RE: Unable to start VM using COWed image
From: Prasad Joshi Sent: 10 November 2010 13:01 To: Stefan Hajnoczi Cc: Keqin Hong; kvm@vger.kernel.org Subject: RE: Unable to start VM using COWed image From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 12:47 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 12:40 PM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 11:12 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Where can I get the code of the qemu-kvm program? I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- qemu-kvm.git contains the qemu-kvm codebase but the binary is built in x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename it to qemu-kvm. Thanks Stefan for your reply. I guess you pointed out the problem in the first mail. QEMU places a restriction on location of the COWed file. The source image and COWed image should be in the same drectory. In my case the source image was in directory /var/lib/libvirt/images/ and the COWed image was in /home/prasad/Virtual directory. While debuging the source code using gdb I realized this limitation. It would be good to fix this problem. I will see if I can solve this problem. This behavior is a feature. You chose to use a relative backing file path when you used qemu-img create -b relative-path. If you want an absolute path you need to use qemu-img create -b /home/prasad/Virtual/... (i.e. specify an absolute path instead of a relative path). Oh I see. I am such a stupid. ha ha ha ha Thanks a lot for letting me know. It worked after using absolute paths. Gr8 Thanks a lot. Though specifying the absolute path for source image worked for me. Can any one please let me know the situation in which one would not want to specify the absolute path? How does relative path help? Advantage of using relative path rather than absolute path. I think using the absolute path would always work. One more question on the same lines, How does QEMU detect the file is COWed and the name of the file (not whole path) from it is COWed? COW support comes from the image file format that you choose. A qcow file is not just a raw image file like the kind you can dd from a real disk. Instead it has its own file format including a header and metadata for tracking allocated space. The header contains the name of the backing file. Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Unable to start VM using COWed image
On Thu, Nov 11, 2010 at 12:17 PM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Though specifying the absolute path for source image worked for me. Can any one please let me know the situation in which one would not want to specify the absolute path? How does relative path help? Advantage of using relative path rather than absolute path. I think using the absolute path would always work. Relative paths are useful when sharing images with other people. An absolute path won't work on another machine unless you use the same parent directory structure. If you send me an image file with an absolute path in your home directory, I won't be able to use it easily on my machine. (Actually the new qemu-img rebase -u command can be used to fix up the image file on the destination machine but it's an extra step and not user-friendly.) Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: Unable to start VM using COWed image
From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 11:12 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Where can I get the code of the qemu-kvm program? I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- qemu-kvm.git contains the qemu-kvm codebase but the binary is built in x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename it to qemu-kvm. Thanks Stefan for your reply. I guess you pointed out the problem in the first mail. QEMU places a restriction on location of the COWed file. The source image and COWed image should be in the same drectory. In my case the source image was in directory /var/lib/libvirt/images/ and the COWed image was in /home/prasad/Virtual directory. While debuging the source code using gdb I realized this limitation. It would be good to fix this problem. I will see if I can solve this problem. One more question on the same lines, How does QEMU detect the file is COWed and the name of the file (not whole path) from it is COWed? Once again thank a lot Stefan and Kegin Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: Unable to start VM using COWed image
Thanks a lot for your reply.
From: Keqin Hong [kh...@redhat.com]
Sent: 10 November 2010 01:56
To: Prasad Joshi
Subject: Re: Unable to start VM using COWed image
- Prasad Joshi p.g.jo...@student.reading.ac.uk wrote:
Hello,
I am trying to run KVM machine from the image created as COW from the
original image. But it not working.
Screenshot that shows the KVM works with the original image
[r...@prasad images]# qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m
512
^Z
[1]+ Stopped qemu-kvm
/var/lib/libvirt/images/Ubuntu.img -m 512
[r...@prasad images]# bg
[1]+ qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# lsmod | grep -i kvm
kvm_intel 42122 3
kvm 257132 1 kvm_intel
1. Created COW copy of the image after stoping the VM that was
running
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# qemu-img create -b Ubuntu.img -f qcow
/home/prasad/Virtual/Ubuntu_copy.ovl
try adding -F base-fmt. Also qcow is obsolete, you'd better use qcow2
e.g. qemu-img create -b Ubuntu.img -F raw -f qcow2
/home/prasad/Virtual/Ubuntu_copy.ovl
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# date; qemu-img create -b Ubuntu.img -F raw -f qcow2
/home/prasad/Virtual/Ubuntu_copy.ovl
Wed Nov 10 09:44:31 GMT 2010
Formatting '/home/prasad/Virtual/Ubuntu_copy.ovl', fmt=qcow2 size=8589934592
backing_file='Ubuntu.img' backing_fmt='raw' encryption=off cluster_size=0
[pra...@prasad Virtual]$ ls -l
total 136
-rw-r--r--. 1 root root 262144 Nov 10 09:44 Ubuntu_copy.ovl
[pra...@prasad Virtual]$ sudo qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl: No such
file or directory
[pra...@prasad Virtual]$ sudo qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: No such file or directory
[pra...@prasad Virtual]$ sudo qemu-kvm ./Ubuntu_copy.ovl -m 512
qemu: could not open disk image ./Ubuntu_copy.ovl: No such file or directory
2. Trying to run VM using the copy created
[pra...@prasad Virtual]$ ls -l
total 36
-rw-r--r--. 1 root root 32832 Nov 9 15:33 Ubuntu_copy.ovl
[pra...@prasad Virtual]$ qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: Permission denied
[pra...@prasad Virtual]$ sudo qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: No such file or
directory
something like this may help:
qemu -drive file=$file,index=0,media=disk,format=qcow2
[pra...@prasad Virtual]$ sudo qemu-kvm ./Ubuntu_copy.ovl -m 512
qemu: could not open disk image ./Ubuntu_copy.ovl: No such file or
directory
[pra...@prasad Virtual]$ qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl:
Permission denied
[pra...@prasad Virtual]$ sudo qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl:
No such file or directory
Why is it failing?
Thanks and Regards,
Prasad Joshi
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--
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RE: Unable to start VM using COWed image
try adding -F base-fmt. Also qcow is obsolete, you'd better use qcow2
e.g. qemu-img create -b Ubuntu.img -F raw -f qcow2
/home/prasad/Virtual/Ubuntu_copy.ovl
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# date; qemu-img create -b Ubuntu.img -F raw -f qcow2
/home/prasad/Virtual/Ubuntu_copy.ovl
Wed Nov 10 09:44:31 GMT 2010
Formatting '/home/prasad/Virtual/Ubuntu_copy.ovl', fmt=qcow2 size=8589934592
backing_file='Ubuntu.img' backing_fmt='raw' encryption=off cluster_size=0
[pra...@prasad Virtual]$ ls -l
total 136
-rw-r--r--. 1 root root 262144 Nov 10 09:44 Ubuntu_copy.ovl
[pra...@prasad Virtual]$ sudo qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl: No such
file or directory
[pra...@prasad Virtual]$ sudo qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: No such file or directory
[pra...@prasad Virtual]$ sudo qemu-kvm ./Ubuntu_copy.ovl -m 512
qemu: could not open disk image ./Ubuntu_copy.ovl: No such file or directory
Where can I get the code of the qemu-kvm program?
I cloned the qemu-lvm git repository and compiled the code. But it looks like
qemu-kvm program is not part of this code.--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Unable to start VM using COWed image
On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Where can I get the code of the qemu-kvm program? I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- qemu-kvm.git contains the qemu-kvm codebase but the binary is built in x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename it to qemu-kvm. Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Unable to start VM using COWed image
On Wed, Nov 10, 2010 at 12:40 PM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 11:12 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Where can I get the code of the qemu-kvm program? I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- qemu-kvm.git contains the qemu-kvm codebase but the binary is built in x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename it to qemu-kvm. Thanks Stefan for your reply. I guess you pointed out the problem in the first mail. QEMU places a restriction on location of the COWed file. The source image and COWed image should be in the same drectory. In my case the source image was in directory /var/lib/libvirt/images/ and the COWed image was in /home/prasad/Virtual directory. While debuging the source code using gdb I realized this limitation. It would be good to fix this problem. I will see if I can solve this problem. This behavior is a feature. You chose to use a relative backing file path when you used qemu-img create -b relative-path. If you want an absolute path you need to use qemu-img create -b /home/prasad/Virtual/... (i.e. specify an absolute path instead of a relative path). One more question on the same lines, How does QEMU detect the file is COWed and the name of the file (not whole path) from it is COWed? COW support comes from the image file format that you choose. A qcow file is not just a raw image file like the kind you can dd from a real disk. Instead it has its own file format including a header and metadata for tracking allocated space. The header contains the name of the backing file. Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
RE: Unable to start VM using COWed image
From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 12:47 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 12:40 PM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: From: Stefan Hajnoczi [stefa...@gmail.com] Sent: 10 November 2010 11:12 To: Prasad Joshi Cc: Keqin Hong; kvm@vger.kernel.org Subject: Re: Unable to start VM using COWed image On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Where can I get the code of the qemu-kvm program? I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- qemu-kvm.git contains the qemu-kvm codebase but the binary is built in x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename it to qemu-kvm. Thanks Stefan for your reply. I guess you pointed out the problem in the first mail. QEMU places a restriction on location of the COWed file. The source image and COWed image should be in the same drectory. In my case the source image was in directory /var/lib/libvirt/images/ and the COWed image was in /home/prasad/Virtual directory. While debuging the source code using gdb I realized this limitation. It would be good to fix this problem. I will see if I can solve this problem. This behavior is a feature. You chose to use a relative backing file path when you used qemu-img create -b relative-path. If you want an absolute path you need to use qemu-img create -b /home/prasad/Virtual/... (i.e. specify an absolute path instead of a relative path). Oh I see. I am such a stupid. ha ha ha ha Thanks a lot for letting me know. It worked after using absolute paths. Gr8 Thanks a lot. One more question on the same lines, How does QEMU detect the file is COWed and the name of the file (not whole path) from it is COWed? COW support comes from the image file format that you choose. A qcow file is not just a raw image file like the kind you can dd from a real disk. Instead it has its own file format including a header and metadata for tracking allocated space. The header contains the name of the backing file. Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Unable to start VM using COWed image
Hello,
I am trying to run KVM machine from the image created as COW from the original
image. But it not working.
Screenshot that shows the KVM works with the original image
[r...@prasad images]# qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512
^Z
[1]+ Stopped qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512
[r...@prasad images]# bg
[1]+ qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# lsmod | grep -i kvm
kvm_intel 42122 3
kvm 257132 1 kvm_intel
1. Created COW copy of the image after stoping the VM that was running
[r...@prasad images]# pwd
/var/lib/libvirt/images
[r...@prasad images]# qemu-img create -b Ubuntu.img -f qcow
/home/prasad/Virtual/Ubuntu_copy.ovl
2. Trying to run VM using the copy created
[pra...@prasad Virtual]$ ls -l
total 36
-rw-r--r--. 1 root root 32832 Nov 9 15:33 Ubuntu_copy.ovl
[pra...@prasad Virtual]$ qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: Permission denied
[pra...@prasad Virtual]$ sudo qemu-kvm Ubuntu_copy.ovl -m 512
qemu: could not open disk image Ubuntu_copy.ovl: No such file or directory
[pra...@prasad Virtual]$ sudo qemu-kvm ./Ubuntu_copy.ovl -m 512
qemu: could not open disk image ./Ubuntu_copy.ovl: No such file or directory
[pra...@prasad Virtual]$ qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl:
Permission denied
[pra...@prasad Virtual]$ sudo qemu-kvm ${PWD}/Ubuntu_copy.ovl -m 512
qemu: could not open disk image /home/prasad/Virtual/Ubuntu_copy.ovl: No such
file or directory
Why is it failing?
Thanks and Regards,
Prasad Joshi
--
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Re: Unable to start VM using COWed image
On Tue, Nov 9, 2010 at 3:36 PM, Prasad Joshi p.g.jo...@student.reading.ac.uk wrote: Hello, I am trying to run KVM machine from the image created as COW from the original image. But it not working. Screenshot that shows the KVM works with the original image [r...@prasad images]# qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512 ^Z [1]+ Stopped qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512 [r...@prasad images]# bg [1]+ qemu-kvm /var/lib/libvirt/images/Ubuntu.img -m 512 [r...@prasad images]# pwd /var/lib/libvirt/images [r...@prasad images]# lsmod | grep -i kvm kvm_intel 42122 3 kvm 257132 1 kvm_intel 1. Created COW copy of the image after stoping the VM that was running [r...@prasad images]# pwd /var/lib/libvirt/images [r...@prasad images]# qemu-img create -b Ubuntu.img -f qcow /home/prasad/Virtual/Ubuntu_copy.ovl 2. Trying to run VM using the copy created [pra...@prasad Virtual]$ ls -l total 36 -rw-r--r--. 1 root root 32832 Nov 9 15:33 Ubuntu_copy.ovl Why is Ubuntu.img not visible in the ls output? Ubuntu.img is a relative path to the backing file. It looks like QEMU will not be able to open the backing file. Also, is there a reason you're using qcow and not qcow2? Stefan -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
