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Dynamically allocate UIDs

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Rather than rely on a nixbld group, we now allocate UIDs/GIDs
dynamically starting at a configurable ID (872415232 by default).

Also, we allocate 2^18 UIDs and GIDs per build, and run the build as
root in its UID namespace. (This should not be the default since it
breaks some builds. We probably should enable this conditional on a
requiredSystemFeature.) The goal is to be able to run (NixOS)
containers in a build. However, this will also require some cgroup
initialisation.

The 2^18 UIDs/GIDs is intended to provide enough ID space to run
multiple containers per build, e.g. for distributed NixOS tests.
This commit is contained in:
Eelco Dolstra 2017-10-31 12:22:29 +01:00
parent 14227aeb32
commit 836573a9a2
2 changed files with 61 additions and 8 deletions
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10
src/libstore/globals.hh
View file

@ -148,6 +148,16 @@ public:
Setting<std::string> buildUsersGroup{this, "", "build-users-group",
"The Unix group that contains the build users."};
#if __linux__
const uint32_t idsPerBuild = 1 << 18;
Setting<uint32_t> startId{this, 872415232, "start-id",
"The first UID and GID to use for dynamic ID allocation. (0 means disable.)"};
Setting<uint32_t> uidCount{this, idsPerBuild * 128, "id-count",
"The number of UIDs/GIDs to use for dynamic ID allocation."};
#endif
Setting<bool> impersonateLinux26{this, false, "impersonate-linux-26",
"Whether to impersonate a Linux 2.6 machine on newer kernels.",
{"build-impersonate-linux-26"}};