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Thread: Xen VM configuration files and VM Persistence

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  1. #1
    Join Date
    Oct 2012
    Location
    Portland, Oregon
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    Question Xen VM configuration files and VM Persistence

    I have a bit of a quandry: I've migrated two PVM's away from the host system but they persist in Xend even though they are not active on the host; they're not in XenStore (/var/lib/xenstore/tdb), and; there are no configuration files for the VM's (in /etc/xen/vm):
    Code:
    xen2:~ # ls /etc/xen/vm
    sles11-1  sles11-1.xml
    
    xen2:~ # xm list
    Name                                        ID   Mem VCPUs      State   Time(s)
    Domain-0                                     0   502     2     r-----   6185.1
    oracle1                                          786     1                15.3
    oracle2                                          786     1                14.0
    
    xen2:~ # xenstore-ls | grep "name = "
       name = "Domain-0"
       name = "Pool-0"
      pool_name = "Pool-0"
      name = "Domain-0"
    Where is this information being stored?

    Eric Pretorious
    Truckee, CA

    From Chapter 3.1, Creating a Virtual Machine, of the SuSE manual Virtualization with Xen:

    The actual configuration file for the Xen guests that is used for the installation is stored at /etc/xen/vm/.
    From Chapter 3.5, Deleting Virtual Machines, also of the SuSE manual Virtualization with Xen:

    To delete all components of a virtual machine configured with a file-backed virtual disk, you must manually delete... its initial startup file (/etc/xen/vm).
    From Chapter 5.3, Configuring a Virtual Machine by Modifying its Xend Settings, also of the SuSE manual Virtualization with Xen:

    It is no longer recommended that you edit the initial start-up files stored in /etc/xen/vm, because they are used only during the creation of a new virtual machine.
    Last edited by epretorious; 26-Feb-2013 at 20:39. Reason: Added the hyperlink to the reference to Chapter 5.3 and the output of the xenstore-ls command

  2. #2
    Join Date
    Oct 2012
    Location
    Portland, Oregon
    Posts
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    Question Re: Xen VM configuration files and VM Persistence

    Quote Originally Posted by epretorious View Post
    Where is this information being stored?
    I should also mention that even though...

    • there are no configuration files stored locally (in /etc/xen) and
    • there's no information stored in XenStore

    ...the VM's can be manually restarted:
    Code:
    xen2:~ # xm list
    Name                                        ID   Mem VCPUs      State   Time(s)
    Domain-0                                     0   502     2     r-----     40.1
    oracle1                                          786     1                18.2
    oracle2                                          786     1                16.9
    
    xen2:~ # xm start oracle1
    
    xen2:~ # xm start oracle2
    
    xen2:~ # xm list
    Name                                        ID   Mem VCPUs      State   Time(s)
    Domain-0                                     0   502     2     r-----     62.8
    oracle1                                      1   786     1     ------     10.8
    oracle2                                      2   786     1     r-----      2.8
    So, this begs the question: Where is this information being stored?

  3. #3

    Re: Xen VM configuration files and VM Persistence

    epretorious wrote:

    > So, this begs the question: Where is this information being stored?


    Your "xm list" reports oracle1 and oracle2. They are not running
    therefore they must exist in the XenStore.

    To see the configuration of the DomU:
    Code:
    xm list -l oracle1
    See here for more information:
    https://forums.suse.com/content.php?...-and-xm-create

    --
    Kevin Boyle - Knowledge Partner
    If you find this post helpful and are logged into the web interface,
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  4. #4
    Join Date
    Oct 2012
    Location
    Portland, Oregon
    Posts
    54

    Question Re: Xen VM configuration files and VM Persistence

    Quote Originally Posted by epretorious View Post
    ...I've migrated two PVM's away from the host system but they persist in Xend even though they are not active on the host; they're not in XenStore (/var/lib/xenstore/tdb), and; there are no configuration files for the VM's (in /etc/xen/vm):
    Code:
    xen2:~ # xenstore-ls | grep "name = "
       name = "Domain-0"
       name = "Pool-0"
      pool_name = "Pool-0"
      name = "Domain-0"
    Quote Originally Posted by KBOYLE View Post
    Your "xm list" reports oracle1 and oracle2. They are not running therefore they must exist in the XenStore.

    To see the configuration of the DomU:
    Code:
    xm list -l oracle1
    See here for more information:
    https://forums.suse.com/content.php?...-and-xm-create
    Thanks for sharing your article "Managing your Xen DomU: Difference between "xm new" and "xm create", Ken:

    However, I'm more confused than before (because now I see that my understanding of Xend & XenStore is not necessarily correct)!

    AFAICT, the xenstore-ls command (above) illustrates that the configuration settings of the PVM's "oracle1" & "oracle2" do not exist in XenStore. However, as you suggested (above) the xm list command contradicts this:
    Code:
    xen2:~ # xm list
    Name                                        ID   Mem VCPUs      State   Time(s)
    Domain-0                                     0   502     2     r-----    267.9
    oracle1                                          786     1               211.9
    oracle2                                          786     1                22.8
    
    xen2:~ # xenstore-ls | grep oracle
    
    xen2:~ # xm list -l oracle1
    (domain
        (cpu_weight 256)
        (cpu_cap 0)
        (pool_name Pool-0)
        (bootloader /usr/bin/pygrub)
        (vcpus 1)
        (cpus (()))
        (on_poweroff destroy)
        (description '')
        (on_crash restart)
        (uuid a8422077-d938-3e6b-0f68-9cc83910ad4a)
        (bootloader_args '')
        (name oracle1)
        (on_reboot restart)
        (maxmem 786)
        (memory 786)
        (shadow_memory 0)
        (features '')
        (on_xend_start ignore)
        (on_xend_stop ignore)
    ...
        (device
            (vbd
                (protocol x86_64-abi)
                (uuid 25b28895-67a7-0656-83e8-6a67a677972a)
                (bootable 1)
                (devid 51712)
                (driver paravirtualised)
                (dev xvda:disk)
                (uname
                    phy:/dev/disk/by-id/scsi-14945540000000000705f69534353492d73616e325f300000
                )
                (mode w)
                (VDI '')
                (backend 0)
            )
        )
    )
    And so does this command:

    Code:
    xen2:~ # file /var/lib/xenstored/tdb 
    /var/lib/xenstored/tdb: TDB database version 6, little-endian hash size 7919 bytes
    
    xen2:~ # strings /var/lib/xenstored/tdb | grep oracle
    oracle2
    oracle1
    oracle1BBBl
    oracle1
    oracle1otocol
    oracle1ol
    oracle1
    oracle1ckend-id
    oracle1otocol
    oracle1ol
    oracle1dT
    So I guess that, without any authoritative instructions for the xenstore command, I'm back to Square #1.

    Hm.

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