10.6 User Accounts

User accounts and groups are entirely managed through the operating-system declaration. They are specified with the user-account and user-group forms:

(user-account
  (name "alice")
  (group "users")
  (supplementary-groups '("wheel"   ;allow use of sudo, etc.
                          "audio"   ;sound card
                          "video"   ;video devices such as webcams
                          "cdrom")) ;the good ol' CD-ROM
  (comment "Bob's sister"))

Here’s a user account that uses a different shell and a custom home directory (the default would be "/home/bob"):

(user-account
  (name "bob")
  (group "users")
  (comment "Alice's bro")
  (shell (file-append zsh "/bin/zsh"))
  (home-directory "/home/robert"))

When booting or upon completion of guix system reconfigure, the system ensures that only the user accounts and groups specified in the operating-system declaration exist, and with the specified properties. Thus, account or group creations or modifications made by directly invoking commands such as useradd are lost upon reconfiguration or reboot. This ensures that the system remains exactly as declared.

Data Type: user-account

Objects of this type represent user accounts. The following members may be specified:

name

The name of the user account.

group

This is the name (a string) or identifier (a number) of the user group this account belongs to.

supplementary-groups (default: '())

Optionally, this can be defined as a list of group names that this account belongs to.

uid (default: #f)

This is the user ID for this account (a number), or #f. In the latter case, a number is automatically chosen by the system when the account is created.

comment (default: "")

A comment about the account, such as the account owner’s full name.

Note that, for non-system accounts, users are free to change their real name as it appears in /etc/passwd using the chfn command. When they do, their choice prevails over the system administrator’s choice; reconfiguring does not change their name.

home-directory

This is the name of the home directory for the account.

create-home-directory? (default: #t)

Indicates whether the home directory of this account should be created if it does not exist yet.

shell (default: Bash)

This is a G-expression denoting the file name of a program to be used as the shell (see G-Expressions). For example, you would refer to the Bash executable like this:

(file-append bash "/bin/bash")

... and to the Zsh executable like that:

(file-append zsh "/bin/zsh")

system? (default: #f)

This Boolean value indicates whether the account is a “system” account. System accounts are sometimes treated specially; for instance, graphical login managers do not list them.

password (default: #f)

You would normally leave this field to #f, initialize user passwords as root with the passwd command, and then let users change it with passwd. Passwords set with passwd are of course preserved across reboot and reconfiguration.

If you do want to set an initial password for an account, then this field must contain the encrypted password, as a string. You can use the crypt procedure for this purpose:

(user-account
  (name "charlie")
  (group "users")

  ;; Specify a SHA-512-hashed initial password.
  (password (crypt "InitialPassword!" "$6$abc")))

Note: The hash of this initial password will be available in a file in /gnu/store, readable by all the users, so this method must be used with care.

See Passphrase Storage in The GNU C Library Reference Manual, for more information on password encryption, and Encryption in GNU Guile Reference Manual, for information on Guile’s crypt procedure.

User group declarations are even simpler:

(user-group (name "students"))

Data Type: user-group

This type is for, well, user groups. There are just a few fields:

name

The name of the group.

id (default: #f)

The group identifier (a number). If #f, a new number is automatically allocated when the group is created.

system? (default: #f)

This Boolean value indicates whether the group is a “system” group. System groups have low numerical IDs.

password (default: #f)

What, user groups can have a password? Well, apparently yes. Unless #f, this field specifies the password of the group.

For convenience, a variable lists all the basic user groups one may expect:

Scheme Variable: %base-groups

This is the list of basic user groups that users and/or packages expect to be present on the system. This includes groups such as “root”, “wheel”, and “users”, as well as groups used to control access to specific devices such as “audio”, “disk”, and “cdrom”.

Scheme Variable: %base-user-accounts

This is the list of basic system accounts that programs may expect to find on a GNU/Linux system, such as the “nobody” account.

Note that the “root” account is not included here. It is a special-case and is automatically added whether or not it is specified.