Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #147
Difficulty: Easy
Linus Torvalds released the Linux kernel as free software under the GNU General Public License in 1991.
True or False?
Linux & Unix Commands - Search Man Pages

pwd_mkdb(8) [mojave man page]

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

NAME
pwd_mkdb -- generate the password databases SYNOPSIS
pwd_mkdb [-c] [-p | -s] [-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: -c Check if the password file is in the correct format. Do not change, add, or remove any files. -d directory Operate in a base directory other than the default of /etc. All absolute paths (including file) will be made relative to directory. Any directories specified as a part of file will be stripped off. This option is used to create password databases in directories other than etc; for instance in a chroot(8) jail. -p Create a Version 7 style password file and install it into /etc/passwd. -s 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. -u 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. This option must never be used if the line number of the user's record in /etc/master.passwd has changed. file The absolute path to a file in master.passwd format, as described in passwd(5). 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)). pwd_mkdb exits zero on success, non-zero on failure. FILES
/etc/master.passwd current password file /etc/passwd a Version 7 format password file /etc/pwd.db insecure password database file /etc/pwd.db.tmp temporary file /etc/spwd.db secure password database file /etc/spwd.db.tmp temporary file SEE ALSO
chpass(1), passwd(1), db(3), getpwent(3), passwd(5), vipw(8) STANDARDS
Previous versions of the system had a program similar to pwd_mkdb, mkpasswd, 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. 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 pwd_mkdb, chpass(1), passwd(1), and vipw(8) handle the locking necessary to avoid this problem. BSD
June 6, 1993 BSD

Check Out this Related Man Page

PWD_MKDB(8)						    BSD 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 lit- tle 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. BSD
August 18, 2010 BSD

Featured Tech Videos