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Micro420 08-02-2006 03:32 PM

How to change user's password on initial log in?
 
I want "joeblow" to log in to the Linux box and have him change his password. I give him a temporary password. When he inputs the temporary password, the computer will ask him to change his password. How do I do this? I have checked the man pages for useradd, usermod, and passwd. None of these options have the ability to do this. I remember doing this in SuSE 9.3. Help?

homey 08-02-2006 03:37 PM

Use chage. For example:
chage -d0 fred

Micro420 08-02-2006 03:53 PM

Thanks, I will give that command a try, even though it's not technically correct. It sounds like I'm just expiring the account. I'm sure it'll do the trick, but...

That isn't the command I was initially thinking of when I had done this awhile back ago on SuSE 9.3. I find it really perplexing for Linux to not be able to assign a temporary password and have the user change their password on initial logon, or at least show how to do this in the man pages. This is so common and useful for any Windows administrator that it should be a feature in Linux.

I remember the command in SuSE being something really easy and logical, like 'useradd -? joeblow', or after having created the user, you just would do 'passwd -? joeblow'. Next time joeblow signs on with the temporary password, he is asked to change it. Pretty simple concept, right?

Micro420 08-02-2006 10:20 PM

I found my answer after Googling different keywords.

the command is:

Code:

passwd -e username
IT's that simple, yet that option is NOT located in the man passwd pages! Nor is it listed on websites that talk about passwd! WHY?!??????

gilead 08-02-2006 11:32 PM

It's odd that none of the distro's you mention would have a man page that doesn't list the expiry information. Here's an extract from the Slackware passwd man page:
Code:

  Password expiry information
      The password aging information may be changed by the super user with the -x, -n, -w, and  -i
      options.  The -x 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 -n 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 -w 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 -i 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 -e option. This in
      effect can force a user to change his/her password at the user's next login.  You  can  also
      use  the -d 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.


Micro420 08-03-2006 11:40 AM

I am using Ubuntu 6.06 mainly. Haven't touched SuSE or Mandriva in a long time. I always assumed the man pages were all standardized. I guess not. :( I guess I'll need to read Slackware's man pages for more options.

Well, at least now we know! And knowing is half the battle!

reddazz 08-03-2006 11:57 AM

Quote:

Originally Posted by Micro420
I am using Ubuntu 6.06 mainly. Haven't touched SuSE or Mandriva in a long time. I always assumed the man pages were all standardized. I guess not. :( I guess I'll need to read Slackware's man pages for more options.

Well, at least now we know! And knowing is half the battle!

Most man pages are standardised but some distros change them to fit whatever patching they will have made to their distro. On Gentoo and Suse, the man pages for passwd list the "-e" flag, but not in as much detail as that posted by gilead.

gilead 08-03-2006 02:18 PM

Quote:

Originally Posted by Micro420
And knowing is half the battle!

Yes it is - and it's also most of the fun, especially that aha! moment when something clicks into place :)

Snowhog 11-16-2007 12:30 AM

Output of man passwd using Kubuntu Feisty Fawn:
Quote:

PASSWD(1) User Commands PASSWD(1)

NAME
passwd - change user password

SYNOPSIS
passwd [options] [LOGIN]

DESCRIPTION
passwd changes passwords for user accounts. A normal user may only
change the password for his/her own account, while the super user may
change the password for any account. passwd also changes account
information, such as the full name of the user, the user’s login shell,
or his/her password expiry date and interval.

Password Changes
The 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 twice for a replacement password. The second
entry is compared against the first and both are required to match in
order for the password to be changed.

Then, the password is tested for complexity. As a general guideline,
passwords should consist of 6 to 8 characters including one or more
characters from each of the following sets:

lower case alphabetics

digits 0 thru 9

punctuation marks

Care must be taken not to include the system default erase or kill
characters. passwd will reject any password which is not suitably
complex.

Hints for user passwords
The security of a password depends upon the strength of the encryption
algorithm and the size of the key space. The UNIX 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 be 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 tolls

which produces

An4wtbt

You 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.

OPTIONS
The options which apply to the passwd command are:

-a, --all
This option can be used only with -S and causes show status for all
users.

-d, --delete
Delete a user’s password (make it empty). This is a quick way to
disable a password for an account. It will set the named account
passwordless.

-e, --expire
Immediately expire an account’s password. This in effect can force a
user to change his/her password at the user’s next login.

-h, --help
Display help message and exit.

-i, --inactive INACTIVE
This 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 INACTIVE days, the user may no longer sign on
to the account.

-k, --keep-tokens
Indicate password change should be performed only for expired
authentication tokens (passwords). The user wishes to keep their
non-expired tokens as before.

-l, --lock
Lock the named account. This option disables an account by changing
the password to a value which matches no possible encrypted value.

-m, --mindays MIN_DAYS
Set the minimum number of days between password changes to MIN_DAYS.
A value of zero for this field indicates that the user may change
his/her password at any time.

-q, --quiet
Quiet mode.

-r, --repository REPOSITORY
change password in REPOSITORY repository

-S, --status
Display account status information. 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.

-u, --unlock
Unlock the named account. This option re-enables an account by
changing the password back to its previous value (to value before
using -l option).

-w, --warndays WARN_DAYS
Set the number of days of warning before a password change is
required. The WARN_DAYS option is the number of days prior to the
password expiring that a user will be warned that his/her password
is about to expire.

-x, --maxdays MAX_DAYS
Set the maximum number of days a password remains valid. After
MAX_DAYS, the password is required to be changed.

CAVEATS
Not 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 or she 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/passwd
User account information.

/etc/shadow
Secure user account information.

EXIT VALUES
The passwd command exits with the following values:

0
success

1
permission denied

2
invalid combination of options

3
unexpected failure, nothing done

4
unexpected failure, passwd file missing

5
passwd file busy, try again

6
invalid argument to option

SEE ALSO
group(5), passwd(5), shadow(5).

User Commands 12/19/2006 PASSWD(1)


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