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Re: [vox-tech] ramdisk error booting Gentoo Linux
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Re: [vox-tech] ramdisk error booting Gentoo Linux

On Sun, 14 Apr 2002, Matt Holland wrote:
> Hey all, has anyone seen an error like this before?
> Gentoo Linux; http://www.gentoo.org
>   Copyright 2001 Gentoo Technologies, Inc.; Distributed under the GPL
>   * Mounting /proc...				[ok]
>   * Starting devfsd...				[ok]
>   * Mounting ramdisk 0 at /mnt/.init.d...      [oops]
>   * the "dd" command failed with error:
> 1024+0 records in
> 1024+0 records out
>   * Since this is a critical task, startup cannot continue.
> Give root password for maintenance
> (or type Control-D for normal startup):

In short, I would examine enabling RAMDisk support and Loopback support in
your kernel. (Check block devices in make menuconfig for RAMDISK and
Loopback if you need them - you can also set your default RAMDIsk size
too for new RAMDisks that are enabled.)

Second, look at what dd is being called. If they size of data being
written by dd is greater than the default RAMDisk, then you may want to
change the default size when setting that option or ???

More suggestions below and some more thoughts...

If you need ramdisk support before other filesystems are mounted make it
part of the kernel not a module.

Verify the mointpoint "/mnt/.init.d..." actually exists if you presently
have ramdisk support enabled.

Also, what is dd being used to do with your RAMdisk?

If you have a ramdisk-device enabled, you cane:
mkfs -t ext2 /dev/ram0
mount -t ext2 /dev/ram0 /mnt/point/here

If the above works, you probably have RAMDIsk support in your running

If dd is being used to create a local file to be used with the loopback
device, then you dont need a RAMDisk unless you are putting a loopback
mountable image/file into a RAMDisk (say a swap file)

like this for example:
/sbin/mkfs -t ext2 /dev/ram0
/bin/mount -n /dev/ram0 /mnt/point/here
/bin/dd if=/dev/zero of=/mnt/point/here/swapfile bs=1024k count=2
/sbin/losetup /dev/loop0 /mnt/point/here/swapfile
/sbin/mkswap /dev/loop0
/sbin/swapon /dev/loop0

But the only use for this that I have found was for a Linux system with
limited memory, and a need for a local non-writeable root like a bootable
CDROM or a diskless network computer that boots from a read-only NFS
export of a different server. Why it works, is that unused lib/so in
memory seem to be unloaded sooner as you push into this loopback mounted
swap within a RAM disk as opposed to not having any swap and the risks
imposed with that. Certainly these systems are at risks of running out of
memory, but at least a small buffer of swap can elp prevent things from
getting flakey and quitting with faults.

Why not try each operation manually from their kernel?

See if you can create a RAMDisk for use as a mountable filesystem. See if
you have the mount point they are looking for.See if it is requiring
writing to the ramdisk monted system.

Of course, anyone with experience in this specific problem will likely
have a direct answer, this may suffice as a place to start testing on your
own until that arrives - assuming it does.

> This is on a new Gentoo Linux system that I built... er, almost built. 
> I suspect that I may have screwed something up in the kernel build 
> (something involving ramdisk support?), or maybe just in configuring 
> Grub.  I'm using a custom compiled version 2.2.20 kernel, because I have 
> an old ATAPI cd-rom that can't seem to mount media under 2.4 kernels. 
> That's a little nonstandard for Gentoo, so it's possible that I followed 
> all of the instructions correctly, but that the instructions were 
> wrong... pardon the rambling.

That seems odd. Care to share your /proc/filesystems ?

Does it include iso9660? Did you include support for this in your 2.4
kernel? How aboiut MS Joliet support?
(These options in kernel compilation can be found in the filesystems

> In any case, I'm wondering if anyone has seen a problem like this after 
> compiling a new kernel; if so, any idea what's causing it?  A newsgroup 
> search didn't turn up anything helpful (or even relevant), so I thought 
> I'd let you guys take a crack at it before turning to gentoo-user.

If the problems exist after a new kernel, but not in earlier ones, and you
are using the stable siries (lik 2.2, 2.4 etc) then odds are in favor of
an unset option in your kernel config.


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