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UIDS-GIDS: document early on, that 32bit uids are a linux 2.4 thing

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Lennart Poettering 2018-01-11 13:08:57 +01:00
parent e3e2cf07b1
commit 9e4b889366
1 changed files with 6 additions and 6 deletions
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UIDS-GIDS.md
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@ -26,13 +26,13 @@ i.e. 0…4294967295. However, four UIDs are special on Linux:
call the `nobody` group `nogroup`. I wish they didn't.)
3. 4294967295, aka "32bit `(uid_t) -1`" → This UID is not a valid user ID, as
setresuid(), chown() and friends treat -1 as a special request to not change
the UID of the process/file. This UID is hence not available for assignment
to users in the user database.
`setresuid()`, `chown()` and friends treat -1 as a special request to not
change the UID of the process/file. This UID is hence not available for
assignment to users in the user database.
4. 65535, aka "16bit `(uid_t) -1`" → Once upon a time `uid_t` used to be 16bit, and
programs compiled for that would hence assume that `(uid_t) -1` is 65535. This
UID is hence not usable either.
4. 65535, aka "16bit `(uid_t) -1`" → Before Linux kernel 2.4 `uid_t` used to be
16bit, and programs compiled for that would hence assume that `(uid_t) -1`
is 65535. This UID is hence not usable either.
The `nss-systemd` glibc NSS module will synthesize user database records for
the UIDs 0 and 65534 if the system user database doesn't list them. This means