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NAME

pw — create, remove, modify & display system users and groups

SYNOPSIS

DESCRIPTION

The pw utility is a command-line based editor for the system user and group files, allowing the superuser an easy to use and standardized way of adding, modifying and removing users and groups. Note that pw only operates on the local user and group files. NIS users and groups must be maintained on the NIS server. The pw utility handles updating the passwd, master.passwd, group and the secure and insecure password database files, and must be run as root.

The first one or two keywords provided to pw on the command line provide the context for the remainder of the arguments. The keywords user and group may be combined with add, del, mod, show, or next in any order. (For example, showuser, usershow, show user, and user show all mean the same thing.) This flexibility is useful for interactive scripts calling pw for user and group database manipulation. Following these keywords, you may optionally specify the user or group name or numeric id as an alternative to using the -n name, -u uid, -g gid options.

The following flags are common to most or all modes of operation:

-V etcdir

This flag sets an alternate location for the password, group and configuration files, and may be used to maintain a user/group database in an alternate location. If this switch is specified, the system /etc/pw.conf will not be sourced for default configuration data, but the file pw.conf in the specified directory will be used instead (or none, if it does not exist). The -C flag may be used to override this behaviour. As an exception to the general rule where options must follow the operation type, the -V flag may be used on the command line before the operation keyword.

-C config

By default, pw reads the file /etc/pw.conf to obtain policy information on how new user accounts and groups are to be created. The -C option specifies a different configuration file. While most of the contents of the configuration file may be overridden via command-line options, it may be more convenient to keep standard information in a configuration file.

-q

Use of this option causes pw to suppress error messages, which may be useful in interactive environments where it is preferable to interpret status codes returned by pw rather than messing up a carefully formatted display.

-N

This option is available in add and modify operations, and tells pw to output the result of the operation without updating the user or group databases. You may use the -P option to switch between standard passwd and readable formats.

-Y

Using this option with any of the update modes causes pw to run make(1) after changing to the directory /var/yp. This is intended to allow automatic updating of NIS database files. If separate passwd and group files are being used by NIS, then use the -y path option to specify the location of the NIS passwd database so that pw will concurrently update it with the system password databases.

USER OPTIONS

The following options apply to the useradd and usermod commands:

-n name

Specify the user/account name.

-u uid

Specify the user/account numeric id.

Usually, you only need to provide one or the other of these options, as the account name will imply the uid, or vice versa. However, there are times when you need to provide both. For example, when changing the uid of an existing user with usermod, or overriding the default uid when creating a new account. If you wish pw to automatically allocate the uid to a new user with useradd, then you should not use the -u option. You may also provide either the account or userid immediately after the useradd, userdel, usermod or usershow keywords on the command line without using the -n or -u options.

-c comment

This field sets the contents of the passwd GECOS field, which normally contains up to four comma-separated fields containing the user's full name, office or location, and work and home phone numbers. These sub-fields are used by convention only, however, and are optional. If this field is to contain spaces, you need to quote the comment itself with double quotes ‘"’. Avoid using commas in this field as these are used as sub-field separators, and the colon ‘:’ character also cannot be used as this is the field separator for the passwd file itself.

-d dir

This option sets the account's home directory. Normally, you will only use this if the home directory is to be different from the default determined from /etc/pw.conf - normally /home with the account name as a subdirectory.

-e date

Set the account's expiration date. Format of the date is either a UNIX time in decimal, or a date in ‘dd-mmm-yy[yy]’ format, where dd is the day, mmm is the month, either in numeric or alphabetic format ('Jan', 'Feb', etc) and year is either a two or four digit year. This option also accepts a relative date in the form ‘+n[mhdwoy]’ where ‘n’ is a decimal, octal (leading 0) or hexadecimal (leading 0x) digit followed by the number of Minutes, Hours, Days, Weeks, Months or Years from the current date at which the expiration date is to be set.

-p date

Set the account's password expiration date. This field is similar to the account expiration date option, except that it applies to forced password changes. This is set in the same manner as the -e option.

-g group

Set the account's primary group to the given group. group may be defined by either its name or group number.

-G grouplist

Set additional group memberships for an account. grouplist is a comma, space or tab-separated list of group names or group numbers. The user's name is added to the group lists in /etc/group, and removed from any groups not specified in grouplist. Note: a user should not be added to their primary group with grouplist. Also, group membership changes do not take effect for current user login sessions, requiring the user to reconnect to be affected by the changes.

-L class

This option sets the login class for the user being created. See login.conf(5) and passwd(5) for more information on user login classes.

-m

This option instructs pw to attempt to create the user's home directory. While primarily useful when adding a new account with useradd, this may also be of use when moving an existing user's home directory elsewhere on the file system. The new home directory is populated with the contents of the skeleton directory, which typically contains a set of shell configuration files that the user may personalize to taste. Files in this directory are usually named dot.⟨config⟩ where the dot prefix will be stripped. When -m is used on an account with usermod, existing configuration files in the user's home directory are not overwritten from the skeleton files.

When a user's home directory is created, it will by default be a subdirectory of the basehome directory as specified by the -b option (see below), bearing the name of the new account. This can be overridden by the -d option on the command line, if desired.

-M mode

Create the user's home directory with the specified mode, modified by the current umask(2). If omitted, it is derived from the parent process' umask(2). This option is only useful in combination with the -m flag.

-k dir

Set the skeleton directory, from which basic startup and configuration files are copied when the user's home directory is created. This option only has meaning when used with the -d or -m flags.

-s shell

Set or changes the user's login shell to shell. If the path to the shell program is omitted, pw searches the shellpath specified in /etc/pw.conf and fills it in as appropriate. Note that unless you have a specific reason to do so, you should avoid specifying the path - this will allow pw to validate that the program exists and is executable. Specifying a full path (or supplying a blank "" shell) avoids this check and allows for such entries as /nonexistent that should be set for accounts not intended for interactive login.

-h fd

This option provides a special interface by which interactive scripts can set an account password using pw. Because the command line and environment are fundamentally insecure mechanisms by which programs can accept information, pw will only allow setting of account and group passwords via a file descriptor (usually a pipe between an interactive script and the program). sh, bash, ksh and perl all possess mechanisms by which this can be done. Alternatively, pw will prompt for the user's password if -h 0 is given, nominating stdin as the file descriptor on which to read the password. Note that this password will be read only once and is intended for use by a script rather than for interactive use. If you wish to have new password confirmation along the lines of passwd(1), this must be implemented as part of an interactive script that calls pw.

If a value of ‘-’ is given as the argument fd, then the password will be set to ‘*’, rendering the account inaccessible via password-based login.

-H fd

Read an encrypted password string from the specified file descriptor. This is like -h, but the password should be supplied already encrypted in a form suitable for writing directly to the password database.

It is possible to use useradd to create a new account that duplicates an existing user id. While this is normally considered an error and will be rejected, the -o option overrides the check for duplicates and allows the duplication of the user id. This may be useful if you allow the same user to login under different contexts (different group allocations, different home directory, different shell) while providing basically the same permissions for access to the user's files in each account.

The useradd command also has the ability to set new user and group defaults by using the -D option. Instead of adding a new user, pw writes a new set of defaults to its configuration file, /etc/pw.conf. When using the -D option, you must not use either -n name or -u uid or an error will result. Use of -D changes the meaning of several command line switches in the useradd command. These are:

-D

Set default values in /etc/pw.conf configuration file, or a different named configuration file if the -C config option is used.

-b dir

Set the root directory in which user home directories are created. The default value for this is /home, but it may be set elsewhere as desired.

-e days

Set the default account expiration period in days. Unlike use without -D, the argument must be numeric, which specifies the number of days after creation when the account is to expire. A value of 0 suppresses automatic calculation of the expiry date.

-p days

Set the default password expiration period in days.

-g group

Set the default group for new users. If a blank group is specified using -g "", then new users will be allocated their own private primary group with the same name as their login name. If a group is supplied, either its name or uid may be given as an argument.

-G grouplist

Set the default groups in which new users are granted membership. This is a separate set of groups from the primary group, and you should avoid nominating the same group as both primary and extra groups. In other words, these extra groups determine membership in groups other than the primary group. grouplist is a comma-separated list of group names or ids, and are always stored in /etc/pw.conf by their symbolic names.

-L class

This option sets the default login class for new users.

-k dir

Set the default skeleton directory, from which prototype shell and other initialization files are copied when pw creates a user's home directory. See description of -k for naming conventions of these files.

-u min,max, -i min,max

These options set the minimum and maximum user and group ids allocated for new accounts and groups created by pw. The default values for each is 1000 minimum and 32000 maximum. min and max are both numbers, where max must be greater than min, and both must be between 0 and 32767. In general, user and group ids less than 100 are reserved for use by the system, and numbers greater than 32000 may also be reserved for special purposes (used by some system daemons).

-w method

The -w option sets the default method used to set passwords for newly created user accounts. method is one of:

no

disable login on newly created accounts

yes

force the password to be the account name

none

force a blank password

random

generate a random password

The ‘random’ or ‘no’ methods are the most secure; in the former case, pw generates a password and prints it to stdout, which is suitable where you issue users with passwords to access their accounts rather than having the user nominate their own (possibly poorly chosen) password. The ‘no’ method requires that the superuser use passwd(1) to render the account accessible with a password.

-y path

This sets the pathname of the database used by NIS if you are not sharing the information from /etc/master.passwd directly with NIS. You should only set this option for NIS servers.

The userdel command has only three valid options. The -n name and -u uid options have already been covered above. The additional option is:

-r

This tells pw to remove the user's home directory and all of its contents. The pw utility errs on the side of caution when removing files from the system. Firstly, it will not do so if the uid of the account being removed is also used by another account on the system, and the 'home' directory in the password file is a valid path that commences with the character ‘/’. Secondly, it will only remove files and directories that are actually owned by the user, or symbolic links owned by anyone under the user's home directory. Finally, after deleting all contents owned by the user only empty directories will be removed. If any additional cleanup work is required, this is left to the administrator.

Mail spool files and crontabs are always removed when an account is deleted as these are unconditionally attached to the user name. Jobs queued for processing by at are also removed if the user's uid is unique and not also used by another account on the system.

The usermod command adds one additional option:

-l name

This option allows changing of an existing account name to ‘name’. The new name must not already exist, and any attempt to duplicate an existing account name will be rejected.

The usershow command allows viewing of an account in one of two formats. By default, the format is identical to the format used in /etc/master.passwd with the password field replaced with a ‘*’. If the -P option is used, then pw outputs the account details in a more human readable form. If the -7 option is used, the account details are shown in v7 format. The -a option lists all users currently on file. Using -F forces pw to print the details of an account even if it does not exist.

The command usernext returns the next available user and group ids separated by a colon. This is normally of interest only to interactive scripts or front-ends that use pw.

GROUP OPTIONS

The -C and -q options (explained at the start of the previous section) are available with the group manipulation commands. Other common options to all group-related commands are:

-n name

Specify the group name.

-g gid

Specify the group numeric id.

As with the account name and id fields, you will usually only need to supply one of these, as the group name implies the uid and vice versa. You will only need to use both when setting a specific group id against a new group or when changing the uid of an existing group.

-M memberlist

This option provides an alternative way to add existing users to a new group (in groupadd) or replace an existing membership list (in groupmod). memberlist is a comma separated list of valid and existing user names or uids.

-m newmembers

Similar to -M, this option allows the addition of existing users to a group without replacing the existing list of members. Login names or user ids may be used, and duplicate users are silently eliminated.

-d oldmembers

Similar to -M, this option allows the deletion of existing users from a group without replacing the existing list of members. Login names or user ids may be used, and duplicate users are silently eliminated.

groupadd also has a -o option that allows allocation of an existing group id to a new group. The default action is to reject an attempt to add a group, and this option overrides the check for duplicate group ids. There is rarely any need to duplicate a group id.

The groupmod command adds one additional option:

-l name

This option allows changing of an existing group name to ‘name’. The new name must not already exist, and any attempt to duplicate an existing group name will be rejected.

Options for groupshow are the same as for usershow, with the -g gid replacing -u uid to specify the group id. The -7 option does not apply to the groupshow command.

The command groupnext returns the next available group id on standard output.

USER LOCKING

The pw utility supports a simple password locking mechanism for users; it works by prepending the string ‘*LOCKED*’ to the beginning of the password field in master.passwd to prevent successful authentication.

The lock and unlock commands take a user name or uid of the account to lock or unlock, respectively. The -V, -C, and -q options as described above are accepted by these commands.

NOTES

For a summary of options available with each command, you can use

The pw utility allows 8-bit characters in the passwd GECOS field (user's full name, office, work and home phone number subfields), but disallows them in user login and group names. Use 8-bit characters with caution, as connection to the Internet will require that your mail transport program supports 8BITMIME, and will convert headers containing 8-bit characters to 7-bit quoted-printable format. sendmail(8) does support this. Use of 8-bit characters in the GECOS field should be used in conjunction with the user's default locale and character set and should not be implemented without their use. Using 8-bit characters may also affect other programs that transmit the contents of the GECOS field over the Internet, such as fingerd(8), and a small number of TCP/IP clients, such as IRC, where full names specified in the passwd file may be used by default.

The pw utility writes a log to the /var/log/userlog file when actions such as user or group additions or deletions occur. The location of this logfile can be changed in pw.conf(5).

FILES

/etc/master.passwd

The user database

/etc/passwd

A Version 7 format password file

/etc/login.conf

The user capabilities database

/etc/group

The group database

/etc/master.passwd.new

Temporary copy of the master password file

/etc/passwd.new

Temporary copy of the Version 7 password file

/etc/group.new

Temporary copy of the group file

/etc/pw.conf

Pw default options file

/var/log/userlog

User/group modification logfile

EXIT STATUS

The pw utility returns EXIT_SUCCESS on successful operation, otherwise pw returns one of the following exit codes defined by sysexits(3) as follows:

EX_USAGE

• Command line syntax errors (invalid keyword, unknown option).

EX_NOPERM

• Attempting to run one of the update modes as non-root.

EX_OSERR

• Memory allocation error.
• Read error from password file descriptor.

EX_DATAERR

• Bad or invalid data provided or missing on the command line or via the password file descriptor.
• Attempted to remove, rename root account or change its uid.

EX_OSFILE

• Skeleton directory is invalid or does not exist.
• Base home directory is invalid or does not exist.
• Invalid or non-existent shell specified.

EX_NOUSER

• User, user id, group or group id specified does not exist.
• User or group recorded, added, or modified unexpectedly disappeared.

EX_SOFTWARE

• No more group or user ids available within specified range.

EX_IOERR

• Unable to rewrite configuration file.
• Error updating group or user database files.
• Update error for passwd or group database files.

EX_CONFIG

• No base home directory configured.

SEE ALSO

chpass(1), passwd(1), umask(2), group(5), login.conf(5), passwd(5), pw.conf(5), pwd_mkdb(8), vipw(8)

HISTORY

The pw utility was written to mimic many of the options used in the SYSV shadow support suite, but is modified for passwd and group fields specific to the 4.4BSD operating system, and combines all of the major elements into a single command.