forked from lix-project/lix
257 lines
8.2 KiB
C++
257 lines
8.2 KiB
C++
#include "command.hh"
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#include "common-args.hh"
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#include "shared.hh"
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#include "store-api.hh"
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#include "derivations.hh"
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#include "local-store.hh"
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#include "finally.hh"
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#include "fs-accessor.hh"
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#include "progress-bar.hh"
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#include "affinity.hh"
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#if __linux__
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#include <sys/mount.h>
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#endif
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#include <queue>
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using namespace nix;
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std::string chrootHelperName = "__run_in_chroot";
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struct CmdRun : InstallablesCommand
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{
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std::vector<std::string> command = { "bash" };
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StringSet keep, unset;
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bool ignoreEnvironment = false;
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CmdRun()
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{
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mkFlag()
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.longName("command")
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.shortName('c')
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.description("command and arguments to be executed; defaults to 'bash'")
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.labels({"command", "args"})
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.arity(ArityAny)
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.handler([&](std::vector<std::string> ss) {
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if (ss.empty()) throw UsageError("--command requires at least one argument");
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command = ss;
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});
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mkFlag()
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.longName("ignore-environment")
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.shortName('i')
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.description("clear the entire environment (except those specified with --keep)")
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.set(&ignoreEnvironment, true);
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mkFlag()
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.longName("keep")
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.shortName('k')
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.description("keep specified environment variable")
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.arity(1)
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.labels({"name"})
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.handler([&](std::vector<std::string> ss) { keep.insert(ss.front()); });
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mkFlag()
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.longName("unset")
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.shortName('u')
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.description("unset specified environment variable")
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.arity(1)
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.labels({"name"})
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.handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
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}
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std::string name() override
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{
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return "run";
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}
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std::string description() override
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{
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return "run a shell in which the specified packages are available";
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}
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Examples examples() override
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{
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return {
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Example{
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"To start a shell providing GNU Hello from NixOS 17.03:",
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"nix run -f channel:nixos-17.03 hello"
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},
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Example{
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"To start a shell providing youtube-dl from your 'nixpkgs' channel:",
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"nix run nixpkgs.youtube-dl"
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},
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Example{
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"To run GNU Hello:",
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"nix run nixpkgs.hello -c hello --greeting 'Hi everybody!'"
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},
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Example{
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"To run GNU Hello in a chroot store:",
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"nix run --store ~/my-nix nixpkgs.hello -c hello"
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},
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};
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}
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void run(ref<Store> store) override
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{
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auto outPaths = toStorePaths(store, Build, installables);
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auto accessor = store->getFSAccessor();
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if (ignoreEnvironment) {
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if (!unset.empty())
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throw UsageError("--unset does not make sense with --ignore-environment");
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std::map<std::string, std::string> kept;
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for (auto & var : keep) {
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auto s = getenv(var.c_str());
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if (s) kept[var] = s;
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}
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clearEnv();
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for (auto & var : kept)
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setenv(var.first.c_str(), var.second.c_str(), 1);
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} else {
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if (!keep.empty())
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throw UsageError("--keep does not make sense without --ignore-environment");
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for (auto & var : unset)
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unsetenv(var.c_str());
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}
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std::unordered_set<Path> done;
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std::queue<Path> todo;
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for (auto & path : outPaths) todo.push(path);
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auto unixPath = tokenizeString<Strings>(getEnv("PATH"), ":");
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while (!todo.empty()) {
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Path path = todo.front();
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todo.pop();
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if (!done.insert(path).second) continue;
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if (true)
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unixPath.push_front(path + "/bin");
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auto propPath = path + "/nix-support/propagated-user-env-packages";
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if (accessor->stat(propPath).type == FSAccessor::tRegular) {
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for (auto & p : tokenizeString<Paths>(readFile(propPath)))
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todo.push(p);
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}
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}
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setenv("PATH", concatStringsSep(":", unixPath).c_str(), 1);
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std::string cmd = *command.begin();
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Strings args;
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for (auto & arg : command) args.push_back(arg);
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stopProgressBar();
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restoreAffinity();
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restoreSignals();
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restoreMountNamespace();
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/* If this is a diverted store (i.e. its "logical" location
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(typically /nix/store) differs from its "physical" location
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(e.g. /home/eelco/nix/store), then run the command in a
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chroot. For non-root users, this requires running it in new
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mount and user namespaces. Unfortunately,
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unshare(CLONE_NEWUSER) doesn't work in a multithreaded
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program (which "nix" is), so we exec() a single-threaded
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helper program (chrootHelper() below) to do the work. */
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auto store2 = store.dynamic_pointer_cast<LocalStore>();
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if (store2 && store->storeDir != store2->realStoreDir) {
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Strings helperArgs = { chrootHelperName, store->storeDir, store2->realStoreDir, cmd };
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for (auto & arg : args) helperArgs.push_back(arg);
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execv(readLink("/proc/self/exe").c_str(), stringsToCharPtrs(helperArgs).data());
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throw SysError("could not execute chroot helper");
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}
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execvp(cmd.c_str(), stringsToCharPtrs(args).data());
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throw SysError("unable to exec '%s'", cmd);
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}
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};
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static RegisterCommand r1(make_ref<CmdRun>());
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void chrootHelper(int argc, char * * argv)
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{
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int p = 1;
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std::string storeDir = argv[p++];
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std::string realStoreDir = argv[p++];
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std::string cmd = argv[p++];
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Strings args;
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while (p < argc)
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args.push_back(argv[p++]);
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#if __linux__
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uid_t uid = getuid();
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uid_t gid = getgid();
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if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == -1)
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throw SysError("setting up a private mount namespace");
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/* Bind-mount realStoreDir on /nix/store. If the latter mount
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point doesn't already exists, we have to create a chroot
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environment containing the mount point and bind mounts for the
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children of /. Would be nice if we could use overlayfs here,
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but that doesn't work in a user namespace yet (Ubuntu has a
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patch for this:
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https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1478578). */
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if (!pathExists(storeDir)) {
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// FIXME: Use overlayfs?
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Path tmpDir = createTempDir();
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createDirs(tmpDir + storeDir);
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if (mount(realStoreDir.c_str(), (tmpDir + storeDir).c_str(), "", MS_BIND, 0) == -1)
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throw SysError("mounting '%s' on '%s'", realStoreDir, storeDir);
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for (auto entry : readDirectory("/")) {
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auto src = "/" + entry.name;
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auto st = lstat(src);
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if (!S_ISDIR(st.st_mode)) continue;
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Path dst = tmpDir + "/" + entry.name;
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if (pathExists(dst)) continue;
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if (mkdir(dst.c_str(), 0700) == -1)
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throw SysError("creating directory '%s'", dst);
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if (mount(src.c_str(), dst.c_str(), "", MS_BIND | MS_REC, 0) == -1)
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throw SysError("mounting '%s' on '%s'", src, dst);
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}
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char * cwd = getcwd(0, 0);
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if (!cwd) throw SysError("getting current directory");
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Finally freeCwd([&]() { free(cwd); });
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if (chroot(tmpDir.c_str()) == -1)
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throw SysError(format("chrooting into '%s'") % tmpDir);
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if (chdir(cwd) == -1)
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throw SysError(format("chdir to '%s' in chroot") % cwd);
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} else
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if (mount(realStoreDir.c_str(), storeDir.c_str(), "", MS_BIND, 0) == -1)
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throw SysError("mounting '%s' on '%s'", realStoreDir, storeDir);
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writeFile("/proc/self/setgroups", "deny");
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writeFile("/proc/self/uid_map", fmt("%d %d %d", uid, uid, 1));
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writeFile("/proc/self/gid_map", fmt("%d %d %d", gid, gid, 1));
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execvp(cmd.c_str(), stringsToCharPtrs(args).data());
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throw SysError("unable to exec '%s'", cmd);
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#else
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throw Error("mounting the Nix store on '%s' is not supported on this platform", storeDir);
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#endif
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}
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