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Old 06-04-2016, 05:34 PM   #16
Registered: Dec 2009
Posts: 357

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Originally Posted by comet.berkeley View Post
To run syslinux the script needs to do something like this:

1) mount --bind /dev /mnt/dev
2) chroot /mnt
3) syslinx ..

wish list: If only syslinux had a -r option like lilo...
I was able to run syslinux from the /mnt directory while in the busybox environment, but
I had to mount the /proc filesystem first:

1) mount --bind /dev /mnt/dev
2) chroot /mnt
3) /bin/mount -t proc proc /proc
3) /usr/bin/syslinux -s /dev/$STICK

The mount /proc and syslinux commands probably need to be put into a temporary script on the /mnt disk and then executed from the chroot command.

Update: 2016 20:15 UTC

After much running around in circles and wild goose chasing, I now find that this patch to the setup.80.make-bootdisk script fixes the problem:
--- setup.80.make-bootdisk.orig	2013-10-05 19:29:33.000000000 -0700
+++ setup.80.make-bootdisk	2016-06-05 12:37:29.215977085 -0700
@@ -11,15 +11,15 @@
 if [ ! -d $TMP ]; then
   mkdir -p $TMP
-if [ -z "$T_PX" ]; then
-  T_PX=/
-  T_PX="$1"
-if [ -z "$2" ]; then
+if [ "$T_PX" =  "/" ]; then
   ROOT_DEVICE=$(mount | head -n 1 | cut -f 1 -d ' ')
+elif [ "$T_PX" =  "/mnt" ]; then
+  ROOT_DEVICE=$(mount | grep ' on /mnt '| head -n 1 | cut -f 1 -d ' ')
+    dialog --title "INTERNAL ERROR CREATING USB BOOT STICK" --msgbox \
+    "Error, the current directory ($ROOT_DEVICE) is neither / nor /mnt" 6 60
+    exit
 while [ 0 ]; do # the bootdisk menu loop
@@ -205,7 +205,7 @@
   umount /dev/$STICK
   rm -r $TMP/bootdisk
   # Make the device bootable:
-  syslinux -s /dev/$STICK 1> /dev/null 2> /dev/null
+  syslinux -s -i /dev/$STICK 1> $RDIR 2> $RDIR
   if [ "$T_PX" = "/" ]; then
     dialog --title "USB BOOT STICK CREATED" --msgbox \
     "The USB boot stick has been successfully created on device /dev/$STICK." 6 60

Last edited by aaazen; 06-05-2016 at 03:15 PM. Reason: problem is simply in the setup.80.make-bootdisk script
Old 06-04-2016, 06:50 PM   #17
Registered: Oct 2004
Distribution: Slackware, Mint
Posts: 122

Original Poster
Rep: Reputation: 16
Some updates:
1. I ran a checksum on /boot/vmlinuz-huge-smp-3.10.17-smp and the vmlinuz on the usb boot disk, and they match.
2. I tried using the rootwait option, and it still got stuck waiting for root.
3. fstab contents:
/dev/myvg/swap swap swap defaults 0 0
/dev/myvg/root / ext4 defaults 1 1
#/dev/cdrom /mnt/cdrom auto noauto,owner,ro,comment=x-gvfs-show 0 0
/dev/fd0 /mnt/floppy auto noauto,owner 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
proc /proc proc defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
Old 06-04-2016, 11:52 PM   #18
Didier Spaier
LQ Addict
Registered: Nov 2008
Location: Paris, France
Distribution: Slint64- on Lenovo Thinkpad W520
Posts: 8,958

Rep: Reputation: Disabled
The script /var/log/setup/setup.80.make-bootdisk writes in syslinux.cfg (lines #135 and #138):
As you run it with no argument, ROOT_DEVICE is set this way (line #20):
ROOT_DEVICE=$(mount | head -n 1 | cut -f 1 -d ' ')
This translates to "the first field of the first line of the output of the mount command", which is the root partition.

In my case for instance as I have in fstab:
/dev/sdb3       /                ext4        rw,suid,dev,exec,auto,nouser,async,noatime,nodiratime   1 1
the value of ROOT_DEVICE is /dev/sdb3. So far, so good.

But in your case, I assume that this value is /dev/myvg/root. As we have no initrd in the boot stick the device /dev/myvg/root is unknown hence the kernel panic.

This is stated in README_LVM.TXT:
... be aware that having your root filesystem on a Logical Volume requires an initial ramdisk (initrd).
Incidentally I would have written the line #20 this way:
ROOT_DEVICE=$(mount|sed -n "1s/ .*//p")
but there is more than one way to skin a cat

Originally Posted by Emerson View Post
Please do not talk unless you know what you are talking about.
You may follow your advice.

Last edited by Didier Spaier; 06-04-2016 at 11:55 PM.
Old 06-05-2016, 06:32 AM   #19
Registered: Oct 2004
Distribution: Slackware, Mint
Posts: 122

Original Poster
Rep: Reputation: 16
OK, I tried it with my generic kernel & initrd file - just copied them onto the boot disk, and added this to the syslinux.cfg file:
label generic
kernel vmlinuzgen
append root=/dev/mapper/myvg-root vga=normal initrd=initrd.gz ro
Booted off the disk, typed in "generic" at the prompt, and it worked great!

So, it looks like the answer is: a boot disk does not work by default if you're using LVM. You have to add the initrd to the boot disk for it to work. Fortunately, that's pretty easy to do.

Thanks everyone for taking the time to reply. I'll mark this as solved.

Note: it'd be cool to have a message or something from the boot disk creation script that tells you that you have to add an initrd...
Old 06-05-2016, 07:54 AM   #20
Senior Member
Registered: Jul 2005
Location: Round Rock, TX
Distribution: Slackware64 14.2 + Multilib
Posts: 1,483

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tuubaaku --

Just being curious and I don't have a slackware lvm volume handy to play with ...

When I run the following `file` command on my plain-ole root partition, I see:

# file --no-dereference --special-files /dev/sda3

/dev/sda3: Linux rev 1.0 ext4 filesystem data, UUID=e1781832-5e18-46a6-832f-17b7ca96c075 (needs journal recovery) (extents) (large files) (huge files)
What do you see if you run:

# file --no-dereference --special-files /dev/mapper/myvg-root
And I wonder if that output ( ? or maybe there's a better way to do it ? ) could detect root-on-lvm and act accordingly to throw the warning ( or even 'do the right thing' ) in /var/log/setup/setup.80.make-bootdisk ?

Or maybe the fact that your lvm root partition is on '/dev/mapper/' is all the hints needed ?

-- kjh

p.s. We've got quite a few CentOS 6.x machines out in the world and I see this ( not much help ):

# file --no-dereference --special-files /dev/mapper/vg_01-lv_root
/dev/mapper/vg_01-lv_root: symbolic link to `../dm-0'

# file --no-dereference --special-files /dev/dm-0
/dev/dm-0: Linux rev 1.0 ext4 filesystem data (needs journal recovery) (extents) (large files) (huge files)
Old 06-05-2016, 12:04 PM   #21
Registered: Oct 2004
Distribution: Slackware, Mint
Posts: 122

Original Poster
Rep: Reputation: 16
Here's the output:
# file --no-dereference --special-files /dev/mapper/myvg-root
/dev/mapper/myvg-root: symbolic link to `../dm-1'
# file --no-dereference --special-files /dev/dm-1
/dev/dm-1: x86 boot sector
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