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. -- *** E-Mail is NOT a SECURE channel *** James B. Byrne mailto:ByrneJB at Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3
On Mon, August 29, 2011 10:46, James B. Byrne wrote:> > Warning: Unable to open /dev/sr0 read-write (Read-only > file system). > /dev/sr0 > has been opened read-only. > Error: /dev/sr0: unrecognised disk labelI discover that this is caused by a piece of OEM software that is embedded in ROM in the LG DVD-RW drive that was 'formerly' installed on this system. This device has been replaced. However, I am still concerned about what the rest of this message means and its implications: 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. I have tried using partprobe and /sbin/blockdev -rereadpt /dev/sda and both report that the device /dev/sda/ is busy. Is this an artifact of using of SATA style disks or has something changed between CentOS-5.6 and CentOS-6.0 that specifically relates to this problem? On 5.6 I can create new lvms, mount and use them without a reboot. On 6.0 I cannot, for the moment at least, discover how this is done. -- *** E-Mail is NOT a SECURE channel *** James B. Byrne mailto:ByrneJB at Harte-Lyne.ca Harte & Lyne Limited http://www.harte-lyne.ca 9 Brockley Drive vox: +1 905 561 1241 Hamilton, Ontario fax: +1 905 561 0757 Canada L8E 3C3
psprojectplanning at gmail.com
2011-Aug-30 22:57 UTC
[CentOS] Question re: CentOS-6.0, KVM, and /dev/sr0
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