PWD_MKDB(8) System Manager's Manual PWD_MKDB(8)

pwd_mkdb — generate the password databases

pwd_mkdb [-ciN] [-p | -s] [-d directory] [-S cachesize] [-u username] file

The pwd_mkdb utility serves no purpose in macOS and is included solely for backward compatibility. The -c and -p flags, and options which modify the behavior of those flags, still work. The -s flag has no effect.

See DirectoryService(8) for information on identity management in macOS.

The pwd_mkdb utility creates db(3) style secure and insecure databases for the specified file. These databases are then installed into /etc/spwd.db and /etc/pwd.db respectively. The file is installed into /etc/master.passwd. The file must be in the correct format (see passwd(5)). It is important to note that the format used in this system is different from the historic Version 7 style format.

The options are as follows:

Check if the password file is in the correct format. Do not change, add, or remove any files.
directoryO
Store databases into specified destination directory instead of /etc.
Ignore locking failure of the master.passwd file. This option is intended to be used to build password files in the release process over NFS where no contention can happen. A non-default directory must also be specified with the -d option for locking to be ignored. Other use of this option is strongly discouraged.
Tell pwd_mkdb to exit with an error if it cannot obtain a lock on the file. By default, we block waiting for a lock on the source file. The lock is held through the rebuilding of the database.
Create a Version 7 style password file and install it into /etc/passwd. Cannot be used in conjunction with the -s flag.
cachesize
Specify in megabytes the size of the memory cache used by the hashing library. On systems with a large user base, a small cache size can lead to prohibitively long database file rebuild times. As a rough guide, the memory usage of pwd_mkdb in megabytes will be a little bit more than twice the figure specified here. The default is 2 megabytes.
Only update the secure version of the database. This is most commonly used in conjunction with the -u flag during a password change. Because the insecure database doesn't contain the password there is no reason to update it if the only change is in the password field. Cannot be used in conjunction with the -p flag.
username
Only update the record for the specified user. Utilities that operate on a single user can use this option to avoid the overhead of rebuilding the entire database.

The two databases differ in that the secure version contains the user's encrypted password and the insecure version has an asterisk (``*'')

The databases are used by the C library password routines (see getpwent(3)).

The pwd_mkdb utility exits zero on success, non-zero on failure.

If the PW_SCAN_BIG_IDS environment variable is set, pwd_mkdb will suppress the warning messages that are normally generated for large user and group IDs. Such IDs can cause serious problems with software that makes assumptions about the values of IDs.

/etc/pwd.db
The insecure password database file.
/etc/pwd.db.tmp
A temporary file.
/etc/spwd.db
The secure password database file.
/etc/spwd.db.tmp
A temporary file.
/etc/master.passwd
The current password file.
/etc/passwd
A Version 7 format password file.

Regenerate the password database after manually editing or replacing the password file:

/usr/sbin/pwd_mkdb -p /etc/master.passwd

Previous versions of the system had a program similar to pwd_mkdb, mkpasswd(8), which built dbm(3) style databases for the password file but depended on the calling programs to install them. The program was renamed in order that previous users of the program not be surprised by the changes in functionality.

chpass(1), passwd(1), db(3), getpwent(3), passwd(5), vipw(8)

Because of the necessity for atomic update of the password files, pwd_mkdb uses rename(2) to install them. This, however, requires that the file specified on the command line live on the same file system as the /etc directory.

There are the obvious races with multiple people running pwd_mkdb on different password files at the same time. The front-ends to pwd_mkdb, chpass(1), passwd(1) and vipw(8), handle the locking necessary to avoid this problem.

December 20, 2023 macOS 15.0