Editing Migration from Linux-VServer to OpenVZ

Current document describes the migration from Linux-VServer based virtualization solution to OpenVZ.

Description of challenge:

The challenge is migration from Linux-Vserver to OpenVZ by booting the OpenVZ kernel and updating the existing configs of 
utility level in purpose to make the existing guest OSes work over OpenVZ kernel.

Details of migration process. Step by step:

1. Initial conditions: the following example of Linux-VServer based solution was used for the experiment:

- Kernel linux-2.6.17.13 was patched by the patch-2.6.17.13-vs2.0.2.1.diff and rebuild;
- Util-vserver-0.30.211 tools were used for creating containers;

<code>
  # vserver-info
  Versions:
  Kernel: 2.6.17.13-vs2.0.2.1
  VS-API: 0x00020002
  util-vserver: 0.30.211; Dec  5 2006, 17:10:21

  Features:
  CC: gcc, gcc (GCC) 3.4.3 20041212 (Red Hat 3.4.3-9.EL4)
  CXX: g++, g++ (GCC) 3.4.3 20041212 (Red Hat 3.4.3-9.EL4)
  CPPFLAGS: ''
  CFLAGS: '-g -O2 -std=c99 -Wall -pedantic -W -funit-at-a-time'
  CXXFLAGS: '-g -O2 -ansi -Wall -pedantic -W -fmessage-length=0 -funit-at-a-time'
  build/host: i686-pc-linux-gnu/i686-pc-linux-gnu
  Use dietlibc: yes
  Build C++ programs: yes
  Build C99 programs: yes
  Available APIs: v13,net
  ext2fs Source: kernel
  syscall(2) invocation: alternative
  vserver(2) syscall#: 273/glibc

  Paths:
  prefix: /usr/local
  sysconf-Directory: ${prefix}/etc
  cfg-Directory: ${prefix}/etc/vservers
  initrd-Directory: $(sysconfdir)/init.d
  pkgstate-Directory: ${prefix}/var/run/vservers
  vserver-Rootdir: /vservers
  #
</code>

VServer v345 was built using vserver vX build utility and populated by using the tarballed template of Fedora Core 4.
 
<code>
  # vserver v345 start
  Starting system logger:                                    [  OK  ]
  Initializing random number generator:                      [  OK  ]
  Starting crond: l:                                         [  OK  ]
  Starting atd:                                              [  OK  ]
  # vserver v345 enter
  [/]# ls -l
  total 44
  drwxr-xr-x    2 root     root         4096 Oct 26  2004 bin
  drwxr-xr-x    3 root     root         4096 Dec  8 17:16 dev
  drwxr-xr-x   27 root     root         4096 Dec  8 15:21 etc
  -rw-r--r--    1 root     root            0 Dec  8 15:33 halt
  drwxr-xr-x    2 root     root         4096 Jan 24  2003 home
  drwxr-xr-x    7 root     root         4096 Oct 26  2004 lib
  drwxr-xr-x    2 root     root         4096 Jan 24  2003 mnt
  drwxr-xr-x    3 root     root         4096 Oct 26  2004 opt
  -rw-r--r--    1 root     root            0 Dec  7 20:17 poweroff
  dr-xr-xr-x   80 root     root            0 Dec  8 11:38 proc
  drwxr-x---    2 root     root         4096 Dec  7 20:17 root
  drwxr-xr-x    2 root     root         4096 Oct 26  2004 sbin
  drwxrwxrwt    2 root     root           40 Dec  8 17:16 tmp
  drwxr-xr-x   15 root     root         4096 Jul 27  2004 usr
  drwxr-xr-x   17 root     root         4096 Oct 26  2004 var
  [/]# sh
  sh-2.05b#
  .........
</code>

As a result we obtain running virtual environment v345:

<code>
  # vserver-stat

  CTX   PROC    VSZ    RSS  userTIME   sysTIME    UPTIME NAME
  0       51  90.9M  26.3M   0m58s75   2m42s57  33m45s93 root server
  49153    4  10.2M   2.8M   0m00s00   0m00s11  21m45s42 v345

  # 
</code>

2. Starting migration to OpenVZ: downloading and installing the stable OpenVZ kernel.

First of all we should download and install the latest stable version of OpenVZ kernel:

<code>
  #  wget http://openvz.org/download/kernel/stable/ovzkernel-2.6.9-023stab032.1.i686.rpm
  #  rpm -ihv ovzkernel-2.6.9-023stab032.1.i686.rpm
</code>

If you use grub bootloader, then before installing the OpenVZ kernel file /boot/grub/grub.conf looked like this:

<code>
  # grub.conf generated by anaconda
  #
  # Note that you do not have to rerun grub after making changes to this file
  # NOTICE:  You have a /boot partition.  This means that
  #          all kernel and initrd paths are relative to /boot/, eg.
  #          root (hd0,0)
  #          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
  #          initrd /initrd-version.img
  #boot=/dev/sda
  default=0
  timeout=5
  splashimage=(hd0,0)/grub/splash.xpm.gz
  hiddenmenu
  title Red Hat Enterprise Linux AS (2.6.17.13-vs2.0.2.1)
          root (hd0,0)
          kernel /vmlinuz-2.6.17.13-vs2.0.2.1 ro root=/dev/VolGroup00/LogVol00 
          initrd /initrd-2.6.17.13-vs2.0.2.1.img
</code>

After installing it should look like this:

<code>
  # grub.conf generated by anaconda
  #
  # Note that you do not have to rerun grub after making changes to this file
  # NOTICE:  You have a /boot partition.  This means that
  #          all kernel and initrd paths are relative to /boot/, eg.
  #          root (hd0,0)
  #          kernel /vmlinuz-version ro root=/dev/VolGroup00/LogVol00
  #          initrd /initrd-version.img
  #boot=/dev/sda
  default=0
  timeout=5
  splashimage=(hd0,0)/grub/splash.xpm.gz
  hiddenmenu
  title Red Hat Enterprise Linux AS (2.6.9-023stab032.1)
          root (hd0,0)
          kernel /vmlinuz-2.6.9-023stab032.1 ro root=/dev/VolGroup00/LogVol00
          initrd /initrd-2.6.9-023stab032.1.img
  title Red Hat Enterprise Linux AS (2.6.17.13-vs2.0.2.1)
          root (hd0,0)
          kernel /vmlinuz-2.6.17.13-vs2.0.2.1 ro root=/dev/VolGroup00/LogVol00
          initrd /initrd-2.6.17.13-vs2.0.2.1.img
</code>

And the default parameter should be set to 0 in purpose to make the OpenVZ kernel work by default after rebooting the machine.

Some more manual configuring needed on this step:
Update the /etc/sysctl.conf file according to the following listing ( Comment all other settings that are not presented 
in listing below ):

<code>
  # On Hardware Node we generally need
  # packet forwarding enabled and proxy arp disabled
  net.ipv4.ip_forward = 1
  net.ipv4.conf.default.proxy_arp = 0
  # Enables source route verification
  net.ipv4.conf.all.rp_filter = 1
  # Enables the magic-sysrq key
  kernel.sysrq = 1
  # TCP Explict Congestion Notification
  #net.ipv4.tcp_ecn = 0
  # we do not want all our interfaces to send redirects
  net.ipv4.conf.default.send_redirects = 1
  net.ipv4.conf.all.send_redirects = 0
</code>

As the SELinux should be disabled, put the following line to /etc/sysconfig/selinux:

<code>
  SELINUX=disabled
</code>

Now reboot the machine. After rebooting and loggin in you will see the following reply on vserver-stat call:

<code>
  # vserver-stat
  can not change context: migrate kernel feature missing and 'compat' API disabled: Function not implemented
  #
</code>

It is a natural thing that now virtual environments v345 is unavailable. The following steps will be devoted to making them
work over OpenVZ kernel.

3. Downloading and istalling vzctl package

OpenVZ solution reqires installing a set of tools: vzctl and vzquota packages. Let us download and install this tools:

<code>
  # wget http://openvz.org/download/utils/vzctl-3.0.13-1.i386.rpm
  # wget http://openvz.org/download/utils/vzquota-3.0.9-1.i386.rpm
  # rpm -Uhv vzctl-3.0.13-1.i386.rpm vzquota-3.0.9-1.i386.rpm
</code>

If rpm complains about unresolved dependencies, you'll have to satisfy them first, then repeat the installation.
Then launch the OpenVZ:

<code>
  # /sbin/service vz start
  Starting OpenVZ:                                           [  OK  ]
  Bringing up interface venet0:                              [  OK  ]
  Configuring interface venet0:                              [  OK  ]
  #
</code>

Currently vzlist util is unable to find any VE:

<code>
  # vzlist
  VE not found
  #
</code>

4. Updating different configurations in purpose to make existing templates work

Move the existing templates of guest OSes to the right place:

<code>
  # cd /vz
  # mkdir private
  # mkdir 345
  # mv /vservers/v345 /vz/private/345
</code>

Now it is time for creating configuration files for OpenVZ VPS. Use the basic sample
configuration presented in /etc/sysconfig/vz-scripts/ve-vps.basic.conf-sample file:

<code>
  # cd /etc/sysconfig/vz-scripts
  # cp ve-vps.basic.conf-sample 345.conf
</code>

Update the ON_BOOT string in 345.conf file by typing:

<code>
  .....
  ONBOOT="yes"
  .....
</code>
to make it boot on node restart, and add a couple of strings related to the particular 345 VE:
<code>
  .....
  VE_ROOT="/vz/root/345"
  VE_PRIVATE="/vz/private/345"
  ORIGIN_SAMPLE="vps.basic"
  HOSTNAME="test345.my.org"
  IP_ADDRESS="192.168.0.145"
  .....
</code>

And reboot the machine:

<code>
  # reboot
</code>

5. Testing how the guest OSes succesfully work over OpenVZ. reference to Users Guide of OpenVZ (vzctl).

After rebooting you will be able to see running VE 345 that have been migrated from vserver:

<code>
  # vzlist -a
  CTID      NPROC  STATUS  IP_ADDR         HOSTNAME
  345          5   running 192.168.0.145   test345.my.org
  #
</code>

And run commands on it:

<code>
  # vzctl exec 345 ls -l
  total 48
  drwxr-xr-x    2 root     root         4096 Oct 26  2004 bin
  drwxr-xr-x    3 root     root         4096 Dec 11 12:42 dev
  drwxr-xr-x   27 root     root         4096 Dec 11 12:44 etc
  -rw-r--r--    1 root     root            0 Dec 11 12:13 fastboot
  -rw-r--r--    1 root     root            0 Dec  8 15:33 halt
  drwxr-xr-x    2 root     root         4096 Jan 24  2003 home
  drwxr-xr-x    7 root     root         4096 Oct 26  2004 lib
  drwxr-xr-x    2 root     root         4096 Jan 24  2003 mnt
  drwxr-xr-x    3 root     root         4096 Oct 26  2004 opt
  -rw-r--r--    1 root     root            0 Dec  7 20:17 poweroff
  dr-xr-xr-x   70 root     root            0 Dec 11 12:42 proc
  drwxr-x---    2 root     root         4096 Dec  7 20:17 root
  drwxr-xr-x    2 root     root         4096 Dec 11 12:13 sbin
  drwxrwxrwt    2 root     root         4096 Dec  8 12:40 tmp
  drwxr-xr-x   15 root     root         4096 Jul 27  2004 usr
  drwxr-xr-x   17 root     root         4096 Oct 26  2004 var
  #
</code>

Potential issues:
This work has in progress status. Some issues may take place with tuning the network for containers. To be continued.

[[Category:HOWTO]]