doc: Better explain the 'password' field of <user-account>.

* doc/guix.texi (User Accounts): Provide an example use of 'crypt', and
mention the security implications.
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Ludovic Courtès 2019-03-04 13:55:41 +01:00
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@ -10695,6 +10695,7 @@ account. System accounts are sometimes treated specially; for instance,
graphical login managers do not list them.
@anchor{user-account-password}
@cindex password, for user accounts
@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
@ -10702,11 +10703,29 @@ users change it with @command{passwd}. Passwords set with
@command{passwd} are of course preserved across reboot and
reconfiguration.
If you @emph{do} want to have a preset password for an account, then
this field must contain the encrypted password, as a string.
@xref{crypt,,, libc, The GNU C Library Reference Manual}, for more information
on password encryption, and @ref{Encryption,,, guile, GNU Guile Reference
Manual}, for information on Guile's @code{crypt} procedure.
If you @emph{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
@code{crypt} procedure for this purpose:
@example
(user-account
(name "charlie")
(home-directory "/home/charlie")
(group "users")
;; Specify a SHA-512-hashed initial password.
(password (crypt "InitialPassword!" "$6$abc")))
@end example
@quotation Note
The hash of this initial password will be available in a file in
@file{/gnu/store}, readable by all the users, so this method must be used with
care.
@end quotation
@xref{Passphrase Storage,,, libc, The GNU C Library Reference Manual}, for
more information on password encryption, and @ref{Encryption,,, guile, GNU
Guile Reference Manual}, for information on Guile's @code{crypt} procedure.
@end table
@end deftp