PWCONV - Online Linux Manual PageSection : 8
Updated : 03/06/2023
Source : shadow−utils 4​.13
Note : System Management Commands

NAMEpwconv, pwunconv, grpconv, grpunconv − convert to and from shadow passwords and groups

SYNOPSISpwconv [options] pwunconv [options] grpconv [options] grpunconv [options]

DESCRIPTIONThe pwconv command creates shadow from passwd and an optionally existing shadow​. The pwunconv command creates passwd from passwd and shadow and then removes shadow​. The grpconv command creates gshadow from group and an optionally existing gshadow​. The grpunconv command creates group from group and gshadow and then removes gshadow​. These four programs all operate on the normal and shadow password and group files: /etc/passwd, /etc/group, /etc/shadow, and /etc/gshadow​. Each program acquires the necessary locks before conversion​. pwconv and grpconv are similar​. First, entries in the shadowed file which don't exist in the main file are removed​. Then, shadowed entries which don't have `x' as the password in the main file are updated​. Any missing shadowed entries are added​. Finally, passwords in the main file are replaced with `x'​. These programs can be used for initial conversion as well to update the shadowed file if the main file is edited by hand​. pwconv will use the values of PASS_MIN_DAYS, PASS_MAX_DAYS, and PASS_WARN_AGE from /etc/login​.defs when adding new entries to /etc/shadow​. Likewise pwunconv and grpunconv are similar​. Passwords in the main file are updated from the shadowed file​. Entries which exist in the main file but not in the shadowed file are left alone​. Finally, the shadowed file is removed​. Some password aging information is lost by pwunconv​. It will convert what it can​.

OPTIONSThe options which apply to the pwconv, pwunconv, grpconv, and grpunconv commands are: −h, −−help Display help message and exit​. −R, −−root ​CHROOT_DIR Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory​. Only absolute paths are supported​.

BUGSErrors in the password or group files (such as invalid or duplicate entries) may cause these programs to loop forever or fail in other strange ways​. Please run pwck and grpck to correct any such errors before converting to or from shadow passwords or groups​.

CONFIGURATIONThe following configuration variable in /etc/login​.defs changes the behavior of grpconv and grpunconv: MAX_MEMBERS_PER_GROUP (number) Maximum members per group entry​. When the maximum is reached, a new group entry (line) is started in /etc/group (with the same name, same password, and same GID)​. The default value is 0, meaning that there are no limits in the number of members in a group​. This feature (split group) permits to limit the length of lines in the group file​. This is useful to make sure that lines for NIS groups are not larger than 1024 characters​. If you need to enforce such limit, you can use 25​. Note: split groups may not be supported by all tools (even in the Shadow toolsuite)​. You should not use this variable unless you really need it​. The following configuration variables in /etc/login​.defs change the behavior of pwconv: PASS_MAX_DAYS (number) The maximum number of days a password may be used​. If the password is older than this, a password change will be forced​. If not specified, −1 will be assumed (which disables the restriction)​. PASS_MIN_DAYS (number) The minimum number of days allowed between password changes​. Any password changes attempted sooner than this will be rejected​. If not specified, 0 will be assumed (which disables the restriction)​. PASS_WARN_AGE (number) The number of days warning given before a password expires​. A zero means warning is given only upon the day of expiration, a negative value means no warning is given​. If not specified, no warning will be provided​.

FILES/etc/login​.defs Shadow password suite configuration​.

SEE ALSOgrpck(8), login.defs(5), pwck(8)​.
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