/etc/fstab entries

muzaffar.k · August 22, 2016, 6:24am

Hi,
Can anyone explain why we use defaults 0 0 in fstab and what does 0 inidicate

 
10.250.104.50:/home/u   /home/u         nfs     defaults        0 0

Thanks in advance
Muzaffar

RavinderSingh13 · August 22, 2016, 6:32am

Hello muzaffar.k,

Simple answer is ,second last field(5th field) determines if it should be dumped, last field(6th field) determines if it should be checked during startup and in what sequence. We could get this information from manual entry of fstab as follows.
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.

Thanks,
R. Singh

muzaffar.k · August 22, 2016, 7:09am

Thanks for the reply Ravinder Singh,

What exactly you mean by dump. what it does can you be more specific about this..?

Thanks,
Muzaffar

orange47 · September 8, 2016, 3:09am

it seems to be used for backup:
"<dump> - used by the dump utility to decide when to make a backup. Dump checks the entry and uses the number to decide if a file system should be backed up. Possible entries are 0 and 1. If 0, dump will ignore the file system; if 1, dump will make a backup. Most users will not have dump installed, so they should put 0 for the <dump> entry."