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One thing I was surprised to learn a couple years ago is that users and groups aren't really tracked much by the Linux kernel: they're just numeric IDs that tra
by LegionMammal978 1y ago
One thing I was surprised to learn a couple years ago is that users and groups aren't really tracked much by the Linux kernel: they're just numeric IDs that track process and file ownership. So if you setuid() to a user ID that doesn't exist in /etc/passwd or anywhere else, the kernel won't stop you.
- latchkey 1y agoIf I have a file on machineA with uid10001 and I copy the file to machineB, I might want it to retain that uid, but it shouldn't matter to machineB that it doesn't map to a real user.
- MrDarcy 1y agoYou’ll see this observation all the time building containers.
- danielrico 1y agoDon't if you only run them with root user.
- kurisufag 1y agoor with ipa-esque authentication schemes and shared mounts
- dimatura 1y agoAnd NFS!
- rafram 1y agoHopefully that user actually doesn’t exist on the second machine!