Partition naming, fstab, and geli

[Ian Smith]

In freebsd-questions Digest, Vol 285, Issue 2, Message 2
On Sun, 15 Nov 2009 19:23:15 -0700 David Allen wrote:

 > Say I have performed a standard installation of FreeBSD onto a single IDE
 > drive with the following entries in /etc/fstab:
 > 
 >     /dev/ad0s1b  none  swap  sw  0  0
 >     /dev/ad0s1a  /     ufs   rw  1  1
 >     /dev/ad0s1d  /var  ufs   rw  2  2
 >     /dev/ad0s1e  /tmp  ufs   rw  2  2
 >     /dev/ad0s1f  /usr  ufs   rw  2  2
 > 
 > Then I added more drives.
 > 
 > 1. The Handbook suggests there is a convention that when partitioning a a
 > drive that's been added, to label the first new partition on that drive as
 > 'e' as opposed to 'a' (which is reserved for the /root partition).  Does
 > the following satisfy that convention, or would starting with 'a' in each
 > case make more sense?
 > 
 >     /dev/ad1e  /foo1  ufs  rw  2  2
 >     /dev/ad1f  /bar1  ufs  rw  2  2
 >     /dev/ad1g  /baz1  ufs  rw  2  2
 > 
 >     /dev/ad2e  /foo2  ufs  rw  2  2
 >     /dev/ad2f  /bar2  ufs  rw  2  2
 > 
 >     /dev/ad3e  /foo3  ufs  rw  2  2
 >     /dev/ad3f  /bar3  ufs  rw  2  2

If you added these with sysinstall (or sade) it will tend to choose 'd' 
for the first partition on other than the / partition (which is named
'a' on install).  Or at least, it's always started with 'd' for me :)

But if you're doing it manually starting with 'e' is fine.  I suspect 
the handbook section you quoted to Polytropon later is more an example 
than definitive.  You can happily mount an 'a' partition from another 
drive that was once a system disk; it's more of a convention really.

 > 2.  My second question is in regards to using the 'xx' fstype to have the
 > system ignore that device.
 > 
 > Consider, for example, a geli encrypted partition.  The .eli device
 > doesn't exist at boot time.  I discovered by accident that the system
 > won't boot with an fstab entry for a device that doesn't exist.  So if I
 > was to record an entry in fstab, I couldn't use
 > 
 >     /dev/ad1e.eli  /home/david/private  ufs  rw  0  0
 > 
 > Does that mean that the following is what's typically to record fstab
 > entries for ignored devices?
 > 
 >     /dev/ad1e.eli  /home/david/private  xx   rw  0  0
 >     /dev/ad3e      /fake                xx   rw  0  0
 >     /dev/ad3f      /reserved            xx   rw  0  0

Yes.  Here I must differ with Polytropon, though your format for the 
options isn't perhaps quite right.  From an old fstab here:

# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/acd0               /cdrom          cd9660  ro,noauto       0       0
/dev/ad0s1              /dos            msdosfs ro,noauto       0       0
/dev/ad0s2b             none            swap    sw              0       0
/dev/ad0s2a             /               ufs     rw              1       1
/dev/ad0s2d             /var            ufs     rw,noatime      2       2
/dev/ad0s2e             /usr            ufs     rw,noatime      2       2
/dev/ad0s4d     /paqi4.5        ufs ro,noauto,nodev,noexec,nosymfollow,noatime 2  3
/dev/ad0s4e     /paqi4.5/var    ufs ro,noauto,nodev,noexec,nosymfollow,noatime 2  4
/dev/ad0s4f     /paqi4.5/usr    ufs ro,noauto,nodev,noexec,nosymfollow,noatime 2  4
# 25Apr06 ext 20Gb USB disk.  DON'T autoadd these, deadly if da0 absent!
# .. xx fsopts, everything incl fsck must ignore ..
/dev/da0s3d     /usbdsk         ufs     xx,noauto,nosymfollow   3       3
/dev/da0s3e     /usbdsk/var     ufs     xx,noauto,nosymfollow   4       4
/dev/da0s3f     /usbdsk/usr     ufs     xx,noauto,nosymfollow   4       4
# 26May06 shintaro 1G flashdrive .. just doc, can't mount using these ..
/dev/da0s1      /flash/dos      msdosfs xx,noauto               0       0
/dev/da0s2d     /flash/ufs      ufs     xx,noauto,noatime       3       3
/dev/da0s3d     /flash/pvt      ufs     xx,noauto,noatime       3       3

As you say they're useful for doc, and not hard to edit into action. 
Note the additions above were assigned starting at 'd' by sysinstall.

cheers, Ian