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User Account Creation

Create User Account in Linux

Create User Account with default configuration:

Create User Account using useradd command:

sudo useradd USERNAME
To check the defaults for user account creation while `useradd` command is used 1\. Check with the command `bash useradd -D` 2\. Check the file `bash cat /etc/default/useradd` `bash cat /etc/login.defs`

Create User Account using adduser command:

sudo adduser USERNAME

To check the default configuration information

Check the files

cat /etc/adduser.conf

cat /etc/default/useradd

cat /etc/login.defs

Process of User Account creation

  1. Selecting UID and GID for the user as per defined in /etc/login.defs (UID_MIN, UID_MAX, GID_MIN and GID_MAX)
  2. Creating new Group Account with same name as the user, adding new line entry to the file /etc/group
  3. Creating the User Account with UID and GID and adding new line entry to /etc/passwd
  4. Adding User Account to the Group Account, modifying the line added to the file /etc/group in step 2
  5. Creating User's Home directory, and modifying the line added to /etc/passwd
  6. Copying file from /etc/skel to user's home directory
  7. If user has setup password, it will modify the file /etc/shadow
  8. If addition info like Full Name, Room Number, Work Phone, Home Phone and Other is set, that will modify the file /etc/passwd

Creating a user account without using the default settings

Manually specifying UID

sudo useradd -u 1051 USERNAME

or

sudo adduser USERNAME --uid 1051

Manually specifying GID of the user account

sudo useradd -g GID USERNAME

or

sudo adduser USERNAME --gid GID

Manually specifying Primary Group Name for the user account

sudo adduser USERNAME --ingroup GROUPNAME

Manually specifying range for UID and GID

sudo adduser USERNAME --firstuid 1101 --lastuid 1150 --firstgid 1101 --lastgid 1150

Manually adding user to secondary groups

sudo useradd -G group1,group2 USERNAME

sudo adduser USERNAME --groups group1,group2

Create User without creating default group

sudo useradd -N USERNAME

or

sudo adduser USERNAME --no-create-home

Manually specifying default shell for user

sudo useradd -s /bin/bash USERNAME

or

sudo adduer USERNAME --shell /bin/bash

:::info

To check available shells on linux host

cat /etc/shells
:::

Creating User Account with custom Home Directory

:::info Ensure that argument mentioned in option -d or -b should not end with /. :::

Manually specifying existing directory as User's Home Directory

sudo useradd -d /Other/Home USERNAME
Note - The user account created using `-d /Other/Home` then the /Other/Home becomes user home directory - The Home directory permissions will not be modified - The contents from the `/etc/skel` will not be copied to the Home directory

Manually specify the not existing directory to be a User's Home Directory

sudo useradd -m -d /Other/Home USERNAME

:::info Note

  • The path to Home directory should exist if not it throws warning
  • The Home directory should not exist if it exists then
    • No files will be copied from /etc/skel
    • User will not be the owner of the Home Directory :::

Creating User Account having Home Directory in Other Directory

sudo useradd -m -b /Other/Base/Dir USERNAME

:::info Note
Base Directory is a directory that holds users home directory :::

Create User Account with Custom Group

Create user account without creating default group account

sudo useradd -N USERNAME

Manually specifying GID or Group Name of the Primary group of the user account

sudo useradd -g <GID|GROUPNAME> USERNAME

or

sudo adduser USERNAME --gid GID

or

sudo adduser USERNAME --ingroup GROUPNAME

:::info Note

Points to be noted

  • In useradd command gid or group name of the Group can be specified as an argument to -g
  • In adduser command GID can be specified in --gid and GROUPNAME can be specified in --ingroup option
  • Ensure that the groups which are specified are already existing on the system :::

Manually specifying range for UID and GID

sudo adduser USERNAME --firstuid 1101 --lastuid 1150 --firstgid 1101 --lastgid 1150

Manually adding user to secondary groups

sudo useradd -G group1,group2 USERNAME

sudo adduser USERNAME --groups group1,group2

Create User Account with Custom Account Settings

Specify different Skel directory

sudo useradd --skel SKEL_DIR USERNAME

Specify UID

sudo useradd -u UID USERNAME

or

sudo adduser USERNAME --uid UID

Specify GID

sudo useradd -g GID USERNAME

or

sudo adduser USERNAME -gid GID

Specify the range of UID

sudo adduser USERNAME --firstuid 1100 --lastuid 1150

Specify the range of GID

sudo adduser USERNAME --firstgid 1100 --lastgid 1150

Specify Shell

sudo useradd -s /bin/sh USERNAME

or

sudo adduser USERNAME --shell /bin/sh

Create Group Account in Linux

Creating group account in linux

groupadd GROUPNAME

or

addgroup GROUPNAME

Creating group account by specifying its GID

groupadd GROUPNAME -g GID

or

addgroup GROUPNAME --gid 1101

Create group by specifying range of GID

addgroup GROUPNAME --firstgid 1101 --lastgid 1140

Create group and add users to it

groupadd GROUPNAME -U user01,user02,user03

Temporarily change my primary group

newgrp GROUPNAME