Unix Server Tech Knowledge Base

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====== Device Naming Conventions ======

===== Block Devices =====

FreeBSD creates block device names based on type, similar to the way Linux does. A device name is a 2-3 letter indicator of device type, followed by an integer showing its hierarchy in the initial search. **Note:** The device number can change if a new device of the same type is added, so use labels in fstab.

FreeBSD creates block device names based on type, similar to the way Linux does.

^ Identifer  ^ Description                      ^
| ada        | SATA and IDE Hard Drives         |
| da         | SCSI hard drives and USB storage |
| cd or scd  | SATA and IDE CD-ROM Drives       |
| cd         | SCSI CD-ROM Drives               |
| fd         | Floppy Drives                    |

Devices are then broken down into slices ("partitions" in the Linux and Windows worlds), designated by the letter "s" followed by a number (max of 4). Thus, //da0s1// would be the first slice on a USB or SCSI hard drive.

Each slice can have a partition (no relationship to Linux and Windows partitions) which is designated by a single letter. //da0s1a// would be the first partition in the first slice on a USB or SCSI hard drive

By convention, partition "a" is a root file system, partition "b" is swap space, partition "c" is a special partition used by the file system management. All other partitions are available for other things (ie, /var, etc...)

Partitions can hold file systems. NOTE: by "partition" I mean a partition of a slice (ie, BSD terms, not Windows/Linux)

See https://www.freebsd.org/doc/handbook/disk-organization.html

Disks can be managed by either fdisk (old school appearantly) or gpart. 

===== Ethernet Devices =====

Ethernet devices are named based on the drive needed to access it and the order in which it was discovered. So, for example, a NIC which uses the ndis drive would be called ndis0. If a second card was found with the same driver, it would be named ndis1.

You can see the ethernet cards recognized by the system with the command:
<code bash>
grep 'Ethernet address:' /var/run/dmesg.boot
</code>

Note that this will **not** find cards which do not have a driver loaded, although the most common ones are built into the GENERIC kernel.

===== RAMDisk =====

RAMDisks are handled a little differently in FreeBSD in that you will want to manually create a directory (say, /mnt/ramdisk) and then execute the appropriate //mdfs// command. Once that is done, you can use RAMDisks as you like. The fstab entry is different from the one used in Linux, obviously.
<code>
# fstab entry creating a RAMDISK mount for /tmp of 16M size.
md              /tmp            mfs     rw,-s16M,nosuid,noatime,noexec 0	0
</code>