|Subject:||Re: [Bug-tar] tar does not recognize nfs device|
|Date:||Sun, 27 Jan 2008 10:48:55 -0500|
|I'll try to be more specific this time. Our institution has a Netapp NAS that exports files via NFS. We are mounting the exports on a heterogenous group of systems, running different OS's. On some of the systems, we have a need to use the incremental option that tar provides on the NFS mounts (what I previously referred to as an NFS device). Each of the NFS mounts has a device number associated with it that is not necessarily static across reboots. According to the tar documentation (http://www.gnu.org/software/automake/manual/tar/Incremental-Dumps.html), tar has a way of handling this situation:|
"Metadata stored in snapshot files include device numbers, which, obviously is supposed to be a non-volatile value. However, it turns out that NFS devices have undependable values when an automounter gets in the picture. This can lead to a great deal of spurious redumping in incremental dumps, so it is somewhat useless to compare two NFS devices numbers over time. The solution implemented currently is to considers all NFS devices as being equal when it comes to comparing directories; this is fairly gross, but there does not seem to be a better way to go."
The indication that tar has recognized a particular file as part of an NFS mount is a leading 1 in the entry of a Version 2 formatted tar snaphots file, as described in http://www.gnu.org/software/tar/manual/html_node/tar_170.html . As I stated in the initial post, tar does not recognize that it is working on a NFS mounted area of the file system as indicated by the leading 0 in the snapshots file.
Which brings me back to my original question, why is this happening, and what can I do to fix it? If I run stat on the files that I am attempting to create a tar archive out of, it reports that they are NFS mounted, but tar does not recognize them as such.
On Jan 27, 2008, at 5:57 AM, Vitaly V. Ch wrote:
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