import: add new minimal tool "systemd-import" for pulling down foreign containers and install them locally

This adds a simply but powerful tool for downloading container images
from the most popular container solution used today. Use it like
this:

       # systemd-import pull-dck mattdm/fedora
       # systemd-nspawn -M fedora

This will donwload the layers for "mattdm/fedora", and make them
available locally as /var/lib/container/fedora.

The tool is pretty complete, as long as it's only about pulling down
images, or updating them. Pushing or searching is not supported yet.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/import/aufs-util.c b/src/import/aufs-util.c
new file mode 100644
index 0000000000..c1301cdb4a
--- /dev/null
+++ b/src/import/aufs-util.c
@@ -0,0 +1,73 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <ftw.h>
+
+#include "util.h"
+#include "aufs-util.h"
+
+static int nftw_cb(
+                const char *fpath,
+                const struct stat *sb,
+                int flag,
+                struct FTW *ftwbuf) {
+
+        const char *fn, *original;
+        char *p;
+        int r;
+
+        fn = fpath + ftwbuf->base;
+
+        /* We remove all whiteout files, and all whiteouts */
+
+        original = startswith(fn, ".wh.");
+        if (!original)
+                return FTW_CONTINUE;
+
+        log_debug("Removing whiteout indicator %s.", fpath);
+        r = rm_rf_dangerous(fpath, false, true, false);
+        if (r < 0)
+                return FTW_STOP;
+
+        if (!startswith(fn, ".wh..wh.")) {
+
+                p = alloca(ftwbuf->base + strlen(original));
+                strcpy(mempcpy(p, fpath, ftwbuf->base), original);
+
+                log_debug("Removing deleted file %s.", p);
+                r = rm_rf_dangerous(p, false, true, false);
+                if (r < 0)
+                        return FTW_STOP;
+        }
+
+        return FTW_CONTINUE;
+}
+
+int aufs_resolve(const char *path) {
+        int r;
+
+        errno = 0;
+        r = nftw(path, nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
+        if (r == FTW_STOP)
+                return errno ? -errno : -EIO;
+
+        return 0;
+}