passwd1User Commandspasswdchange user passwordpasswd-f -s namepasswd-g -r -R grouppasswd-x max-n min-w warn-i inactloginpasswd-l -u -d -S -e loginDESCRIPTIONpasswd changes passwords for user and group
accounts. A normal user may only change the password for his/her own
account, the super user may change the password for any account. The
administrator of a group may change the password for the group.
passwd also changes account information, such as
the full name of the user, user's login shell, or password expiry date
and interval.
The option makes passwd call
chsh to change the user's shell. The
option makes passwd call
chfn to change the user's gecos information. These
two options are only meant for compatibility, since the other programs
can be called directly.
Password ChangesThe user is first prompted for his/her old password, if one is
present. This password is then encrypted and compared against the
stored password. The user has only one chance to enter the correct
password. The super user is permitted to bypass this step so that
forgotten passwords may be changed.
After the password has been entered, password aging information
is checked to see if the user is permitted to change the password at
this time. If not, passwd refuses to change the
password and exits.
The user is then prompted for a replacement password. This
password is tested for complexity. As a general guideline, passwords
should consist of 6 to 8 characters including one or more from each
of following sets:
lower case alphabeticsdigits 0 thru 9punctuation marksCare must be taken not to include the system default erase or
kill characters. passwd will reject any password
which is not suitably complex.
If the password is accepted, passwd will
prompt again and compare the second entry against the first. Both
entries are required to match in order for the password to be
changed.
Group passwords
When the option is used, the password for the
named group is changed. The user must either be the super user, or a
group administrator for the named group. The current group password
is not prompted for. The option is used with the
option to remove the current password from the
named group. This allows group access to all members. The
option is used with the
option to restrict the named group for all users.
Password expiry informationThe password aging information may be changed by the super user
with the , ,
, and options. The
option is used to set the maximum number of days
a password remains valid. After max
days, the password is required to be changed. The
option is used to set the minimum number of days
before a password may be changed. The user will not be permitted to
change the password until min days
have elapsed. The option is used to set the
number of days of warning the user will receive before his/her
password will expire. The warning occurs warn days before the expiration, telling the
user how many days remain until the password is set to expire. The
option is used to disable an account after the
password has been expired for a number of days. After a user account
has had an expired password for inact
days, the user may no longer sign on to the account.
If you wish to immediately expire an account's password, you can
use the option. This in effect can force a user
to change his/her password at the user's next login. You can also
use the option to delete a user's password (make
it empty). Use caution with this option since it can make an account
not require a password at all to login, leaving your system open to
intruders.
Account maintenance User accounts may be locked and unlocked with the
and flags. The
option disables an account by changing the
password to a value which matches no possible encrypted value. The
option re-enables an account by changing the
password back to its previous value.
The account status may be viewed with the
option. The status information consists of 7 fields. The first
field is the user's login name. The second field indicates if the
user account is locked (L), has no password (NP), or has a usable
password (P). The third field gives the date of the last password
change. The next four fields are the minimum age, maximum age,
warning period, and inactivity period for the password. These ages
are expressed in days. See Password expiry
information above for a discussion of these fields.
Hints for user passwordsThe security of a password depends upon the strength of the
encryption algorithm and the size of the key space. The \s-2UNIX System encryption method is based on
the NBS DES algorithm and is very secure. The size of the key space
depends upon the randomness of the password which is selected.
Compromises in password security normally result from careless
password selection or handling. For this reason, you should not
select a password which appears in a dictionary or which must be
written down. The password should also not be a proper name, your
license number, birth date, or street address. Any of these may be
used as guesses to violate system security.
Your password must easily remembered so that you will not be
forced to write it on a piece of paper. This can be accomplished by
appending two small words together and separating each with a
special character or digit. For example, Pass%word.
Other methods of construction involve selecting an easily
remembered phrase from literature and selecting the first or last
letter from each word. An example of this is:
Ask not for whom the bell tollswhich producesAn4wtbtYou may be reasonably sure few crackers will have included this
in their dictionaries. You should, however, select your own methods
for constructing passwords and not rely exclusively on the methods
given here.
Notes about group passwordsGroup passwords are an inherent security problem since more than
one person is permitted to know the password. However, groups are a
useful tool for permitting co-operation between different users.
CAVEATSNot all options may be supported. Password complexity checking
may vary from site to site. The user is urged to select a password as
complex as he feels comfortable with. Users may not be able to change
their password on a system if NIS is enabled and they are not logged
into the NIS server.
FILES/etc/passwduser account information/etc/shadowsecure user account informationEXIT VALUES
The passwd command exits with the following values:
0success1permission denied2invalid combination of options3unexpected failure, nothing done4unexpected failure, passwd file missing5passwd file busy, try again6invalid argument to optionSEE ALSOgroup5,
passwd5,
shadow5AUTHORJulianne Frances Haugh <jockgrrl@ix.netcom.com>