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The last two fields on each line in fstab (dump and pass) are some numbers (usually, 0).

What do these numbers mean?

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
UUID=030ccf66-5195-4835-ba3e-f5d7a5403c05 /               ext4    errors=remount-ro 0       1
Alexander Abakumov
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elzapp
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2 Answers2

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Copy/paste from man fstab:

The fifth field, (fs_freq), is used for these filesystems by the dump(8) command to determine which filesystems need to be dumped. If the fifth field is not present, a value of zero is returned and dump will assume that the filesystem does not need to be dumped.

The sixth field, (fs_passno), is used by the fsck(8) program to determine the order in which filesystem checks are done at reboot time. The root filesystem should be specified with a fs_passno of 1, and other filesystems should have a fs_passno of 2. Filesystems within a drive will be checked sequentially, but filesystems on different drives will be checked at the same time to utilize parallelism available in the hardware. If the sixth field is not present or zero, a value of zero is returned and fsck will assume that the filesystem does not need to be checked.

Community
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JanC
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    But, what does the dump-utility do? (It has no man-page) – elzapp Oct 28 '10 at 09:34
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    If you don't have a dump man page, then you don't have dump installed. See http://manpages.ubuntu.com/manpages/maverick/en/man8/dump.8.html - it's for backup purposes. – htorque Oct 28 '10 at 10:36
  • @JanC by check you mean file system error check ? – Alex Jones Dec 05 '14 at 14:03
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    Related: https://superuser.com/questions/247523/fstab-when-do-you-use-the-dump-and-fsck-options TL;DR: just set dump to zero always, and pass to 1 for root drive, 2 for any other drive. – Niko Fohr Oct 13 '17 at 10:45
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    @np8 you don't want fsck running on something like a NFS for example, so "2 for any other drive" isn't entirely correct – Enrico May 01 '19 at 21:26
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Simple blockhead answer is , first field determines if it should be dumped, second field determines if it should be checked during startup and in what sequence. Check the manual for the rest!

g24l
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    Define dump FFS – chx101 Apr 03 '21 at 19:00
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    @chx101 see here: https://superuser.com/questions/247523/fstab-when-do-you-use-the-dump-and-fsck-options -- short answer is that 'dump' seems to be rarely used anymore, so you would almost always expect this to be zero. The second number is used by the more widely used fsck to check the filesystem, and if so in what order (root should be 1, rest should increment, or zero to skip checking the filesystem) – pzkpfw Mar 07 '22 at 12:17