lost boot partition on drive failure
We had a drive failure on /dev/sda. Everything 'except' boot was on raid5 across sda, sdb, sdc, sdd. I know how to repartition a new drive and rebuild the raid etc, but I don't know how to regenerate the files that reside on the boot partition. I really don't want to re-install as we have lot of custom code and software that may depend on our current libraries and build environment. Any advice would be appreciated.
Re: lost boot partition on drive failure
/boot contains kernel images, (almost certainly) initramfs images, system maps, and a few other less important kernel boot files. All these may have to be recovered from the CD although you can also download them. You will need as an absolute minimum a kernel image (vmlinux) and an initramfs (initrd.img) to boot. Once you are booted up again, a forced reinstall of your current kernel image package should give you the miscellaneous files.
Most important, /boot contains a grub directory but this can easily be recreated. Create yourself a good /boot partition and run update-grub to recreate your grub data. From the Live CD obviously
Hint for the future: place custom code on a separate partition, something like /opt is often convenient. Then it is much simpler to do a full reinstall without losing anything hard to replace.