recommended Filesystem for DoC?

recommended Filesystem for DoC?

[Erich Schubert]

I'm preparing a thin client employing a 8 MB M-Systems DoC.
My current system is at 6 MB uncompressed, but i'd like to add some
local fonts, and lpd and a sound server, so i'd like to use some
compression.
I was thinking about setting up the static part using a cramfs;
but i need some files on the flash to be writeable
(configuration files such as IP address, X11 server address etc.)

I've seen these two JFFS file systems; but actually i don't need much
journalling (after all i don't change the config too often ;)
and JFFS seems to be designed for the other flash type.
Should i use an ext2 filesystem then?
I was thinking about mounting a cramfs ro as root, a tmpfs in some other
dir for automatic files (such as xserver output) and the actual
filesytem on the device in /writefs.
On that i should then store the kernel and the cramfs-initrd?

any recommendations for the system?
grub or lilo? (right now i'm using grub to boot the system off a small
partition ~8 MB)
any good howto for installing the bootloader?

Gruss,
Erich Schubert
-- 
        erich@(mucl.de|debian.org)        --        GPG Key ID: 4B3A135C
          Go away or i'll replace you with a very small shell script.
            Ein Freund ist ein Geschenk, das man sich selbst macht.
               Humor sollte immmer dabeisein, auch bei Problemen.

Re: recommended Filesystem for DoC?

[Marc Singer]

On Sun, Sep 15, 2002 at 01:51:39AM +0200, Erich Schubert wrote:
> I'm preparing a thin client employing a 8 MB M-Systems DoC.
> My current system is at 6 MB uncompressed, but i'd like to add some
> local fonts, and lpd and a sound server, so i'd like to use some
> compression.
> I was thinking about setting up the static part using a cramfs;
> but i need some files on the flash to be writeable
> (configuration files such as IP address, X11 server address etc.)

I've been looking into something similar.  Presently, I use ext3
because I have enough space space for a 1M journal.  However, I don't
recommend this.  I've been considering using cloop (KNOPPIX) because
it doesn't require a ramdisk and then installing JFFS as the root
filesystem.  This means that the static part is always compressed and
mounted at boot time.

> I've seen these two JFFS file systems; but actually i don't need much
> journalling (after all i don't change the config too often ;)
> and JFFS seems to be designed for the other flash type.
> Should i use an ext2 filesystem then?

Ext2 can get you in trouble.  You might be able to minimize your
exposure by guaranteeing that the fs is sync'd after performing a
write.

> I was thinking about mounting a cramfs ro as root, a tmpfs in some other
> dir for automatic files (such as xserver output) and the actual
> filesytem on the device in /writefs.
> On that i should then store the kernel and the cramfs-initrd?

I don't think you can put the kernel in the initrd.  After all, the
kernel *reads* the initrd.  Instead, the kernel goes into the root
filesystem (lilo/grub style) or in an MSDOS partition (syslinux
style).


>  any recommendations for the system?  grub or lilo? (right now i'm
> using grub to boot the system off a small partition ~8 MB) any good
> howto for installing the bootloader?

I stopped using lilo because it is a little too complex and because it
doesn't handle serial consoles as well as syslinux.  I'd have used
grub, but it crashes on my hardware.  IMHO, grub is the most
attractive because it has the best feature set.


> 
> Gruss,
> Erich Schubert
> -- 
>         erich@(mucl.de|debian.org)        --        GPG Key ID: 4B3A135C
>           Go away or i'll replace you with a very small shell script.
>             Ein Freund ist ein Geschenk, das man sich selbst macht.
>                Humor sollte immmer dabeisein, auch bei Problemen.
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: recommended Filesystem for DoC?

[David Woodhouse]

elf@buici.com said:
>  I've been looking into something similar.  Presently, I use ext3
> because I have enough space space for a 1M journal.  However, I don't
> recommend this.  I've been considering using cloop (KNOPPIX) because
> it doesn't require a ramdisk and then installing JFFS as the root
> filesystem.  This means that the static part is always compressed and
> mounted at boot time.

Yeah. Using a journalling pseudo-filesystem to emulate a block device, and 
having to set aside a hunk of the space it provides for journalling of a
'normal' file system, is crazy. IMHO, you only have an excuse for pretending
that flash is a block device if you're still running DOS.

The JFFS2 NAND support is almost complete -- just a few corner cases to be 
fixed up. AFAIK it should work on DoC without too much trouble -- after 
all, a DoC is just a bunch of NAND flash chips.

--
dwmw2

Re: recommended Filesystem for DoC?

[Erich Schubert]

> The JFFS2 NAND support is almost complete -- just a few corner cases to be 
> fixed up. AFAIK it should work on DoC without too much trouble -- after 
> all, a DoC is just a bunch of NAND flash chips.

Can lilo or grub boot a system off a JFFS2 filesystem?
(with compression enabled... or i'll need my cramdiscs anyway)
Is the JFFS2 in 2.4.19 new enough, or do i need additional patches?
Which corner cases aren't fixed yet?

What are the drawbacks with ext2 on a DoC using nftl?
when i hopefully will never have to mount the filesystem rw?

Gruss,
Erich Schubert
-- 
        erich@(mucl.de|debian.org)        --        GPG Key ID: 4B3A135C
        To understand recursion you first need to understand recursion.
                Liebe ist eine schwere Geisteskrankheit (Platon)
            "Wissen ist Macht" - wenn man das richtige daraus macht.

Re: recommended Filesystem for DoC?

[David Woodhouse]

On Sun, 15 Sep 2002, Erich Schubert wrote:

> > The JFFS2 NAND support is almost complete -- just a few corner cases to be 
> > fixed up. AFAIK it should work on DoC without too much trouble -- after 
> > all, a DoC is just a bunch of NAND flash chips.
> 
> Can lilo or grub boot a system off a JFFS2 filesystem?

No. RedBoot has JFFS2 support and should manage with a little persuasion 
though.

> (with compression enabled... or i'll need my cramdiscs anyway)
> Is the JFFS2 in 2.4.19 new enough, or do i need additional patches?
> Which corner cases aren't fixed yet?

You need the newer code from CVS. It's mainly error handling and the 
subtleties of doing fsync() efficiently that are missing. And possibly 
details about using the DiskOnChip HW ECC instead of SW ECC, etc.

> What are the drawbacks with ext2 on a DoC using nftl?
> when i hopefully will never have to mount the filesystem rw?

If it's always readonly it's sane enough.

Hmmm... Pine on iPAQ with WaveLAN is surprisingly usable :)

-- 
dwmw2

Re: recommended Filesystem for DoC?

[Erich Schubert]

> Ext2 can get you in trouble.  You might be able to minimize your
> exposure by guaranteeing that the fs is sync'd after performing a
> write.

Why is ext3 better here?
I was planning to have my ext2 read-only unless i need to change
something; then remount,rw; change the settings; remount,ro...

> > I was thinking about mounting a cramfs ro as root, a tmpfs in some other
> > dir for automatic files (such as xserver output) and the actual
> > filesytem on the device in /writefs.
> > On that i should then store the kernel and the cramfs-initrd?
> 
> I don't think you can put the kernel in the initrd.  After all, the
> kernel *reads* the initrd.  Instead, the kernel goes into the root
> filesystem (lilo/grub style) or in an MSDOS partition (syslinux
> style).

you misunderstood what i said. I said i put a ext2 there containing the
kernel, the cramfs and the file i need to be able to change easily.

> I stopped using lilo because it is a little too complex and because it
> doesn't handle serial consoles as well as syslinux.  I'd have used
> grub, but it crashes on my hardware.  IMHO, grub is the most
> attractive because it has the best feature set.

i don't need serial consoles; the machine is a X11 terminal - that makes
no sense without a real screen and keyboard ;)

Gruss,
Erich Schubert
-- 
        erich@(mucl.de|debian.org)        --        GPG Key ID: 4B3A135C
     A man doesn't know what he knows until he knows what he doesn't know.
        Die kürzeste Verbindung zwischen zwei Menschen ist ein Lächeln.
    Für jedes Problem gibt es eine Lösung, die einfach, klar und falsch ist.

Re: recommended Filesystem for DoC?

[Marc Singer]

On Sun, Sep 15, 2002 at 12:41:55PM +0200, Erich Schubert wrote:
> > Ext2 can get you in trouble.  You might be able to minimize your
> > exposure by guaranteeing that the fs is sync'd after performing a
> > write.
> 
> Why is ext3 better here?
> I was planning to have my ext2 read-only unless i need to change
> something; then remount,rw; change the settings; remount,ro...

Certainly, that would work.  There is the small chance that something
will fail while the filesystem is r/w.  On my (embedded) application,
even that is too much of a risk.  

> 
> > > I was thinking about mounting a cramfs ro as root, a tmpfs in some other
> > > dir for automatic files (such as xserver output) and the actual
> > > filesytem on the device in /writefs.
> > > On that i should then store the kernel and the cramfs-initrd?
> > 
> > I don't think you can put the kernel in the initrd.  After all, the
> > kernel *reads* the initrd.  Instead, the kernel goes into the root
> > filesystem (lilo/grub style) or in an MSDOS partition (syslinux
> > style).
> 
> you misunderstood what i said. I said i put a ext2 there containing the
> kernel, the cramfs and the file i need to be able to change easily.

Indeed, I did misunderstand.

> 
> > I stopped using lilo because it is a little too complex and because it
> > doesn't handle serial consoles as well as syslinux.  I'd have used
> > grub, but it crashes on my hardware.  IMHO, grub is the most
> > attractive because it has the best feature set.
> 
> i don't need serial consoles; the machine is a X11 terminal - that makes
> no sense without a real screen and keyboard ;)

Of course.  LILO works for many folks, too.

> 
> Gruss,
> Erich Schubert
> -- 
>         erich@(mucl.de|debian.org)        --        GPG Key ID: 4B3A135C
>      A man doesn't know what he knows until he knows what he doesn't know.
>         Die k?rzeste Verbindung zwischen zwei Menschen ist ein L?cheln.
>     F?r jedes Problem gibt es eine L?sung, die einfach, klar und falsch ist.
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: recommended Filesystem for DoC?

[Charles Manning]

On Sun, 15 Sep 2002 11:51, Erich Schubert wrote:

> any recommendations for the system?
> grub or lilo? (right now i'm using grub to boot the system off a small
> partition ~8 MB)
> any good howto for installing the bootloader?

If a DOC is "just a bunch of NAND chips" then maybe YAFFS will work with DOC. 
 I'd have to look at the DOC geometry to be able to tell. Right now YAFFS 
wants its flash to be in pages of 512+16 with eraseable blocks being 32 
pages. Nothing that can't be adjusted with a sledge hammer.

There are pros and cons to both YAFFS and JFFS2, that's why both exist.

-- CHarles