Vnx-modify-rootfs

Updating or modifying a VNX root filesystem

KVM root filesystem

In order to update or modify a VNX root filesystem (rootfs from now on), you have two possible methods:

Mount the root filesystem from the host

The fastest way to modify a root filesystem is by mounting it from the host and directly modifying it without starting a virtual machine. To do that:

• Create a ndb device with the filesystem:

modprobe nbd
qemu-nbd -c /dev/nbd0 <rootfs_name>

being <rootfs_name> the rootfs filename.

• Consult the rootfs partitions with:

fdisk -l /dev/ndb0

• Mount the desired partition with:

mount /dev/nbd0p1 /mnt

• Do the modifications desired directly accesing files. You can chroot the the mount directory in order to install software.
• At the end, unmount the particition and release nbd device:

umount /mnt
qemu-nbd -d /dev/nbd0

Examples:

• Ubuntu rootfs

$ modprobe nbd
$ qemu-nbd -c /dev/nbd0 vnx_rootfs_kvm_ubuntu-12.04-v024.qcow2 
$ fdisk -l /dev/nbd0

Disco /dev/nbd0: 8589 MB, 8589934592 bytes
255 cabezas, 63 sectores/pista, 1044 cilindros, 16777216 sectores en total
Unidades = sectores de 1 * 512 = 512 bytes
Tamaño de sector (lógico / físico): 512 bytes / 512 bytes
Tamaño E/S (mínimo/óptimo): 512 bytes / 512 bytes
Identificador del disco: 0x0000e82c

Dispositivo Inicio    Comienzo      Fin      Bloques  Id  Sistema
/dev/nbd0p1   *        2048    15728639     7863296   83  Linux
/dev/nbd0p2        15730686    16775167      522241    5  Extendida
/dev/nbd0p5        15730688    16775167      522240   82  Linux swap / Solaris
$ mount /dev/nbd0p1 /mnt/
...
$ umount /mnt 
$ qemu-nbd -d /dev/nbd0
/dev/nbd0 disconnected

• FreeBSD rootfs:

$ modprobe nbd
$ qemu-nbd -c /dev/nbd0 vnx_rootfs_kvm_freebsd64-9.1-v025m2.qcow2
$ fdisk -l /dev/nbd0

AVISO: GPT (Tabla de partición GUID) detectado en '/dev/nbd0'! La utilidad fdisk no soporta GPT. Use GNU Parted.


Disco /dev/nbd0: 12.9 GB, 12884901888 bytes
256 cabezas, 63 sectores/pista, 1560 cilindros, 25165824 sectores en total
Unidades = sectores de 1 * 512 = 512 bytes
Tamaño de sector (lógico / físico): 512 bytes / 512 bytes
Tamaño E/S (mínimo/óptimo): 512 bytes / 512 bytes
Identificador del disco: 0x00000000

Dispositivo Inicio    Comienzo      Fin      Bloques  Id  Sistema
/dev/nbd0p1   *           1    25165823    12582911+  ee  GPT
$ parted /dev/nbd0 print
Modelo: Desconocida (unknown)
Disco /dev/nbd0: 12,9GB
Tamaño de sector (lógico/físico): 512B/512B
Tabla de particiones. gpt

Numero  Inicio  Fin     Tamaño  Sistema de archivos  Nombre  Banderas
 1      17,4kB  82,9kB  65,5kB
 2      82,9kB  11,8GB  11,8GB  freebsd-ufs
 3      11,8GB  12,5GB  644MB

$ mount -r -t ufs -o ufstype=ufs2 /dev/nbd0p2 /mnt/
$ ls /mnt/
bin  boot  COPYRIGHT  dev  etc  lib  libexec  media  mnt  proc  rescue  root  sbin  sys  tmp  usr  var
$ umount /mnt 
$ qemu-nbd -d /dev/nbd0
/dev/nbd0 disconnected

Start a virtual machine in direct mode

To start a virtual machine directly mounting a rootfs and having Internet connection, you can use vnx command with the following parameters:

vnx --modify_rootfs <rootfs_name>

being <rootfs_name> the rootfs filename.

Alternatively, you can create a libvirt XML virtual machine definition (see examples in /usr/share/vnx/examples directory) and start it using virsh:

virsh create rootfs_XXX.xml

and manually opening the console using:

virt-viewer <vmname>

being <vmname> the name assigned by libvirt to the virtual machine (you can get it with "virsh list" command).

Once the virtual machine is started and you have access to the console, you can make the modifications desired.

At the end, halt the virtual machine using the vnx_halt command. This will clean some log and history files, clean the apt cache and optionally leave a text message in /etc/vnx_rootfs_version describing the modifications done.

Updating VNXACE daemon

If you have a rootfs with the autoconfiguration and command execution daemon (ACE) already installed, you can use the autoupdate functionality to update the daemon to a newer version. Just follow this procedure:

Linux and FreeBSD

• Start the virtual machine with the following command line options:

vnx --modify-rootfs <rootfs_name> --update-aced -y

being <rootfs_name> the rootfs filename. This command will try to update the VNXACE daemon to the latest version automatically (-y option).

• If everything goes well, a message informing the new version installed will be shown in the virtual machine console before halting it.
• If the daemon is not updated automatically, you can do it manually from inside the virtual machine:
• Mounting the update disk:

mount /dev/sdb /mnt               # For Linux
mount -t msdosfs /dev/ad1 /mnt    # For FreeBSD

• Installing VNXACED:

perl /mnt/vnxaced-lf/install_vnxaced

Windows

To be completed

Olive

To be completed