Forum Topic - tmpfs:
   
tmpfs  
Hi,

I am currently looking for information on using tmpfs under QNX. I am using qdb and the documentation for it mentions 
being able to use tmpfs as a RAM based temporary storage. I have also seen other mentions of people using tmpfs on these
 forums.

However, I can't seem to find any further reference to tmpfs in the documentation, or on my development system. Is it 
something that I'd need to port from Linux? Or am I better using ETFS in RAM? I thought having a transaction based FS 
would be overkill.

Cheers.
RE: tmpfs  
Hi David,

I believe typically io-fs-media is used for the RAM disk:

e.g. 
# io-fs-media -dtmp

Cheers,
Andy


-----Original Message-----
From: David McMinn [mailto:community-noreply@qnx.com] 
Sent: Monday, April 18, 2011 6:44 AM
To: general-filesystems
Subject: tmpfs

Hi,

I am currently looking for information on using tmpfs under QNX. I am
using qdb and the documentation for it mentions being able to use tmpfs
as a RAM based temporary storage. I have also seen other mentions of
people using tmpfs on these forums.

However, I can't seem to find any further reference to tmpfs in the
documentation, or on my development system. Is it something that I'd
need to port from Linux? Or am I better using ETFS in RAM? I thought
having a transaction based FS would be overkill.

Cheers.




_______________________________________________

General
http://community.qnx.com/sf/go/post85078
Re: RE: tmpfs  
Hi Andy,

Thanks for your reply.

I should probably mention the setup I'm using:

Commercial QNX 6.5.0 Windows hosted for x86 target.
Standard Neutrino RTOS, nothing else (i.e. I don't have Aviage)

I can't seem to find io-fs-media on my system either, nor any docs about it, probably because I don't have Aviage.

However, io-fs-media is mentioned in the multimedia document overview (http://www.qnx.com/developers/docs/6.5.0/index.
jsp?topic=/com.qnx.doc.neutrino_sys_arch/mme.html), but the link to the docs for io-fs-media (http://www.qnx.com/
developers/docs/6.5.0/topic/com.qnx.doc.mme_en_mme_utils_ref/io-fs.html) seems to go nowhere:

Is there any other information about it, even just to confirm that it only comes with Aviage?

If that's the case am I back to using etfs?

Cheers.


> Hi David,
> 
> I believe typically io-fs-media is used for the RAM disk:
> 
> e.g. 
> # io-fs-media -dtmp
> 
> Cheers,
> Andy
> 
> 
> -----Original Message-----
> From: David McMinn [mailto:community-noreply@qnx.com] 
> Sent: Monday, April 18, 2011 6:44 AM
> To: general-filesystems
> Subject: tmpfs
> 
> Hi,
> 
> I am currently looking for information on using tmpfs under QNX. I am
> using qdb and the documentation for it mentions being able to use tmpfs
> as a RAM based temporary storage. I have also seen other mentions of
> people using tmpfs on these forums.
> 
> However, I can't seem to find any further reference to tmpfs in the
> documentation, or on my development system. Is it something that I'd
> need to port from Linux? Or am I better using ETFS in RAM? I thought
> having a transaction based FS would be overkill.
> 
> Cheers.
> 
> 
> 
> 
> _______________________________________________
> 
> General
> http://community.qnx.com/sf/go/post85078


Re: tmpfs  
David-

The requirement for qdb is for an underlying "posix" filesystem.  It won't work on a simple link to /dev/shmem - so you 
are right looking for tmpfs.  Apparently, tmpfs satisfies the posix requirement, but more efficiently than a full-blown 
ram filesystem.

Short of having tmpfs, you can create a qnx4 filesystem in ram - more overhead but should work fine!

Create 4M ramdisk - it  will show up as /dev/hd1t77 or something similar...

# devb-ram ram capacity=8192 & 

Then format and mount...

# dinit -h /dev/hd1t77
# mount /dev/hd1t77 /ram

Denniis
Re: tmpfs  
Hi Denniis,

Thanks for the tips. I'll give it a go.

Cheers.

> David-
> 
> The requirement for qdb is for an underlying "posix" filesystem.  It won't 
> work on a simple link to /dev/shmem - so you are right looking for tmpfs.  
> Apparently, tmpfs satisfies the posix requirement, but more efficiently than a
>  full-blown ram filesystem.
> 
> Short of having tmpfs, you can create a qnx4 filesystem in ram - more overhead
>  but should work fine!
> 
> Create 4M ramdisk - it  will show up as /dev/hd1t77 or something similar...
> 
> # devb-ram ram capacity=8192 & 
> 
> Then format and mount...
> 
> # dinit -h /dev/hd1t77
> # mount /dev/hd1t77 /ram
> 
> Denniis