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Full Discussion: Perl script - changing passwords
Top Forums Shell Programming and Scripting Perl script - changing passwords Post 20744 by Perderabo on Thursday 2nd of May 2002 09:30:26 PM
Old 05-02-2002
I think that you are writing this for SunOS. I don't know SunOS super well, but I think you missed an issue.

With the versions of UNIX that I do know, programs like passwd use some kind of locking scheme. This prevents two or more users from stepping on each other if they to change their password at the same time.

With early versions of Unix, the trick was to invoke the link system call to link /etc/passwd to /etc/ptmp. The link system call is atomic. And it will fail, even for root, if the target exists. If the link was successful, the program could proceed. If not, it would back off. Sysadmins would get a call from a user sometimes about the password file being locked. The trick was then to remove /etc/ptmp. HP-UX was still using this method a few years ago, but I haven't checked since HP-UX 9.0.

Beats me what Sun is using. I just ran the passwd command on a Sun. A "lt -ltc /etc | head" showed that oshadow had popped into existence. It is listed without comment on Sun's man page for passwd.

If you going to run the script in single user mode you can ignore this issue. Otherwise, you might want to do some research....
 

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LEARN ABOUT OSX

pwconv

pwconv(1M)                                                System Administration Commands                                                pwconv(1M)

NAME

       pwconv - installs and updates /etc/shadow with information from /etc/passwd

SYNOPSIS

       pwconv

DESCRIPTION

       The pwconv command creates and updates /etc/shadow with information from /etc/passwd.

       pwconv relies on a special value of 'x' in the password field of /etc/passwd. This value of 'x' indicates that the password for the user is
       already in /etc/shadow and should not be modified.

       If the /etc/shadow file does not exist, this command will create /etc/shadow with  information  from  /etc/passwd.  The  command  populates
       /etc/shadow  with  the  user's  login  name,  password,  and  password  aging  information. If password aging information does not exist in
       /etc/passwd for a given user, none will be added to  /etc/shadow. However, the last changed information will always be updated.

       If the  /etc/shadow file does exist, the following tasks will be performed:

                Entries that are in the  /etc/passwd file and not in the /etc/shadow file will be added to the /etc/shadow file.

                Entries that are in the  /etc/shadow file and not in the /etc/passwd file will be removed from /etc/shadow.

                Password attributes (for example, password and aging information)  that exist in an /etc/passwd entry will be moved to the  corre-
                sponding entry in  /etc/shadow.

       The pwconv command can only be used by the super-user.

FILES

       /etc/opasswd

       /etc/oshadow

       /etc/passwd

       /etc/shadow

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       passwd(1), passmgmt(1M), usermod(1M), passwd(4), attributes(5)

DIAGNOSTICS

       pwconv exits with one of the following values:

       0        SUCCESS.

       1        Permission denied.

       2        Invalid command syntax.

       3        Unexpected failure.  Conversion not done.

       4        Unexpected failure.  Password file(s) missing.

       5        Password file(s) busy.  Try again later.

       6        Bad entry in /etc/shadow file.

SunOS 5.10                                                          9 Mar 1993                                                          pwconv(1M)
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