Re: [gentoo-user] problem with raid1: error while booting

[Richard Fish]

Jarry wrote:

> Richard Fish wrote:
>
> > Just an FYI, the md driver does not create sysfs entries and thus udev
> > does not create device nodes if autodetection is not performed by the
> > driver.  Autodetection is not performed if either:
> >
> > 1. The md driver is a module (not a problem according to your original
> > email)
> > 2. You are using an initramfs (vs an initrd) to bring up the system
> > 3. or if you do not have the right partition types defined.
>
> I think I can unselect options 1. and 3. (md-support is in kernel, and
> partitions are marked as type "fd - Linux raid autodetect").
>
> Concerning 2, I'm not sure if I understand correctly:
> Do you mean turning off initramfs support in kernel-configuration?
>
> Jarry


Actually, it is pretty much impossible to turn off initramfs support in
the kernel.  A couple of quick definitions:

1. initrd - an initial ramdisk of a fixed size loaded into memory by the
boot loader used to get the system ready to mount the root filesystem. 
The /linuxrc script in the ramdisk is responsible for this, and requires
"RAM disk support" and "Initial RAM disk (initrd) support" in the kernel
configuration.

2. initramfs - A compressed (optional) cpio archive linked directly into
the kernel, or possibly loaded into memory by the boot loader, used to
provide early-userspace services.  If the initramfs contains /init, it
will be executed and is expected to mount the root filesystem, move the
system root to it, and execute the real init on the root.  If the user
doesn't specify an initramfs, the kernel makes a very small one of its
own, without the /init.  This is the "rootfs" you see in /proc/mounts.

#1 you are probably already familiar with...it is the traditional way
for loading modules needed for the root filesystem to become available.

#2 is fairly recent...but growing in usage.  fbsplash uses
early-userspace to provide a splash image as soon as the graphics system
is initialized in the kernel, for example.  Unless you have specified
something for "Device Drivers->Block Devices->Initramfs source file" in
the kernel configuration, or your "initrd" option to grub/lilo specifies
an initramfs, this is not a problem for you.

In short, if you don't really know what initramfs is, you are probably
not using it!  So I am not sure why you are having this problem.  Could
you double check that /etc/udev/rules.d/50-udev.rules contains:

# md block devices
KERNEL=="md[0-9]*",     NAME="md/%n", SYMLINK+="%k", GROUP="disk"

Also, do you have any custom rules files in /etc/udev/rules.d?

In the maintenance mode, does /sys/block/md0/* exist?  What does "cat
/proc/mdstat" report?

-Richard


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