PWD_MKDB(8)

NAME
pwd_mkdb - generate the password databases

SYNOPSIS
pwd_mkdb [-BLps] [-c cachesize] [-d directory] [-u username] file

DESCRIPTION
pwd_mkdb 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:

-B  Store data in big-endian format (see also -L).

-c cachesize
    Specify the size of the memory cache in megabytes 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. If unspecified, this value will be calculated based on the size of the input file up to a maximum of 8 megabytes.

-d directory
    Change the root directory of the generated files from “/” to directory.

-L  Store data in little-endian format (see also -B).

-p  Create a Version 7 style password file and install it into “/etc/passwd”.

-s  Update the secure database only. This is useful when only encrypted passwords have changed. This option negates the effect of any -p option.

-u name
    Don't re-build the database files, but instead modify or add entries for the specified user only. This option may only be used when the line number and user name in the password file have not changed, or when adding a new user from the last line in the password file.

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)).

EXIT STATUS
pwd_mkdb exits zero on success, non-zero on failure.

FILES
/etc/master.passwd
    The current password file.
/etc/passwd
    A Version 7 format password file.
/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.

BUGS
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 chpass(1), passwd(1), useradd(8), userdel(8), usermod(8), and vipw(8) handle the locking necessary to avoid this problem.

The database files are copied when the -u option is used. Real locking would make this unnecessary.

Although the DB format is endian-transparent, the data stored in the DB is not. Also, the format doesn't lend itself to insertion or removal of records from arbitrary locations in the password file. This is difficult to fix without breaking compatibility.

Using the -u option on a system where multiple users share the same UID can have unexpected results.

COMPATIBILITY
Previous versions of the system had a program similar to pwd_mkdb which built dbm 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.

SEE ALSO
chpass(1), passwd(1), pwhash(1), db(3), getpwent(3), pw_mkdb(3), passwd(5), useradd(8), userdel(8), usermod(8), vipw(8)