This ensures the following gptfdisk warning won't happen:
```
Warning: File size is not a multiple of 512 bytes! Misbehavior is likely!
```
Additionally, helps towards aligning the partition to be more optimal
for the underlying storage.
It is actually impossible to align for the actual underlying storage
optimally because we don't know what the block device will be!
But aligning on 1MiB should help.
This is a bit of a thorny issue. See, the actual `diskSize` variable is
for the *total* disk size, not for the filesystem!
The automatic numbers are meant to compute the *filesystem* required
space. So we have to add any other reserved space!
We have different requirements for reserved space. E.g. there could be
none (when it's actually a filesystem image). There could also be 1MiB
for alignment for an MBR image, legacy+gpt needs 2MiB, then GPT with an
ESP ("bootSize") needs to take the boot partition and GPT size into
account too!
Though luckily(?) for this latter situation we can cheat! As noted in the
change, `bootSize` is NOT the boot partition size. It is actually the
offset where the target filesystem starts.
Reserved space includes:
- inodes space in use (2 blocks per)
- about 5.2% of the space
The 5.2% reserved space was computed empirically when working on a
previous EXT4 image builder. It seems to stabilize around 5% even for
much larger filesystems.
On some filesystems, `du` without `--apparent-size` will not give the
actual size for a file. Using `--apparent-size` will give us the actual
file size.
Though, this is not actually correct still. 1000 × 1 bytes is not 1000
bytes. It is 1000 × ceil(filesize/blockSize)*blockSize.
So instead of adding up the actual file sizes. We are adding up the
block sizes.
Note that this also changes the builder to work with *bytes*, rather
than with any other units. Doing maths on bytes is less likely to go
awry than doing it on other units.
This might be a bit debatable but upstream uses "xx" instead of "++"
when using it as identifier / in the code (file/directory names, build
scripts, website URLs, etc.) so we should probably too.
And at least the attribute name and pname will be consistent now.
Samuel Dionne-Riel
lassulus
Martin Weinelt
Guillaume Girol
Thomas Gerbet
Lassulus
Domen Kožar
Graham Christensen
Izorkin
Fabian Affolter
Jonathan Ringer
John Ericson
Michele Guerini Rocco
Symphorien Gibol
Mario Rodas
Jan Tojnar
José Romildo Malaquias
Sandro
rnhmjoj
Luke Granger-Brown
Michael Weiss
Fabian Affolter
Robert Schütz