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docs: add comment about high 32bit range and signed uids

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Lennart Poettering 2019-05-13 15:23:47 +02:00 committed by Zbigniew Jędrzejewski-Szmek
parent 8550506439
commit a305eda35f
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docs/UIDS-GIDS.md
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@ -237,7 +237,8 @@ the artifacts the container manager persistently leaves in the system.
| 65535 | 16bit `(uid_t) -1` | Linux | |
| 65536…524287 | Unused | | |
| 524288…1879048191 | Container UID ranges | `systemd` | `nss-mymachines` |
| 1879048192…4294967294 | Unused | | |
| 1879048191…2147483647 | Unused | | |
| 2147483648…4294967294 | HIC SVNT LEONES | | |
| 4294967295 | 32bit `(uid_t) -1` | Linux | |
Note that "Unused" in the table above doesn't meant that these ranges are
@ -246,6 +247,13 @@ pre-defined purposes between Linux, generic low-level distributions and
`systemd`. There might very well be other packages that allocate from these
ranges.
Note that the range 2147483648…4294967294 (i.e. 2^31…2^32-2) should be handled
with care. Various programs (including kernel file systems, see `devpts`) have
trouble with UIDs outside of the signed 32bit range, i.e any UIDs equal to or
above 2147483648. It is thus strongly recommended to stay away from this range
in order to avoid complications. This range should be considered reserved for
future, special purposes.
## Notes on resolvability of user and group names
User names, UIDs, group names and GIDs don't have to be resolvable using NSS