On 29/08/2011 15:46, James B. Byrne wrote:
I am experimenting with KVM and I wish to create a virtual machine image in a logical volume. I can create the new lv without problem but when I go to format its file system then I get these warnings:
Warning: WARNING: the kernel failed to re-read the partition table on /dev/sda (Device or resource busy). As a result, it may not reflect all of your changes until after reboot. Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only.
When I take a look at things using parted I see this:
# parted -l print Model: ATA WDC WD5000AAKS-0 (scsi) Disk /dev/sda: 500GB Sector size (logical/physical): 512B/512B Partition Table: msdos
Number Start End Size Type File system Flags 1 1049kB 525MB 524MB primary ext4 boot 2 525MB 500GB 500GB primary lvm
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_guest01: 129GB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 129GB 129GB ext4
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_log: 1049MB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 1049MB 1049MB ext4
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_tmp: 8389MB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 8389MB 8389MB ext4
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_home: 4194MB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 4194MB 4194MB ext4
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_swap: 8321MB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 8321MB 8321MB linux-swap(v1)
Model: Linux device-mapper (linear) (dm) Disk /dev/mapper/vg_inet02-lv_root: 53.7GB Sector size (logical/physical): 512B/512B Partition Table: loop
Number Start End Size File system Flags 1 0.00B 53.7GB 53.7GB ext4
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0 has been opened read-only. Error: /dev/sr0: unrecognised disk label
The host system is CentOS-6.0 with updates applied. I did a manual disc configuration on initial install but I do not recall specifically dealing with /dev/sr0 at any point.
Can anyone explain to me what is happening here and what I should do? Am I constrained to reboot the server each time that I make changes to an LV? Is there some configuration change I need make to the base system?
The favour of a direct copy of any reply to the mailing list is requested as I am a digest subscriber.
You do not need to reboot every time you adjust a Logical Volume. Do you also need to format the file system for a KVM guest's Logical Volume?
I'm currently juggling servers to try and get a free machine to test KVM on Centos 6, but i have recently found, with another RHEL clone I'm testing, that if you do not set up the LogVol with virsh or i suppose virt-manager you will have issues getting the guest machines to run.
If you look at chapter 26.1.4.1 & 26.1.4.2 of the Red Hat Visualization Guide, for RHEL6, it explains how to use fdisk to create an partition for the Logical Volume, set it to a Linux LVM type and create the storage pool for the KVM guests (page 217 & 218).
On my current RHEL clone test system, to create the VolGroup / Storage pool i used the virsh commands on pages 222 & 223 of the Red Hat Visualization Guide (which were similar to the following):
# virsh pool-define-as guest_images_lvm logical - - /dev/cciss/c0d0p3 libvirt_lvm /dev/libvirt_lvm # virsh pool-build VolGroupGuests # virsh pool-start guest_images_lvm # virsh pool-autostart guest_images_lvm # virsh pool-list --all
Name State Autostart ----------------------------------------- guest_images_lvm active yes
To create the actual logical volume for the virtual machine I used the following command: # virsh --connect qemu:///system vol-create-as guest_images_lvm volume1 20G
I don't remember formatting a file system prior to installing the KVM guest, but new i am new to KVM and I'm experimenting as well.
jk