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Installing, Upgrading, Backing Up, and Recovery of VM Host

You can install the Junos OS software package and host software package on the device. The following installation options are available:


The VM Host installation works differently on the QFX10002-60C switch and PTX10002-60C router. See Installing Software Packages on QFX Series Devices and Installing the Software on PTX10002-60C Routers for more details. However, the information on the rollback and snapshot features work the same on QFX10002-60C switches and PTX10002-60C routers.

  • Fresh installation— This installation method can be used for factory installation as well as for recovery after corruption. Fresh installation can be done using Preboot Execution Environment (PXE)/NetBoot or a USB install media package. This method of installation installs the host OS, tools, and the Junos VMs.

    A PXE boot is an environment to boot devices using a network interface independent of available data storage devices or installed operating systems. The PXE environment is built on a foundation of Internet protocols and services . These include TCP/IP, DHCP, and TFTP. This method of installation mostly used for installing the operating system on a device, without depending on the state of the internal media. The required software for network installation is stored on a TFTP server. PXE boot method supports remote installation thereby overcoming the need for an in-person assistance for installation. For more information, see Copying VM Host Installation Package to the PXE Boot Server. After you copy the VM Host Installation Package to the PXE Boot Server, you can use the request vmhost reboot network command and reboot the device to install the software. The device boots from the PXE server and installs the software on both the SSDs.

    You can choose to use the USB disk installation method when the device fails to reboot because of internal media failure or when there is no installed Junos OS. For more information, see Creating an Emergency Boot Device for Routing Engines with VM Host Support.

    On a fresh installation using USB, the following directories are populated with the Junos OS image on both the SSDs:

    • Current.p

    • Backup.p

    • Backup.b

  • Regular installation— This installation method is generally for an upgrade or a downgrade. This procedure can be used to install the runtime installation package on the currently running Junos VM to upgrade or downgrade relevant components. Junos VM performs the dependency check to identify the software components that require an upgrade or a downgrade to ensure compatibility.


The RE-S-X6-64G-LT and RE-MX2K-X8-64G-LT Routing Engines are restricted to boot only the Junos OS with upgraded FreeBSD Limited image. They fail to boot if you try to install or upgrade the device with an image other than the Limited image, which begins with the junos-vmhost-install prefix.

VM Host Upgrade

Every Junos OS release is a group of files bundled together. The Routing Engines RE-MX-X6, RE-MX-X8, and RE-PTX-X8 support only the 64-bit version of Junos OS.


If you have important files in directories other than /config and /var, copy the files to a secure location before upgrading the device. The files under /config and /var (except /var/etc) are preserved after the VM host upgrade.


Before installing software on a device that has one or more custom YANG data models added to it, back up and remove the configuration data corresponding to the custom YANG data models from the active configuration. For more information see Managing YANG Packages and Configurations During a Software Upgrade or Downgrade.

In order to perform VM Host upgrade, use the junos-vmhost-install-x.tgz image. This upgrade installs the host image along with the compatible Junos OS.


To upgrade the Junos OS on RE-S-X6, RE-MX-X8, and RE-PTX-X8 Routing Engines, always use the VM Host Installation Package. Do not use the jinstall package.


Starting with Junos OS Release 21.4R1 and later, on the ACX5448, MX204, MX240, MX480, MX960,MX2010, MX2020, and MX2008 routers with VM host support, during an upgrade or reboot, the root login is required for copying the image from the Junos VM to the Linux host. Before the upgrade, you must delete the system services ssh root-login deny statement or change the configuration to system services ssh root-login deny-password. Once the upgrade is complete, you can add the system service ssh root-login deny statement back to your configuration. See

The following example illustrates the upgrade operation. You can Install multiple software packages and software add-on packages at the same time.

VM Host Rollback

You can revert to the software version that was loaded at the last successful request vmhost software add operation. You can roll back to the previous set of software packages, including the host OS packages, by using the request vmhost software rollback command.

The following example illustrates the software rollback operation. The Routing Engine that has booted from the primary disk by using the set p had booted using the set b before the upgrade.

VM Host Snapshot

The snapshot feature enables you to create copies of the currently running and active file system partitions on a device.

On the device, you can back up the snapshot of the host OS image along with the Junos  OS image. You can use the request vmhost snapshot command to create a VM host recovery snapshot on the backup disk.

Disk Recovery Using the VM Host Snapshot

If the state of the primary disk (disk1) is good and the backup disk (disk2) has to be recovered then use the request vmhost snapshot command to recover the backup disk assuming the Routing Engine is booted from the primary disk. If the state of the secondary disk is not known or the file systems in disk are not in a consistent state, then include partition option in the command i.e. request vmhost snapshot partition.

If the state of the backup disk (disk2) is good and the primary disk (disk1) has to be recovered then use the request vmhost snapshot recovery command to recover the primary disk assuming the Routing Engine is booted from the backup disk. If the state of the primary disk is not known or the partition tables are in bad condition, then include partition option in the command i.e. request vmhost snapshot recovery partition.

To boot from desired disk, you can execute request vmhost reboot { disk1, disk2} command.