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Re: Mount or disable devfs, was: inode missing



On Thu, Oct 10, 2002 at 06:58:53AM -0700, Michael Olds wrote:
> Mount or disable devfs?
> 
> Device File System
> 
> For a good discussion of devfs see:
> http://www.atnf.csiro.au/people/rgooch/linux/docs/devfs.html#what-is-it
> 
> In attempting to set up and run Partition Image, I got the message:
> "Inode Missing" /dev/ide/host0/bus0/target0/lun0/disc with an offer to
> create it. I contacted the PI board and asked: "Can someone explain what
> this is and what it means and whether or not it is safe to allow PI to
> create the inodes?" and was told:
> 
> "In your case not (safe)."
> 
> "ext2/3 inode is almost like clusters in FAT file system."
> 
> "I think you enabled devfs support in kernel but you haven't mounted
> devfs partition into /dev. Partimage can't work in such situation.
> You'll have to remove devfs support from kernel or mount devfs in /dev."
> 
> "Cat your /proc/partitions file. If you read
> /dev/ide/host0/bus0/target0/lun0/partXXX you enabled devfs support."
> 
> I have apparently enabled devfs support as I have a fair number of these
> listed, apparently one for each partition and extended partition.
> 
> "Now if you ls /dev and you only see hdaXX without ide subdirectory, you
> haven't mounted devfs in /dev."
> 
> And I have no subdirectory /dev/ide

devfs support is compiled into stock Debian GNU/Linux 2.4.x kernel
images. If you mount devfs on /dev, /edv/ide will be created.

> 
> So the questions to the Debian folk are:
> 
> [As far as I can tell, this devfs thing is primarily of use to those with
> external devices such as scanners and so forth. I have only one external
> device connected to this computer: a printer.]
> 
> What are the advantages/disadvantages in my situation?
> 
> 1. Should I mount devfs?

From the above answers it looks like you need to mount devfs to use
Partition Image. The alterntive is to recompile your kernel and remove
devfs support. 
 
> 2. If so: how do I go about mounting it? 

mount -n -t devfs none /dev

or 

on boot append "devfs=mount" boot parameter.

However, if you have changed permissions or file ownership of any
devices, read up on devfsd and make needed changes to files in
/etc/devfs before you mount devfs on /dev since devfsd will set device
permissions and ownership to default values.

> I have read some of the
> discussions, but they are generally on a higher level than my own. Is it the
> same as mounting any other device? Do I need to mount each (one for each
> partition) individually, or will mount /devfs mount what is need? 

One time. Once you mount devfs, all devices will be created in
/dev. devfsd will also create symlinks in /dev so you can still use
devices such as /dev/hdaX. 
  
> If this is
> an advisable setup, can it be set up to happen automatically on
> boot?

Yes, you can manually enter "devfs=mount" when you boot, configure
lilo or grub to do this, or, if you compile your kernel, there is a
configuration option that can be set, i.e, "CONFIG_DEVFS_MOUNT=y".

> 3. If not: how do I go about removing devfs support? Is this going to
> require a Kernel Rebuild?

Yes. set line in .config to "# CONFIG_DEVFS_FS is not set." But I never
tried this, so I'm not sure is anything else may need to be changed.

> 4. How did I get into this mess in the first place? i.e. What did I say yes
> to that I didn't need?

I would guess you selected to use 2.4.x kernel rather than a 2.2.x, since
devfs is built into stock 2.4.x kernels and not in 2.2.x.

> 
> A lot of questions; I am still reading, but I could use any thoughts anyone
> here has on the matter.

I've been mounting devfs on /dev for months. Works great.

> 
> Best Wishes!
> Mike Olds www.buddhadust.org
> 
> 

-- 
Jerome

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