dracut: New package.

[people/teissler/ipfire-2.x.git] / src / dracut / switch_root.c

diff --git a/src/dracut/switch_root.c b/src/dracut/switch_root.c
new file mode 100644 (file)
index 0000000..1520387
--- /dev/null
+++ b/src/dracut/switch_root.c
@@ -0,0 +1,188 @@
+/*
+ * switchroot.c - switch to new root directory and start init.
+ *
+ * Copyright 2002-2008 Red Hat, Inc.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors:
+ *     Peter Jones <pjones@redhat.com>
+ *     Jeremy Katz <katzj@redhat.com>
+ */
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/param.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <dirent.h>
+
+#ifndef MS_MOVE
+#define MS_MOVE 8192
+#endif
+
+enum {
+       ok,
+       err_no_directory,
+       err_usage,
+};
+
+/* remove all files/directories below dirName -- don't cross mountpoints */
+static int
+recursiveRemove(char * dirName)
+{
+       struct stat sb,rb;
+       DIR * dir;
+       struct dirent * d;
+       char * strBuf = alloca(strlen(dirName) + 1024);
+
+       if (!(dir = opendir(dirName))) {
+               printf("error opening %s: %m\n", dirName);
+               return 0;
+       }
+
+       if (fstat(dirfd(dir),&rb)) {
+               printf("unable to stat %s: %m\n", dirName);
+               closedir(dir);
+               return 0;
+       }
+
+       errno = 0;
+
+       while ((d = readdir(dir))) {
+               errno = 0;
+
+               if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")) {
+                       errno = 0;
+                       continue;
+               }
+
+               strcpy(strBuf, dirName);
+               strcat(strBuf, "/");
+               strcat(strBuf, d->d_name);
+
+               if (lstat(strBuf, &sb)) {
+                       printf("failed to stat %s: %m\n", strBuf);
+                       errno = 0;
+                       continue;
+               }
+
+               /* only descend into subdirectories if device is same as dir */
+               if (S_ISDIR(sb.st_mode)) {
+                       if (sb.st_dev == rb.st_dev) {
+                               recursiveRemove(strBuf);
+                               if (rmdir(strBuf))
+                                       printf("failed to rmdir %s: %m\n", strBuf);
+                       }
+                       errno = 0;
+                       continue;
+               }
+               if (unlink(strBuf)) {
+                       printf("failed to remove %s: %m\n", strBuf);
+                       errno = 0;
+                       continue;
+               }
+       }
+
+       if (errno) {
+               closedir(dir);
+               printf("error reading from %s: %m\n", dirName);
+               return 1;
+       }
+
+       closedir(dir);
+       return 0;
+}
+
+static int switchroot(const char *newroot)
+{
+       /*  Don't try to unmount the old "/", there's no way to do it. */
+       const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
+       int errnum;
+       int i;
+
+       for (i = 0; umounts[i] != NULL; i++) {
+               char newmount[PATH_MAX];
+               strcpy(newmount, newroot);
+               strcat(newmount, umounts[i]);
+               if (mount(umounts[i], newmount, NULL, MS_MOVE, NULL) < 0) {
+                       fprintf(stderr, "Error mount moving old %s %s %m\n",
+                               umounts[i], newmount);
+                       fprintf(stderr, "Forcing unmount of %s\n", umounts[i]);
+                       umount2(umounts[i], MNT_FORCE);
+               }
+       }
+
+       if (chdir(newroot) < 0) {
+               errnum=errno;
+               fprintf(stderr, "switchroot: chdir failed: %m\n");
+               errno=errnum;
+               return -1;
+       }
+       recursiveRemove("/");
+       if (mount(newroot, "/", NULL, MS_MOVE, NULL) < 0) {
+               errnum = errno;
+               fprintf(stderr, "switchroot: mount failed: %m\n");
+               errno = errnum;
+               return -1;
+       }
+
+       if (chroot(".")) {
+               errnum = errno;
+               fprintf(stderr, "switchroot: chroot failed: %m\n");
+               errno = errnum;
+               return -2;
+       }
+       return 1;
+}
+
+static void usage(FILE *output)
+{
+       fprintf(output, "usage: switchroot <newrootdir> <init> <args to init>\n");
+       if (output == stderr)
+               exit(err_usage);
+       exit(ok);
+}
+
+int main(int argc, char *argv[])
+{
+       char *newroot = argv[1];
+       char *init = argv[2];
+       char **initargs = &argv[2];
+
+       if (newroot == NULL || newroot[0] == '\0' ||
+           init == NULL || init[0] == '\0' ) {
+               usage(stderr);
+       }
+
+       if (switchroot(newroot) < 0) {
+               fprintf(stderr, "switchroot has failed.  Sorry.\n");
+               return 1;
+       }
+       if (access(initargs[0], X_OK))
+               fprintf(stderr, "WARNING: can't access %s\n", initargs[0]);
+
+       /* get session leader */
+       setsid();
+       /* set controlling terminal */
+       ioctl (0, TIOCSCTTY, 1);
+
+       execv(initargs[0], initargs);
+}
+