Writeable Replacement for /dev

Writeable Replacement for /dev

[Lucas Hartmann]

Hello.

I've been using kernel 2.6.12 with the /dev pseudo filesystem activated.
When i try to move to newer kernels, the /dev is no longer supported. This
causes the system to hang as the kernel tries to "open an initial console".

How do I set a writable tmpfs filesystem on the /dev? Is there any other
better way of doing this?

Using u-boot, loading kernel over tftp and root filesystem is on NFS.

Thanks.
-- 
Lucas Vinicius Hartmann
(83) 9967-4628

"There are 10 kinds of people in the world: The ones who understand binary
and the ones who don't."

Re: Writeable Replacement for /dev

[andrzej zaborowski]

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Hi,

On 16/05/06, Lucas Hartmann <lucas.hartmann@gmail.com> wrote:
> Hello.
>
> I've been using kernel 2.6.12 with the /dev pseudo filesystem activated.
> When i try to move to newer kernels, the /dev is no longer supported. This
> causes the system to hang as the kernel tries to "open an initial console".
>
> How do I set a writable tmpfs filesystem on the /dev? Is there any other
> better way of doing this?
>

If I'm not mistaken, the usual way of doing that is having static
/dev/console and /dev/null nodes (only these two?) on the underlaying
/ filesystem which later are covered with whatever is mounted at /dev
from fstab. Otherwise you can always use a initramfs.
Nevertheless I think the kernel shouldn't hang when there's no
/dev/console, it should just give a warning.

> Using u-boot, loading kernel over tftp and root filesystem is on NFS.
>
> Thanks.
> --
> Lucas Vinicius Hartmann
> (83) 9967-4628
>
> "There are 10 kinds of people in the world: The ones who understand binary
> and the ones who don't."
> _______________________________________________
> Linux-omap-open-source mailing list
> Linux-omap-open-source@linux.omap.com
> http://linux.omap.com/mailman/listinfo/linux-omap-open-source
>

Regards,
Andrew
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Re: Writeable Replacement for /dev

[Kanagesh R]

> 
> Hello.
> 
> I've been using kernel 2.6.12 with the /dev pseudo filesystem activated.
> When i try to move to newer kernels, the /dev is no longer supported. This
> causes the system to hang as the kernel tries to "open an initial console".
> 
> How do I set a writable tmpfs filesystem on the /dev? Is there any other
> better way of doing this?
> 
> Using u-boot, loading kernel over tftp and root filesystem is on NFS.
> 
> Thanks.
> -- Lucas Vinicius Hartmann
> (83) 9967-4628
> 

Hello,

I had the same problem too, but on checking the kernel source I found that the support for devfs is available but just that means to turn it on using the menu (make menuconfig) is removed.  You need to add some lines into fs/Kconfig and that does the trick for you.  

Check the following patch, I added this to fs/Kconfig which enabled me to turn on support for devfs and compile the kernel. 

Hope this helps!

Warm regards,
Kanagesh

diff -urN -X /home/kanagesh/work/kernel/src/dontdiff /home/kanagesh/work/kernel/src/linux-2.6.13-omap1/fs/Kconfig ./fs/Kconfig
--- /home/kanagesh/work/kernel/src/linux-2.6.13-omap1/fs/Kconfig	2005-08-29 05:11:01.000000000 +0530
+++ ./fs/Kconfig	2005-09-21 10:31:58.000000000 +0530
@@ -783,6 +783,56 @@
 
 	Designers of embedded systems may wish to say N here to conserve space.
 
+config DEVFS_FS
+	bool "/dev file system support (OBSOLETE)"
+	depends on EXPERIMENTAL
+	help
+	  This is support for devfs, a virtual file system (like /proc) which
+	  provides the file system interface to device drivers, normally found
+	  in /dev. Devfs does not depend on major and minor number
+	  allocations. Device drivers register entries in /dev which then
+	  appear automatically, which means that the system administrator does
+	  not have to create character and block special device files in the
+	  /dev directory using the mknod command (or MAKEDEV script) anymore.
+
+	  This is work in progress. If you want to use this, you *must* read
+	  the material in <file:Documentation/filesystems/devfs/>, especially
+	  the file README there.
+
+	  Note that devfs no longer manages /dev/pts!  If you are using UNIX98
+	  ptys, you will also need to mount the /dev/pts filesystem (devpts).
+
+	  Note that devfs has been obsoleted by udev,
+	  <http://www.kernel.org/pub/linux/utils/kernel/hotplug/>.
+	  It has been stripped down to a bare minimum and is only provided for
+	  legacy installations that use its naming scheme which is
+	  unfortunately different from the names normal Linux installations
+	  use.
+
+	  If unsure, say N.
+
+config DEVFS_MOUNT
+	bool "Automatically mount at boot"
+	depends on DEVFS_FS
+	help
+	  This option appears if you have CONFIG_DEVFS_FS enabled. Setting
+	  this to 'Y' will make the kernel automatically mount devfs onto /dev
+	  when the system is booted, before the init thread is started.
+	  You can override this with the "devfs=nomount" boot option.
+
+	  If unsure, say N.
+
+config DEVFS_DEBUG
+	bool "Debug devfs"
+	depends on DEVFS_FS
+	help
+	  If you say Y here, then the /dev file system code will generate
+	  debugging messages. See the file
+	  <file:Documentation/filesystems/devfs/boot-options> for more
+	  details.
+
+	  If unsure, say N.
+
 config DEVPTS_FS_XATTR
 	bool "/dev/pts Extended Attributes"
 	depends on UNIX98_PTYS




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Re: Writeable Replacement for /dev

[David Brownell]

> > How do I set a writable tmpfs filesystem on the /dev? Is there any other
> > better way of doing this?

Use udev...

Re: Writeable Replacement for /dev

[Lucas Hartmann]

Problem solved. Using devfs for now... I'm having a look at udev also.

Hanging was not for the lack of /dev, really. But is solved also.

-- 
Lucas Vinicius Hartmann
(83) 9967-4628

"As amizades duram enquanto cada amigo se acha ligeiramente superior ao
outro."