How to increase /boot partition size when installing Ubuntu 14.04 using the "use entire disk and set up encrypted LVM" option?
Solution 1:
Guided partition sizes are specified in /lib/partman/recipes[-arch]/*. The file format is here: http://ftp.dc.volia.com/pub/debian/preseed/partman-auto-recipe.txt
To increase the /boot size, change the maximum size (third number) in the boot section of the default recipe: sudo nano /lib/partman/recipes/30atomic
...
128 512 256 ext2
...
mountpoint{ /boot } .
....
Change the 256 to a something bigger and save. Then, start the installer and use the guided option.