nanobsd: Add an optional CIDATA partition

[senguptaangshuman17_gmail.com]

Summary

To be used when provisioning via nuageinit.

Nuageinit still needs to understand read-only root filesystems and
persist the changes to /cfg.

[senguptaangshuman17_gmail.com]

Address review comments: clarify nanobsd.sh is_defined() comment

[senguptaangshuman17_gmail.com]

Clean up merge conflict markers in defaults.sh

[imp]

Why FAT?

tools/tools/nanobsd/gpt.sh

78

Why FAT?

[senguptaangshuman17_gmail.com]

In D58982#1355684, @imp wrote:

Why FAT?

As per my knowledge, nuageinit(7) manpage accepts either msdosfs (FAT) or cd9660 (ISO9660).
For why FAT was chosen over ISO9660, I need @jlduran's views on this.

[jlduran]

In D58982#1356214, @senguptaangshuman17_gmail.com wrote:

In D58982#1355684, @imp wrote:

Why FAT?

As per my knowledge, nuageinit(7) manpage accepts either msdosfs (FAT) or cd9660 (ISO9660).
For why FAT was chosen over ISO9660, I need @jlduran's views on this.

I have no preference of one over the other. iso9660 sounds like a nice fit since it is inherently read-only; however, msdos is easier to provision. The idea was to replicate what Raspberry Pi images do: the user inserts the SD card into their PC, and it gets mounted as a FAT device that they can modify and easily provision.

tools/tools/nanobsd/customizations.sh

142 ↗

(On Diff #184850)

This change seems unrelated.

tools/tools/nanobsd/defaults.sh

157

This change seems unrelated.

1563

This change seems unrelated.

tools/tools/nanobsd/gpt.sh

290

Why remove this comment?

358

This change seems unrelated.

361

This change seems unrelated.

374

This change seems unrelated.

382

This change seems unrelated.
I think some of these changes should be squashed with D58964.

tools/tools/nanobsd/nanobsd.sh

38

This comment seems unrelated.

[senguptaangshuman17_gmail.com]

Rebase stack on top of D59043 update