PWD_MKDB(8)

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

# NAME

pwd_mkdb — generate the password databases

# SYNOPSIS

pwd_mkdb | [-BLlpsvw] [-c cachesize] [-d directory] [-u username] [-V version] 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).
-l
  Use syslog(3) to report errors.
-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.
-V version
  Upgrade or downgrade databases to the numbered version. Version 0 is the old format (up to and including NetBSD 5.0) with the 4 byte time fields and version 1 is the new format with the 8 byte time fields (greater than NetBSD 5.0). NetBSD 5.0 cannot read version 1 databases. All versions above NetBSD 5.0 can read and write both version 0 and version 1 databases. By default the databases stay in the version they were before the command was run.
-v
  Mention when a version change occurs.
-w
  Print a warning if the system is using old style databases.

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)).

# 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.

# EXIT STATUS

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

# 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), syslog(3), passwd(5), useradd(8), userdel(8), usermod(8), vipw(8)

# 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.

August 18, 2010 | NetBSD 5.99