[OpenAFS] Cron, script and keytab on Ubuntu x86

Jacob Volstrup volstrup@s-et.aau.dk
Thu, 15 Feb 2007 15:11:04 +0100

Hi list,

For quite some time I have tried to debug a script running from a
cronjob but I just cannot find my error.

* The short version *
I have a keytab which is used from my cronscript. The script is executed
every 5 minutes and has a local non-AFS lockfile to prevent multiple
scripts working on data at the same time.
For convenience we call the running script R and the starting/checking
script S. The S script exits if the lockfile exists, if not it
initializes the AFS credentials with kinit and the keytab file and
becomes R. When S exits R will loose its AFS credentials, which is the
part I just do not understand as I would expect that the different
executions of the cronjob have their own running environment.

* The longer version *
I use a local script for initialising the AFS credentials and further
execute a script which resides on AFS:

#!/usr/bin/perl -w
# cronscript-initialize.pl

$lockfile = "/home/cdvwww/tmp/cronscript.lck";
$execute_script = "/afs/s-et.aau.dk/scripts/cronscript-execute.pl";
$keytab = "/home/cdvwww/keytab-cdvwww";

createLockfile($lockfile, 36);



sub initAFS {
    $res_kinit = system("kinit", "-k", "-t", $keytab, "cdvwww");
    if ($res_kinit == 0) {
        $res_aklog = system("aklog");
        if ($res_aklog != 0) {
            die("Could not establish credentials (error in aklog)\n");
    } else {
        die("Could not establish credentials (error in kinit)\n");

# Creates lockfile if it does not exist already
sub createLockfile {
    (local $lockfile, local $number) = @_;

    if (-e $lockfile) {
        open (FILE, $lockfile);
        writeCounter($lockfile, ($counter + 1));
        if ($counter < $number) {
        } else {
            if ($counter % $number == 0) {
                die "Lock file " . $lockfile . " exists\n";
            } else {
    } else {
        writeCounter($lockfile, 0);
        if (!(-e $lockfile)) {
            die "Could not create lockfile $lockfile! Aborting.";

sub writeCounter {
    (local $filename, local $counter) = @_;
    open (WRITE,">$filename");
    print WRITE "$counter";


The rest is like explained in the short version. I am pretty sure that
the error resides inside my script but I cannot figure out where it is.

The running system is an AMD-K6 300MHz with Ubuntu 6.06 256MB of ram.

Any help will be appreciated.

Sincerely, Jacob Volstrup