TrueNAS SCALETrueNAS SCALE Nightly Development Documentation
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Boot Pool Management

System Settings > Boot contains options for monitoring and managing the ZFS pool and devices that store the TrueNAS operating system.

Changing the Scrub Interval

The Stats/Settings option displays current system statistics and provides the option to change the scrub interval, or how often the system runs a data integrity check on the operating system device.

Go to System Settings > Boot screen and click Stats/Settings. The Stats/Settings window displays statistics for the operating system device: Boot pool Condition as ONLINE or OFFLINE, Size in GiB and the space in use in Used, and Last Scrub Run with the date and time of the scrub. By default, the operating system device is scrubbed every 7 days.

Boot Environment Stats/Settings
Figure 1: Boot Environment Stats/Settings

To change the default scrub interval, input a different number in Scrub interval (in days) and click Update Interval.

Boot Pool Device Management

From the System Settings > Boot screen, click the Boot Pool Status button to open the Boot Pool Status screen. This screen shows the boot-pool and expands to show the devices that are allocated to that pool. Read, write, or checksum errors are also shown for the pool.

Boot Pool Status
Figure 2: Boot Pool Status
Replace Device (Click to expand)

Click the more_vert to open the Actions options. Click Replace, select the device from the Member Disk dropdown, and then click Save.

Attach Device (Click to expand)

Click the more_vert to open the Actions options for a device.

Click Attach, then select a device from the Member Disk dropdown.

Select Use all disk space to use the entire capacity of the new device.

Click Save.

Scrubbing a Boot Pool

A manual data integrity check (scrub) of the operating system device can be initiated at any time.

On the System Settings > Boot screen, and click Scrub Boot Pool to open the Scrub dialog.

Boot Pool Scrub
Figure 5: Boot Pool Scrub

Click Confirm and then Start Scrub.

Boot Environments

TrueNAS supports a ZFS feature known as boot environments. These are snapshot clones of the TrueNAS boot-pool install location that TrueNAS boots into. Only one boot environment is used for booting at a time.

A boot environment allows rebooting into a specific point in time and greatly simplifies recovering from system misconfigurations or other potential system failures. With multiple boot environments, the process of updating the operating system becomes a low-risk operation.

For example, the TrueNAS update process automatically creates a snapshot of the current boot environment and adds it to the boot menu before applying the update. If anything goes wrong during the update, the system administrator can activate the snapshot of the pre-update environment and reboot TrueNAS to restore system functionality.

Boot environments do not preserve or restore the state of any attached storage pools or apps, only the system boot-pool. Storage backups must be handled through the ZFS snapshot feature or other backup options. TrueNAS applications also use separate upgrade and container image management methods to provide app update and rollback features.

To view the list of boot environments on the system, go to System Settings > Boot. Each boot environment entry contains this information:

  • Name: the name of the boot entry as it appears in the boot menu.
  • Active: indicates which entry boots by default if a boot environment is not active.
  • Date Created: indicates the boot environment creation date and time.
  • Space: shows boot environment size.
  • Keep: indicates whether or not TrueNAS deletes this boot environment when a system update does not have enough space to proceed.

To access more options for a boot environment, click to display the list of options:

Activate (Click to expand)

The option to activate a boot environment only displays for boot entries not set to Active

Activating an environment means the system boots into the point of time saved in that environment the next time it is started. Click the more_vert for an inactive boot environment, and then select Activate to open the Activate dialog.

Click Confirm, and then click Activate.

The System Boot screen status changes to Reboot and the current Active entry changes from Now/Reboot to Now, indicating that it is the current boot environment but is not used on next boot.

Clone (Click to expand)

Cloning copies the selected boot environment into a new inactive boot environment that preserves the boot-pool state at the clone creation time.

Click the more_vert for a boot environment, and then select Clone to open the Clone Boot Environment window.

Enter a new name using only alphanumeric characters, and/or the allowed dashes (-), underscores (_), and periods (.) characters.

The Source field displays the boot environment you are cloning. If the displayed name is incorrect, close the window and select the correct boot environment to clone.

Click Save.

Rename (Click to expand)

You can change the name of any boot environment on the System Settings > Boot screen. Click the more_vert for a boot environment, and then select Rename to open the Rename Boot Environment window.

Enter a new name using only alphanumeric characters, and/or the allowed dashes (-), underscores (_), and periods (.) characters.

Verify the boot environment in Name is the one you want to rename.

Click Save.

Delete (Click to expand)

Deleting a boot environment removes it from the System Settings > Boot screen and from the boot menu.

Click the more_vert for a boot environment, and then select Delete to open the Delete dialog. Select Confirm and then click Delete.

You cannot delete the default or any active entries. Because you cannot delete an activated boot entry, this option does not display for activated boot environments. To delete the active boot environment, first activate another entry and then delete the environment you want to remove.

Keep/Unkeep (Click to expand)

By default, TrueNAS prunes boot environments when the boot-pool has no remaining storage space.

Keep toggles with the Unkeep option, and they determine whether the TrueNAS updater can automatically delete this boot environment if there is not enough space to proceed with an update.

Click the more_vert for a boot environment, and then select Keep to open the Keep dialog. Select Confirm and then click Keep Flag.

The boot environment action list removes the Keep option and adds Unkeep.

This makes the boot environment subject to automatic deletion if the TrueNAS updater needs space for an update.