Juniper SYSTEM BASICS - CONFIGURATION GUIDE V 11.1.X Configuration Manual page 543

NOTE: This command is functionally equivalent to specifying no backup
image/configuration, but it allows you to leave the backup settings alone and to toggle
autoreversion on and off. This command is undone by using the no boot
revert-tolerance command, which restores the default settings, or the boot
revert-tolerance command. The default settings are count = 3 (crashes) and time
= 1800 (seconds); that is, 3 crashes in 30 minutes.
boot subsystem
boot system
CAUTION: This command attempts to reprogram the SRP boot PROMs, if necessary.
The SRP has a primary and, typically, a backup boot PROM. If the boot system
command is executed on an SRP with no backup boot PROM, the following message
is displayed: " Write to Backup Boot ROM failed." In this instance, this message is
correct, and you can ignore it.
Use to set the boot logic to never revert to the backup image/configuration.
This command does not reboot the system.
Example
host1(config)#boot revert-tolerance never
There is no no version.
See boot revert-tolerance never.
Use to configure the software release the selected subsystem will use the next
time it reboots.
This command does not reboot the subsystem.
Example 1
host1(config)#boot subsystem ct3 rel_1_0_1.rel
The boot backup subsystem version of this command enables you to configure
a backup subsystem for booting.
Example 2
host1(config)#boot backup subsystem ct3 rel_1_0_1.rel
Use the no version to remove the configuration setting.
See boot subsystem.
Use to specify the software release (.rel) file that your system will use when
rebooting.
This command does not reboot the system.
Chapter 9: Booting the System
Configuring Your System for Booting
513