Table of contents
- What Junos commit check validates
- Why commit check and commit are different
- What to do after a successful commit check
What Junos commit check validates
Use commit check before activation
commit check validates pending configuration for syntax and dependencies without applying the changes.
The command is useful when you want to validate a proposed configuration without applying it immediately. A pending configuration can therefore be checked while the changes remain unapplied. That gives you a validation-only step before deciding whether to proceed with activation.
The scope of the check is specific. commit check validates syntax and dependencies. It is appropriate for checking whether the pending configuration satisfies those configuration requirements. The check should not be treated as proof of a particular runtime outcome; its role is to validate the configuration within the stated syntax and dependency scope.
A basic validation step is:
commit check
After entering the command, use the result to decide whether the pending configuration is ready for the next stage. A successful check means that the configuration has passed the relevant validation step. It does not mean that the new settings are already active, because commit check does not apply the pending changes.
This distinction matters when activation is not yet wanted. If the immediate goal is only to validate the pending configuration, the check addresses that goal without changing the active configuration. The validation result and the activation decision remain separate, so a successful check does not automatically turn into an active configuration.
What a failed check means
A configuration commit can fail when the configuration includes incorrect syntax, and incorrect syntax causes the commit check to fail. Dependencies are also part of the validation scope. A failed check therefore indicates that the pending configuration has not passed the requirements being checked and should not be treated as ready for direct activation.
The appropriate response is to review and correct the pending configuration rather than interpret the failure as an activation result. The check identifies a configuration problem within its validation scope. Once the relevant problem has been resolved, run commit check again before deciding whether to activate the changes.
This keeps the workflow focused. The command answers whether the pending configuration passes syntax and dependency validation without applying it. It does not establish a particular operational result, and it does not perform the later activation step. Treating those as separate questions helps prevent a failed check from being mistaken for a completed configuration change or a successful check from being mistaken for an active one.
Why commit check and commit are different
Validation is not activation
The difference between commit check and commit is the stage completed by each command. commit check validates the pending configuration while leaving the changes unapplied. The activation stage is different: the previously prepared configuration is activated and becomes the current, operational device configuration.
Choose commit check when the immediate objective is validation without activation. Choose a real commit when the pending changes have passed the relevant validation and are intended to become active. The commands are therefore not interchangeable names for the same result. One stops at validation, while the other carries the prepared configuration through the activation stage.
The workflow has a preparation stage and an activation stage. In the preparation stage, the commit is validated and a new database along with necessary files is generated. In the activation stage, the previously prepared configuration is activated and becomes the current operational device configuration. The first stage prepares and validates; the second changes which configuration is operational.
A successful commit check should consequently be read as a validation result, not as evidence that the device is already using the pending settings. If the changes are not meant to take effect yet, stopping after the check preserves the validation-only objective. If the changes are meant to take effect, the activation step still has to be completed.
A real commit also performs a check
When you enter the commit command, the configuration is first checked for syntax errors. A comparison of commit check and commit also shows that both validate the new configuration. This is why a syntax problem can appear during either workflow.
The final state is different when the commands complete successfully. commit check stops after validation and does not activate the configuration. A real commit continues to the activation stage, where the prepared configuration becomes the current operational device configuration. The real commit therefore does not bypass validation; it is used when validation and activation should be completed together.
Running commit check first does not eliminate the need for a real commit. The earlier command validates the pending configuration without applying it. If the changes should later become active, a real commit is still required to perform that activation. The commands can appear in sequence because they serve different purposes: the first creates a validation decision point, and the second activates the accepted changes.
When choosing between them, ask whether the goal is only to validate the pending configuration or to make the prepared changes active. For validation only, use commit check. For activation, use commit, understanding that the real commit also checks the configuration before completing its activation work.
What to do after a successful commit check
The transition from checking to activation
After a successful commit check, the next step depends on the intended state of the pending changes. If they should remain unapplied, the validation step has met its purpose. If they should take effect, issue a real commit. Because commit check does not activate the configuration, a real commit is needed when the pending changes should become active.
The decision can be represented as:
commit check
If the changes should remain pending, stop after validation. If the changes should become active, enter:
commit
This is the transition from checking to activation. A successful check supports moving forward, but it does not itself complete the transition. The activation decision determines whether the pending configuration should become the device's current operational configuration.
The sequence is useful when activation should remain a deliberate decision. First validate the pending configuration without applying it. Then, when the changes are intended to take effect, perform the real commit. This aligns each command with its intended result: checking first and activating only when appropriate.
What the real commit does
The configuration-mode commit command saves configuration changes to the configuration database and activates the configuration on the device. Its result is therefore different from the result of commit check. The check validates pending changes without applying them; the real commit saves and activates them.
The command can be issued from any hierarchy level. A documented configuration-mode workflow is:
[edit]
user@host# commit
commit complete
[edit]
The important distinction is the result represented by the command. A real commit is the activation step for changes that should take effect. The command first checks the configuration for syntax errors as part of the commit process, and the prepared configuration can then become the current operational device configuration when the commit completes.
After a successful check, use commit only when the pending changes are intended to be saved and activated. If activation is not desired, do not confuse successful validation with an already completed configuration change. commit check leaves the changes unapplied, while commit is used to save and activate them.
The complete workflow is therefore straightforward: enter commit check, address any syntax or dependency problem identified by validation, and then enter commit when the pending configuration should become active. This preserves the distinction between acceptance by the configuration checks and the separate decision to activate the prepared settings.
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