# tmpmfs formal documentation



## alvaro (Nov 27, 2011)

is there any formal doc over the option 
	
	



```
tmpmfs="YES"
```
 in /etc/rc.conf?

what is the difference with using md or mfs in fstab?


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## Beastie (Nov 27, 2011)

alvaro said:
			
		

> is there any formal doc over the option
> 
> 
> 
> ...


/etc/defaults/rc.conf (also check rc.conf(5)) says

```
[...]
tmpmfs="AUTO"		# Set to [highlight]YES to always create an mfs /tmp[/highlight], NO to never
[...]
```



			
				alvaro said:
			
		

> what is the difference with using md or mfs in fstab?


The md(4) driver uses the mfs (or memory filesystem) to create a memory disk. The created MD just has a fixed location (/tmp). It also has a size option (set by *tmpsize*) and extra options (set by *tmpmfs_flags*) that you can override.

But you could create the MD anywhere you want (not just on /tmp) and with any additional option. See mdmfs(8) and the examples in it:

```
Create and mount a 32 megabyte swap-backed file system on /tmp:

           mdmfs -s 32m md /tmp

     The same file system created as an entry in /etc/fstab:

           md /tmp mfs rw,-s32m 2 0
```
(simply change /tmp)

And alternatively you could use the tmpfs(5) driver to do the same on /tmp or anywhere else.


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