Hi Folks,
Just my 2 cents on this…
Starting in Junos OS Release 15.1, certain hardware platforms run an upgraded FreeBSD kernel instead of older versions of FreeBSD.
Direct validation of the running configuration does not work for upgrading to Junos OS with upgraded FreeBSD from Junos OS based on older versions of the FreeBSD kernel. Therefore, when upgrading or downgrading between Junos OS and Junos OS with upgraded FreeBSD, you might have to validate on a different host. It does not matter where that other host is, as long as you can reach it with NETCONF over SSH (see Establishing an SSH Connection for a NETCONF Session). The target system uses the network to contact the other host, run the validation and authentication, and return the result.
Upgrading to Junos OS with upgraded FreeBSD reformats the file system. Only specific files and directories are preserved unless precautions are taken. By default, the upgrade process only preserves the following directories:
/config
/etc/localtime
/var/db
/var/etc/master.passwd
/var/etc/inetd.conf
/var/etc/pam.conf
/var/etc/resolv.conf
/var/etc/syslog.conf
/var/etc/localtime
/var/etc/exports
/var/etc/extensions.allow
/var/preserve
/var/tmp/baseline-config.conf
/var/tmp/preinstall_boot_loader.conf
Table 1: Upgrade Path to Junos OS with the Upgraded FreeBSD
Current Router’s Junos OS Release
|
Release Supporting Junos OS with Upgraded FreeBSD
|
Upgrade Path
|
Example
|
earlier than Release 12.3
|
15.1
|
Upgrade in multiple steps, skipping no more than two releases in one upgrade.
|
To upgrade from Release 12.1, upgrade first to Release 13.1, then to Release 14.1, then from there to either Release 15.1 or 16.1.
|
12.3 to 13.2
|
15.1
|
Upgrade in two steps.
|
To upgrade from Release 12.3, first upgrade to Release 13.3, then upgrade to Release 15.1.
To upgrade from Release 13.2, first upgrade to Release 14.2, then upgrade to Release 15.1, 16.1, or 17.1.
|
13.3 to 14.2
|
15.1
|
Upgrade in a single step.
|
To upgrade from Release 13.3, upgrade directly to Release 15.1.
To upgrade from Release 14.2, upgrade directly to either Release 15.1, 16.1, or 17.1.
|
https://www.juniper.net/documentation/en_US/junos/topics/task/installation/junos-os-upgrading-kernel-freebsd10.html