nspawn: create essential base directories at system bootup

This allows us to bootup a rootfs with a /usr directory only.

2 files changed, 106 insertions, 0 deletions

diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c
new file mode 100644
index 0000000000..a2201017e0
--- /dev/null
+++ b/src/shared/base-filesystem.c
@@ -0,0 +1,82 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Kay Sievers
+
+  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 <errno.h>
+#include <sys/stat.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+
+#include "base-filesystem.h"
+#include "log.h"
+#include "macro.h"
+#include "util.h"
+#include "label.h"
+#include "mkdir.h"
+
+typedef struct BaseFilesystem {
+        const char *dir;
+        mode_t mode;
+        const char *target;
+} BaseFilesystem;
+
+static const BaseFilesystem table[] = {
+        { "bin",      0, "usr/bin"   },
+        { "lib",      0, "usr/lib"   },
+        { "lib64",    0, "usr/lib64" },
+        { "root",  0755, NULL },
+        { "sbin",     0, "usr/sbin"  },
+};
+
+int base_filesystem_create(const char *root) {
+        _cleanup_close_ int fd = -1;
+        unsigned i;
+        int r;
+
+        fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
+        if (fd < 0)
+                return -errno;
+
+        for (i = 0; i < ELEMENTSOF(table); i ++) {
+                if (table[i].target) {
+                        /* check if target exists */
+                        if (faccessat(fd, table[i].target, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
+                                continue;
+
+                        r = symlinkat(table[i].target, fd, table[i].dir);
+                        if (r < 0 && errno != EEXIST) {
+                                log_error("Failed to create symlink at %s/%s: %m", root, table[i].dir);
+                                return -errno;
+                        }
+                        continue;
+                }
+
+                RUN_WITH_UMASK(0000)
+                        r = mkdirat(fd, table[i].dir, table[i].mode);
+                if (r < 0 && errno != EEXIST) {
+                        log_error("Failed to create directory at %s/%s: %m", root, table[i].dir);
+                        return -errno;
+                }
+        }
+
+        return 0;
+}
diff --git a/src/shared/base-filesystem.h b/src/shared/base-filesystem.h
new file mode 100644
index 0000000000..03201f7083
--- /dev/null
+++ b/src/shared/base-filesystem.h
@@ -0,0 +1,24 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Kay Sievers
+
+  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/>.
+***/
+
+int base_filesystem_create(const char *root);