre>		</pre>
	# You probably need to use [[wikipedia:en:Sudo\|Sudo]] command.		# You probably need to use [[wikipedia:en:Sudo\|Sudo]] command.
-	$ sudo useradd <username>	+	$ sudo useradd <username>


Line 16:		Line 16:

	<pre>		<pre>
-	$ useradd -d <home directory path> -m <username>	+	$ useradd -d <home directory path> -m <username>

-	$ useradd -d /home/newuser -m newuser	+	$ useradd -d /home/newuser -m newuser
	</pre>		</pre>

Line 25:		Line 25:

	<pre>		<pre>
-	$ useradd -d <home directory path> -m <username> -s <shell>	+	$ useradd -d <home directory path> -m <username> -s <shell>

-	$ useradd -d /home/newuser -m newuser -s /bin/bash	+	$ useradd -d /home/newuser -m newuser -s /bin/bash
	</pre>		</pre>

Line 33:		Line 33:
	To get valid login shell list, check out ''/etc/shells'' file.		To get valid login shell list, check out ''/etc/shells'' file.
	<pre>		<pre>
-	$ cat /etc/shells	+	$ cat /etc/shells
	# /etc/shells: valid login shells		# /etc/shells: valid login shells
	/bin/csh		/bin/csh
Line 55:		Line 55:
	=== '''useradd''' Help Result ===		=== '''useradd''' Help Result ===
	<pre>		<pre>
-	$ useradd --help	+	$ useradd --help
	Usage: useradd [options] LOGIN		Usage: useradd [options] LOGIN

Line 90:		Line 90:

	<pre>		<pre>
-	$ userdel <username>	+	$ userdel <username>
	</pre>		</pre>
	# You probably need to use [[wikipedia:en:Sudo\|Sudo]] command.		# You probably need to use [[wikipedia:en:Sudo\|Sudo]] command.
-	$ sudo userdel <username>	+	$ sudo userdel <username>

	=== Also Remove Home Directory ===		=== Also Remove Home Directory ===

	<pre>		<pre>
-	$ userdel -r <username>	+	$ userdel -r <username>
-	$ userdel -r newuser	+	$ userdel -r newuser
	</pre>		</pre>

	=== Help Result ===		=== Help Result ===
	<pre>		<pre>
-	$ userdel --help	+	$ userdel --help
	Usage: userdel [options] LOGIN		Usage: userdel [options] LOGIN

Line 119:		Line 119:

	<pre>		<pre>
-	$visudo	+	$visudo
	</pre>		</pre>

Line 133:		Line 133:
	-Do not forget to have at least one sudoer user before running this.		-Do not forget to have at least one sudoer user before running this.
	<pre>		<pre>
-	$ passwd -l root	+	$ passwd -l root
	</pre>		</pre>

	=== Help Result ===		=== Help Result ===
	<pre>		<pre>
-	$ passwd --help	+	$ passwd --help
	Usage: passwd [options] [LOGIN]		Usage: passwd [options] [LOGIN]

Line 165:		Line 165:
	If you need a persistent root login, use		If you need a persistent root login, use
	<pre>		<pre>
-	$ sudo -i	+	$ sudo -i
	</pre>		</pre>

Line 178:		Line 178:
	-To display all the processes belong to the user.		-To display all the processes belong to the user.
	<pre>		<pre>
-	$ ps aux \| grep ${USER}	+	$ ps aux \| grep ${USER}
	</pre>		</pre>

	-To display only PIDs and processes belong to the user		-To display only PIDs and processes belong to the user
	<pre>		<pre>
-	$ ps aux \| grep ${USER} \| awk '{print $2 " " $11}' \| sort -gr	+	$ ps aux \| grep ${USER} \| awk '{print $2 " " $11}' \| sort -gr
	</pre>		</pre>

	-To kill the process		-To kill the process
	<pre>		<pre>
-	$ sudo kill -s 9 <PID number>	+	$ sudo kill -s 9 <PID number>
	</pre>		</pre>

Line 196:		Line 196:
	# username is 'user'		# username is 'user'

-	$ ps aux \| grep ${USER}	+	$ ps aux \| grep ${USER}
	root 19087 0.0 0.7 67964 2904 ? Ss 13:32 0:00 sshd: user [priv]		root 19087 0.0 0.7 67964 2904 ? Ss 13:32 0:00 sshd: user [priv]
	user 19089 0.0 0.4 67964 1724 ? S 13:32 0:00 sshd: user@pts/0		user 19089 0.0 0.4 67964 1724 ? S 13:32 0:00 sshd: user@pts/0
Line 204:		Line 204:
	</pre>		</pre>

-	$ ps aux \| grep ${USER} \| awk '{print $2 " " $11}' \| sort -gr	+	$ ps aux \| grep ${USER} \| awk '{print $2 " " $11}' \| sort -gr
	19105 sort		19105 sort
	19104 awk		19104 awk
Line 225:		Line 225:
	-Kill the bash		-Kill the bash
	<pre>		<pre>
-	$ sudo kill -s 9 19090	+	$ sudo kill -s 9 19090
	</pre>		</pre>


	===To Kick out Another Login of Yours===		===To Kick out Another Login of Yours===
-	$ who	+	$ who
	user pts/0 2008-08-24 13:25		user pts/0 2008-08-24 13:25
	'''user pts/1 2008-08-24 12:50 ''' <= to kick this out.		'''user pts/1 2008-08-24 12:50 ''' <= to kick this out.

-	$ ps a	+	$ ps a
	PID TTY STAT TIME COMMAND		PID TTY STAT TIME COMMAND
	2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1		2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1
Line 241:		Line 241:
	19078 pts/0 R+ 0:00 ps a		19078 pts/0 R+ 0:00 ps a

-	$ kill -s 9 18988	+	$ kill -s 9 18988

-	$ who	+	$ who
	user pts/0 2008-08-24 13:25		user pts/0 2008-08-24 13:25

-	$ ps a	+	$ ps a
	PID TTY STAT TIME COMMAND		PID TTY STAT TIME COMMAND
	2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1		2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1
	19044 pts/0 Ss 0:00 -bash		19044 pts/0 Ss 0:00 -bash
	19080 pts/0 R+ 0:00 ps a		19080 pts/0 R+ 0:00 ps a

Kevin: Linux User Management

2008-09-29T05:13:37Z

Linux User Management

New page

[[Category:Linux]]
== Add a new user on Linux ==
=== Essential ===
One way to add a new user on Linux is using ''useradd'' command.

<pre>
$ useradd <username>
</pre>
# You probably need to use [[wikipedia:en:Sudo|Sudo]] command.
$ sudo useradd <username>

=== With Home Directory ===
However, the user added will have neither the password nor the home directory.
If you want to specify the home directory, you can use -d option. If you also want to create home directory and set it for the user when adding a new user, you can use -m option with -d.

<pre>
$ useradd -d <home directory path> -m <username>

$ useradd -d /home/newuser -m newuser
</pre>

=== With Specifying Login Shell ===
After using useradd above, you may realise that the new user's login shell is not the one you want him or her to have. So in order to specify the login shell, you can -s option.

<pre>
$ useradd -d <home directory path> -m <username> -s <shell>

$ useradd -d /home/newuser -m newuser -s /bin/bash
</pre>

To get valid login shell list, check out ''/etc/shells'' file.
<pre>
$ cat /etc/shells
# /etc/shells: valid login shells
/bin/csh
/usr/bin/es
/usr/bin/ksh
/bin/ksh
/usr/bin/rc
/usr/bin/tcsh
/bin/tcsh
/usr/bin/esh
/usr/bin/screen
/bin/sh
/bin/dash
/bin/false
/bin/bash
/bin/rbash
</pre>

=== '''useradd''' Help Result ===
<pre>
$ useradd --help
Usage: useradd [options] LOGIN

Options:
-b, --base-dir BASE_DIR base directory for the new user account
home directory
-c, --comment COMMENT set the GECOS field for the new user account
-d, --home-dir HOME_DIR home directory for the new user account
-D, --defaults print or save modified default useradd
configuration
-e, --expiredate EXPIRE_DATE set account expiration date to EXPIRE_DATE
-f, --inactive INACTIVE set password inactive after expiration
to INACTIVE
-g, --gid GROUP force use GROUP for the new user account
-G, --groups GROUPS list of supplementary groups for the new
user account
-h, --help display this help message and exit
-k, --skel SKEL_DIR specify an alternative skel directory
-K, --key KEY=VALUE overrides /etc/login.defs defaults
-m, --create-home create home directory for the new user
account
-o, --non-unique allow create user with duplicate
(non-unique) UID
-p, --password PASSWORD use encrypted password for the new user
account
-r, --system create a system account
-s, --shell SHELL the login shell for the new user account
-u, --uid UID force use the UID for the new user account
</pre>

== Remove User ==
=== Essential ===
A simple way to remove the existing Linux user is using ''userdel'' command.

<pre>
$ userdel <username>
</pre>
# You probably need to use [[wikipedia:en:Sudo|Sudo]] command.
$ sudo userdel <username>

=== Also Remove Home Directory ===

<pre>
$ userdel -r <username>
$ userdel -r newuser
</pre>

=== Help Result ===
<pre>
$ userdel --help
Usage: userdel [options] LOGIN

Options:
-f, --force force removal of files, even if not owned by user
-h, --help display this help message and exit
-r, --remove remove home directory and mail spool
</pre>

== Sudoer ==
=== Add User to <code>sudo</code> List ===
-To add a uer to sudo list, run the command below

<pre>
$visudo
</pre>

-Add the '''username''' after <code>root</code>

# User privilege specification
root,'''username''' ALL=(ALL) ALL
<code>i -> edit -> ESC -> : -> wq</code>

=== Disable root User ID ===
-Do not forget to have at least one sudoer user before running this.
<pre>
$ passwd -l root
</pre>

=== Help Result ===
<pre>
$ passwd --help
Usage: passwd [options] [LOGIN]

Options:
-a, --all report password status on all accounts
-d, --delete delete the password for the named account
-e, --expire force expire the password for the named account
-h, --help display this help message and exit
-k, --keep-tokens change password only if expired
-i, --inactive INACTIVE set password inactive after expiration
to INACTIVE
-l, --lock lock the named account
-n, --mindays MIN_DAYS set minimum number of days before password
change to MIN_DAYS
-q, --quiet quiet mode
-r, --repository REPOSITORY change password in REPOSITORY repository
-S, --status report password status on the named account
-u, --unlock unlock the named account
-w, --warndays WARN_DAYS set expiration warning days to WARN_DAYS
-x, --maxdays MAX_DAYS set maximim number of days before password
change to MAX_DAYS
</pre>

=== Root Login ===
If you need a persistent root login, use
<pre>
$ sudo -i
</pre>

=== References ===
[[https://help.ubuntu.com/community/RootSudo RootSudo]]

==Kick Out User Logged in==
===How to===
-Check the processes of the user whom you want to kick out, then kill the user's login shell (e.g. bash)

-To display all the processes belong to the user.
<pre>
$ ps aux | grep ${USER}
</pre>

-To display only PIDs and processes belong to the user
<pre>
$ ps aux | grep ${USER} | awk '{print $2 " " $11}' | sort -gr
</pre>

-To kill the process
<pre>
$ sudo kill -s 9 <PID number>
</pre>

=== Example ===
<pre>
# username is 'user'

$ ps aux | grep ${USER}
root 19087 0.0 0.7 67964 2904 ? Ss 13:32 0:00 sshd: user [priv]
user 19089 0.0 0.4 67964 1724 ? S 13:32 0:00 sshd: user@pts/0
user 19090 0.0 0.6 19336 2248 pts/0 Ss 13:32 0:00 -bash
user 19100 0.0 0.2 15056 1088 pts/0 R+ 13:32 0:00 ps aux
user 19101 0.0 0.2 5160 828 pts/0 S+ 13:32 0:00 grep user
</pre>

$ ps aux | grep ${USER} | awk '{print $2 " " $11}' | sort -gr
19105 sort
19104 awk
19103 grep
19102 ps
'''19090 -bash'''
19089 sshd:
19087 sshd:

-awk option.
<pre>
#print the 2nd and the 11th columns
print $2 " " $11

(sort options
-g, --general-numeric-sort compare according to general numerical value
-r, --reverse reverse the result of comparisons)
</pre>

-Kill the bash
<pre>
$ sudo kill -s 9 19090
</pre>

===To Kick out Another Login of Yours===
$ who
user pts/0 2008-08-24 13:25
'''user pts/1 2008-08-24 12:50 ''' <= to kick this out.

$ ps a
PID TTY STAT TIME COMMAND
2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1
'''18988 pts/1 Ss+ 0:00 -bash'''
19044 pts/0 Ss 0:00 -bash
19078 pts/0 R+ 0:00 ps a

$ kill -s 9 18988

$ who
user pts/0 2008-08-24 13:25

$ ps a
PID TTY STAT TIME COMMAND
2552 tty1 Ss+ 0:00 /sbin/getty 38400 tty1
19044 pts/0 Ss 0:00 -bash
19080 pts/0 R+ 0:00 ps a