user add Linux
This is a fundamental low level tool for user creation. To create user with default configurations use useradd as shown below.
Syntax: # useradd LOGIN-NAME
$ useradd -D GROUP=1001 HOME=/home INACTIVE=-1 EXPIRE= SHELL=/bin/sh SKEL=/etc/skel CREATE_MAIL_SPOOL=no
Example 1: Creating user with all the default options, and with his own group.
Following example creates user ramesh with group ramesh. Use Linux passwd command to change the password for the user immediately after user creation.
# useradd ramesh # passwd ramesh Changing password for user ramesh. New UNIX password: Retype new UNIX password: passwd: all authentication tokens updated successfully. # grep ramesh /etc/passwd ramesh:x:500:500::/home/ramesh:/bin/bash # grep ramesh /etc/group ramesh:x:500: [Note: default useradd command created ramesh as username and group]
Example 2: Creating an user with all the default options, and with the default group.
# useradd -n sathiya # grep sathiya /etc/passwd sathiya:x:511:100::/home/sathiya:/bin/bash # grep sathiya /etc/group [Note: No rows returned, as group sathiya was not created] # grep 100 /etc/group users:x:100: [Note: useradd -n command created user sathiya with default group id 100] # passwd sathiya Changing password for user sathiya. New UNIX password: Retype new UNIX password: passwd: all authentication tokens updated successfully. [Note: Always set the password immediately after user creation]
Example 3: Editing the default options used by useradd.
The following example shows how to change the default shell from /bin/bash to /bin/ksh during user creation.
Syntax: # useradd -D --shell=<SHELLNAME> # useradd -D GROUP=100 HOME=/home INACTIVE=-1 EXPIRE= SHELL=/bin/bash SKEL=/etc/skel [Note: The default shell is /bin/bash] # useradd -D -s /bin/ksh # useradd -D GROUP=100 HOME=/home INACTIVE=-1 EXPIRE= SHELL=/bin/ksh SKEL=/etc/skel [Note: Now the default shell changed to /bin/ksh] # adduser priya # grep priya /etc/passwd priya:x:512:512::/home/priya:/bin/ksh [Note: New users are getting created with /bin/ksh] # useradd -D -s /bin/bash [Note: Set it back to /bin/bash, as the above is only for testing purpose]
Method 2: Linux useradd Command — Create Users With Custom Configurations
Instead of accepting the default values (for example, group, shell etc.) that is given by the useradd command as shown in the above method, you can specify custom values in the command line as parameters to the useradd command.
Syntax: # useradd -s <SHELL> -m -d <HomeDir> -g <Group> UserName
Example 4: Create Linux User with Custom Configurations Using useradd Command
The following example creates an account (lebron) with home directory /home/king, default shell as /bin/csh and with comment “LeBron James”.
# useradd -s /bin/csh -m -d /home/king -c "LeBron James" -g root lebron # grep lebron /etc/passwd lebron:x:513:0:LeBron James:/home/king:/bin/csh
Method 3: Linux adduser Command – Create Users Interactively
These are the friendlier tools to the low level useradd. By default it chooses the Debian policy format for UID and GID. A very simple way of creating user in the command line interactively is using adduser command.
Syntax: # adduser USERNAME
Example 5: Creating an User Interactively With adduser Command
# adduser spidey Adding user `spidey' ... Adding new group `spidey' (1007) ... Adding new user `spidey' (1007) with group `spidey' ... Creating home directory `/home/spidey' ... Copying files from `/etc/skel' ... Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully Changing the user information for spidey Enter the new value, or press ENTER for the default Full Name : Peter Parker Room Number : Work Phone : Home Phone : Other : Is the information correct? [y/N] y
Method 4: Linux newusers Command — Creating bulk users
Sometimes you may want to to create multiple users at the same time. Using any one of the above 3 methods for bulk user creation can be very tedious and time consuming. Fortunately, Linux offers a way to upload users using newusers command. This can also be executed in batch mode as it cannot ask any input.
# newusers FILENAME
Example 6: Creating Large Number of Users Using newusers Command
If Simpson family decides to join your organization and need access to your Linux server, you can create account for all of them together using newusers command as shown below.
# cat homer-family.txt homer:HcZ600a9:1008:1000:Homer Simpson:/home/homer:/bin/bash marge:1enz733N:1009:1000:Marge Simpson:/home/marge:/bin/csh bart:1y5eJr8K:1010:1000:Bart Simpson:/home/bart:/bin/ksh lisa:VGz638i9:1011:1000:Lisa Simpson:/home/lisa:/bin/sh maggie:5lj3YGQo:1012:1000:Maggie Simpson:/home/maggie:/bin/bash
Method #1: getent command to lookup username and group name
The syntax is as follows to find out if user named foo exists in system:
getent passwd userNameHere getent passwd foo
if you are able to see ! in the second field starting that indicates that password is disabled, you have to enable it back by using passwd with -u option
passwd -u username
passwd -u surendra
Unlocking password for user temp.
Example2: Check if the user expiry date is reached or not by using chage command
chage -l username
chage -l surendra
If you see that the account expires use usermod or chage command to extend the user expiry time.
usermod -e yyyy-mm-dd username
usermod -e 2012-05-10 surendra
chage -E yyyy-mm-dd username
chage -E 2012-05-10 surendra
this will extend user expiry time to 5 more months.
Example3: Check if the user shell is set to a valid shell or not, if it’s not set it to a valid one.
grep ‘username’ /etc/passwd
grep ‘surendra’ /etc/passwd
If the user shell in seventh feild is set to /sbin/nologin or /bin/false set it back to /bin/bash or /bin/ksh
usermod -s /bin/bash usrename
usermod -s /bin/bash surendra
Share your thoughts on this and let us know if you have other ideas to unlock user accounts in Linux.