vzupgrade tool can be used to upgrade VHS 7 to 8 and CentOS 7 to VzLinux 8.
Normally, the vzupgrade script shouldbe installed via the RPM package from VzLinux repos:
yum install -y yum-utils
yum-config-manager --add-repo http://repo.virtuozzo.com/vzlinux/7/x86_64/os/
yum install -y --nogpgcheck vzupgrade
Make sure to disable the VzLinux repo before real upgrade
rm -f /etc/yum.repos.d/repo.virtuozzo*
Before running vzupgrade, installall CentOS updates:
yum update -y
Now run the pre-upgrade check, for CentOS one should use "--skip-vz" option:
vzupgrade check --skip-vz
If no problems were found, then the upgrade itself:
vzupgrade install --skip-vz
The system will be rebooted into a special mode (using "Upgrade-initramfs" initrd image). One can specify --reboot option to make this reboot happen automatically.
Once the upgrade is finished, the system will be automatically rebooted once again into upgraded system.
The tool supports launching custom scripts before the check and before the upgrade phases. All executable files found inside the /usr/share/vzupgrade/pre-check folder will be launched just before the check, and all executable files found inside the /usr/share/vzupgrade/pre-install folder will be launched just before the upgrade stage starts.
Note that we don't expect these custom scripts to print anything on the screen. They should use their own log files if needed.
Also make sure that it is possible that user will launch 'check' or 'install' multiple times. The custom scripts should be ready for this.