PWCK(8) System Management Commands PWCK(8)

pwck - verify the integrity of password files

pwck [options] [PASSWORDFILE [ SHADOWFILE ]]

The pwck command verifies the integrity of the users and authentication information. It checks that all entries in /etc/passwd and /etc/shadow have the proper format and contain valid data. The user is prompted to delete entries that are improperly formatted or which have other uncorrectable errors.

Vengono fatti controlli per verificare che ogni voce abbia:

•il corretto numero di campi
•un nome utente univoco e valido
•identificatori validi dell'utente e del gruppo
•un gruppo primario valido
•una home directory valida
•una shell di login valida

Checks for shadowed password information are enabled when the second file parameter SHADOWFILE is specified or when /etc/shadow exists on the system.

Le verifiche sono le seguenti:

•ogni elemento del file passwd deve avere un corrispondente elemento in shadow, e viceversa
•le password sono specificate nel file shadow
•gli elementi di shadow hanno il corretto numero di campi
•gli elementi di shadow sono unici
•le date di ultima modifica non sono nel futuro

The checks for correct number of fields and unique user name are fatal. If the entry has the wrong number of fields, the user will be prompted to delete the entire line. If the user does not answer affirmatively, all further checks are bypassed. An entry with a duplicated user name is prompted for deletion, but the remaining checks will still be made. All other errors are warnings and the user is encouraged to run the usermod command to correct the error.

The commands which operate on the /etc/passwd file are not able to alter corrupted or duplicated entries. pwck should be used in those circumstances to remove the offending entry.

The -r and -s options cannot be combined.

The options which apply to the pwck command are:


Allow names that do not conform to standards.

-h, --help

Mostra un messaggio di aiuto ed esce.

-q, --quiet

Riporta solo gli errori. Gli avvisi che non richiedono azioni da parte dell'utente non sono mostrati.

-r, --read-only

Execute the pwck command in read-only mode.

-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.

-s, --sort

Sort entries in /etc/passwd and /etc/shadow by UID.

By default, pwck operates on the files /etc/passwd and /etc/shadow. The user may select alternate files with the passwd and shadow parameters.

The following configuration variables in /etc/login.defs change the behavior of this tool:


Informazioni sugli account di gruppo.


Informazioni sugli account utente.


Informazioni sicure sugli account utente.

The pwck command exits with the following values:




invalid command syntax


one or more bad password entries


can't open password files


can't lock password files


can't update password files


can't sort password files

group(5), grpck(8), passwd(5), shadow(5), usermod(8).

24/09/2023 shadow-utils 4.14.0