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Old 12-27-2016, 06:29 PM   #1
JockVSJock
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mkisofs of RHEL7 isos fails, /dev/root does not exist


I'm trying to create an ISO to be used by KVM under RHEL7.

- I mount the RHEL7 iso
- I then copy all of the contents to /var/tmp/isos
- Create a tar file and move it to another directory under /tmp

Code:
tar -czf /tmp/isos/rhel7.tar.gz .
- I run file and stat against the .iso file and it appears ok
- I uncompress the .tar.gz under /tmp/isos
- I then run the following mkisofs with the following:

Code:
mkisofs -o rhel7.iso -b isolinux/isolinux.bin -c isolinux/boot.cat 
-no-emul-boot -boot-load-size 4 -boot-info-table -J -R -V rhel7.iso .
Using the information to mkisofs from this URL:

http://bencane.com/2013/06/12/mkisof...x-install-iso/

No errors so I launch KVM and start it up and once it boots up, I get the following error:

Code:
dracut-initqueue[548]:  Warning:  dracut-initqueue timeout - starting timeout scripts 
dracut-initqueue[548]: Warning:  Could not boot 
dracut-initqueue[548]: Warning:  /dev/root does not exist 
     Starting Dracut Emergency Shell...
Warning: /dev/root does not exist 

Generating "/run/initramfs/rdsosrepot.txt"

Entering emergency mode.  Exit the shell to continue. 
Type "journalctl" to view system logs. 
You might want to save "/run/initramfs/rdsosrepot.txt" to a USB stick or /boot 
after mounting them and attach it to a bug report.

dracut:/#
I was under the impression that dracut for if there was no initram-fs under /boot.

So I'm not understanding if I didn't run mkisofs correctly or if I need to do something else to kick off this ISO correctly.

thanks

Last edited by JockVSJock; 12-27-2016 at 06:31 PM.
 
Old 12-27-2016, 09:06 PM   #2
pressman57
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This may be a dumb question but if you have the iso why not install it in the usual way?

https://wiki.archlinux.org/index.php/QEMU
 
Old 12-28-2016, 07:10 AM   #3
jpollard
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I believe the problem is in the fstab entry.

The device doesn't have a /dev/root until the initrd creates one using udev. So unless there are rules for udev to create it, it won't exist.

All of mine specify the UUID for the root filesystem - not a /dev/root which does not normally exist.
 
Old 12-28-2016, 12:50 PM   #4
JockVSJock
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Quote:
Originally Posted by jpollard View Post
I believe the problem is in the fstab entry.

The device doesn't have a /dev/root until the initrd creates one using udev. So unless there are rules for udev to create it, it won't exist.

All of mine specify the UUID for the root filesystem - not a /dev/root which does not normally exist.

Even those this is systemd with RHEL7, will it still utilize initrd?
 
Old 12-28-2016, 01:25 PM   #5
AwesomeMachine
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Yes, it will.
 
Old 12-28-2016, 02:10 PM   #6
jpollard
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Quote:
Originally Posted by JockVSJock View Post
Even those this is systemd with RHEL7, will it still utilize initrd?
Yes.

The initrd is loaded with the kernel, and doesn't require any devices as it is a memory resident filesystem. Once it is created from the initrd file (a cpio output file I believe it is), the initrd is deallocated.

At that point the system root is the memory resident filesystem - and udev (and even systemd) get started from that. udev then queries for the devices attached, loads drivers (which get added to the /dev), and other utilities can make scans for logical volumes/device raid/filesystem labels... all of which get added to /dev - somewhere, most are in /dev/disk/*/* as symbolic links pointing to the current devices (/dev/sdx).

To have a /dev/root as a device requires udev to create the entry (or a symbolic link to the physical name).

It has been quite a while since I've used a system as /dev/root (which started with SGI, and got carried over to RH), but even RH stopped a while back. My problem with it, as originally done, was that I couldn't easily tell WHICH device was really the root device.
 
Old 12-30-2016, 06:33 PM   #7
JockVSJock
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Quote:
Originally Posted by pressman57 View Post
This may be a dumb question but if you have the iso why not install it in the usual way?

https://wiki.archlinux.org/index.php/QEMU
There is a flaw with the version of KVM, that I can't point it to the ISO and create a VM.

I have to download the contents and go thru the steps of creating an ISO.
 
Old 01-03-2017, 07:22 PM   #8
JockVSJock
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Got it to work, with the install ISO physically in the CDROM tray

Code:
dd if=/dev/sr0 of=/tmp/rhel7.2.iso
dd saves the day again, such a powerful command. I am able to boot off of this iso in KVM.

thanks
 
  


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