We have a problem with file locking which occurs every few months. We have finally worked out at least part of what is happening.
We have a Windows 95 system filestore exported as a read-only CIFS share. There are 1200 or so PCs which access this.
Just occasionally when a user launches the Telnet client (Hummingbird) it complains that it can't access its keyboard mapping file. Once this starts to happen, it is the same for every PC. A unix user running as root can't read or do anything to this file either - it gets "permission denied".
Yesterday when this happened we used (rc_toggle_basic) lock_dump -f to look at the locks, and we found that a PC appeared to have taken out an exclusive read lock on the file:
========00003a31:0006b48e \95APPLIB\york.hts state=GRANTED mode=Excl-denyA host=OFFICE1
When we found the PC called "office1", it was turned off. The user said it had hung up and she had switched it off.
We managed to restore normal service by doing a "cifs terminate -t 0 office1".
This raises several issues:
1) If a CIFS client is switched off, is there any sort of keepalive timer on the Filer that closes down open files and locks?
2) Should a PC with read-only access to a filestore be allowed to lock files for exclusive read? Should this perhaps be an option on a qtree or share?
3) This particular application obviously doesn't expect this file to be shared. But could any malicious user take out locks on random important files and freeze the whole network?
Dave Atkin -- Dave Atkin, Head of Technical Services Computing Service, University of York, YORK YO10 5DD Phone: +44-1904-433804 (ddi) Fax: +44-1904-433740 Email: D.Atkin@york.ac.uk