[libvirt-users] Detach disk from VM - virsh (working) vs. PHP (not working)

Jan Horak horak at gransy.com
Thu Aug 1 08:12:15 UTC 2019


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




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