[libvirt-users] Detach disk from VM - virsh (working) vs. PHP (not working)
Hi all, i created a script in PHP for create a virtual server with two QCOW2 discs … one is our system for installation and second is target system. After successfully instalation (create a blank Debian system, prepare all files and grub partitions) i need a restart virtual without a installation disk. If i use Virsh: detach-disk --domain debian-test2 --persistent --target vda reset debian-test2 everything works well. If i use a PHP, there is „complicated“ way and „simple“ way: 1, complicated: libvirt_domain_destroy($domain); libvirt_domain_undefine($domain); $xml = domain_create_xml($name,$uuid,$memory,$cpu,$vnc,$mac); $domain = libvirt_domain_define_xml($server->conn, $xml); libvirt_domain_disk_add($domain, "/users/".$name.".img", "vdb", "virtio", "qcow2", NULL); libvirt_domain_create($domain); (or instead libvirt_domain_disk_add i can define disk directly in XML) But in this case, the server will not boot (GRUB error) 2, simple: libvirt_domain_disk_remove($domain,“vda“); libvirt_domain_reboot($domain); The problem of this solution is thats not working. The remove disk is failing with error „Unable attach disk“ - i looks to source code, and yes, there is a mystake with „attach“/„detach“, but main problem i see in log from libvirt: Aug 1 02:57:05 ry libvirtd[19051]: missing source information for device vda I try to put source detail to xml in source of PHP module libvirt-domain.c: 822 if (asprintf(&newXml, 823 " <disk type='file' device='disk'>\n" 824 " <target dev='%s'/>\n" 825 " </disk>", dev) < 0) { 826 set_error("Out of memory" TSRMLS_CC); 827 goto error; 828 } but my attempts was unsuccesfull (i’m not C programmer). Questions: A, why complicated way is not working and system dont want boot (GRUB error) if virsh works fine B, why libvirt_domain_disk_remove is not work ? I use libvirt and libvirt-php latest from git. Thank you, Jan
On Thu, Aug 01, 2019 at 10:12:15AM +0200, Jan Horak wrote:
Hi all,
i created a script in PHP for create a virtual server with two QCOW2 discs … one is our system for installation and second is target system.
After successfully instalation (create a blank Debian system, prepare all files and grub partitions) i need a restart virtual without a installation disk.
If i use Virsh:
detach-disk --domain debian-test2 --persistent --target vda reset debian-test2
Hi, I cannot really help you with the PHP part and I'm not sure about more things, but this particular scenario is something that libvirt is actually prepared to do (kind of) and for example virt-install uses it. The approach is as follows: 1) You create the XML that you want the VM to have when installing the machine, let's call it the "install xml". 2) You create the XML that the VM should start with when it is already installed and it is the one that will persist in the libvirt configuration for long time (well, longer than the install xml). Let's call this the "persistent xml". 3) You define the VM using the persistent xml. That will get you a VM that is not started. 4) Then, you start the machine with the install xml, using the create API (analogous to virsh create vm.xml). Just make sure the name and UUID are the same. That will get you a VM running with the install xml that, when turned off and then started again (without reboot/reset/restart, you need to have it shut down completely before starting it) will start with the persistent xml. No need to have support for disk hot-(un)plug, no magic. Even better way to use this is registering a callback for the VM's lifecycle event, starting the VM after the event was fired. That way you can automate the installation to turn off the machine after it is completed and there is no need for any polling. I'm not sure, however, how relevant that is or if it is possible to be used from the PHP bindings. Have a nice day, Martin
On 8/1/19 10:12 AM, Jan Horak wrote:
Hi all,
i created a script in PHP for create a virtual server with two QCOW2 discs … one is our system for installation and second is target system.
After successfully instalation (create a blank Debian system, prepare all files and grub partitions) i need a restart virtual without a installation disk.
If i use Virsh:
detach-disk --domain debian-test2 --persistent --target vda reset debian-test2
everything works well.
If i use a PHP, there is „complicated“ way and „simple“ way:
1, complicated:
libvirt_domain_destroy($domain); libvirt_domain_undefine($domain);
$xml = domain_create_xml($name,$uuid,$memory,$cpu,$vnc,$mac); $domain = libvirt_domain_define_xml($server->conn, $xml); libvirt_domain_disk_add($domain, "/users/".$name.".img", "vdb", "virtio", "qcow2", NULL); libvirt_domain_create($domain);
(or instead libvirt_domain_disk_add i can define disk directly in XML)
But in this case, the server will not boot (GRUB error)
Question is, how GRUB refers to the disk where kernel is to be found. Also, I suspect it is not GRUB that is complaining, but SeaBIOS which hasn't found any bootable device. It's only an assumption becasue I don't know how domain_create_xml() works - it's not a libvirt-php function. There are two possibilities here: 1) make sure domain_create_xml() sets boot devices 2) construct disk XML yourself, and put "<boot order='N'/>" into it
2, simple:
libvirt_domain_disk_remove($domain,“vda“); libvirt_domain_reboot($domain);
The problem of this solution is thats not working. The remove disk is failing with error „Unable attach disk“ - i looks to source code, and yes, there is a mystake with „attach“/„detach“, but main problem i see in log from libvirt:
Oh, that's only typo in the error message. In fact the detach API is called. And it fails.
Aug 1 02:57:05 ry libvirtd[19051]: missing source information for device vda
I try to put source detail to xml in source of PHP module
libvirt-domain.c:
822 if (asprintf(&newXml, 823 " <disk type='file' device='disk'>\n" 824 " <target dev='%s'/>\n" 825 " </disk>", dev) < 0) { 826 set_error("Out of memory" TSRMLS_CC); 827 goto error; 828 }
but my attempts was unsuccesfull (i’m not C programmer).
Yes, this minimalistic XML is not good as detach API requires full device XML. I'll fix this soon.
Questions:
A, why complicated way is not working and system dont want boot (GRUB error) if virsh works fine B, why libvirt_domain_disk_remove is not work ? I use libvirt and libvirt-php latest from git.
I've pushed fixes here: Please give it a try. Michal
Thank you for your help! 1, i used vda as install disk and vdb as target disk, because i boot from the first. After setup boot order flag i was able change install disk to vdb and target disk to vda. With this configuration when i boot from vdb i can install OS with grub and after it redefine XML without vdb without problem. Thanks a lot. 2, maybe i have something wrong, but still not working: Now in libvirt log i got error: device not found: no target device vdb but: from VPS: root@debian:~# ls /dev/vd* /dev/vda /dev/vda1 /dev/vdb /dev/vdb1 from XML (virsh dumpxml): <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/users/debian-test2.img'/> <backingStore/> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/> </disk> <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/users/debian-test2-install.img'/> <backingStore/> <target dev='vdb' bus='virtio'/> <boot order='1'/> <alias name='virtio-disk1'/> <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/> </disk> and from libvirt_domain_get_disk_devices($domain): Array ( [0] => vda [1] => vdb [num] => 2 ) As you see, there is vdb device in all cases. PHP code is very simple: $server = libvirt_connect("qemu+tls://".$ip.“:“.$port."/system", false); $domain = libvirt_domain_lookup_by_name($server, "debian-test2"); libvirt_domain_disk_remove($domain,"vdb"); print_r(libvirt_get_last_error()); res: Unable to detach disk
2. 8. 2019 v 14:15, Michal Privoznik <mprivozn@redhat.com>:
On 8/1/19 10:12 AM, Jan Horak wrote:
Hi all, i created a script in PHP for create a virtual server with two QCOW2 discs … one is our system for installation and second is target system. After successfully instalation (create a blank Debian system, prepare all files and grub partitions) i need a restart virtual without a installation disk. If i use Virsh: detach-disk --domain debian-test2 --persistent --target vda reset debian-test2 everything works well. If i use a PHP, there is „complicated“ way and „simple“ way: 1, complicated: libvirt_domain_destroy($domain); libvirt_domain_undefine($domain); $xml = domain_create_xml($name,$uuid,$memory,$cpu,$vnc,$mac); $domain = libvirt_domain_define_xml($server->conn, $xml); libvirt_domain_disk_add($domain, "/users/".$name.".img", "vdb", "virtio", "qcow2", NULL); libvirt_domain_create($domain); (or instead libvirt_domain_disk_add i can define disk directly in XML) But in this case, the server will not boot (GRUB error)
Question is, how GRUB refers to the disk where kernel is to be found. Also, I suspect it is not GRUB that is complaining, but SeaBIOS which hasn't found any bootable device. It's only an assumption becasue I don't know how domain_create_xml() works - it's not a libvirt-php function. There are two possibilities here:
1) make sure domain_create_xml() sets boot devices 2) construct disk XML yourself, and put "<boot order='N'/>" into it
2, simple: libvirt_domain_disk_remove($domain,“vda“); libvirt_domain_reboot($domain); The problem of this solution is thats not working. The remove disk is failing with error „Unable attach disk“ - i looks to source code, and yes, there is a mystake with „attach“/„detach“, but main problem i see in log from libvirt:
Oh, that's only typo in the error message. In fact the detach API is called. And it fails.
Aug 1 02:57:05 ry libvirtd[19051]: missing source information for device vda I try to put source detail to xml in source of PHP module libvirt-domain.c: 822 if (asprintf(&newXml, 823 " <disk type='file' device='disk'>\n" 824 " <target dev='%s'/>\n" 825 " </disk>", dev) < 0) { 826 set_error("Out of memory" TSRMLS_CC); 827 goto error; 828 } but my attempts was unsuccesfull (i’m not C programmer).
Yes, this minimalistic XML is not good as detach API requires full device XML. I'll fix this soon.
Questions: A, why complicated way is not working and system dont want boot (GRUB error) if virsh works fine B, why libvirt_domain_disk_remove is not work ? I use libvirt and libvirt-php latest from git.
I've pushed fixes here:
Please give it a try.
Michal
On 8/2/19 6:26 PM, Jan Horak wrote:
Thank you for your help!
1, i used vda as install disk and vdb as target disk, because i boot from the first. After setup boot order flag i was able change install disk to vdb and target disk to vda. With this configuration when i boot from vdb i can install OS with grub and after it redefine XML without vdb without problem. Thanks a lot.
2, maybe i have something wrong, but still not working:
Now in libvirt log i got error: device not found: no target device vdb
Ah, of coure. I overlooked that virDomainDetachDeviceFlags() is called with VIR_DOMAIN_AFFECT_CONFIG, which means that live configuration is not affected and if the disk you're trying to detach exists only in live XML then the API fails. The same problem was found in libvirt_domain_disk_add, libvirt_domain_nic_add and libvirt_domain_nic_remove. I've pushed the fixes to the master. Thanks for the report. Michal
Hi, i confirm thats works very well now! Thank you for your support! Jan
3. 8. 2019 v 8:54, Michal Prívozník <mprivozn@redhat.com>:
On 8/2/19 6:26 PM, Jan Horak wrote:
Thank you for your help!
1, i used vda as install disk and vdb as target disk, because i boot from the first. After setup boot order flag i was able change install disk to vdb and target disk to vda. With this configuration when i boot from vdb i can install OS with grub and after it redefine XML without vdb without problem. Thanks a lot.
2, maybe i have something wrong, but still not working:
Now in libvirt log i got error: device not found: no target device vdb
Ah, of coure. I overlooked that virDomainDetachDeviceFlags() is called with VIR_DOMAIN_AFFECT_CONFIG, which means that live configuration is not affected and if the disk you're trying to detach exists only in live XML then the API fails. The same problem was found in libvirt_domain_disk_add, libvirt_domain_nic_add and libvirt_domain_nic_remove.
I've pushed the fixes to the master. Thanks for the report.
Michal
participants (4)
-
Jan Horak -
Martin Kletzander -
Michal Privoznik -
Michal Prívozník