Dumps of mounted file systems, dump size estimates and GNU tar

Dumps of mounted file systems, dump size estimates and GNU tar

Post by Tor Lillqvi » Fri, 22 Dec 1995 04:00:00

What's the current general opinion on using dump to backup active file
systems? Is this asking for trouble? What kinds of problems can be
expeted when restoring dumps made from active file systems? The
machined in question would be running HP-UX 9 and 10, and SunOS 4.1.3
and 5.4.

I have until now used mainly tar and cpio to do my backups, but have
been considering switching to Amanda, and Amanda really needs dump's
feature of a quick estimate of the number of blocks the dump will
need. Emulating dump with tar or cpio means getting the size estimate
(GNU tar's --totals) is very slow.

Perhaps a good idea would be to implement a --no-output switch to GNU
tar that would cause it not to actually open any files or write any
archive, just calculate the size the archive would be, and write it
out as with --totals. Or maybe GNU tar could automatically check if
the archive is actually being written to /dev/null, and in that case
skip opening and reading the files.

-Tor Lillqvist


1. unix dump: dumped twice to same dumpfile; restore if file displays only last dump

-rw-r--r--    1 root     root     554221568 Nov 22 16:07 /mnt/cc/cc

restore > ls
System.map              grub/                   map
System.map-2.4.8-26mdk  kernel.h                message
boot.0300               kernel.h-2.4.8          os2_d.b
boot.b                  lilo                    us.klt
chain.b                 lilo-graphic/           vmlinuz
config                  lilo-menu/              vmlinuz-2.4.8-26mdk
config-2.4.8-26mdk      lilo-text/

That's a mighty big filesize for /boot which i know to be 23 MB.
So i must assume that the first dump (of / ) is still there.
But restore only lets me see the latest dump (on top of that "layer")

Anyone ever encounter this and recover the first dump?

cave jabberwockum

2. recv problem...

3. formula to Estimate Dump Size

4. NIS (Debian/Unstable)

5. skipping system dump : no dump device configured. Rebooting...

6. binary file ip and assigning ip in a loopback network

7. GNU tar 1.11.8 Dumping CORE!

8. cdrecord and SCSI bus problem

9. GNU Tar vs. dump (The faster one wins...maybe)

10. dump/restore vs gnu tar

11. DUMP/RESTORE File -> TAR File Converter?

12. dump - estimated tape blocks

13. Dumping to Large File Enabled File Systems