diff options
| -rw-r--r-- | doc/manual/release-notes.xml | 3 | ||||
| -rw-r--r-- | nix.conf.example | 38 | ||||
| -rw-r--r-- | src/libstore/build.cc | 48 | ||||
| -rw-r--r-- | src/libutil/util.cc | 8 | ||||
| -rw-r--r-- | src/libutil/util.hh | 2 |
5 files changed, 80 insertions, 19 deletions
diff --git a/doc/manual/release-notes.xml b/doc/manual/release-notes.xml index b19d9a38231f..c702fb45aaf6 100644 --- a/doc/manual/release-notes.xml +++ b/doc/manual/release-notes.xml @@ -116,6 +116,9 @@ limited form of caching. This is used by <command>nix-channel</command> to prevent unnecessary downloads when the channel hasn’t changed.</para></listitem> + + + <listitem><para>TODO: chroot support.</para></listitem> </itemizedlist> diff --git a/nix.conf.example b/nix.conf.example index be6a955a8d5f..99a94bfb9173 100644 --- a/nix.conf.example +++ b/nix.conf.example @@ -135,6 +135,44 @@ #build-users-group = +### Option `build-use-chroot' +# +# If set to `true', builds will be performed in a chroot environment, +# i.e., the build will be isolated from the normal file system +# hierarchy and will only see the Nix store, the temporary build +# directory, and the directories configured with the +# `build-chroot-dirs' option (such as /proc and /dev). This is useful +# to prevent undeclared dependencies on files in directories such as +# /usr/bin. +# +# The use of a chroot requires that Nix is run as root (but you can +# still use the "build users" feature to perform builds under +# different users than root). Currently, chroot builds only work on +# Linux because Nix uses "bind mounts" to make the Nix store and other +# directories available inside the chroot. +# +# The default is `false'. +# +# Example: +# build-use-chroot = true +#build-use-chroot = false + + +### Option `build-chroot-dirs' +# +# When builds are performed in a chroot environment, Nix will mount +# (using `mount --bind' on Linux) some directories from the normal +# file system hierarchy inside the chroot. These are the Nix store, +# the temporary build directory (usually /tmp/nix-<pid>-<number>) and +# the directories listed here. The default is "/dev /proc". Files +# in /dev (such as /dev/null) are needed by many builds, and some +# files in /proc may also be needed occasionally. +# +# Example: +# build-use-chroot = /dev /proc /bin +#build-chroot-dirs = /dev /proc + + ### Option `system' # # This option specifies the canonical Nix system name of the current diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 3c988ea42b95..6e2b748618b7 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -586,7 +586,8 @@ void deletePathWrapped(const Path & path) #include <sys/mount.h> -/* Helper class for automatically unmounting bind-mounts in chroots. */ +/* Helper RAII class for automatically unmounting bind-mounts in + chroots. */ struct BindMount { Path source, target; @@ -612,7 +613,7 @@ struct BindMount void bind(const Path & source, const Path & target) { - printMsg(lvlError, format("bind mounting `%1%' to `%2%'") % source % target); + debug(format("bind mounting `%1%' to `%2%'") % source % target); this->source = source; this->target = target; @@ -626,7 +627,8 @@ struct BindMount void unbind() { if (source == "") return; - printMsg(lvlError, format("umount `%1%'") % target); + + debug(format("unmount bind-mount `%1%'") % target); /* Urgh. Unmount sometimes doesn't succeed right away because the mount point is still busy. It shouldn't be, because @@ -644,16 +646,18 @@ struct BindMount sleep(1); } else - throw SysError(format("unmounting `%1%' failed") % target); + throw SysError(format("unmounting bind-mount `%1%' failed") % target); } /* Get rid of the directories for the mount point created in bind(). */ for (Paths::reverse_iterator i = created.rbegin(); i != created.rend(); ++i) { - printMsg(lvlError, format("delete `%1%'") % *i); + debug(format("deleting `%1%'") % *i); if (remove(i->c_str()) == -1) throw SysError(format("cannot unlink `%1%'") % *i); } + + source = ""; } }; @@ -704,11 +708,14 @@ private: /* Whether we're currently doing a chroot build. */ bool useChroot; + /* A RAII object to delete the chroot directory. */ + boost::shared_ptr<AutoDelete> autoDelChroot; + /* In chroot builds, the list of bind mounts currently active. The destructor of BindMount will cause the binds to be unmounted. */ list<boost::shared_ptr<BindMount> > bindMounts; - + typedef void (DerivationGoal::*GoalState)(); GoalState state; @@ -797,18 +804,11 @@ DerivationGoal::~DerivationGoal() /* Careful: we should never ever throw an exception from a destructor. */ try { - printMsg(lvlError, "DESTROY"); killChild(); deleteTmpDir(false); } catch (...) { ignoreException(); } - try { - //sleep(1); - bindMounts.clear(); - } catch (...) { - ignoreException(); - } } @@ -1646,7 +1646,27 @@ void DerivationGoal::startBuilder() Path tmpRootDir; if (useChroot) { - tmpRootDir = createTempDir(); + /* Create a temporary directory in which we set up the chroot + environment using bind-mounts. + + !!! Big danger here: since we're doing this in /tmp, there + is a risk that the admin does something like "rm -rf + /tmp/chroot-nix-*" to clean up aborted builds, and if some + of the bind-mounts are still active, then "rm -rf" will + happily recurse into those mount points (thereby deleting, + say, /nix/store). Ideally, tmpRootDir should be created in + some special location (maybe in /nix/var/nix) where Nix + takes care of unmounting / deleting old chroots + automatically. */ + tmpRootDir = createTempDir("", "chroot-nix"); + + /* Clean up the chroot directory automatically, but don't + recurse; that would be very very bad if the unmount of a + bind-mount fails. Instead BindMount::unbind() unmounts and + deletes exactly those directories that it created to + produce the mount point, so that after all the BindMount + destructors have run, tmpRootDir should be empty. */ + autoDelChroot = boost::shared_ptr<AutoDelete>(new AutoDelete(tmpRootDir, false)); printMsg(lvlChatty, format("setting up chroot environment in `%1%'") % tmpRootDir); diff --git a/src/libutil/util.cc b/src/libutil/util.cc index 428b1ff9a755..ed095717e262 100644 --- a/src/libutil/util.cc +++ b/src/libutil/util.cc @@ -318,19 +318,19 @@ void makePathReadOnly(const Path & path) } -static Path tempName(const Path & tmpRoot) +static Path tempName(const Path & tmpRoot, const Path & prefix) { static int counter = 0; Path tmpRoot2 = canonPath(tmpRoot.empty() ? getEnv("TMPDIR", "/tmp") : tmpRoot, true); - return (format("%1%/nix-%2%-%3%") % tmpRoot2 % getpid() % counter++).str(); + return (format("%1%/%2%-%3%-%4%") % tmpRoot2 % prefix % getpid() % counter++).str(); } -Path createTempDir(const Path & tmpRoot) +Path createTempDir(const Path & tmpRoot, const Path & prefix) { while (1) { checkInterrupt(); - Path tmpDir = tempName(tmpRoot); + Path tmpDir = tempName(tmpRoot, prefix); if (mkdir(tmpDir.c_str(), 0777) == 0) { /* Explicitly set the group of the directory. This is to work around around problems caused by BSD's group diff --git a/src/libutil/util.hh b/src/libutil/util.hh index 0ed98118c53b..657f45ced6e8 100644 --- a/src/libutil/util.hh +++ b/src/libutil/util.hh @@ -70,7 +70,7 @@ void deletePath(const Path & path, unsigned long long & bytesFreed); void makePathReadOnly(const Path & path); /* Create a temporary directory. */ -Path createTempDir(const Path & tmpRoot = ""); +Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix"); /* Create a directory and all its parents, if necessary. Returns the list of created directories, in order of creation. */ |