NAMN

       passwd - ändra användarlösenord

SYNOPSIS

       passwd [options] [LOGIN]

BESKRIVNING

       The passwd command changes passwords for user accounts. A normal user may only change the
       password for their own account, while the superuser may change the password for any
       account. passwd also changes the account or associated password validity period.

   Lösenordsändringar
       The user is first prompted for their old password, if one is present. This password is
       then encrypted and compared against the stored password. The user has only one chance to
       enter the correct password. The superuser is permitted to bypass this step so that
       forgotten passwords may be changed.

       After the password has been entered, password aging information is checked to see if the
       user is permitted to change the password at this time. If not, passwd refuses to change
       the password and exits.

       Användaren frågas sedan två gånger efter ett ersättande lösenord. Den andra inmatningen
       jämförs mot den första och båda måste stämma överens för att lösenordet ska ändras.

       Then, the password is tested for complexity. passwd will reject any password which is not
       suitably complex. Care must be taken not to include the system default erase or kill
       characters.

   Tips för användarlösenord
       The security of a password depends upon the strength of the encryption algorithm and the
       size of the key space. The legacy UNIX System encryption method is based on the NBS DES
       algorithm. More recent methods are now recommended (see ENCRYPT_METHOD). The size of the
       key space depends upon the randomness of the password which is selected.

       Problem i lösenordssäkerheten brukar normalt komma från slarvigt valda lösenord eller
       hantering. Av denna anledning bör du inte välja ett lösenord som finns i en ordbok eller
       som måste skrivas ner. Lösenordet bör heller inte vara ett korrekt namn, ditt
       personnummer, födelsedatum eller gatuadress. Dessa kan användas som gissningar för att ta
       sig in i systemet.

       As a general guideline, passwords should be long and random. It's fine to use simple
       character sets, such as passwords consisting only of lowercase letters, if that helps
       memorizing longer passwords. For a password consisting only of lowercase English letters
       randomly chosen, and a length of 32, there are 26^32 (approximately 2^150) different
       possible combinations. Being an exponential equation, it's apparent that the exponent (the
       length) is more important than the base (the size of the character set).

       You can find advice on how to choose a strong password on
       http://en.wikipedia.org/wiki/Password_strength

FLAGGOR

       The options which apply to the passwd command are:

       -a, --all
           This option can be used only with -S and causes show status for all users.

       -d, --delete
           Ta bort en användares lösenord (gör det blankt). Detta är ett snabbt sätt att
           inaktivera ett lösenord för ett konto. Det kommer att ta bort det angivna kontots
           lösenord.

       -e, --expire
           Lösenordet för ett konto sätts omedelbart som utgånget. Detta kan tvinga en användare
           att ändra sitt lösenord vid nästa inloggningsförsök.

       -h, --help
           Visa hjälpmeddelande och avsluta.

       -i, --inactive INACTIVE
           This option is used to disable an account after the password has been expired for a
           number of days. After a user account has had an expired password for INACTIVE days,
           the user may no longer sign on to the account.

       -k, --keep-tokens
           Indicate password change should be performed only for expired authentication tokens
           (passwords). The user wishes to keep their non-expired tokens as before.

       -l, --lock
           Lock the password of the named account. This option disables a password by changing it
           to a value which matches no possible encrypted value (it adds a ´!´ at the beginning
           of the password).

           Note that this does not disable the account. The user may still be able to login using
           another authentication token (e.g. an SSH key). To disable the account, administrators
           should use usermod --expiredate 1 (this set the account's expire date to Jan 2, 1970).

           Users with a locked password are not allowed to change their password.

       -n, --mindays MIN_DAYS
           Set the minimum number of days between password changes to MIN_DAYS. A value of zero
           for this field indicates that the user may change their password at any time.

       -q, --quiet
           Tyst läge.

       -r, --repository REPOSITORY
           change password in REPOSITORY repository

       -R, --root CHROOT_DIR
           Apply changes in the CHROOT_DIR directory and use the configuration files from the
           CHROOT_DIR directory. Only absolute paths are supported.

       -P, --prefix PREFIX_DIR
           Apply changes to configuration files under the root filesystem found under the
           directory PREFIX_DIR. This option does not chroot and is intended for preparing a
           cross-compilation target. Some limitations: NIS and LDAP users/groups are not
           verified. PAM authentication is using the host files. No SELINUX support.

       -S, --status
           Display account status information. The status information consists of 7 fields. The
           first field is the user's login name. The second field indicates if the user account
           has a locked password (L), has no password (NP), or has a usable password (P). The
           third field gives the date of the last password change. The next four fields are the
           minimum age, maximum age, warning period, and inactivity period for the password.
           These ages are expressed in days.

       -u, --unlock
           Unlock the password of the named account. This option re-enables a password by
           changing the password back to its previous value (to the value before using the -l
           option).

       -w, --warndays WARN_DAYS
           Set the number of days of warning before a password change is required. The WARN_DAYS
           option is the number of days prior to the password expiring that a user will be warned
           that their password is about to expire.

       -x, --maxdays MAX_DAYS
           Set the maximum number of days a password remains valid. After MAX_DAYS, the password
           is required to be changed.

           Passing the number -1 as MAX_DAYS will remove checking a password's validity.

       -s, --stdin
           This option is used to indicate that passwd should read the new password from standard
           input, which can be a pipe.

TÄNK PÅ

       Password complexity checking may vary from site to site. The user is urged to select a
       password as complex as he or she feels comfortable with.

       Users may not be able to change their password on a system if NIS is enabled and they are
       not logged into the NIS server.

       passwd uses PAM to authenticate users and to change their passwords.

FILER

       /etc/passwd
           Användarkontoinformation.

       /etc/shadow
           Säker användarkontoinformation.

       /etc/pam.d/passwd
           PAM configuration for passwd.

AVSLUTNINGSVÄRDEN

       The passwd command exits with the following values:

       0
           success

       1
           permission denied

       2
           invalid combination of options

       3
           unexpected failure, nothing done

       4
           unexpected failure, passwd file missing

       5
           passwd file busy, try again

       6
           invalid argument to option

SE OCKSÅ

       chpasswd(8), makepasswd(1), passwd(5), shadow(5), usermod(8).

       The following web page comically (yet correctly) compares the strength of two different
       methods for choosing a password: "https://xkcd.com/936/"