Within JUNOS there is a flexible and power way to control your configuration. This gives detail to co-workers, allows you to schedule commits a head, or prepare for rollback and commit when doing risky remote work. It is important to note, unlike IOS, JUNOS does not apply changes immediately. To activate the changes to your candidate configuration you must perform the commit command. Lets explore the commit commands and where you can use them.
Commit is used to make changes to the active candidate configuration.
Commit check runs a check on your syntax to confirm it is correct but does not apply to candidate configuration. Note that it also will not cover you if the changes you are applying will disconnect your remote session.
This will commit will commit a change to the candidate configuration. It will expect another commit in 10 minutes. If it doesn’t receive this it performs a rollback 1, commit, and will revert the device back. Great for those who use remote access to do changes. By default it is 10 minutes but can be configured in minutes from 1 to 65,535. I will cover some rollback tricks in some upcoming posts.
commit at <time>
 [email protected]# commit at 03:00:00 configuration check succeeds commit at will be executed at 2012-11-29 03:00:00 AEST Exiting configuration mode
To confirm and clear a scheduled commit the following commands and verification are used.
show system commit
[email protected]> show system commit commit requested by root via cli @ 2012-11-29 03:00:00 AEST 0 2012-11-28 13:23:18 AEST by root via cli
clear system commit
[email protected]> clear system commit Pending commit cleared
This allow documentation and annotation of what the commit and change to candidate configuration actually did. I cannot recommend this feature ENOUGH!
 [email protected]# commit comment "Changed OSPF Router-ID and area type stanza" commit complete [email protected]> show system commit 0 2012-11-28 15:32:00 AEST by root via cli Changed OSPF Router-ID and area type stanza 1 2012-11-26 12:52:37 AEST by root via cli Added Management interface to FE-0/0/7.0
This commits the configuration and drops the CLI prompt back to operational mode. This is just to make it easier.
This feature is used for platforms that have a redundant Routing engines. It allows the configuration changes to be replicated across engines effortlessly.
Here are some great ways to save configurations and manage them. It is important to understand what each one does to enable to identify where it is appropriate to use what method.