Managing Multiple Boot Environments

A boot environment, also called a BE, is a bootable instance of an OpenSolaris operating system image, plus any other application software packages that are installed into that image. You can maintain multiple boot environments on a single system, and each boot environment can have a different software version installed.

Upon the initial installation of the OpenSolaris operating system, a boot environment is created on your system. Use the Boot Environment Management tool or the beadm command to administer additional boot environments on your system.

Why Use Multiple Boot Environments?

With multiple boot environments, the process of updating software becomes a low risk operation because you are able to create backup boot environments before making any software updates to your system. If necessary, you have can boot a backup BE.

Note - The process of creating backup boot environments does not create a backup of all the files on your system and is not the same as backing up a file system.

The ability to create different boot environments enables you to have different environments for different versions of tools that you use. Shared files are not affected by creating a new boot environment. If you modify files in a newer boot environment, and then boot to an older boot environment, the files are also modified for that boot environment. You cannot retrieve an older version of a shared file from an older boot environment.

Here are some specific examples where having more than one OpenSolaris boot environment is useful:

The process of updating all of the packages in your active OpenSolaris boot environment that have updates available automatically creates a clone of that boot environment. Packages are updated in the clone, rather than in the original boot environment. After the new clone is activated, it becomes the new default boot environment on the next reboot. The original boot environment remains on the GRUB menu as an alternate selection.
Use the Boot Environment Management tool or the beadm list command to display a list of all the boot environments on the system, including the backup boot environment that still has its original, unchanged software. If you are not satisfied with the updates made to the current default boot environment, you can use the beadm activate command to make the backup boot environment the default boot environment.
You can maintain more than one boot environment on your system at the same time and perform various upgrades on each of them. For example, you can clone a boot environment by using the beadm create command. A clone is a bootable copy of a boot environment. Then, you can install, test, and update different software packages on the original boot environment and on its clone.
Although only one boot environment can be active at any given time, you can mount an inactive boot environment by using the beadm mount command. Then you can use the pkg image-update command with the -R option to update all of the packages in that inactive, mounted environment that have available updates. Or, you can use the pkg install package-name command, with the -R option to update specific packages in that boot environment.

Using the Boot Environment Management Tool

You can use the Boot Environment Management tool to manage your boot environments. The tool is part of the Package Manager application.

With the Boot Environment Management tool, you can do the following:

Display information about all of the boot environments on your installed system
Delete old or unused boot environments
Change the default boot environment on your system
Activate a boot environment

Note - Using the Boot Environment Management tool does not provide all of the options for managing your boot environments that is available by using the beadm command. For more information, see the beadm(1M) man page.

How to Access the Boot Environment Tool

Start Package Manager by choosing System > Administration > Package Manager, or by clicking the Package Manager icon on the desktop.
Choose File > Boot Environment Management.
The Boot Environment Management window opens, displaying all of the available boot environments that are on your installed system. Also displayed is the name of the operating system, the date the boot environment was created, and the size of the boot environment, in Gbytes.
- To delete a boot environment, click the Delete radio button, then click Ok.
- To change the default boot environment, place a check mark next the new default boot environment, then click Ok.
- To activate a new boot environment, click the Active on Reboot radio button, then click Ok.
  The new boot environment becomes active on the next system reboot.