Supported Platforms
Resilient Dual-Root Partitions Frequently Asked Questions
This FAQ addresses questions regarding resilient dual-root partitions on EX Series switches and upgrading to Junos OS releases that support resilient dual-root partitions. The resilient dual-root partition feature was introduced on EX Series switches at Junos OS Release 10.4R3. It provides additional resiliency for EX Series switches.
This FAQ covers the following questions:
- How Does Upgrading to Junos OS Release 10.4R3 and Later Differ from Normal Upgrades?
- What Happens If I Do Not Upgrade Both the Loader Software and Junos OS at the Same Time?
- Can I Downgrade Junos OS Without Downgrading the Loader Software?
- Can I Upgrade to a Resilient Dual-Root Partition Release by Using the CLI?
- Will I Lose My Configuration During an Upgrade?
- How Long Will the Upgrade Process Take?
- What Happens to My Files If the System Detects a File System Corruption and Automatic Snapshot is Enabled?
- What Happens to My Files If the System Detects a File System Corruption and Automatic Snapshot is Not Enabled?
- How Will I Be Informed If My Switch Boots from the Alternate Slice Because of Corruption in the Root File System?
- Can I Use Automatic Software Update and Download to Upgrade to a Resilient Dual-Root Partition Release?
- Why Is the Message "At least one package installed on this device has limited support" Displayed When Users Log In to a Switch?
- Where Can I Find Instructions for Upgrading?
How Does Upgrading to Junos OS Release 10.4R3 and Later Differ from Normal Upgrades?
Upgrading from Junos OS Release 10.4R2 or earlier to Release 10.4R3 or later differs from other upgrades in these ways:
- You must upgrade the loader software in addition to installing the new Junos OS image.
- Rebooting after the upgrade reformats the disk from three partitions to four partitions.
- The upgrade process and the reboot take longer time because of the additional time required for upgrading the loader software and for the first reboot after the Junos OS installation (longer than normal because it reformats the disk from three partitions to four). Also, EX8200 switches require an additional reboot per Routing Engine as part of the loader software upgrade.
What Happens If I Do Not Upgrade Both the Loader Software and Junos OS at the Same Time?
You must install a new loader software package if you are upgrading to a release that supports resilient dual-root partitions (Release 10.4R3 and later) from an earlier release (Release 10.4R2 and earlier).
If you upgrade to Release 10.4R3 or later from Release 10.4R2 or earlier and do not upgrade the loader software, the switch will come up and function normally. However, if the switch encounters a problem and cannot boot from the active root partition, it cannot transparently boot from the alternate root partition and you will need to perform a manual reboot.
Table 1: Combinations of Junos OS Versions and Loader Software Versions
Junos OS Release | Loader Software | Notes |
|---|---|---|
Release 10.4R3 and later | New loader software For all EX Series switches except EX8200 switches: For EX8200 switches: | Recommended |
Release 10.4R2 and earlier | Old loader software | If you downgrade to Release 10.4R2 or earlier after having upgraded to the new loader software version, you do not need to downgrade the loader software. The switch will function normally. |
Release 10.4R3 and later | Old loader software For all EX Series switches except EX8200 switches: For EX8200 switches: | The switch will come up and function normally. However, in the event that the switch cannot boot from the active root partition, it will not transparently boot up from the alternate root partition. |
Release 10.4R2 and earlier | New loader software Note: For EX Series switches except EX8200 switches, in Release 10.4R2 and earlier the version number after the timestamp (shown in the previous row) is not displayed, and you cannot verify whether the old or the new loader software version is installed. | The switch will come up and function normally. |
Can I Downgrade Junos OS Without Downgrading the Loader Software?
Yes, when you downgrade from most releases, the new loader software runs seamlessly with the earlier Junos OS version.
 | Note: If you downgrade specifically from Release 10.4R3 or Release 11.1R1 to 10.4R2 or earlier (that is, to a release that does not support resilient dual-root partitions), you must disable the boot-sequencing function. If you do not take this action, the switch will boot on each subsequent reboot from the alternate root partition rather than from the active partition. Disable the boot-sequencing function in one of two ways:
If you are downgrading from Release 10.4R4 or from Release 11.1R2 or later to Release 10.4R2 or earlier, you do not need to disable the boot-sequencing function—the software does it automatically. |
Can I Upgrade to a Resilient Dual-Root Partition Release by Using the CLI?
Yes, you can perform the entire upgrade to resilient dual-root partitions from the CLI. You download both the new loader software and Junos OS packages and install them from the CLI. During the final reboot, the disk is automatically reformatted from three to four partitions.
Will I Lose My Configuration During an Upgrade?
Configuration files are preserved and restored during the reformatting of the disk. We recommend that you save your configuration before upgrading because if there is a power interruption during the installation process, the files might be lost.
How Long Will the Upgrade Process Take?
The process of upgrading to a resilient dual-root partition release takes longer than other upgrades because of the additional step of upgrading the loader software and the longer reboot time required while the disk is reformatted to four partitions during the reboot of the switch that completes the Junos OS upgrade. The reformat results in an additional reboot time of 5 to 10 minutes for EX2200, EX3200, EX4200, and EX4500 switches. For EX8200 switches, the reboot time increases by 10 to 25 minutes per Routing Engine, and additional reboots are required.
What Happens to My Files If the System Detects a File System Corruption and Automatic Snapshot is Enabled?
If you have enabled automatic snapshot, during a reboot, the system automatically takes a snapshot of Junos OS from the alternate root partition (Slice 2) and copies it onto the primary root partition (Slice 1). The system checks each file system partition for corruption. Table 2 shows the action the system takes if corruption is detected and the corrective action that you can take.
Table 2: Actions If Corrupt Files Are Found and Automatic Snapshot is Enabled
Slice 1 | Slice 2 | Slice 3 | Slice 4 | |
|---|---|---|---|---|
s1a | s2a | s3e | s3d | s4d |
/ (root Junos OS) | / (root Junos OS) | /var | /var/tmp | /config |
If a root directory (/) is corrupted, the corrupted file system is not mounted. The switch automatically takes a snapshot of the Junos OS root file system and copies it onto the primary root partition. It boots from the alternate slice, but the next reboot happens from the primary slice. | During early boot, the integrity of /var, /var/tmp, and /config files is verified. If they are corrupted, the corrupted slice is reformatted and the file directory in that slice is lost. | |||
Corrective action: No corrective action is required. | Corrective action: Restore the /var or /config files from the external backup. | |||
What Happens to My Files If the System Detects a File System Corruption and Automatic Snapshot is Not Enabled?
During a reboot, the system checks each file system partition for corruption. Table 3 shows the action the system takes if corruption is detected and the corrective action that you can take.
Table 3: Actions If Corrupt Files Are Found
Slice 1 | Slice 2 | Slice 3 | Slice 4 | |
|---|---|---|---|---|
s1a | s2a | s3e | s3d | s4d |
/ (root Junos OS) | / (root Junos OS) | /var | /var/tmp | /config |
If a root directory (/) is corrupted, the corrupted file system is not mounted and the switch boots from the alternate slice. | During early boot, the integrity of /var, /var/tmp, and /config files is verified. If they are corrupted, the corrupted slice is reformatted and the file directory in that slice is lost. | |||
Corrective action: Issue a request system snapshot command from the good root directory to the corrupted slice. | Corrective action: Restore the /var or /config files from the external backup. | |||
How Will I Be Informed If My Switch Boots from the Alternate Slice Because of Corruption in the Root File System?
If the switch detects corruption in the primary root file system, it boots from the alternate root partition. When this occurs, the type of notification depends on whether you have enabled the automatic snapshot feature or not:
- If the automatic snapshot feature is not enabled:
- If you are logged in through the console port or the management
port:
WARNING: THIS DEVICE HAS BOOTED FROM THE BACKUP JUNOS IMAGE It is possible that the primary copy of JUNOS failed to boot up properly, and so this device has booted from the backup copy. Please re-install JUNOS to recover the primary copy in case it has been corrupted. - The following message is displayed when you issue show chassis alarms:
user@switch> show chassis alarms1 alarms currently active Alarm time Class Description 2011-02-17 05:48:49 PST Minor Host 0 Boot from backup root
- If you are logged in through the console port or the management
port:
- If the automatic snapshot feature
is enabled:
- A banner message appears, indicating that an automatic snapshot operation is in progress. The banner message disappears when the snapshot operation is complete.
- No alarm is issued to indicate that the switch has been rebooted from the alternate partition. However, the switch does log the event.
Can I Use Automatic Software Update and Download to Upgrade to a Resilient Dual-Root Partition Release?
Automatic software update and automatic software download are both supported with upgrading to releases that support resilient dual-root partitions. However, after an automatic installation, you must take the extra step of upgrading the loader software.
Automatic software update is for new members added to a Virtual Chassis that do not have the same software as the master. Once this feature is configured on the Virtual Chassis, any new member added with a different software version will be upgraded automatically.
Automatic software download uses the DHCP message exchange process to download and install software packages.
Why Is the Message "At least one package installed on this device has limited support" Displayed When Users Log In to a Switch?
The following message might be displayed when a user logs in:
Logging to master
..Password:
--- JUNOS 10.4R3.4 built 2011-03-19 22:06:32 UTC
At least one package installed on this device has limited support.
Run 'file show /etc/notices/unsupported.txt' for details.
This message can be safely ignored or you can permanently remove it. It appears because the jloader package file has been detected, and it only appears when Junos OS is installed before the loader software is upgraded (required only for EX8200 switches).
You can permanently remove this message by removing the jloader package and rebooting the system:
user@switch> request system software delete jloader-ex-zzzz
user@switch> request
system rebootWhere jloader-ex-zzzz represents the name of the jloader software package for your platform—jloader-ex2200 for an EX2200 switch, jloader-ex3242 for an EX3200 or EX4200 switch, or jloader-ex8200 for an EX8200 switch.
Where Can I Find Instructions for Upgrading?
The procedure for upgrading to a release that supports resilient dual-root partitions (from a release that does not) is different from the normal upgrade procedure. For instructions on upgrading to a resilient dual-root partition release, see the Release Notes.
