Cisco IOS Configuration Fundamentals Configuration Guide, Release 12.2SR

Configuration Logger Persistency

The Configuration Logger Persistency feature increases the operational robustness of Cisco IOS configuration and provisioning actions by implementing a "quick-save" functionality. When the Configuration Logger Persistency feature is configured, Cisco IOS software saves just the commands entered since the last startup-config file was generated, rather than saving the entire startup configuration.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for Configuration Logger Persistency" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for Configuration Logger Persistency

•Information About Configuration Logger Persistency

•How to Configure the Configuration Logger Persistency Feature

•Configuration Examples for the Configuration Logger Persistency Feature

•Additional References

•Command Reference

•Feature Information for Configuration Logger Persistency

Prerequisites for Configuration Logger Persistency

To enable the Configuration Logger Persistency feature, you must have disk0: configured and an external flash card inserted on the router.

To achieve optimum results from the Configuration Logger Persistency feature, you must have Cisco IOS Release 12.2(33)SRA, Release 12.4(11)T, Release 12.2(33)SXH, or Release 12.2(33)SB installed on your system.

Information About Configuration Logger Persistency

To understand and use the Configuration Logger Persistency feature, you should be familiar with the following concepts:

•Use of Configuration Logger Persistency to Save Configuration Files

•Persisted Commands

Use of Configuration Logger Persistency to Save Configuration Files

Cisco IOS software uses the startup-config file to save router configuration commands across reloads. This single file contains all the commands that need to be applied when the router reboots. The startup-config file gets updated every time a write memory command or copy url startup-config command is entered. As the size of the running-config file grows, the time to save the startup-config file to the NVRAM file system increases as well. Startup-config files can be 1 MB and larger. For files of this size, making a single-line change to the startup-config file requires that the entire startup-config file is saved again even though most of the configuration has not changed.

The Configuration Logger Persistency feature implements a "quick-save" functionality. The aim is to provide a "configuration save" mechanism where the time to save changes from the startup-config file is proportional to the size of the incremental changes (with respect to the startup-config file) that need to be saved.

The Cisco IOS configuration logger logs all changes that are manually entered at the command-line prompt. This feature also notifies the registered clients when changes to the log occur. The contents of the configuration log are stored in the run-time memory—the contents of the log are not persisted after reboots.

The Configuration Logger Persistency feature provides a mechanism to persist the configuration commands entered by users across reloads. Only the commands entered at the command-line interface (CLI) (that is, the commands entered in configuration mode) are persisted across reload. This feature uses the Cisco IOS secure file system to persist the configuration commands that are generated.

Note The Cisco IOS configuration logger is different from the system message logging (syslog) facility. Syslog is a general logging facility for tracking system messages. The configuration logger tracks information about configuration commands entered at the CLI.

Persisted Commands

The persisted commands from the Cisco IOS configuration logger are used as an extension to the startup configuration. These saved commands provide a quick-save capability. Rather than saving the entire startup-config file, Cisco IOS software saves just the commands entered since the last startup-config file was generated.

Only the logged commands are persisted. The following additional data from the configuration logger are not persisted:

•User who logged the command

•IP address from which the user logged in

•Session and log indexes for the logged command

•Time when the command was entered

•Pre- and post-NVGEN output associated with the entered command

•Parser return code output for the entered command

The persisted commands' primary purpose is for use as a quick-save extension to the startup-config file. The additional information associated with a configuration command is not useful for quick-save purposes. If you need the additional information to be persisted across reboots (for auditing purposes), complete the following steps:

1. Enable configuration logger notification to syslog

2. Enable the syslog persistence feature

Alternatively, Cisco Networking Services, CiscoView, or other Network Management systems that manage Cisco IOS devices to keep track of configuration changes in an off-the-box storage solution can be used.

By default, upon reload, the persisted commands are appended to the startup-config file. These commands are applied only when you explicitly configure this behavior using a CLI configuration command.

How to Configure the Configuration Logger Persistency Feature

This section provides information about the following:

•Enabling the Configuration Logger Persistency Feature (required)

•Verifying and Troubleshooting the Configuration Logger Persistency Feature (optional)

Enabling the Configuration Logger Persistency Feature

The Configuration Logger Persistency feature implements a quick-save mechanism so that the time to save changes from the startup configuration is proportional to the size of the incremental changes (with respect to the startup configuration) that need to be saved. The persisted commands from the Cisco IOS configuration logger will be used as an extension to the startup configuration. The saved commands, which are used as an extension to the startup configuration, provide a quick-save ability. Rather than saving the entire startup-config file, Cisco IOS software saves just the commands entered since the last startup-config file was generated.

To enable the Configuration Logger Persistency feature, perform the following task.

SUMMARY STEPS

1. enable

2. configure terminal

3. archive

4. log config

5. logging persistent {auto | manual}

6. logging persistent reload

7. logging size entries

DETAILED STEPS

Verifying and Troubleshooting the Configuration Logger Persistency Feature

Three commands can be used to verify, archive, and clear the contents of the configuration log. For troubleshooting purposes, the command in Step 4 turns on debugging.

SUMMARY STEPS

1. show archive log config persistent

2. clear archive log config persistent

3. archive log config persistent save

4. debug archive log config persistent

DETAILED STEPS

Step 1 show archive log config persistent

This command displays the persisted commands in the configuration log. The commands appear in a configlet format. The following is sample output from this command:

Router# show archive log config persistent

!Configuration logger persistentarchive 

 log config 

 logging persistent auto 

 logging persistent reload 

archive 

 log config 

logging size 10

logging console 

interface loop 101 

 ip address 10.1.1.1 255.255.255.0

 ip address 10.2.2.2 255.255.255.0

 no shutdown 

Step 2 clear archive log config persistent

This command clears the configuration logging persistent database entries. Only the entries in the configuration logging database file are deleted. The file itself is not deleted because it will be used to log new entries. After this command is entered, a message is returned to indicate that the archive log is cleared.

Router# clear archive log config persistent 

Purged the config log persist database entries successfully 

Router# 

Step 3 archive log config persistent save

This command saves the configuration log to the Cisco IOS secure file system. For this command to work, the archive log config persistent save command must be configured.

Step 4 debug archive log config persistent

This command turns on the debugging function. A message is returned to indicate that debugging is turned on.

Router# debug archive log config persistent 

debug archive log config persistent debugging is on

Configuration Examples for the Configuration Logger Persistency Feature

This section provides a sample configuration of the Configuration Logger Persistency feature on a Cisco 7200 series router.

•Configuration Logger Persistency Configuration on a Cisco 7200 Series Router: Example

Configuration Logger Persistency Configuration on a Cisco 7200 Series Router: Example

In this example, each configuration command is saved automatically to the Cisco IOS secure file system, configuration commands saved in the configuration logger database (since the last write memory command) are applied sequentially to the running-config file, and the maximum number of entries retained in the configuration log is set to 10:

Router> enable

Router# configure terminal

Enter configuration commands, one per line. End with CNTL/Z. 

Router(config)# archive

Router(config-archive)# log config

Router(config-archive-log-config)# logging persistent auto

configuration log persistency feature enabled. Building configuration... [OK] 

Router(config-archive-log-config)# logging persistent reload

Router(config-archive-log-config)# logging size 10

Router(config-archive-log-config)# archive log config persistent save

Router(config-archive-log-config)# end

Router#

Additional References

The following sections provide references related to the Configuration Logger Persistency feature.

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Configuration Fundamentals Command Reference at http://www.cisco.com/en/US/docs/ios/fundamentals/command/reference/
cf_book.html. For information about all Cisco IOS commands, use the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or a Cisco IOS master commands list.

•archive log config persistent save

•clear archive log config

•debug archive log config persistent

•logging persistent (config-archive-log-cfg)

•logging persistent reload

•show archive log config

Feature Information for Configuration Logger Persistency

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Glossary

API—application programming interface.

CAF—command action function.

CDP—Cisco Discovery Protocol.

CSB—Command Status Block.

HA—high-availability architecture.

MIB—Management Information Base.

NAF—NVGEN action function.

NVGEN—nonvolatile generation.

NVRAM—nonvolatile Random Access Memory.

parse chain—A sequence of C language macros defining the syntax of a Cisco IOS command.

RP—Route Processor.

SNMP—Simple Network Management Protocol.

XML—eXtensible Markup Language.

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Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

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