watonomous.github.io
[ Software Division : Knowledge Dump ]
Created by [ Stephen Wang] on Jul 03, 2021
Temporary stuff to be sorted later (or not)
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It's very useful to know the distinction between primary partition and
logical partitions. In short, in an MBR schemed disk (which is probably
what you deal with all the time since you want your boot drives to be
legacy-compatible), there can only be four primary partitions in total.
Three actual partitions that carry a "bootable" flag so that BIOS can
tell the bootloader where to look to initialize an operating system
(https://neosmart.net/wiki/mbr-boot-process/); plus an "extended"
partition, that acts like the parent for all logical partitions. Keep in
mind that the most significant difference (afaik) is that logical
partitions can not be considered bootable. That means you can create
an arbitrary number of them and they can all have their own partition
schemes (such as FAT32, ext4, or NTFS) but I think their start/end
sectors (https://en.wikipedia.org/wiki/Disk_sector) has to fall inside
that "extended" parent. With that knowledge in mind, you should now
know not to panic when you see a "partition table invalid" error (when
using gparted and whatnot). Intead, use
sudo fdisk -lu /dev/sda, where the last argument is the
device in question, to query sector allocation information. That's
gonna tell you how large the physical sectors are in that drive (in
modern drives it's probably 512 bytes / 4096 bytes meaning that each
virtual/logical sector is worth 512 bytes for backwards compatibility
while each "physical" sector is worth 4096 bytes) and where each
partition starts and ends. With this information, you should be able to
identify simple issues like partitions overlapping or "partition x does
not start/end on physical sector boundary", which means that the
partition x does not start/end on a sector that's a multiple of the
physical sector size divided by virtual size (ratio of 8 in my
example). Now you may follow
https://gparted.org/h2-fix-msdos-pt.php#instructions and use parted to
correct that problem.
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[In the case that you need to completely wipe a drive, use
]sudo dd if=/dev/zero of=/dev/sda bs=5M status=progress{.inline
style=””}[ to fill/rewrite the entire drive with 0s, which will wipe the
partition table along with ]all[
information. ]
Here if is output file,
bs is the size of a singular chunk (refer to
https://man7.org/linux/man-pages/man1/dd.1.html), and
status=progress verbose for the
sake of sanity :)
[More info about partition not aligned with physical sectors: ]https://askubuntu.com/questions/156994/partition-does-not-start-on-physical-sector-boundary
Btw the command I use to compress and archive to gdrive is
tar -c dir | piz | rclone rcat archive_dest:path/to/dir.tar.gz
if rclone is configured already. This command creates a
pipeline/stream to first archive that directory, then sends it to a
multithreaded gzip compressor, and finally uploads it chunk by chunk
into a single file. Very useful for backing up a directory full of many
smol files
This headache may not need to exist since it applies to MBR. GPT+EFI sounds better.
Document generated by Confluence on Dec 10, 2021 04:01