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PWD_MKDB(8) NetBSD System Manager's Manual PWD_MKDB(8)
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pwd_mkdb -- generate the password databases
pwd_mkdb [-BLps] [-c cachesize] [-d directory] [-u username] file
pwd_mkdb creates db(3) style secure and insecure databases for the speci-
fied 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).
Specify the size of the memory cache in megabytes used by the hash-
ing 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 unspeci-
fied, this value will be calculated based on the size of the input
file up to a maximum of 8 megabytes.
Change the root directory of the generated files from ``/'' to
-L Store data in little-endian format (see also -B).
-p Create a Version 7 style password file and install it into
-s Update the secure database only. This is useful when only
encrypted passwords have changed. This option negates the effect
of any -p option.
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 pass-
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
pwd_mkdb exits zero on success, non-zero on failure.
/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.
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 dif-
ferent 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.
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 call-
ing programs to install them. The program was renamed in order that pre-
vious users of the program not be surprised by the changes in functional-
chpass(1), passwd(1), pwhash(1), db(3), getpwent(3), pw_mkdb(3),
passwd(5), useradd(8), userdel(8), usermod(8), vipw(8)
NetBSD 5.0.1 September 23, 2006 NetBSD 5.0.1