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activation: Remove undeclared user accounts and groups.

Fixes <>.
Reported by David Thompson <>.

* gnu/build/activation.scm (enumerate, current-users, current-groups,
  delete-user, delete-group): New procedures.
  (activate-users+groups): Add calls to 'delete-user' and
* doc/guix.texi (User Accounts): Add a paragraph about statelessness.
  Explain that passwords are preserved.
Ludovic Courtès 7 years ago
  1. 16
  2. 49


@ -4238,7 +4238,9 @@ command, from the same-named package. This relies on the
@node User Accounts
@subsection User Accounts
User accounts are specified with the @code{user-account} form:
User accounts and groups are entirely managed through the
@code{operating-system} declaration. They are specified with the
@code{user-account} and @code{user-group} forms:
@ -4252,6 +4254,14 @@ User accounts are specified with the @code{user-account} form:
(home-directory "/home/alice"))
@end example
When booting or upon completion of @command{guix system reconfigure},
the system ensures that only the user accounts and groups specified in
the @code{operating-system} declaration exist, and with the specified
properties. Thus, account or group creations or modifications made by
directly invoking commands such as @command{useradd} are lost upon
reconfiguration or reboot. This ensures that the system remains exactly
as declared.
@deftp {Data Type} user-account
Objects of this type represent user accounts. The following members may
be specified:
@ -4291,7 +4301,9 @@ graphical login managers do not list them.
@item @code{password} (default: @code{#f})
You would normally leave this field to @code{#f}, initialize user
passwords as @code{root} with the @command{passwd} command, and then let
users change it with @command{passwd}.
users change it with @command{passwd}. Passwords set with
@command{passwd} are of course preserved across reboot and
If you @emph{do} want to have a preset password for an account, then
this field must contain the encrypted password, as a string.


@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014 Ludovic Courtès <>
;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <>
;;; Copyright © 2015 Mark H Weaver <>
;;; This file is part of GNU Guix.
@ -40,6 +40,24 @@
;;; Code:
(define (enumerate thunk)
"Return the list of values returned by THUNK until it returned #f."
(let loop ((entry (thunk))
(result '()))
(if (not entry)
(reverse result)
(loop (thunk) (cons entry result)))))
(define (current-users)
"Return the passwd entries for all the currently defined user accounts."
(enumerate getpwent))
(define (current-groups)
"Return the group entries for all the currently defined user groups."
(enumerate getgrent))
(define* (add-group name #:key gid password system?
(log-port (current-error-port)))
"Add NAME as a user group, with the given numeric GID if specified."
@ -128,6 +146,17 @@ properties. Return #t on success."
(zero? (apply system* "usermod" args))))
(define* (delete-user name #:key (log-port (current-error-port)))
"Remove user account NAME. Return #t on success. This may fail if NAME is
logged in."
(format log-port "deleting user '~a'...~%" name)
(zero? (system* "userdel" name)))
(define* (delete-group name #:key (log-port (current-error-port)))
"Remove group NAME. Return #t on success."
(format log-port "deleting group '~a'...~%" name)
(zero? (system* "groupdel" name)))
(define* (ensure-user name group
#:key uid comment home shell password system?
(supplementary-groups '())
@ -186,8 +215,22 @@ numeric gid or #f."
#:system? system?))))
;; Finally create the other user accounts.
(for-each activate-user users))
;; Create the other user accounts.
(for-each activate-user users)
;; Finally, delete extra user accounts and groups.
(for-each delete-user
(lset-difference string=?
(map passwd:name (current-users))
(match users
(((names . _) ...)
(for-each delete-group
(lset-difference string=?
(map group:name (current-groups))
(match groups
(((names . _) ...)
(define (activate-etc etc)
"Install ETC, a directory in the store, as the source of static files for