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Xen rescue paravirtualization

===Rescue===

Shut down the GuestOS safely by logging into the GuestOS and issuing the command poweroff or

$ xm shutdown alfa

Copy or download the ”’initrd.img”’ and ”’vmlinuz”’ files from /images/xen/ directory of Red Hat Enterprise Linux install media tree to Red Hat Enterprise Linux Virtualization Host. In this test case these files are copied to the directory ”’/var/lib/xen/images/tmp/”’ of the Virtualization host.

Modify the GuestOS configuration file on the Virtualization Host itself to enable boot it from rescue environment. In this test case the GuesOS in question is called alfa and its configuration file is /etc/xen/alfa

1. copy the config file ”’/etc/xen/alfa”’ to ”’/etc/xen/alfa_rescue”’

2. In the config file ”’/etc/xen/alfa_rescue”’, comment the bootloader line:

#bootloader="/usr/bin/pygrub"

3. Append the following to the configuration before the ”’disk =”’ line file temporarily and save it.

kernel = "/var/lib/xen/images/tmp/vmlinuz"
ramdisk = "/var/lib/xen/images/tmp/initrd.img"
extra = "rescue"

4. Sample

name = "alfa"
uuid = "96b6da3e-70a7-a0a0-7c68-67a0f83d8264"
maxmem = 512
memory = 512
vcpus = 1
#bootloader = "/usr/bin/pygrub"
on_poweroff = "destroy"
on_reboot = "restart"
on_crash = "restart"
vfb = [  ]
kernel = "/var/lib/xen/images/tmp/vmlinuz"
ramdisk = "/var/lib/xen/images/tmp/initrd.img"
extra = "rescue"
disk = [ "tap:aio:/var/lib/xen/images/alfa.img,xvda,w" ]
vif = [ "mac=00:16:3e:13:62:2f,bridge=xenbr0" ]

5. Re-create (start) the GuestOS with xm command

 
 xm create -c alfa_rescue

6.

                   +---------+ Choose a Language +---------+
                   |                                       |
                   | What language would you like to use   |
                   | during the installation process?      |
                   |                                       |
                   |       Catalan                ^        |
                   |       Chinese(Simplified)    :        |
                   |       Chinese(Traditional)   #        |
                   |       Croatian               :        |
                   |       Czech                  :        |
                   |       Danish                 :        |
                   |       Dutch                  :        |
                   |       English                v        |
                   |                                       |
                   |                +----+                 |
                   |                | OK |                 |
                   |                +----+                 |
                   |                                       |
                   |                                       |
                   +---------------------------------------+

7. Chose HTTP

               +---------------+ Rescue Method +----------------+
               |                                                |
               | What type of media contains the rescue image?  |
               |                                                |
               |                  Local CDROM                   |
               |                  Hard drive                    |
               |                  NFS image                     |
               |                  FTP                           |
               |                  HTTP                          |
               |                                                |
               |        +----+                 +------+         |
               |        | OK |                 | Back |         |
               |        +----+                 +------+         |
               |                                                |
               |                                                |
               +------------------------------------------------+

8. Set IP

             +----------------+ Configure TCP/IP +----------------+
             |                                                    |
             | [*] Enable IPv4 support                            |
             |        ( ) Dynamic IP configuration (DHCP)         |
             |        (*) Manual configuration                    |
             |                                                    |
             | [ ] Enable IPv6 support                            |
             |        (*) Automatic neighbor discovery (RFC 2461) |
             |        ( ) Dynamic IP configuration (DHCP)         |
             |        ( ) Manual configuration                    |
             |                                                    |
             |          +----+                  +------+          |
             |          | OK |                  | Back |          |
             |          +----+                  +------+          |
             |                                                    |
             |                                                    |
             +----------------------------------------------------+

         +--------------+ Manual TCP/IP Configuration +---------------+
         |                                                            |
         | Enter the IPv4 and/or the IPv6 address and prefix          |
         | (address / prefix).  For IPv4, the dotted-quad netmask     |
         | or the CIDR-style prefix are acceptable. The gateway and   |
         | name server fields must be valid IPv4 or IPv6 addresses.   |
         |                                                            |
         | IPv4 address: 192.168.y.yy__ / 255.255.255.0_____          |
         | Gateway:      192.168.z.zz____________________________    |
         | Name Server:  192.168.z.zz____________________________    |
         |                                                            |
         |            +----+                      +------+            |
         |            | OK |                      | Back |            |
         |            +----+                      +------+            |
         |                                                            |
         |                                                            |
         +------------------------------------------------------------+

9. Http setting

    +---------------------------+ HTTP Setup +----------------------------+
    |                                                                     |
    |           Please enter the following information:                   |
    |                                                                     |
    |               o the name or IP number of your Web server            |
    |               o the directory on that server containing             |
    |                 Red Hat Enterprise Linux Server for                 |
    |           your architecture                                         |
    |                                                                     |
    | Web site name:                             192.168.x.x___________ |
    | Red Hat Enterprise Linux Server directory: rhelxxx_________________ |
    |                                                                     |
    |              +----+                           +------+              |
    |              | OK |                           | Back |              |
    |              +----+                           +------+              |
    |                                                                     |
    |                                                                     |
    +---------------------------------------------------------------------+

10. Rescue

            +---------------------+ Rescue +----------------------+
            |                                                     |
            | The rescue environment will now attempt to find   ^ |
            | your Linux installation and mount it under the    # |
            | directory /mnt/sysimage.  You can then make any   : |
            | changes required to your system.  If you want     : |
            | to proceed with this step choose 'Continue'.      : |
            | You can also choose to mount your file systems    : |
            | read-only instead of read-write by choosing       : |
            | 'Read-Only'.                                      : |
            |                                                   : |
            | If for some reason this process fails you can     : |
            | choose 'Skip' and this step will be skipped and   : |
            | you will go directly to a command shell.          v |
            |                                                     |
            |   +----------+      +-----------+      +------+     |
            |   | Continue |      | Read-Only |      | Skip |     |
            |   +----------+      +-----------+      +------+     |
            |                                                     |
            |                                                     |
            +-----------------------------------------------------+

                  +---------------+ Rescue +----------------+
                  |                                         |
                  | Your system has been mounted under      |
                  | /mnt/sysimage.                          |
                  |                                         |
                  | Press  to get a shell. If you   |
                  | would like to make your system the      |
                  | root environment, run the command:      |
                  |                                         |
                  |         chroot /mnt/sysimage            |
                  |                                         |
                  | The system will reboot automatically    |
                  | when you exit from the shell.           |
                  |                                         |
                  |                 +----+                  |
                  |                 | OK |                  |
                  |                 +----+                  |
                  |                                         |
                  |                                         |
                  +-----------------------------------------+

Your system is mounted under the /mnt/sysimage directory.
When finished please exit from the shell and your system will reboot.

sh-3.2#

January 6, 2010 - Posted by derwynd | Uncategorized