Linux User Management
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(Difference between revisions)
(Linux User Management) |
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<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 | ||
Revision as of 05:50, 29 March 2009
Contents |
Add a new user on Linux
Essential
One way to add a new user on Linux is using useradd command.
$ useradd <username>
# You probably need to use 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.
$ useradd -d <home directory path> -m <username> $ useradd -d /home/newuser -m newuser
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.
$ useradd -d <home directory path> -m <username> -s <shell> $ useradd -d /home/newuser -m newuser -s /bin/bash
To get valid login shell list, check out /etc/shells file.
$ 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
useradd Help Result
$ 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
Remove User
Essential
A simple way to remove the existing Linux user is using userdel command.
$ userdel <username>
# You probably need to use Sudo command. $ sudo userdel <username>
Also Remove Home Directory
$ userdel -r <username> $ userdel -r newuser
Help Result
$ 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
Sudoer
Add User to sudo List
-To add a uer to sudo list, run the command below
$visudo
-Add the username after root
# User privilege specification root,username ALL=(ALL) ALL
i -> edit -> ESC -> : -> wq
Disable root User ID
-Do not forget to have at least one sudoer user before running this.
$ passwd -l root
Help Result
$ 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
Root Login
If you need a persistent root login, use
$ sudo -i
References
[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.
$ ps aux | grep ${USER}
-To display only PIDs and processes belong to the user
$ ps aux | grep ${USER} | awk '{print $2 " " $11}' | sort -gr
-To kill the process
$ sudo kill -s 9 <PID number>
Example
# 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
$ 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.
#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)
-Kill the bash
$ sudo kill -s 9 19090
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
