Issue with swap file

[Lowell Gilbert]

Andre Goree <andre at drenet.net> writes:

> On 12/03/2014 5:10 pm, Lowell Gilbert wrote:
>> Andre Goree <andre at drenet.net> writes:
>>
>>> Several months ago, I followed the procedure here[1] for creating a
>>> swap file.  This worked great for a long time, up until my last reboot
>>> which coincided with an update to 10.1.
>>>
>>> agoree at fbsd10-atl ~ % grep swap /etc/fstab
>>> md99            none            swap    sw,file=/usr/swap 0     0
>>> agoree at fbsd10-atl ~ % sudo swapon -a
>>> swapon: mdconfig (attach) error: md99 on file=/usr/swap
>>>
>>> I've also tried zero-writing the file again, to no avail.  Any ideas?
>>>
>>> [1] https://www.freebsd.org/doc/handbook/adding-swap-space.html
>>
>> Strange, I haven't run into any problems. And annoying that the error
>> message is so unhelpful. When that error message gets printed, swapon
>> has tried to run mdconfig and gotten an error back, but has no idea
>> what
>> the problem was. At that point, it has already checked that the md
>> device is available, which eliminates my best guess at a diagnosis.
>>
>> The way you can get more information is by running the mdconfig command
>> by hand, just as swapon would have, and see what *it* reports to you.
>> 	mdconfig -a -t vnode -n -f /usr/swap
>>
>> Very likely, it will tell you exactly what to fix.
>
> I tried creating a new one (hence the '/usr/swap0' vs. '/usr/swap' in
> the output below) and still got the same error.  Here's the
> [disheartening] output from the command you gave:
>
> agoree at fbsd10-atl ~ % sudo swapon -a
> swapon: mdconfig (attach) error: md99 on file=/usr/swap0
> agoree at fbsd10-atl ~ % sudo mdconfig -a -t vnode -n -f /usr/swap0
> 0

Okay, that means mdconfig can attach the file to an md device. That
eliminates my next guess, which was that md support wasn't working for
some reason (such as not being in your kernel configuration).

The only difference I can see is the unit number, which I forgot to
include in the command. Maybe if you try
 	mdconfig -a -t vnode -n -f /usr/swap -u 99
that will fail with an informative error message. If that doesn't help,
I'm baffled.