Commit graph

334 commits

Author SHA1 Message Date
Eelco Dolstra 94f9c14d52 Fix some clang warnings 2014-01-21 18:29:55 +01:00
Eelco Dolstra 11cb4bfb25 Fix checking of NAR hashes
*headdesk*
*headdesk*
*headdesk*

So since commit 22144afa8d, Nix hasn't
actually checked whether the content of a downloaded NAR matches the
hash specified in the manifest / NAR info file.  Urghhh...
2014-01-08 17:35:49 +01:00
Domen Kožar 485f4740ee wording 2014-01-06 11:38:24 +01:00
Eelco Dolstra c5b8fe3151 Print a trace message if a build fails due to the platform being unknown 2013-12-05 14:31:57 -05:00
Eelco Dolstra a478e8a7bb Remove nix-setuid-helper
AFAIK, nobody uses it, it's not maintained, and it has no tests.
2013-11-14 11:57:37 +01:00
Eelco Dolstra b29d3f4aee Only show trace messages when tracing is enabled 2013-09-02 12:01:04 +02:00
Eelco Dolstra efe4289464 Add an option to limit the log output of builders
This is mostly useful for Hydra to deal with builders that get stuck
in an infinite loop writing data to stdout/stderr.
2013-09-02 11:58:18 +02:00
Gergely Risko c6c024ca6f Fix personality switching from x86_64 to i686
On Linux, Nix can build i686 packages even on x86_64 systems.  It's not
enough to recognize this situation by settings.thisSystem, we also have
to consult uname().  E.g. we can be running on a i686 Debian with an
amd64 kernel.  In that situation settings.thisSystem is i686-linux, but
we still need to change personality to i686 to make builds consistent.
2013-08-26 11:12:35 +02:00
Eelco Dolstra a583a2bc59 Run the daemon worker on the same CPU as the client
On a system with multiple CPUs, running Nix operations through the
daemon is significantly slower than "direct" mode:

$ NIX_REMOTE= nix-instantiate '<nixos>' -A system
real    0m0.974s
user    0m0.875s
sys     0m0.088s

$ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system
real    0m2.118s
user    0m1.463s
sys     0m0.218s

The main reason seems to be that the client and the worker get moved
to a different CPU after every call to the worker.  This patch adds a
hack to lock them to the same CPU.  With this, the overhead of going
through the daemon is very small:

$ NIX_REMOTE=daemon nix-instantiate '<nixos>' -A system
real    0m1.074s
user    0m0.809s
sys     0m0.098s
2013-08-07 14:02:04 +02:00
Eelco Dolstra a4921b8ceb Revert "build-remote.pl: Enforce timeouts locally"
This reverts commit 69b8f9980f.

The timeout should be enforced remotely.  Otherwise, if the garbage
collector is running either locally or remotely, if will block the
build or closure copying for some time.  If the garbage collector
takes too long, the build may time out, which is not what we want.
Also, on heavily loaded systems, copying large paths to and from the
remote machine can take a long time, also potentially resulting in a
timeout.
2013-07-18 12:52:29 +02:00
Shea Levy 16591eb3cc Allow bind-mounting regular files into the chroot
mount(2) with MS_BIND allows mounting a regular file on top of a regular
file, so there's no reason to only bind directories. This allows finer
control over just which files are and aren't included in the chroot
without having to build symlink trees or the like.

Signed-off-by: Shea Levy <shea@shealevy.com>
2013-07-15 16:01:33 +02:00
Eelco Dolstra 7ccd946407 Don't set $preferLocalBuild and $requiredSystemFeatures in builders
With C++ std::map, doing a comparison like ‘map["foo"] == ...’ has the
side-effect of adding a mapping from "foo" to the empty string if
"foo" doesn't exist in the map.  So we ended up setting some
environment variables by accident.
2013-06-20 18:07:27 +00:00
Eelco Dolstra 5558652709 Don't substitute derivations that have preferLocalBuild set
In particular this means that "trivial" derivations such as writeText
are not substituted, reducing the number of GET requests to the binary
cache by about 200 on a typical NixOS configuration.
2013-06-20 19:26:31 +02:00
Eelco Dolstra 1b6ee8f4c7 Allow hard links between the outputs of a derivation 2013-06-13 17:29:56 +02:00
Eelco Dolstra cd49ee0897 Fix a security bug in hash rewriting
Before calling dumpPath(), we have to make sure the files are owned by
the build user.  Otherwise, the build could contain a hard link to
(say) /etc/shadow, which would then be read by the daemon and
rewritten as a world-readable file.

This only affects systems that don't have hard link restrictions
enabled.
2013-06-13 17:12:24 +02:00
Eelco Dolstra 1e2c7c04b1 Fix assertion failure in canonicalisePathMetaData() after hash rewriting
The assertion in canonicalisePathMetaData() failed because the
ownership of the path already changed due to the hash rewriting.  The
solution is not to check the ownership of rewritten paths.

Issue #122.
2013-06-13 17:12:06 +02:00
Eelco Dolstra 6cc2a8f8ed computeFSClosure: Only process the missing/corrupt paths
Issue #122.
2013-06-13 16:43:20 +02:00
Eelco Dolstra f9ff67e948 In repair mode, update the hash of rebuilt paths
Otherwise subsequent invocations of "--repair" will keep rebuilding
the path.  This only happens if the path content differs between
builds (e.g. due to timestamps).
2013-06-13 14:46:07 +02:00
Eelco Dolstra 2ee9da9e22 In trace messages, don't print the output path
This doesn't work if there is no output named "out".  Hydra didn't use
it anyway.
2013-05-10 00:24:33 +02:00
Eelco Dolstra 6eba05613a Communicate build timeouts to Hydra 2013-05-09 18:39:04 +02:00
Eelco Dolstra 69b8f9980f build-remote.pl: Enforce timeouts locally
Don't pass --timeout / --max-silent-time to the remote builder.
Instead, let the local Nix process terminate the build if it exceeds a
timeout.  The remote builder will be killed as a side-effect.  This
gives better error reporting (since the timeout message from the
remote side wasn't properly propagated) and handles non-Nix problems
like SSH hangs.
2013-05-09 17:17:17 +02:00
Eelco Dolstra 772b70952f Fix --timeout
I'm not sure if it has ever worked correctly.  The line "lastWait =
after;" seems to mean that the timer was reset every time a build
produced log output.

Note that the timeout is now per build, as documented ("the maximum
number of seconds that a builder can run").
2013-04-23 18:04:59 +02:00
Eelco Dolstra 934cf2d1f4 Nix daemon: respect build timeout from the client 2013-04-23 16:59:06 +02:00
Eelco Dolstra 258897c265 Complain if /homeless-shelter exists 2013-04-04 11:16:26 +02:00
Eelco Dolstra bdd4646338 Revert "Prevent config.h from being clobbered"
This reverts commit 28bba8c44f.
2013-03-08 01:24:59 +01:00
Eelco Dolstra 28bba8c44f Prevent config.h from being clobbered 2013-03-07 23:55:55 +01:00
Eelco Dolstra 5526a282b5 Security: Don't allow builders to change permissions on files they don't own
It turns out that in multi-user Nix, a builder may be able to do

  ln /etc/shadow $out/foo

Afterwards, canonicalisePathMetaData() will be applied to $out/foo,
causing /etc/shadow's mode to be set to 444 (readable by everybody but
writable by nobody).  That's obviously Very Bad.

Fortunately, this fails in NixOS's default configuration because
/nix/store is a bind mount, so "ln" will fail with "Invalid
cross-device link".  It also fails if hard-link restrictions are
enabled, so a workaround is:

  echo 1 > /proc/sys/fs/protected_hardlinks

The solution is to check that all files in $out are owned by the build
user.  This means that innocuous operations like "ln
${pkgs.foo}/some-file $out/" are now rejected, but that already failed
in chroot builds anyway.
2013-02-26 02:30:19 +01:00
Ludovic Courtès 5ea138dc4b Enable chroot support on old glibc versions. 2013-02-19 10:19:11 +01:00
Eelco Dolstra 536c85ea49 Store build logs in /nix/var/log/nix/drvs/<XX>
...where <XX> is the first two characters of the derivation.
Otherwise /nix/var/log/nix/drvs may become so large that we run into
all sorts of weird filesystem limits/inefficiences.  For instance,
ext3/ext4 filesystems will barf with "ext4_dx_add_entry:1551:
Directory index full!" once you hit a few million files.
2013-01-17 15:47:26 +01:00
Eelco Dolstra def5160b61 Clear any immutable bits in the Nix store
Doing this once makes subsequent operations like garbage collecting
more efficient since we don't have to call makeMutable() first.
2013-01-03 12:59:23 +01:00
Eelco Dolstra 299141ecbd If a substitute closure is incomplete, build dependencies, then retry the substituter
Issue #77.
2013-01-02 12:38:28 +01:00
Eelco Dolstra 1b3a78a459 Automatically fall back if the references of a substitute are not substitutable
Fixes #77.
2013-01-02 12:00:26 +01:00
Eelco Dolstra b7629778ef Allow mounting a path in a different location in the chroot
Fixes #24.
2012-12-29 23:04:02 +01:00
Eelco Dolstra fbf0b2fa45 Kill the build hook rather than shutting it down cleanly
Waiting for the hook to shut down cleanly sometimes seems to lead to
hangs.
2012-12-19 11:47:42 +01:00
Eelco Dolstra 228ea7c2f9 Revert brain fart
This reverts commit cc511fd65b.
2012-12-18 20:43:47 +01:00
Eelco Dolstra cc511fd65b Check for potential infinite select() loops when building 2012-12-18 18:50:05 +01:00
Eelco Dolstra 8d8d47abd2 Only substitute wanted outputs of a derivation
If a derivation has multiple outputs, then we only want to download
those outputs that are actuallty needed.  So if we do "nix-build -A
openssl.man", then only the "man" output should be downloaded.
Likewise if another package depends on ${openssl.man}.

The tricky part is that different derivations can depend on different
outputs of a given derivation, so we may need to restart the
corresponding derivation goal if that happens.
2012-11-26 17:15:09 +01:00
Eelco Dolstra 46a369ad95 Make "nix-build -A <derivation>.<output>" do the right thing
For example, given a derivation with outputs "out", "man" and "bin":

  $ nix-build -A pkg

produces ./result pointing to the "out" output;

  $ nix-build -A pkg.man

produces ./result-man pointing to the "man" output;

  $ nix-build -A pkg.all

produces ./result, ./result-man and ./result-bin;

  $ nix-build -A pkg.all -A pkg2

produces ./result, ./result-man, ./result-bin and ./result-2.
2012-11-26 15:39:10 +01:00
Eelco Dolstra f794465ca8 Disable use of vfork()
vfork() is just too weird.  For instance, in this build:

  http://hydra.nixos.org/build/3330487

the value fromHook.writeSide becomes corrupted in the parent, even
though the child only reads from it.  At -O0 the problem goes away.
Probably the child is overriding some spilled temporary variable.

If I get bored I may implement using posix_spawn() instead.
2012-11-15 19:35:18 +01:00
Eelco Dolstra 8541d27fce Don't use std::cerr in a few places
Slightly scared of using std::cerr in a vforked process...
2012-11-15 15:01:02 +01:00
Eelco Dolstra ea89df2b76 Use vfork() instead of fork() if available
Hopefully this reduces the chance of hitting ‘unable to fork: Cannot
allocate memory’ errors.  vfork() is used for everything except
starting builders.
2012-11-09 18:00:33 +01:00
Eelco Dolstra 198dbe7fa1 Remove some redundant close() calls
They are unnecessary because we set the close-on-exec flag.
2012-11-09 16:58:51 +01:00
Eelco Dolstra 10dcee99ed Remove the quickExit function 2012-11-09 16:42:10 +01:00
Eelco Dolstra 4c34d384e6 If hashes do not match, print them in base-32 for SHA-1/SHA-256
Fixes #57.
2012-10-23 18:05:50 +02:00
Eelco Dolstra e345182055 Shorten the names of temporary build directories 2012-10-11 14:03:06 -04:00
Eelco Dolstra 2bbc4a214e nix-env: Support ‘--repair’ flag 2012-10-03 15:35:42 -04:00
Eelco Dolstra a807edfae8 Handle repairing paths that are in build-chroot-dirs 2012-10-03 11:20:16 -04:00
Eelco Dolstra a3f205b249 When repairing a derivation, check and repair the entire output closure
If we find a corrupted path in the output closure, we rebuild the
derivation that produced that particular path.
2012-10-03 10:38:09 -04:00
Eelco Dolstra 2001895f3d Add a --repair flag to ‘nix-store -r’ to repair derivation outputs
With this flag, if any valid derivation output is missing or corrupt,
it will be recreated by using a substitute if available, or by
rebuilding the derivation.  The latter may use hash rewriting if
chroots are not available.
2012-10-02 17:13:46 -04:00
Eelco Dolstra 9958bd6992 Add operation ‘nix-store --repair-path’
This operation allows fixing corrupted or accidentally deleted store
paths by redownloading them using substituters, if available.

Since the corrupted path cannot be replaced atomically, there is a
very small time window (one system call) during which neither the old
(corrupted) nor the new (repaired) contents are available.  So
repairing should be used with some care on critical packages like
Glibc.
2012-10-02 14:08:59 -04:00
Eelco Dolstra e666e1156f Handle octal escapes in /proc/self/mountinfo 2012-09-28 21:39:30 -04:00
Eelco Dolstra f406288cc7 Print a more descriptive error message if setting up the build environment fails 2012-09-28 21:37:02 -04:00
Eelco Dolstra b9c2b4d5b4 Remove setting of the immutable bit
Using the immutable bit is problematic, especially in conjunction with
store optimisation.  For instance, if the garbage collector deletes a
file, it has to clear its immutable bit, but if the file has
additional hard links, we can't set the bit afterwards because we
don't know the remaining paths.

So now that we support having the entire Nix store as a read-only
mount, we may as well drop the immutable bit.  Unfortunately, we have
to keep the code to clear the immutable bit for backwards
compatibility.
2012-09-19 16:17:54 -04:00
Eelco Dolstra 76e88871b2 Templatise tokenizeString() 2012-09-19 15:43:23 -04:00
Eelco Dolstra 00092b2d35 Keep build directory if not all expected outputs were produced
Fixes issue #123 in Nixpkgs.
2012-09-18 10:11:42 -04:00
Eelco Dolstra e56f71edaf In startBuilder(), only print the new paths we're building 2012-09-13 10:06:24 -04:00
Eelco Dolstra 479e9172b3 Build hook: Pass the timeout to the remote builder
Note that this will only work if the client has a very recent Nix
version (post 15e1b2c223), otherwise the
--option flag will just be ignored.

Fixes #50.
2012-09-12 12:18:14 -04:00
Eelco Dolstra 5e2ffd0b8a Fix "non-zero padding" error
Probably it's not a good idea to pass a temporary object to
StringSource.
2012-09-11 19:09:01 -04:00
Eelco Dolstra 8cf672091e Support building a derivation if some outputs are already valid (non-chroot case)
This uses scary hash rewriting.

Fixes #21.
2012-09-11 18:39:22 -04:00
Eelco Dolstra 9dbda2b3fe Remove debug line 2012-09-11 17:05:35 -04:00
Eelco Dolstra a2785b7391 Support building a derivation if some outputs are already valid
This handles the chroot and build hook cases, which are easy.
Supporting the non-chroot-build case will require more work (hash
rewriting!).

Issue #21.
2012-09-11 16:59:59 -04:00
Eelco Dolstra cfd968dd94 Fix stupid type error in calling std::max 2012-08-27 14:17:13 -04:00
Eelco Dolstra e94806d030 Merge branch 'master' into no-manifests 2012-08-27 11:09:07 -04:00
Eelco Dolstra d950cfe70b Check if MS_PRIVATE is defined
http://hydra.nixos.org/build/2955671
2012-08-20 15:55:49 -04:00
Eelco Dolstra 56e30e161c In the chroot, make all mounted filesystems private
This is required on systemd, which mounts filesystems as "shared"
subtrees.  Changes to shared trees in a private mount namespace are
propagated to the outside world, which is bad.
2012-08-20 15:27:30 -04:00
Eelco Dolstra f0eab0636b Don't bind-mount /proc since we mount our own 2012-08-20 15:27:00 -04:00
Eelco Dolstra 862c4c5ec5 Fix 1755 permission on temporary directories left behind by ‘-K’ 2012-08-19 16:32:42 -04:00
Eelco Dolstra 01d56c1eec Drop the block count in the garbage collector 2012-08-01 22:34:46 -04:00
Eelco Dolstra 97421eb5ec Refactor settings processing
Put all Nix configuration flags in a Settings object.
2012-07-30 19:55:41 -04:00
Eelco Dolstra d059bf48e4 Pass configuration settings to the substituters
Previously substituters could read nix.conf themselves, but this
didn't take --option flags into account.
2012-07-30 16:09:54 -04:00
Eelco Dolstra 73acb8b836 Let build.cc verify the expected hash of a substituter's output
Since SubstitutionGoal::finished() in build.cc computes the hash
anyway, we can prevent the inefficiency of computing the hash twice by
letting the substituter tell Nix about the expected hash, which can
then verify it.
2012-07-27 12:16:02 -04:00
Eelco Dolstra fbf59d95f6 Remove more tabs 2012-07-27 10:56:33 -04:00
Eelco Dolstra b4ea83249b Remove trailing whitespace / tabs 2012-07-27 09:59:18 -04:00
Eelco Dolstra 8c79100839 Merge branch 'master' into no-manifests 2012-07-26 15:14:33 -04:00
Eelco Dolstra 3a4623afbb Set permissions on temporary build directories to 0700
Fixes #39.
2012-07-26 15:04:40 -04:00
Eelco Dolstra 6193105710 Automatically optimise the Nix store when a new path is added
Auto-optimisation is enabled by default.  It can be turned off by
setting auto-optimise-store to false in nix.conf.
2012-07-23 17:14:15 -04:00
Eelco Dolstra fe241ece29 Merge branch 'master' into no-manifests 2012-07-18 10:47:59 -04:00
Eelco Dolstra 3a9fdf2747 Return an exit code of 100 for cached failed builds
Exit code 100 should be returned for all permanent failures.  This
includes cached failures.

Fixes #34.
2012-07-17 15:55:30 -04:00
Eelco Dolstra 6c01fb4d68 Update Nix 1.1 release notes 2012-07-17 10:06:20 -04:00
Eelco Dolstra 53b24f3518 Allow disabling log compression 2012-07-17 09:40:12 -04:00
Eelco Dolstra 425cc612ad build.cc: Don't use hasSubstitute()
Instead make a single call to querySubstitutablePathInfo() per
derivation output.  This is faster and prevents having to implement
the "have" function in the binary cache substituter.
2012-07-08 18:39:24 -04:00
Eelco Dolstra 11800e6198 download-from-binary-cache: parallelise fetching of NAR info files
Getting substitute information using the binary cache substituter has
non-trivial latency overhead.  A package or NixOS system configuration
can have hundreds of dependencies, and in the worst case (when the
local info cache is empty) we have to do a separate HTTP request for
each of these.  If the ping time to the server is t, getting N info
files will take tN seconds; e.g., with a ping time of 0.1s to
nixos.org, sequentially downloading 1000 info files (a typical NixOS
config) will take at least 100 seconds.

To fix this problem, the binary cache substituter can now perform
requests in parallel.  This required changing the substituter
interface to support a function querySubstitutablePathInfos() that
queries multiple paths at the same time, and rewriting queryMissing()
to take advantage of parallelism.  (Due to local caching,
parallelising queryMissing() is sufficient for most use cases, since
it's almost always called before building a derivation and thus fills
the local info cache.)

For example, parallelism speeds up querying all 1056 paths in a
particular NixOS system configuration from 116s to 2.6s.  It works so
well because the eccentricity of the top-level derivation in the
dependency graph is only 9.  So we only need 10 round-trips (when
using an unlimited number of parallel connections) to get everything.

Currently we do a maximum of 150 parallel connections to the server.
Thus it's important that the binary cache server (e.g. nixos.org) has
a high connection limit.  Alternatively we could use HTTP pipelining,
but WWW::Curl doesn't support it and libcurl has a hard-coded limit of
5 requests per pipeline.
2012-07-06 19:08:20 -04:00
Eelco Dolstra 1aba0bf0fa nix-store -r: do substitutions in parallel
I.e. when multiple non-derivation arguments are passed to ‘nix-store
-r’ to be substituted, do them in parallel.
2012-06-27 16:58:15 -04:00
Eelco Dolstra 42f5a2fc29 Mount an empty /dev/shm tmpfs in the chroot
This ensures that whatever the builder writes in /dev/shm is
automatically cleaned up.
2012-06-27 09:52:27 -04:00
Eelco Dolstra 3ee208516f Check the return code of the clone() call 2012-06-27 09:52:06 -04:00
Eelco Dolstra 1db38ae81b When using chroots, use a private PID namespace
In a private PID namespace, processes have PIDs that are separate from
the rest of the system.  The initial child gets PID 1.  Processes in
the chroot cannot see processes outside of the chroot.  This improves
isolation between builds.  However, processes on the outside can see
processes in the chroot and send signals to them (if they have
appropriate rights).

Since the builder gets PID 1, it serves as the reaper for zombies in
the chroot.  This might turn out to be a problem.  In that case we'll
need to have a small PID 1 process that sits in a loop calling wait().
2012-06-25 15:45:16 -04:00
Eelco Dolstra 5489086456 Use a private UTS namespace to provide a deterministic host/domain name to builders
In chroot builds, set the host name to "localhost" and the domain name
to "(none)" (the latter being the kernel's default).  This improves
determinism a bit further.

P.S. I have to idea what UTS stands for.
2012-06-25 14:12:17 -04:00
Eelco Dolstra 723a68c826 Improve error message 2012-06-23 00:57:14 -04:00
Eelco Dolstra 7ffa523fd1 In chroot builds, use a private SysV IPC namespace
This improves isolation a bit further, and it's just one extra flag in
the unshare() call.

P.S. It would be very cool to use CLONE_NEWPID (to put the builder in
a private PID namespace) as well, but that's slightly more risky since
having a builder start as PID 1 may cause problems.
2012-06-23 00:51:40 -04:00
Eelco Dolstra df716c98d2 In chroot builds, use a private network namespace
On Linux it's possible to run a process in its own network namespace,
meaning that it gets its own set of network interfaces, disjunct from
the rest of the system.  We use this to completely remove network
access to chroot builds, except that they get a private loopback
interface.  This means that:

- Builders cannot connect to the outside network or to other processes
  on the same machine, except processes within the same build.

- Vice versa, other processes cannot connect to processes in a chroot
  build, and open ports/connections do not show up in "netstat".

- If two concurrent builders try to listen on the same port (e.g. as
  part of a test), they no longer conflict with each other.

This was inspired by the "PrivateNetwork" flag in systemd.
2012-06-23 00:28:35 -04:00
Eelco Dolstra f5398d374b Compress build logs on the fly using bzip2 2012-05-30 10:12:29 -04:00
Eelco Dolstra 2c26985835 Add option ‘build-keep-log’ to enable/disable writing of build logs
Fixes #26.
2012-05-29 16:42:05 -04:00
Eelco Dolstra db5b86ef13 * Add an option ‘build-use-substitutes’, which can be set to ‘false’
to disable use of substitutes; i.e., force building from source.
  Fixes Nix/221.
2012-04-30 19:15:34 -04:00
Eelco Dolstra 46cdc6ad51 Handle EPERM when creating a hard link for the chroot
There is a race condition when doing parallel builds with chroots and
the immutable bit enabled.  One process may call makeImmutable()
before the other has called link(), in which case link() will fail
with EPERM.  We could retry or wrap the operation in a lock, but since
this condition is rare and I'm lazy, we just use the existing copy
fallback.

Fixes #9.
2012-04-30 10:58:04 -04:00
Eelco Dolstra 31e34fcf93 Close almost all file descriptors in the builder
This regression was accidentally introduced in
35355fc1fc.
2012-04-15 00:20:32 +02:00
Eelco Dolstra f2467eb6a0 On Linux, pretend we're building on Linux 2.6
Setting the UNAME26 personality causes "uname" to return "2.6.x",
regardless of the kernel version.  This improves determinism in
a few misbehaved packages.
2012-04-05 13:03:19 +02:00
Eelco Dolstra 35355fc1fc Set the close-on-exec flag on file descriptors 2012-03-05 20:29:00 +01:00
Eelco Dolstra 7b22bec252 Don't leak a file descriptor in commonChildInit() 2012-03-05 20:28:09 +01:00
Eelco Dolstra 1c94524458 Fix an uninitialised variable
The variable ‘useChroot’ was not initialised properly.  This caused
random failures if using the build hook.  Seen on Mac OS X 10.7 with Clang.
Thanks to KolibriFX for finding this :-)
2012-03-01 16:06:49 +01:00
Eelco Dolstra 6fe13e6aba Fix chroots builds
Chroots are initialised by hard-linking inputs from the Nix store to
the chroot.  This doesn't work if the input has its immutable bit set,
because it's forbidden to create hard links to immutable files.  So
temporarily clear the immutable bit when creating and destroying the
chroot.

Note that making regular files in the Nix store immutable isn't very
reliable, since the bit can easily become cleared: for instance, if we
run the garbage collector after running ‘nix-store --optimise’.  So
maybe we should only make directories immutable.
2012-02-18 01:23:52 +01:00