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useradd

Create a new user account (and by default its private group and home folder).

Niveau
RHCSA-examen
Groep
Gebruikers en groepen
Root nodig
Ja
Pakket
shadow-utils

Dit deel is nog niet vertaald. Je ziet de Engelse tekst.

Wat het doet

useradd writes the new account to /etc/passwd, /etc/shadow, /etc/group and /etc/gshadow. On RHEL it also creates a group with the same name and a home folder in /home, with a copy of the files in /etc/skel.

The new account has no password yet, so nobody can log in with it. Set one with passwd.

Values you do not give come from /etc/login.defs (UID range, password aging, home mode) and /etc/default/useradd (shell, home base, skel). useradd -D shows and changes the second file.

Zo schrijf je het

useradd [OPTION]... LOGIN
useradd -D
useradd -D [-b BASE] [-e DATE] [-f DAYS] [-g GROUP] [-s SHELL]

Opties 26

Meest gebruikt

Account data

-c, --comment COMMENT
Comment, mostly the full name (GECOS field).
-u, --uid UID
Use this UID.
-o, --non-unique
Allow a UID that is already used (with -u).
-s, --shell SHELL
Login shell, like /bin/bash or /sbin/nologin.
-e, --expiredate DATE
The account expires on this date (YYYY-MM-DD).
-f, --inactive DAYS
Lock the account this many days after the password expired (-1 = never).
-p, --password HASH
Set an already hashed password (not the clear text; not recommended).
-r, --system
Create a system account: UID under 1000, no aging, no home folder by default.
--badname
Allow names that do not follow the normal rules.

Groups

-g, --gid GROUP
The primary group (name or GID; it must exist).
-G, --groups GROUP1[,GROUP2...]
Extra (supplementary) groups.
-U, --user-group
Create a group with the same name as the user (default on RHEL).
-N, --no-user-group
Do not create a private group; use -g or the default GROUP.

Home folder

-d, --home-dir DIR
Use this home folder.
-m, --create-home
Create the home folder (default on RHEL via CREATE_HOME).
-M, --no-create-home
Do not create the home folder.
-b, --base-dir DIR
Base folder for homes (home = DIR/LOGIN).
-k, --skel DIR
Copy the start files from this folder instead of /etc/skel (with -m).

Other

-D, --defaults
Show or change the defaults in /etc/default/useradd.
-K, --key KEY=VALUE
Override a value of /etc/login.defs, like -K UID_MIN=5000.
-l, --no-log-init
Do not add the user to the lastlog and faillog files.
-F, --add-subids-for-system
Add subuid/subgid ranges also for system accounts.
-Z, --selinux-user SEUSER
The SELinux user for this login (like staff_u).
-R, --root DIR
Work in this chroot folder.
-P, --prefix DIR
Use the files under this prefix folder.
-h, --help
Show help.

Voorbeelden 11

$ als gewone gebruiker# als root (of met sudo)

  1. 1Create a user with a full name

    useradd -c "Lisa Hassan" lisa
passwd lisa

    Without a password nobody can log in.

  2. 2Create a user with extra groups

    useradd -G wheel,webadmins omar
id omar
uid=1002(omar) gid=1002(omar) groups=1002(omar),10(wheel),1100(webadmins)

    The groups must exist.

  3. 3Choose the UID

    useradd -u 1500 sam

    Same UID on all servers keeps NFS file owners right.

  4. 4Create a service account

    useradd -r -s /sbin/nologin -d /var/lib/myapp -M myapp

    No login shell, no home, UID under 1000 (least privilege for an app).

  5. 5Create a temporary account that expires

    useradd -e 2026-12-31 -c "Contractor" contractor1

    After this date the account cannot log in.

  6. 6Show the defaults

    useradd -D
GROUP=100
HOME=/home
INACTIVE=-1
EXPIRE=
SHELL=/bin/bash
SKEL=/etc/skel

    These values come from /etc/default/useradd.

  7. 7Change the default shell for new users

    useradd -D -s /bin/zsh

    Only new users get it.

  8. 8Use another start folder for a team

    useradd -m -k /etc/skel-dev dev1

    Developers get their own .bashrc and tools config.

  9. 9Map a user to a confined SELinux user

    useradd -Z staff_u admin2

    A confined admin cannot do everything even as root (hardening).

  10. 10Create many users from a list

    for u in anna bob carol; do useradd -G sales "$u"; echo password | passwd --stdin "$u"; done

    Only for labs: real users need a good password each.

  11. 11Check the new account

    getent passwd lisa; ls -la /home/lisa
lisa:x:1001:1001:Lisa Hassan:/home/lisa:/bin/bash

    The home folder has the files from /etc/skel.

Let op

  • useradd does not set a password. Use passwd after it.
  • -p wants a hash, not the password text. useradd -p secret gives an account that cannot log in.
  • Changes in /etc/skel or login.defs only affect new users.

Bestanden

/etc/passwd, /etc/shadow
Account and password data.
/etc/group, /etc/gshadow
Group data.
/etc/login.defs
UID/GID ranges, password aging, home mode, umask.
/etc/default/useradd
Defaults for shell, home base and skel.
/etc/skel/
Start files for new home folders.

Exitcodes

0Done.
1Could not update the password file.
2Wrong syntax.
3Wrong value for an option.
4UID already used.
6The group does not exist.
9The user name is already used.
12Could not create the home folder.
14Could not update the SELinux user mapping.

Volledige handleiding

Deze pagina legt het commando uit in eenvoudige woorden. De originele handleiding heeft elk detail.

In je terminal: man 8 useradd

Open de man-pagina (linux.die.net)man7.org