SUMMARY: UFS hard links and CD-ROM images (Rock Ridge)

From: Sean Walmsley (sean.p.walmsley@hydro.on.ca)
Date: Mon Apr 21 1997 - 08:59:03 CDT


Thanks to

Glenn.Satchell@uniq.com.au
casper@holland.Sun.COM (Casper Dik)
mrs@cadem.mc.xerox.com (Mike Salehi)

for their responses.

As Glenn pointed out, the hsfs(7FS) man page clearly states that:

  "This filesystem also contains support for the Rock Ridge
  Extensions. If the extensions are contained on the CD-
  ROM, then the filesystem will provide all of the filesystem
  semantics and file types of UFS, except for writability and
  hard links."
  -----------

I'm still not sure if the Rock Ridge standard itself supports hard
links (I think that it does based on the information on my original
post), but it's clear that the Solaris implementation of hsfs with
RR extensions does not.

I guess that the work around for this is to burn a tar archive of
filesystems containing hard links to CDR, rather than burning the
filesystem itself. Given the (slow) speed of CD's, this is a suboptimal
solution because it means that you have to extract the entire archive to
retrieve a small file at the end of it.

My original question follows:

----------------------------------------------------
      
Anyone out there know how Solaris deals with hard links in Rock Ridge formatted
CD images?

I'm using mkisofs and cdrecord to copy ~ 350Mb of data (containing a fair
number of large, hard linked files) to a CD Recordable disk. The hard linked
file pairs in the source tree share the same i-node number (as expected).

The size of the image file created by the mkisofs utility is consistent with
the actual amount of data in the source tree as reported by du -ks, so
I'm reasonably confident that the image correctly represents the hard links
(i.e. it's not just including two copies of each file).

When I finish recording the CD-R and mount it using the automounter, an ls -i
on the CD directories displays all the previously hard linked files with
distinct i-node numbers. When I tar from the CD back to a UFS filesystem
for recovery purposes, I get two distinct files for each pair of files that
were previously hard linked. This is a problem since the receiving UFS file
system isn't big enough with the duplicated files!

Interestingly, when I put the SAME CD (prepared under Solaris) into my Windows
NT machine and do an ls -i (MKS utilities), the 'i-node numbers' show up
correctly for the hard linked file pairs.

All of this leads me to believe that the problem is not the CD itself, but in
the mounting of the CD file system under Solaris. Does anyone know if this
is the case, and if so, if there is a work around.

Thanks - I'll summarize.

--
Sean Walmsley
Reactor Safety and Operational Analysis Dept,
Ontario Hydro (H11-G26)
Tel. (416) 592 4608  Fax (416) 592 4966
EMail: Sean.P.Walmsley@hydro.on.ca



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