Linux – Check logical volume mount point (command line)

I am not aware of any requirement that swap space be contiguous on disk under Linux, with LVM or otherwise. I have never arranged for my swap LVs to be contiguous and have never run into any problem (it's possible that all my swap LVs just happened to be contiguous, I've never looked).

Linux supports non-contiguous swap files, it would be odd to have such a restriction on LVM volumes. I can't find any reference to this in any official documentation or anyone explaning why swap LVs should be contiguous. This has all the hallmarks of an urban legend.

The origin may lie in HP-UX, which Linux's LVM is partly inspired from, and which did (does?) require swap space to be contiguous. I don't know that this has ever been the case on Linux.

There may be a perceived performance benefit, but with 4MB extents, I very much doubt there is any performance benefit, and I can't find any benchmark.

If you have volume groups that span over multiple disks, you may want to constrain what PV the swap LV is on. But I wouldn't require a contiguous volume.

Same as you would with any other block device. e.g.

file -s /dev/vg1/lv1

If it's ext4, it'll say something like:

/dev/vg1/lv1: Linux rev 1.0 ext4 filesystem data, UUID=xxxx, volume name "yyyy" (needs journal recovery) (extents) (large files) (huge files)

Alternatively, you could run blkid /dev/vg1/lv1. That would report something like:

/dev/vg1/lv1: LABEL="yyyy" UUID="xxxx" TYPE="ext4"

From man file:

-s, --special-files

Normally, file only attempts to read and determine the type of argument files which stat(2) reports are ordinary files. This prevents problems, because reading special files may have peculiar consequences. Specifying the -s option causes file to also read argument files which are block or character special files.

This is useful for determining the filesystem types of the data in raw disk partitions, which are block special files. This option also causes file to disregard the file size as reported by stat(2) since on some systems it reports a zero size for raw disk partitions.