a few observations on converting /dev old device names to devfs, a few hints
On 29 Jan 2002, Dave Carrigan wrote:
> Walter Tautz <wtautz@math.uwaterloo.ca> writes:
>
> > Would it not be better to have CONFIG_DEVFS_FS=n
>
> Why?
>
i suppose I was thinking interms of the overhead of having to do
what you mention below. Granted I experienced no real problems
without having to change anything. But it does seem to be a bit
of surprise as the default in the kernel documentation is not to
turn it on. At least this is what one reads in:
/usr/src/kernel-source-2.4.17/Documentation/filesystems/devfs/README:
<quote>
NOTE that devfs is entirely optional. If you prefer the old
disc-based device nodes, then simply leave CONFIG_DEVFS_FS=n (the
default). In this case, nothing will change. ALSO NOTE that if you do
enable devfs, the defaults are such that full compatibility is
maintained with the old devices names.
</quote>
So the last line shows why I was still able to mount my partitions using
the old device names--good thing. I
> > Anyone know how to create devfs?
>
> mount -t devfs - /dev
That worked but it creates weird time stamps:
# ls -al /dev/
total 4
drwxr-xr-x 1 root root 0 Dec 31 1969 .
drwxr-xr-x 26 root root 4096 Jan 29 14:58 ..
crw------- 1 root root 8, 0 Dec 31 1969 .devfsd
crw------- 1 root root 5, 1 Jan 29 15:08 console
drwxr-xr-x 1 root root 0 Dec 31 1969 cpu
drwxr-xr-x 1 root root 0 Dec 31 1969 cua
drwxr-xr-x 1 root root 0 Dec 31 1969 discs
drwxr-xr-x 1 root root 0 Dec 31 1969 fb
crw-rw-rw- 1 root root 1, 7 Dec 31 1969 full
drwxr-xr-x 1 root root 0 Dec 31 1969 ide
prw------- 1 root root 0 Jan 29 15:05 initctl
drwxr-xr-x 1 root root 0 Dec 31 1969 input
crw-r----- 1 root root 1, 2 Dec 31 1969 kmem
crw-r----- 1 root root 1, 1 Dec 31 1969 mem
drwxr-xr-x 1 root root 0 Dec 31 1969 misc
crw-rw-rw- 1 root root 1, 3 Dec 31 1969 null
crw-r----- 1 root root 1, 4 Dec 31 1969 port
crw-rw-rw- 1 root root 5, 2 Dec 31 1969 ptmx
drwxr-xr-x 1 root root 0 Dec 31 1969 pts
drwxr-xr-x 1 root root 0 Dec 31 1969 pty
crw-r--r-- 1 root root 1, 8 Dec 31 1969 random
drwxr-xr-x 1 root root 0 Dec 31 1969 rd
lr-xr-xr-x 1 root root 4 Dec 31 1969 root -> rd/0
drwxr-xr-x 1 root root 0 Dec 31 1969 shm
drwxr-xr-x 1 root root 0 Dec 31 1969 tts
crw-rw-rw- 1 root root 5, 0 Dec 31 1969 tty
crw-r--r-- 1 root root 1, 9 Dec 31 1969 urandom
drwxr-xr-x 1 root root 0 Dec 31 1969 usb
drwxr-xr-x 1 root root 0 Dec 31 1969 vc
drwxr-xr-x 1 root root 0 Dec 31 1969 vcc
crw-rw-rw- 1 root root 1, 5 Dec 31 1969 zero
And even worse, it got rid of the old device names, yikes. Warning folks!
> apt-get install devfsd
Good news....this step recreates the old device names
as softlinks. Whew! Boy these kernel dudes are way cool!
>
> > cramfs: wrong magic
> >
> > What is cramfs?
>
> Compressed ramdisk filesystem. Useful for initrd's. The wrong magic
> message is probably from the kernel's attempt to auto-determine the
> filesystem during a mount.
>
> > Just curious to hear other people's opinions on this matter, i.e.
> > don't use devfs. It seems to me the debian kernel should have
> > CONFIG_DEVFS_FS=n.
>
> Some people want devfs. Devfs can't be created as a module. Hence, the
> logical choice is to build the kernel with devfs support. Nothing's
> forcing you to use devfs, even if your kernel has devfs support, and the
> overhead is not very much.
>
> --
You're quite right...as it turns out things worked even without constructed
devfs. Thanks Dave!
-walter
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