Swap partition for FreeBSD

[Polytropon]

On Sat, 16 May 2015 16:16:13 +0530, Avinash Sonawane wrote:
> I have 4 Primary partitions. Out of which one ada0s1 has FreeBSD,
> ada0s2 has Debian, ada0s3 is one extra Primary partition (which
> currently holds data) and ada0s4 is an extended partition (to create
> further logical partitions like linux-swap, data partitions etc.)

Okay, so you should be able to put the swap into ada0s1.



> >> After searching a bit on the web I came to know that default kernel
> >> build options specify "options GEOM_PART_EBR_COMPAT" which prevents
> >> GEOM from editing EBR partition schemes. So to create a partition of
> >> type freebsd-swap in extended partition it looks like I need to
> >> recompile the kernel without the GEOM_PART_EBR_COMPAT kernel option.
> >
> > It seems to be that way. Using "extended DOS partitions" has never
> > been a good idea. :-)
> >
> > However, as I initially wrote, this isn't _needed_ when you put
> > the swap partition into the slice where the rest of your FreeBSD
> > installation resides. You can have up to 4 "DOS primary partitions"
> > (slices), and each one could carry an independent OS install.
> 
> I have Freebsd installed in ada0s1a so can I create ada0s1b inside
> ada0s1 to have freebsd-swap? How do I do that?

Using bsdlabel, for example. As shown in the manpage as well
as in the "legacy parts" of the FreeBSD handbook, you'd have
to modify the partition table entry to include a swap space.
This typically involves either re-installing, or the more
common dump + restore process (for ada0s1a, /, holding your
installation).

This is a comparable process:

https://www.freebsd.org/doc/en/books/handbook/install-steps.html

See 3.6.5.

Also read "man bsdlabel". You will use a command like

	# bsdlabel -e ada0s1

to make the changes to how the slice will be used.

You have to come from something like this:

	#        size   offset    fstype   [fsize bsize bps/cpg]
	  a:  1000000       16    4.2BSD     2048 16384  5128
	  c:  1000016        0    unused        0     0

to something like this:

	#        size   offset    fstype   [fsize bsize bps/cpg]
	  a:   900000       16    4.2BSD     2048 16384  5128
	  b:   100000   900000      swap
	  c:  1000016        0    unused        0     0

Numbers are nonsense here. :-)

You need to create a type "swap" partition, and / will be
resized in that process of course. Space will be consumed
from ada0s1, not ada0s6.

I surely don't have to mention that it's considered mandatory
to have a good backup before making changes with such impact.



> Or should I create ada0s6b as swap partition inside ada0s6 slice?

That is probably also possible, but I've never actually used
"extended DOS partitions" in production, so I can't tell you
if FreeBSD will deal with them in the same way as Linux. But
it should be possible.

I don't know if it's possible to "dynamically resize" the /
partition without data loss, that's why I mentioned backups.


-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...