Run script after package install, update?

[Boyan Penkov <boyan.penkov@gmail.com>]

Hello folks,

I'm wiring to ask how to get apt to run a script after a particular
package is installed or updated.  Am I looking for dpkg-triggers or
some apt conf?

Specifically, I have GRUB installed to *every* drive, with the
expectation that all but one drives can fail and the machine will
still boot (to something...).  To this end, after I see apt has
updated grub, I manually run something like:
```
sudo update-grub
sudo grub-install /dev/sda
sudo grub-install /dev/sdb
sudo update-grub
```
I'd like to automate this; if grub is changed, run this script automatically.

Thanks kindly, and cheers!

-- 
Boyan Penkov