Using Kron to Roll Back Configurations
Today I was chatting on IRC with some colleagues, and we were trying to come up with the best way to roll back to the startup-config without a reboot. This would be useful in situations where you are working remotely and may potentially lose access to the device you are configuring.
The best method I came up with was to use the Kron command:
kron occurrence RELOAD-CONFIG in x oneshot policy-list RELOAD-CONFIG ! kron policy-list RELOAD-CONFIG cli configure replace nvram:startup-config force !
Where x is the number of minutes before the configuration refresh.
Very nice when you can’t afford the downtime of having your device reboot, especially a device like a 6500 that just seems to take for ever to come back up fully.
Edit:
I decided to try to see if I could run it using one command. TCL could be used, but honestly… TCL for 4 lines? That’s just… silly. So instead I used a combination of macros and aliases:
switch# switch#conf t Enter configuration commands, one per line. End with CNTL/Z. switch(config)#macro name refresh_config Enter macro commands one per line. End with the character '@'. kron occ CFG in 2 oneshot policy-list CFG kron policy-list CFG cli configure replace nvram:startup-config force @ switch(config)#alias configure ref macro global apply refresh_config switch(config)#do sh run | i ipv6 switch(config)#ref Kron: Policy Accepted, Policy CFG needs to be configured switch(config)#ipv6 unicast-routing switch(config)#end switch#sh 00:40:26: %SYS-5-CONFIG_I: Configured from console by conso switch#sh run | i ipv6 ipv6 unicast-routing switch#sh kron sch Kron Occurrence Schedule CFG inactive, will run once in 0 days 00:01:22 switch#sh kron sch Kron Occurrence Schedule CFG inactive, will run once in 0 days 00:00:58 switch#sh kron sch Kron Occurrence Schedule CFG inactive, will run once in 0 days 00:00:24 switch#sh kron sch Kron Occurrence Schedule CFG inactive, will run once in 0 days 00:00:05 switch# 00:42:16: Rollback:Acquired Configuration lock. switch#sh kron sch Kron Occurrence Schedule switch#sh run | i ipv6 switch#
Just as convoluted, and just as pointless. But it IS do-able. But again, for 4 lines, it’s not worth the effort.
