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Add FAQ: "Help! I'm getting ``panic: can't mount root''"

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PR:		docs/7336
Submitted by:	dwhite@FreeBSD.ORG
This commit is contained in:
Tim Vanderhoek 1998-07-21 03:19:06 +00:00
parent acbbb9ac93
commit 8511c4cee5
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=3141
1 changed files with 46 additions and 1 deletions

47
FAQ/install.sgml
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<!-- $Id: install.sgml,v 1.6 1998-07-13 07:48:07 hoek Exp $ -->
<!-- $Id: install.sgml,v 1.7 1998-07-21 03:19:06 hoek Exp $ -->
<!-- The FreeBSD Documentation Project -->
<sect>
@ -490,5 +490,50 @@
After the system is installed you can reconnect the drive. Hopefully
this will be fixed in a later release.
<sect1>
<heading>I get a ``panic: cant mount root'' error when rebooting the system after installation.</heading>
<p>This error comes from confusion between the boot block's and the
kernel's understanding of the disk devices. The error usually
manifests on two-disk IDE systems, with the hard disks arranged as the
master or single device on separate IDE controllers, with FreeBSD
installed on the secondary IDE controller. The boot blocks think
the system is installed on wd1 (the second BIOS disk) while the kernel
assigns the first disk on the secondary controller device wd2. After
the device probing, the kernel tries to mount what the boot blocks
think is the boot disk, wd1, while it is really wd2, and fails.
<p>To fix the problem, do one of the following:
<enum>
<item>At the Boot: prompt, enter
<tt>1:wd(2,a)/kernel</tt> and press Enter. If the system starts, then
run the command
<verb>
echo "1:wd(2,a)/kernel" > /boot.config
</verb>
to make it the default boot string.
<item>Move the FreeBSD disk onto the primary IDE controller, so the
hard disks are consecutive.
<item><url url="../handbook/kernelconfig.html" name="Rebuild your kernel,">
modify the wd configuration lines to read:
<verb>
controller wdc0 at isa? port "IO_WD1" bio irq 14 vector wdintr
disk wd0 at wdc0 drive 0
# disk wd1 at wdc0 drive 1 # comment out this line
controller wdc1 at isa? port "IO_WD2" bio irq 15 vector wdintr
disk wd1 at wdc1 drive 0 # change from wd2 to wd1
disk wd2 at wdc1 drive 1 # change from wd3 to wd2
</verb>
Install the new kernel.
If you moved your disks and wish to restore the previous
configuration, replace the disks in the desired configuration and reboot.
Your system should boot successfully.
</enum>
</sect>