Boot disk volume layout is intricate in Big Sur. M1 Macs lose the EFI partition on their internal SSDs and gain two more for APFS. Contents of /System/Volumes has also changed.
Disk structure diagrammed for comparison, from the partition table, to HFS+ and APFS volumes, with further references.
What you need to know about the APFS file system, its containers and volumes, so you can understand errors and how to repair them.
What you need to know about the HFS+ file system, so you can understand error reports and how to repair it using Disk Utility and other tools.
What you need to know about disk formatting using the GUID Partition Table (GPT) to understand its problems and how to repair it.
What do you know about the hidden and unmounted EFI partition on all the disks you use with your Mac? It could be very important.
Want one external drive from which you can boot two (or more) different versions of macOS? Here’s how to make it.
How does the volume structure differ between Fusion Drives in HFS+ and APFS formats? Does Disk Utility show an accurate picture?
I’ve got two volumes showing in the Finder. So how come diskutil list tells me I’ve got four disks with a total of 12 partitions?
In recent years, most Mac users have stopped partitioning drives into volumes. In High Sierra, you will probably want to use volumes again. Lots.