Re: how to properly mount an external usb hard drive & other questions

[Jim Salter <jim@jrs-s.net>]

On 01/05/2014 01:02 PM, Jim Salter wrote:
> If you want LZO compression, as you specified:
>
>           /dev/sdc /path/to/mountpoint compress=lzo,noauto,users,user 0 0
>
> Better yet, if your btrfs is actually on /dev/sdc right now, let's get 
> that fstab entry mounting it by UUID instead.
>
>           ls -l /dev/disk/by-uuid | grep sdc
>           lrwxrwxrwx 1 root root 10 Jan  3 09:40 
> 12345678-9abc0-1234-5678-9a0123456789 -> ../../sdc
>
> So then:
>
>           # this is not a real UUID, you need to check 
> /dev/disk/by-uuid on your machine for a real UUID
>           UUID=12345678-9abc0-1234-5678-9a0123456789 
> /path/to/mountpoint   compress=lzo,noauto,users,user   0   0
>
> This is EXTRA important with a USB drive, since it's HIGHLY likely it 
> won't always be on the same physical devicename.

One other note: in this particular case, you might actually be better 
served setting compression by mounting the drive normally, then:

          cd /path/to/drive
          chattr +c . ; chattr +c * ; chattr +c .*

This will set compression on by default for any future files stored on 
that USB drive, *without* needing any special mount options.

Why might this be a better idea? Well, if it's a USB drive, presumably 
you might want to mount it on foreign systems from time to time. This 
way, even if you mount the drive on a foreign system that doesn't know 
anything about your preferences, it will see the +c on the root 
directory of the drive, and store any new data on the drive compressed.

The only caveat: +c won't set the compression algorithm to LZO. It'll be 
gzip, which is the default algorithm. (And, of course, this won't 
compress any EXISTING data already stored there - only NEW data written 
to it after you set the +c attribute.)