Juniper MX480 Hardware Manual page 272

NOTE: To reinstall Junos OS, you boot the router from the removable media. Do not insert the
removable media during normal operations. The router does not operate normally when it is
booted from the removable media.
When the router boots from the storage media (removable media, CompactFlash card, or hard disk) it
expands its search in the /config directory of the routing platform for the following files in the following
order: juniper.conf (the main configuration file), rescue.conf (the rescue configuration file), and juniper.conf.1
(the first rollback configuration file). When the search finds the first configuration file that can be loaded
properly, the file loads and the search ends. If none of the file can be loaded properly, the routing platform
does not function properly. If the router boots from an alternate boot device, Junos OS displays a message
indication this when you log in to the router.
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