using kppp debian periodically something is changing permissions of
dev/ttys0 to all forbidden

i hve to periodically as root change them to all a  +rw

how can i monitor whatever is chaging this files permissions?

tia
peter

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ilaboo wrote:

> using kppp debian periodically something is changing permissions of
> dev/ttys0 to all forbidden
>
> i hve to periodically as root change them to all a  +rw
>
> how can i monitor whatever is chaging this files permissions?
>
> tia
> peter

Give a try with FAM (file access monitor).

JP.

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Jean-Philippe Blais wrote:

> ilaboo wrote:
> 
>
> Give a try with FAM (file access monitor).
>
> JP.

Oups it is not file access monitor but File Alteration Monitor.

JP.

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What are the exact permissions on /dev/ttyS0 and the kppp executable?
What's the group membership of the user?  Can you use minicom to access
/dev/ttyS0?

If kppp is changing /dev/ttyS0, you should be able to use strace to see
the system calls kppp made to change the permissions or ownership of
the file (maybe chown32 or chmod32).

Try "strace -o strace.out kppp".  This should run kppp and save the
stack trace output in strace.out.  In another window, monitor the
system calls with "tail -f strace.out".  You could also do an "ls -l
/dev/ttyS0" to note when the permissions have changed.

If you're not sure whether or not kppp is the culprit, you can use the
"-r" switch with the lsof command to monitor which program is opening
/dev/ttyS0.

To check for any processes that have opened /dev/ttyS0 once every
second, you can use the "-r 1" like this:

bbrock@queue:~> lsof -r 1 /dev/ttyS0
=======
=======
=======
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
=======
=======
=======

bbrock@queue:~>

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What are the exact permissions on /dev/ttyS0 and the kppp executable?
What's the group membership of the user?  Can you use minicom to access
/dev/ttyS0?

If kppp is changing /dev/ttyS0, you should be able to use strace to see
the system calls kppp made to change the permissions or ownership of
the file (maybe chown32 or chmod32).

Try "strace -o strace.out kppp".  This should run kppp and save the
stack trace output in strace.out.  In another window, monitor the
system calls with "tail -f strace.out".  You could also do an "ls -l
/dev/ttyS0" to note when the permissions have changed.

If you're not sure whether or not kppp is the culprit, you can use the
"-r" switch with the lsof command to monitor which program is opening
/dev/ttyS0.

To check for any processes that have opened /dev/ttyS0 once every
second, you can use the "-r 1" like this:

bbrock@queue:~> lsof -r 1 /dev/ttyS0
=======
=======
=======
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
COMMAND   PID   USER   FD   TYPE DEVICE SIZE  NODE NAME
minicom 13413 bbrock    3u   CHR   4,64      34953 /dev/ttyS0
=======
=======
=======
=======

bbrock@queue:~>

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