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Support optional sandbox paths

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For example, you can now set

  build-sandbox-paths = /dev/nvidiactl?

to specify that /dev/nvidiactl should only be mounted in the sandbox
if it exists in the host filesystem. This is useful e.g. for EC2
images that should support both CUDA and non-CUDA instances.
This commit is contained in:
Eelco Dolstra 2016-10-31 17:09:52 +01:00
parent c4969aebaf
commit 18b7363a69
2 changed files with 32 additions and 10 deletions
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7
doc/manual/command-ref/conf-file.xml
View file

@ -268,7 +268,12 @@ flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
to mount a path in a different location in the sandbox; for
instance, <literal>/bin=/nix-bin</literal> will mount the path
<literal>/nix-bin</literal> as <literal>/bin</literal> inside the
sandbox.</para>
sandbox. If <replaceable>source</replaceable> is followed by
<literal>?</literal>, then it is not an error if
<replaceable>source</replaceable> does not exist; for example,
<literal>/dev/nvidiactl?</literal> specifies that
<filename>/dev/nvidiactl</filename> will only be mounted in the
sandbox if it exists in the host filesystem.</para>
<para>Depending on how Nix was built, the default value for this option
may be empty or provide <filename>/bin/sh</filename> as a

33
src/libstore/build.cc
View file

@ -768,7 +768,14 @@ private:
GoalState state;
/* Stuff we need to pass to initChild(). */
typedef map<Path, Path> DirsInChroot; // maps target path to source path
struct ChrootPath {
Path source;
bool optional;
ChrootPath(Path source = "", bool optional = false)
: source(source), optional(optional)
{ }
};
typedef map<Path, ChrootPath> DirsInChroot; // maps target path to source path
DirsInChroot dirsInChroot;
typedef map<string, string> Environment;
Environment env;
@ -1865,12 +1872,18 @@ void DerivationGoal::startBuilder()
dirsInChroot.clear();
for (auto & i : dirs) {
for (auto i : dirs) {
if (i.empty()) continue;
bool optional = false;
if (i[i.size() - 1] == '?') {
optional = true;
i.pop_back();
}
size_t p = i.find('=');
if (p == string::npos)
dirsInChroot[i] = i;
dirsInChroot[i] = {i, optional};
else
dirsInChroot[string(i, 0, p)] = string(i, p + 1);
dirsInChroot[string(i, 0, p)] = {string(i, p + 1), optional};
}
dirsInChroot[tmpDirInSandbox] = tmpDir;
@ -1878,8 +1891,8 @@ void DerivationGoal::startBuilder()
PathSet closure;
for (auto & i : dirsInChroot)
try {
if (worker.store.isInStore(i.second))
worker.store.computeFSClosure(worker.store.toStorePath(i.second), closure);
if (worker.store.isInStore(i.second.source))
worker.store.computeFSClosure(worker.store.toStorePath(i.second.source), closure);
} catch (Error & e) {
throw Error(format("while processing ‘build-sandbox-paths’: %s") % e.what());
}
@ -2325,12 +2338,16 @@ void DerivationGoal::runChild()
environment. */
for (auto & i : dirsInChroot) {
struct stat st;
Path source = i.second;
Path source = i.second.source;
Path target = chrootRootDir + i.first;
if (source == "/proc") continue; // backwards compatibility
debug(format("bind mounting ‘%1%’ to ‘%2%’") % source % target);
if (stat(source.c_str(), &st) == -1)
if (stat(source.c_str(), &st) == -1) {
if (i.second.optional && errno == ENOENT)
continue;
else
throw SysError(format("getting attributes of path ‘%1%’") % source);
}
if (S_ISDIR(st.st_mode))
createDirs(target);
else {