Junos OS Commit Model for Configurations
The device configuration is saved using a commit model—a
candidate configuration is modified as desired and then committed
to the system. When a configuration is committed, the device checks
the configuration for syntax errors, and if no errors are found, the
configuration is saved as
juniper.conf.gz and activated. The formerly active configuration file is saved as
the first rollback configuration file (
juniper.conf.1.gz), and any other rollback configuration files are incremented by
1. For example,
juniper.conf.1.gz is incremented to
juniper.conf.2.gz, making it the second rollback configuration file. The device can
have a maximum of 49 rollback configurations (numbered 1 through 49)
saved on the system.
On the device, the active configuration file and the first three
rollback files (
juniper.conf.gz.3) are located in the
/config directory. If the file
rescue.conf.gz is saved on the system, this file should also be saved in the
/config directory. The factory default files are
located in the
There are two mechanisms used to propagate the configurations between Routing Engines within a device:
Synchronization—Propagates a configuration from one Routing Engine to a second Routing Engine within the same device chassis.
The QFX3500 switch has only one Routing Engine.
To synchronize configurations, use the commit synchronize CLI command. If one of the Routing Engines is locked, the synchronization fails. If synchronization fails because of a locked configuration file, you can use the commit synchronize force command. This command overrides the lock and synchronizes the configuration files.
Distribution—Propagates a configuration across the routing plane on a multichassis device. Distribution occurs automatically. There is no user command available to control the distribution process. If a configuration is locked during a distribution of a configuration, the locked configuration does not receive the distributed configuration file, so the synchronization fails. You need to clear the lock before the configuration and resynchronize the routing planes.
When you use the commit synchronize force CLI command on a multichassis platform, the forced synchronization of the configuration files does not affect the distribution of the configuration file across the routing plane. If a configuration file is locked on a device remote from the device where the command was issued, the synchronization fails on the remote device. You need to clear the lock and reissue the synchronization command.
Committing a Junos OS Configuration and Exiting Configuration Mode
To save Junos OS configuration changes, activate the configuration on the device and exit configuration mode, using the commit and-quit configuration mode command. This command succeeds only if the configuration contains no errors.
We do not recommend performing a commit operation on the backup Routing Engine when graceful Routing Engine switchover is enabled on the router.