Creating a disk image in FreeBSD
What?
Sometimes you just need a small filesystem in an image file. In Linux, mkfs accepts any file as its argument - it's not that easy with FreeBSD. I decided to share this because there was no clear documentation I could quickly find in Google.
OK, Get to business now
First, create an empty file, just as in Linux
uranus# dd if=/dev/zero of=partfile.dd bs=1M count=1100 1100+0 records in 1100+0 records out 1153433600 bytes transferred in 10.793702 secs (106861725 bytes/sec)
Then, you need to attach it as a memory disk
uranus# mdconfig -a -t vnode -f partfile.dd -u 0 mdconfig: ioctl(/dev/mdctl): Device busy
Oops, device 0 is already taken (-u 0 is responsible for device number). Let's see what's available
uranus# mdconfig -l md0 md1
So let's use md2.
uranus# mdconfig -a -t vnode -f partfile.dd -u 2
It succeeded, yay! Now we're free to create a filesystem.
uranus# bsdlabel -w -B md2 auto uranus# newfs -m 0 md2a Warning: changing optimization to space because minfree is less than 8% /dev/md2a: 1100.0MB (2252784 sectors) block size 16384, fragment size 2048 using 6 cylinder groups of 183.72MB, 11758 blks, 23552 inodes. super-block backups (for fsck -b #) at: 160, 376416, 752672, 1128928, 1505184, 1881440
And the moment of truth: Will it mount?
uranus# mount /dev/md2a /media
Yes it will.
Now, how to get rid of it?
uranus# umount /media uranus# mdconfig -d -u 2 uranus# rm partfile.dd