[libvirt-users] Detach disk from VM - virsh (working) vs. PHP (not working)
Jan Horak
horak at gransy.com
Fri Aug 2 16:26:33 UTC 2019
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 at 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($domain,"vdb");
print_r(libvirt_get_last_error());
res: Unable to detach disk
> 2. 8. 2019 v 14:15, Michal Privoznik <mprivozn at redhat.com>:
>
> On 8/1/19 10:12 AM, Jan Horak wrote:
>> Hi all,
>> i created a script in PHP for create a virtual server with two QCOW2 discs … one is our system for installation and second is target system.
>> After successfully instalation (create a blank Debian system, prepare all files and grub partitions) i need a restart virtual without a installation disk.
>> If i use Virsh:
>> detach-disk --domain debian-test2 --persistent --target vda
>> reset debian-test2
>> everything works well.
>> If i use a PHP, there is „complicated“ way and „simple“ way:
>> 1, complicated:
>> libvirt_domain_destroy($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
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