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Configuring Root Partitions on ACX Series Routers

 

The dual-root partitions help your ACX Series routers to remain functional even if the file system is corrupted. Also, it helps to recover the file system in case of corruption.

Dual-Root Partitioning ACX Series Routers Overview

Dual-root partitioning allows the ACX Series router to remain functional even if there is file system corruption and to facilitate easy recovery of the file system. Dual-root partitioning means that the primary and backup Junos OS images are kept in two independently bootable root partitions. If the primary root partition becomes corrupted, the system can still boot from the backup Junos OS image located in the other root partition and remain fully functional.

Note

ACX5048 and ACX5096 routers do not support dual-root partitioning. All other ACX routers run with dual-root partitioning.

This section contains the following topics:

Boot Media and Boot Partition on the ACX Series Routers

With dual-root partitioning, the ACX Series router first tries to boot the Junos OS from the primary root partition and then from the backup root partition on the internal NAND flash. If both primary and backup root partitions of the internal NAND flash fail to boot, you must insert a USB storage media with a copy of the Junos OS from which to boot.

The following is the storage media available on the ACX Series router:

  • USB media emergency boot device

    Note

    The USB media device is not dual-root partitioned.

  • Dual, internal NAND flash device (first daOs1, then daOs2)

Important Features of the Dual-Root Partitioning Scheme

The dual-root partitioning scheme has the following important features:

  • The primary and backup copies of Junos OS images reside in separate partitions. The partition containing the backup copy is mounted only when required. With the single-root partitioning scheme, there is one root partition that contains both the primary and the backup Junos OS images.

  • The request system software add command for a Junos OS package erases the contents of the other root partition. The contents of the other root partition will not be valid unless software installation is completed successfully.

  • Add-on packages, such as jais or jfirmware, can be reinstalled as required after a new Junos OS image is installed.

  • The request system software rollback command does not delete the current Junos OS image. It is possible to switch back to the image by issuing the rollback command again.

Understanding How the Primary Junos OS Image with Dual-Root Partitioning Recovers on the ACX Series Router

If the ACX Series Universal Metro router is unable to boot from the primary Junos OS image and boots up from the backup Junos OS image in the backup root partition, a message appears on the console at the time of login indicating that the device has booted from the backup Junos OS image.

Note

ACX5048 and ACX5096 routers do not support dual-root partitioning.

Because the system is left with only one functional root partition, you should immediately restore the primary Junos OS image using one of the following methods:

  • Install a new image using the CLI. When you install the new image, the new image is installed on only one partition–the alternate partition, meaning the router is now running two images. When you reboot, the router boots from the newly installed image, which becomes the primary image. So now there are two different images running on the router. Run the installation process again to update the other partition.

  • Use a snapshot of the backup root partition by entering the request system snapshot slice alternate command. After the primary root partition is recovered using this method, the device will successfully boot from the primary root partition on the next reboot. After the procedure, the primary root partition will contain the same version of Junos OS as the backup root partition.

    Note

    You can use the CLI command request system snapshot slice alternate to back up the currently running root file system (primary or secondary) to the other root partition on the system.

    You can use this command to:

    • Save an image of the primary root partition in the backup root partition when the system boots from the primary root partition.

    • Save an image of the backup root partition in the primary root partition when the system boots from the backup root partition.

    Warning

    The process of restoring the alternate root by using the CLI command request system snapshot slice alternate takes several minutes to complete. If you terminate the operation before completion, the alternate root might not have all required contents to function properly.

Junos OS Release 12.2 or Later Upgrades with Dual-Root Partitioning on ACX Series Routers

Note

If you are upgrading to Junos OS Release 12.2 without transitioning to dual-root partitioning, use the conventional CLI installation method.

To format the media with dual-root partitioning while upgrading to Junos OS Release 12.2 or later, use either of the following installation methods:

Note

ACX5048 and ACX5096 routers do not support dual-root partitioning. All other ACX routers run with dual-root partitioning.

  • Installation using a USB storage device. We recommend this method if console access to the system is available and the system can be physically accessed to plug in a USB storage device. See Installing Junos OS Using a USB Storage Device on ACX Series Routers.

  • Installation from the CLI. We recommend this method only if console access is not available. This installation can be performed remotely. See Installing Junos OS Upgrades from a Remote Server on ACX Series Routers.

Example: Installing Junos OS and Configuring a Dual-Root Partition on ACX Series Routers Using the CLI

This example shows how to install Junos OS Release 12.2 or later and configure a dual-root partition on ACX Series routers with the CLI.

Requirements

This example requires an ACX Series router. Before you begin, back up any important data.

Overview

This example formats the NAND Flash device and installs the new Junos OS image on the media with dual-root partitioning. Install the Junos OS Release 12.2 or later image from the CLI by using the request system software add command. Partitions are automatically created on ACX Series routers and no option needs to be manually entered for creating partitions. This command copies the image to the device, and then reboots the device for installation. The device boots with the Release 12.2 or later image installed with the dual-root partitioning scheme. The formatting and installation process is scheduled to run on the next reboot. Therefore, we recommend that this option be used together with the reboot option.

Note

The process might take 15 to 20 minutes. The system is not accessible over the network during this time.

Caution

Using the request system software add command erases the existing contents of the media. Only the current configuration is preserved. You should back up any important data before starting the process.

Note

Dual, internal NAND Flash device (first daOs1, then daOs2) and USB storage device are the storage media available on the ACX Series router. The USB storage device is not dual-root partitioned.

In this example, add the software package junos-juniper-12.2R1.9-domestic.tgz with the following options:

  • no-copy option to install the software package. However, do not save the copies of the package files. You should include this option if you do not have enough space on the internal media to perform an upgrade that keeps a copy of the package on the device.

  • no-validate option to bypass the compatibility check with the current configuration before installation starts.

  • reboot option to reboot the device after installation is completed.

Configuration

CLI Quick Configuration

To install Junos OS Release 12.2 or later and configure dual-root partitioning on ACX Series routers, copy the following command, paste it in a text file, remove any line break, and then copy and paste the command into the CLI.

From operational mode, enter:

Step-by-Step Procedure

To install Junos OS Release 12.2 or later and configure a dual-root partition:

  1. Upgrade the ACX Series router to Junos OS Release 12.2 or later using the CLI.
  2. Install Junos OS Release 12.2 or later and configure the dual-root partition.

Results

In operational mode, confirm your configuration by entering the show system storage command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Sample output on a system with dual-root partitioning that displays information about the root partition that is mounted (only one root partition is mounted at a point in time):

If you are done configuring the device, enter commit in configuration mode.

You can issue the fdisk command from the Junos prompt to display information about the entire partition format on the NAND Flash device. All ACX Series routers run with dual-root partitioning. The following example displays the partition details on an ACX Series router with dual-root partitions:

In the preceding example, partition 1 and 2 contain two partitions each internally, a root partition and a configuration partition.

Verification

Confirm that the configuration is working properly.

Verifying the Partitioning Scheme Details

Purpose

Verify that the partitioning scheme details on the ACX Series router were configured.

Action

In operational mode, enter the show system storage command. For details about the output of this command and the descriptions of the output fields, see show system storage.