Besides the disks you physically insert into your computer; floppies, CDs, hard drives, and so forth, other forms of disks are understood by FreeBSD - the virtual disks.
These include network filesystems such as the Network Filesystem and Coda, memory-based filesystems such as md and file-backed filesystems created by vnconfig.
vnconfig(8) configures and enables vnode pseudo disk devices. A vnode is a representation of a file, and is the focus of file activity. This means that vnconfig(8) uses files to create and operate a filesystem. One possible use is the mounting of floppy or CD images kept in files.
To mount an existing filesystem image:
Example 10-1. Using vnconfig to mount an existing filesystem image
# vnconfig vn0 diskimage
# mount /dev/vn0c /mnt
To create a new filesystem image with vnconfig:
Example 10-2. Creating a New File-Backed Disk with vnconfig
# dd if=/dev/zero of=newimage bs=1k count=5k
5120+0 records in
5120+0 records out
# vnconfig -s labels -c vn0 newimage
# disklabel -r -w vn0 auto
# newfs vn0c
Warning: 2048 sector(s) in last cylinder unallocated
/dev/rvn0c: 10240 sectors in 3 cylinders of 1 tracks, 4096 sectors
5.0MB in 1 cyl groups (16 c/g, 32.00MB/g, 1280 i/g)
super-block backups (for fsck -b #) at:
32
# mount /dev/vn0c /mnt
# df /mnt
Filesystem 1K-blocks Used Avail Capacity Mounted on
/dev/vn0c 4927 1 4532 0% /mnt
md is a simple, efficient means to do memory filesystems.
Simply take a filesystem you've prepared with, for example, vnconfig(8), and:
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