Is there a way to tell what kind of operating system current system has?

Question

My question is as follows: Is there a way for a linux installation disk (ubuntu 18.xx LTS on bootable stick) to know what operating systems computer has on a disk ?

I've found similiar topics here: How do I tell what version and edition of Windows is on the filesystem?

Which give adequate answer regarding Windows side. But what if USB is booted from Macbook or some other LaptopPC that has Linux?

Is there some sort of script or open-source application that (if executed) could detect all operating systems located on system ?

Answer 1

All Unixy systems should have a file /etc/*-release (perhaps several!) or similar, containing the name and version of the operating system. Sure, a mischievous sysadmin can very well fake that, but it should be rather reliable. That presupposes that you can mount and read the relevant filessytem.