From a305eda35f18fbacc771cc1582b688d60890a9d2 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Mon, 13 May 2019 15:23:47 +0200 Subject: docs: add comment about high 32bit range and signed uids --- docs/UIDS-GIDS.md | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'docs/UIDS-GIDS.md') diff --git a/docs/UIDS-GIDS.md b/docs/UIDS-GIDS.md index 25345a918f..480ee231e7 100644 --- a/docs/UIDS-GIDS.md +++ b/docs/UIDS-GIDS.md @@ -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 -- cgit v1.2.1