Questions about ramdisk in FreeBSD

PeteS · Dec 19, 2010

Hi,

I need a ramdisk similar to the tmpfs /dev/shm that is automatically setup in debian.

Is FreeBSD doing anything similar automatically?

If not, what is the recommended way to set this up in the boot process?

Thanks in advance for your help,
Pete S

wblock@ · Dec 19, 2010

You might explain what /dev/shm does, and why you need a ramdisk. The situation may be different on FreeBSD.

For automatic setup, see mdmfs(8). For background, see mdconfig(8).

PeteS · Dec 19, 2010

I want to use a ramdisk to exchange information between different scripts and programs. Since these files will be written and read continuously I don't want to place them on the SSD I use as a system drive.

In debian (and most other linux distros) a tmpfs ramdisk is always created and mounted on /dev/shm during boot. So I used that location in the past but as I have switched to running FreeBSD I was wondering what options I have.

Thanks,
Pete

jalla · Dec 19, 2010

Put this in /etc/rc.conf

Code:

tmpmfs="YES" 
tmpsize="100m" 
tmpmfs_flags="-S"

Beastie · Dec 19, 2010

FreeBSD has its own implementation of tmpfs(5). Just create a directory somewhere and add this to /etc/fstab in order to mount it on startup:

Code:

tmpfs /path/to/the/directory tmpfs rw 0 0

That's it.

PeteS · Dec 19, 2010

Thanks, it worked perfectly after I removed the partition already mounted on /tmp in /etc/fstab.

PeteS · Dec 19, 2010

Thanks! I'll stick to the mfs as the man page says that tmpfs is currently considered an experimental feature.

Beastie · Dec 19, 2010

It has been "experimental" for the past two years and I've been using it every single day for as long. It's currently holding my browser's profile.

wblock@ · Dec 19, 2010

PeteS said:
Thanks! I'll stick to the mfs as the man page says that tmpfs is currently considered an experimental feature.

Look at /etc/rc.d/tmp; it's the same thing. tmpmfs="YES" creates a ramdisk with mdconfig(8). It's just a little more specialized.