Problem: You want to know which Linux partitions exist on a file system.
Solution: Use ‘fdisk -l’
Reference:
man fdisk
-l List the partition tables for the specified devices and then exit. If no devices are given, those mentioned in /proc/partitions (if that exists) are used.
See also:
9 Linux commands to look at disks
https://www.binarytides.com/linux-command-check-disk-partitions/