On Tue, Jul 24, 2012 at 6:39 PM, Marios Titas <redneb8888@xxxxxxxxx> wrote:
> When I create a btrfs volume of size strictly less than 256 MiB then if I do
> mount /dev/sdb1 /mnt/test
> the kernel tries unsuccessfully to do the mount with many other file systems
> before successfully trying with btrfs. For volumes of size larger than
> or equal to
> 256 MiB it just mounts the volume without doing that. Why is this discrepancy?
If I understand correctly, the kernel does not implement any fs
detection; this is performed by the mount utility, which indeed may
try a bunch of different filesystems until it finds one that works.
>From man mount:
If no -t option is given, or if the auto type is specified,
mount will try to guess the desired type. Mount uses the blkid
or volume_id library for guessing the filesystem type; if that
does not turn up anything that looks familiar, mount will try to
read the file /etc/filesystems, or, if that does not exist,
/proc/filesystems. All of the filesystem types listed there
will be tried, except for those that are labeled "nodev" (e.g.,
devpts, proc and nfs). If /etc/filesystems ends in a line with
a single * only, mount will read /proc/filesystems afterwards.
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