useradd command

`useradd` - create a new user or update default new user information

The useradd command in Linux is a utility used to create new user accounts on a system. It’s a low-level tool for adding users, often followed by passwd to set their password.

Note: useradd requires root privileges (sudo). On some systems, adduser (a friendlier wrapper) is preferred, but useradd is more granular.

Usage: useradd [options] LOGIN

LOGIN: This is the required argument, which specifies the username (login name) for the new account.
options: Flags to customize the user account.

Common Options Summary

Option	Description
`-m`	Create home directory
`-d`	Specify home directory
`-s`	Set login shell (e.g., `/bin/bash`)
`-g`	Set primary group
`-G`	Add to supplementary groups
`-c`	Add a comment (e.g., full name)
`-u`	Set custom UID

Examples

Basic Usage

Create a new user with default settings.
```
sudo useradd alice
```
- Adds user alice to the system.
- Defaults (e.g., home directory, shell) come from /etc/default/useradd.
Set Password:
```
sudo passwd alice
```
- Prompts for a password for alice.
Specifying Home Directory

Use -d to set a custom home directory.
```
sudo useradd -d /home/alice alice
```
- Sets /home/alice as the home directory (won’t create it yet).
Create Home Directory:

Add -m to make the home directory:
```
sudo useradd -m -d /home/alice alice
```
- Creates /home/alice and sets it.
Setting a Shell

Use -s to specify the login shell.
```
sudo useradd -m -s /bin/bash alice
```
- Sets bash as alice’s shell (default is often /bin/sh).
Assigning a Group

Use -g for the primary group and -G for additional groups.
```
sudo useradd -m -g users -G developers alice
```
- -g users: Primary group is users.
- -G developers: Adds alice to the developers group.
Adding a Comment

Use -c to add a comment (e.g., full name).
```
sudo useradd -m -c "Alice Smith" alice
```
- Stores "Alice Smith" in /etc/passwd’s GECOS field.
Setting User ID

Use -u to specify a custom UID.
```
sudo useradd -m -u 1500 alice
```
- Assigns UID 1500 to alice (default starts at 1000+).
Checking the Result

Verify the user in /etc/passwd.
```
grep alice /etc/passwd
```
- Output: alice:x:1500:100:Alice Smith:/home/alice:/bin/bash.

To get help related to the `useradd` command use `--help` option

$ useradd --help
Usage: useradd [options] LOGIN
       useradd -D
       useradd -D [options]

Options:
      --badnames                do not check for bad names
  -b, --base-dir BASE_DIR       base directory for the home directory of the
                                new account
      --btrfs-subvolume-home    use BTRFS subvolume for home directory
  -c, --comment COMMENT         GECOS field of the new account
  -d, --home-dir HOME_DIR       home directory of the new account
  -D, --defaults                print or change default useradd configuration
  -e, --expiredate EXPIRE_DATE  expiration date of the new account
  -f, --inactive INACTIVE       password inactivity period of the new account
  -g, --gid GROUP               name or ID of the primary group of the new
                                account
  -G, --groups GROUPS           list of supplementary groups of the new
                                account
  -h, --help                    display this help message and exit
  -k, --skel SKEL_DIR           use this alternative skeleton directory
  -K, --key KEY=VALUE           override /etc/login.defs defaults
  -l, --no-log-init             do not add the user to the lastlog and
                                faillog databases
  -m, --create-home             create the user's home directory
  -M, --no-create-home          do not create the user's home directory
  -N, --no-user-group           do not create a group with the same name as
                                the user
  -o, --non-unique              allow to create users with duplicate
                                (non-unique) UID
  -p, --password PASSWORD       encrypted password of the new account
  -r, --system                  create a system account
  -R, --root CHROOT_DIR         directory to chroot into
  -P, --prefix PREFIX_DIR       prefix directory where are located the /etc/* files
  -s, --shell SHELL             login shell of the new account
  -u, --uid UID                 user ID of the new account
  -U, --user-group              create a group with the same name as the user
  -Z, --selinux-user SEUSER     use a specific SEUSER for the SELinux user mapping
      --extrausers              Use the extra users database

For more details, check the manual with man useradd

useradd - create a new user or update default new user information​

Examples​

To get help related to the useradd command use --help option​

`useradd` - create a new user or update default new user information

Examples

To get help related to the `useradd` command use `--help` option