lix/src/nix/run.cc

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#include "run.hh"
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#include "command.hh"
#include "common-args.hh"
#include "shared.hh"
#include "store-api.hh"
#include "derivations.hh"
#include "local-store.hh"
#include "finally.hh"
#include "fs-accessor.hh"
#include "progress-bar.hh"
#include "eval.hh"
#if __linux__
#include <sys/mount.h>
#endif
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#include <queue>
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using namespace nix;
std::string chrootHelperName = "__run_in_chroot";
namespace nix {
void runProgramInStore(ref<Store> store,
const std::string & program,
const Strings & args)
{
stopProgressBar();
restoreProcessContext();
/* If this is a diverted store (i.e. its "logical" location
(typically /nix/store) differs from its "physical" location
(e.g. /home/eelco/nix/store), then run the command in a
chroot. For non-root users, this requires running it in new
mount and user namespaces. Unfortunately,
unshare(CLONE_NEWUSER) doesn't work in a multithreaded program
(which "nix" is), so we exec() a single-threaded helper program
(chrootHelper() below) to do the work. */
auto store2 = store.dynamic_pointer_cast<LocalFSStore>();
if (!store2)
throw Error("store '%s' is not a local store so it does not support command execution", store->getUri());
if (store->storeDir != store2->getRealStoreDir()) {
Strings helperArgs = { chrootHelperName, store->storeDir, store2->getRealStoreDir(), program };
for (auto & arg : args) helperArgs.push_back(arg);
execv(getSelfExe().value_or("nix").c_str(), stringsToCharPtrs(helperArgs).data());
throw SysError("could not execute chroot helper");
}
execvp(program.c_str(), stringsToCharPtrs(args).data());
throw SysError("unable to execute '%s'", program);
}
}
struct CmdShell : InstallablesCommand, MixEnvironment
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{
using InstallablesCommand::run;
std::vector<std::string> command = { getEnv("SHELL").value_or("bash") };
CmdShell()
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{
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addFlag({
.longName = "command",
.shortName = 'c',
.description = "Command and arguments to be executed, defaulting to `$SHELL`",
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.labels = {"command", "args"},
.handler = {[&](std::vector<std::string> ss) {
if (ss.empty()) throw UsageError("--command requires at least one argument");
command = ss;
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}}
});
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}
std::string description() override
{
return "run a shell in which the specified packages are available";
}
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std::string doc() override
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{
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return
#include "shell.md"
;
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}
void run(ref<Store> store) override
{
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auto outPaths = Installable::toStorePaths(getEvalStore(), store, Realise::Outputs, OperateOn::Output, installables);
auto accessor = store->getFSAccessor();
std::unordered_set<StorePath> done;
std::queue<StorePath> todo;
for (auto & path : outPaths) todo.push(path);
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setEnviron();
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auto unixPath = tokenizeString<Strings>(getEnv("PATH").value_or(""), ":");
while (!todo.empty()) {
auto path = todo.front();
todo.pop();
if (!done.insert(path).second) continue;
if (true)
unixPath.push_front(store->printStorePath(path) + "/bin");
auto propPath = store->printStorePath(path) + "/nix-support/propagated-user-env-packages";
if (accessor->stat(propPath).type == FSAccessor::tRegular) {
for (auto & p : tokenizeString<Paths>(readFile(propPath)))
todo.push(store->parseStorePath(p));
}
}
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setenv("PATH", concatStringsSep(":", unixPath).c_str(), 1);
Strings args;
for (auto & arg : command) args.push_back(arg);
runProgramInStore(store, *command.begin(), args);
}
};
static auto rCmdShell = registerCommand<CmdShell>("shell");
struct CmdRun : InstallableCommand
{
using InstallableCommand::run;
std::vector<std::string> args;
CmdRun()
{
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expectArgs({
.label = "args",
.handler = {&args},
.completer = completePath
});
}
std::string description() override
{
return "run a Nix application";
}
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std::string doc() override
{
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return
#include "run.md"
;
}
Strings getDefaultFlakeAttrPaths() override
{
Strings res{
"apps." + settings.thisSystem.get() + ".default",
"defaultApp." + settings.thisSystem.get(),
};
for (auto & s : SourceExprCommand::getDefaultFlakeAttrPaths())
res.push_back(s);
return res;
}
Strings getDefaultFlakeAttrPathPrefixes() override
{
Strings res{"apps." + settings.thisSystem.get() + "."};
for (auto & s : SourceExprCommand::getDefaultFlakeAttrPathPrefixes())
res.push_back(s);
return res;
}
void run(ref<Store> store) override
{
auto state = getEvalState();
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lockFlags.applyNixConfig = true;
auto app = installable->toApp(*state).resolve(getEvalStore(), store);
Strings allArgs{app.program};
for (auto & i : args) allArgs.push_back(i);
runProgramInStore(store, app.program, allArgs);
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}
};
static auto rCmdRun = registerCommand<CmdRun>("run");
void chrootHelper(int argc, char * * argv)
{
int p = 1;
std::string storeDir = argv[p++];
std::string realStoreDir = argv[p++];
std::string cmd = argv[p++];
Strings args;
while (p < argc)
args.push_back(argv[p++]);
#if __linux__
uid_t uid = getuid();
uid_t gid = getgid();
if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == -1)
/* Try with just CLONE_NEWNS in case user namespaces are
specifically disabled. */
if (unshare(CLONE_NEWNS) == -1)
throw SysError("setting up a private mount namespace");
/* Bind-mount realStoreDir on /nix/store. If the latter mount
point doesn't already exists, we have to create a chroot
environment containing the mount point and bind mounts for the
children of /. Would be nice if we could use overlayfs here,
but that doesn't work in a user namespace yet (Ubuntu has a
patch for this:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1478578). */
if (!pathExists(storeDir)) {
// FIXME: Use overlayfs?
Path tmpDir = createTempDir();
createDirs(tmpDir + storeDir);
if (mount(realStoreDir.c_str(), (tmpDir + storeDir).c_str(), "", MS_BIND, 0) == -1)
throw SysError("mounting '%s' on '%s'", realStoreDir, storeDir);
for (auto entry : readDirectory("/")) {
auto src = "/" + entry.name;
Path dst = tmpDir + "/" + entry.name;
if (pathExists(dst)) continue;
auto st = lstat(src);
if (S_ISDIR(st.st_mode)) {
if (mkdir(dst.c_str(), 0700) == -1)
throw SysError("creating directory '%s'", dst);
if (mount(src.c_str(), dst.c_str(), "", MS_BIND | MS_REC, 0) == -1)
throw SysError("mounting '%s' on '%s'", src, dst);
} else if (S_ISLNK(st.st_mode))
createSymlink(readLink(src), dst);
}
char * cwd = getcwd(0, 0);
if (!cwd) throw SysError("getting current directory");
Finally freeCwd([&]() { free(cwd); });
if (chroot(tmpDir.c_str()) == -1)
throw SysError("chrooting into '%s'", tmpDir);
if (chdir(cwd) == -1)
throw SysError("chdir to '%s' in chroot", cwd);
} else
if (mount(realStoreDir.c_str(), storeDir.c_str(), "", MS_BIND, 0) == -1)
throw SysError("mounting '%s' on '%s'", realStoreDir, storeDir);
writeFile("/proc/self/setgroups", "deny");
writeFile("/proc/self/uid_map", fmt("%d %d %d", uid, uid, 1));
writeFile("/proc/self/gid_map", fmt("%d %d %d", gid, gid, 1));
execvp(cmd.c_str(), stringsToCharPtrs(args).data());
throw SysError("unable to exec '%s'", cmd);
#else
throw Error("mounting the Nix store on '%s' is not supported on this platform", storeDir);
#endif
}