[rancid] Rollback functionality and potential pitfalls

[andrew.brennan+rancid at drexel.edu]

One complication would be cases where a command's default state was one that 
isn't normally displayed in the configs.  You could do the CVS diff between 
good/bad configs and then parse for +/- to remove/add any change that was 
shown.  Then, parse the "no shutdown" so that you weren't doing something like 
"no no shutdown" (remove 'no' when present, add 'no' for other diff'd lines).

That *might* address the non-displayed default config lines, but I'm not sure 
I've thought through this completely yet.  You'll still have issues where lines 
are eliminated from the RANCID store (passwds, etc.).

The other option would be to create a copy of the old/good config file and copy 
it directly to startup-config for the next reboot.  You still have an issue 
with lines eliminated by RANCID, though.

andrew.

On Tue, 12 Feb 2013, Ramon wrote:

> Hello all,
> 
> I am currently looking in to a way to implement rollback functionality using
> rancid. What would it take to reverse bad changes and restore the config of
> a cisco device back to a previous saved version?
> 
> I ask because just pushing the original config on top of the modified
> version would not remove or flush out certain statements, possibly leaving
> duplicates that would have to be removed manually.
> 
> My first idea was to create a negative file, by generating a "no statement"
> for every line in the new config that does not match the old config. After
> pushing the negative file and removing the changes I would push the old
> config to restore any of the deleted statements.
> 
> Feedback on any foreseeable issues such as possible hierarchical problems
> (interfaces, acls, bgp) would be very welcomed.
> 
> Thanks,
> Ramon
> 
>