The switch_root shell script did not work with bash-4.0-2, because
"exec" gets the real path of the executable which is then
"/sysroot/lib/ld-linux.so.2" instread of "./lib/ld-linux.so.2".
Also the required chroot binary might live in /usr/bin, which can
be mounted later.
Here is the switch_root code from nash, which can be stripped down
further, but which works.
>From f1b1e4f8694104f007e4483c36b0bf40a5760167 Mon Sep 17 00:00:00 2001
From: Harald Hoyer <harald@xxxxxxxxxx>
Date: Wed, 4 Mar 2009 13:41:07 +0100
Subject: [PATCH] replace switch_root shell script with binary
The switch_root shell script did not work with bash-4.0-2, because
"exec" gets the real path of the executable which is then
"/sysroot/lib/ld-linux.so.2" instead of "./lib/ld-linux.so.2".
Also the required chroot binary might live in /usr/bin, which can
be mounted later.
Here is the switch_root code from nash, which can be stripped down
further, but which works.
---
Makefile | 11 +-
init | 3 +
switch_root | 111 ------------
switch_root.c | 556 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 566 insertions(+), 115 deletions(-)
delete mode 100755 switch_root
create mode 100644 switch_root.c
diff --git a/Makefile b/Makefile
index dbc2a7d..9441bbe 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,9 @@
-all:
- @echo "Nothing to do"
+switch_root: switch_root.c
+ gcc -o switch_root switch_root.c
-install:
+all: switch_root
+
+install: all
mkdir -p $(DESTDIR)/usr/libexec/dracut
mkdir -p $(DESTDIR)/sbin
mkdir -p $(DESTDIR)/usr/libexec/dracut/hooks
@@ -16,6 +18,7 @@ install:
for module in modules/*.sh; do install -m 0755 $$module $(DESTDIR)/usr/libexec/dracut ; done
clean:
rm -f *~
+ rm -f switch_root
-archive:
+archive:
git archive --format=tar HEAD --prefix=dracut/ |bzip2 > dracut-$(shell git rev-list --abbrev-commit -n 1 HEAD |cut -b 1-8).tar.bz2
diff --git a/init b/init
index 9605141..a0e83a7 100755
--- a/init
+++ b/init
@@ -103,6 +103,9 @@ INIT=$(getarg init); INIT=${INIT#init=}
}
source_all pre-pivot
+
+kill $(pidof udevd)
+
echo "Switching to real root filesystem $root"
exec switch_root "$NEWROOT" "$INIT" $CMDLINE || {
# davej doesn't like initrd bugs
diff --git a/switch_root b/switch_root
deleted file mode 100755
index d142e97..0000000
--- a/switch_root
+++ /dev/null
@@ -1,111 +0,0 @@
-#!/bin/sh
-# Copyright (c) Victor Lowther <victor.lowther@xxxxxxxxx>
-# Licensed under the terms of the GNU GPL v2 or later.
-
-# some utility functions first
-# this is so we can scroll back.
-
-die() { echo "${1}, dying horribly."; while :;do read line; done }
-
-# jsut enough to get the job done
-simple_find() {
- # $1 = file to look for
- # $rest = places to look for it
- local file=$1
- shift
- for loc in "$@"; do
- [ -f "$NEWROOT$loc/$file" ] && { echo "$loc/$file"; return 0; }
- done
- return 1
-}
-
-# We really should not be doing this from here, but...
-find_interp() {
- local ldso=$("$NEWROOT$CHROOT" "$NEWROOT" "$LDD" "$1" |
- while read interp rest; do
- [ -f "${NEWROOT}$interp" ] || continue
- echo "$interp"
- break
- done);
- [ "$ldso" ] && echo $ldso
-}
-
-# this makes it easier to run a command entirely from newroot
-# $1 = elf interpreter (must pass empty string if none)
-# $2 = command or "exec"
-# $3 = command if exec was passed
-run_from_newroot() {
- local ldso="$1" cmd="$2"; shift; shift
- if [ "$cmd" = "exec" ]; then
- cmd="$1"; shift
- if [ "$ldso" ]; then
- exec "$NEWROOT$ldso" --library-path "$LIBPATH" "$NEWROOT$cmd" "$@"
- else
- exec "$NEWROOT$cmd" "$@"
- fi
- else
- if [ "$ldso" ]; then
- "$NEWROOT$ldso" --library-path "$LIBPATH" "$NEWROOT$cmd" "$@"
- else
- "$NEWROOT$cmd" "$@"
- fi
- fi
-}
-# update the path to find our dynamic libraries on newroot
-update_newroot_libpath() {
- local x
- LIBPATH=":"
- LIBDIRS="$(echo $NEWROOT/lib* $NEWROOT/usr/lib*)"
- for x in $LIBDIRS; do
- [ -d "$x" ] && LIBPATH="${LIBPATH}${x}:"
- done
- LIBPATH="${LIBPATH%:}"; LIBPATH="${LIBPATH#:}"
- [ "$LIBPATH" ] || die "Cannot find shared library diectories on $NEWROOT"
-}
-NEWROOT="$1"
-INIT="$2"
-[ -d "$NEWROOT" ] || die "$NEWROOT is not a directory"
-[ -x "$NEWROOT$INIT" ] || die "$NEWROOT/$INIT is not executable."
-shift; shift
-
-update_newroot_libpath
-
-# start looking for required binaries and bits of infrastructure
-BINDIRS="/bin /sbin /usr/bin /usr/sbin"
-RM=$(simple_find rm $BINDIRS) || die "Cannnot find rm on $NEWROOT"
-CHROOT=$(simple_find chroot $BINDIRS) || die "Cannot find chroot on $NEWROOT"
-LDD=$(simple_find ldd $BINDIRS) || die "Cannot find ldd on $NEWROOT"
-MOUNT=$(simple_find mount $BINDIRS) || die "Cannot find mount on $NEWROOT"
-
-# now, start the real process of switching the root
-cd /
-
-# kill udevd, move all our mounts over to the new root
-kill $(pidof udevd)
-mount --move /proc $NEWROOT/proc
-mount --move /sys $NEWROOT/sys
-mount --move /dev $NEWROOT/dev
-
-# Find the binary interpreter for our three required binaries.
-# We do it here so that ldd does not complain about a missing /dev/null.
-CHROOT_LDSO=$(find_interp "$CHROOT")
-RM_LDSO=$(find_interp "$RM")
-MOUNT_LDSO=$(find_interp "$MOUNT")
-
-# redirect to new console. Our old initramfs will not be freed otherwise
-CONSOLE=$NEWROOT/dev/console
-[ -c $CONSOLE ] && exec >$CONSOLE 2>&1 <$CONSOLE
-for x in *; do
- [ "/$x" = "$NEWROOT" ] || run_from_newroot "$RM_LDSO" "$RM" -rf -- "$x"
-done
-# switch to our new root dir
-cd "$NEWROOT"
-# this moves rootfs to the actual root...
-run_from_newroot "$MOUNT_LDSO" "$MOUNT" -n --move . /
-# but does not update where / is in directory lookups.
-# Therefore, newroot is now ".". Update things accordingly, then chroot and
-# exec init.
-NEWROOT="."
-update_newroot_libpath
-run_from_newroot "$CHROOT_LDSO" exec "$CHROOT" "$NEWROOT" "$INIT" "$@" || \
- die "The chroot did not take for some reason"
diff --git a/switch_root.c b/switch_root.c
new file mode 100644
index 0000000..5e2f54f
--- /dev/null
+++ b/switch_root.c
@@ -0,0 +1,556 @@
+/*
+ * switch_root.c
+ *
+ * Code to switch from initramfs to system root.
+ * Based on nash.c from mkinitrd
+ *
+ * Copyright 2002-2009 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/>.
+ *
+ * Author(s): Erik Troan <ewt@xxxxxxxxxx>
+ * Jeremy Katz <katzj@xxxxxxxxxx>
+ * Peter Jones <pjones@xxxxxxxxxx>
+ * Harald Hoyer <harald@xxxxxxxxxx>
+ */
+
+#define _GNU_SOURCE 1
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <alloca.h>
+#include <string.h>
+#include <errno.h>
+#include <mntent.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <sys/mount.h>
+#include <fcntl.h>
+#include <linux/fs.h>
+
+#ifndef MNT_FORCE
+#define MNT_FORCE 0x1
+#endif
+
+#ifndef MNT_DETACH
+#define MNT_DETACH 0x2
+#endif
+
+
+#define asprintfa(str, fmt, ...) ({ \
+ char *_tmp = NULL; \
+ int _rc; \
+ _rc = asprintf((str), (fmt), __VA_ARGS__); \
+ if (_rc != -1) { \
+ _tmp = strdupa(*(str)); \
+ if (!_tmp) { \
+ _rc = -1; \
+ } else { \
+ free(*(str)); \
+ *(str) = _tmp; \
+ } \
+ } \
+ _rc; \
+ })
+
+
+
+static inline int
+setFdCoe(int fd, int enable)
+{
+ int rc;
+ long flags = 0;
+
+ rc = fcntl(fd, F_GETFD, &flags);
+ if (rc < 0)
+ return rc;
+
+ if (enable)
+ flags |= FD_CLOEXEC;
+ else
+ flags &= ~FD_CLOEXEC;
+
+ rc = fcntl(fd, F_SETFD, flags);
+ return rc;
+}
+
+static char *
+getArg(char * cmd, char * end, char ** arg)
+{
+ char quote = '\0';
+
+ if (!cmd || cmd >= end)
+ return NULL;
+
+ while (isspace(*cmd) && cmd < end)
+ cmd++;
+ if (cmd >= end)
+ return NULL;
+
+ if (*cmd == '"')
+ cmd++, quote = '"';
+ else if (*cmd == '\'')
+ cmd++, quote = '\'';
+
+ if (quote) {
+ *arg = cmd;
+
+ /* This doesn't support \ escapes */
+ while (cmd < end && *cmd != quote)
+ cmd++;
+
+ if (cmd == end) {
+ printf("error: quote mismatch for %s\n", *arg);
+ return NULL;
+ }
+
+ *cmd = '\0';
+ cmd++;
+ } else {
+ *arg = cmd;
+ while (!isspace(*cmd) && cmd < end)
+ cmd++;
+ *cmd = '\0';
+ if (**arg == '$')
+ *arg = getenv(*arg+1);
+ if (*arg == NULL)
+ *arg = "";
+ }
+
+ cmd++;
+
+ while (isspace(*cmd))
+ cmd++;
+
+ return cmd;
+}
+
+static int
+mountCommand(char * cmd, char * end)
+{
+ char * fsType = NULL;
+ char * device, *spec;
+ char * mntPoint;
+ char * opts = NULL;
+ int rc = 0;
+ int flags = MS_MGC_VAL;
+ char * newOpts;
+
+ if (!(cmd = getArg(cmd, end, &spec))) {
+ printf(
+ "usage: mount [--ro] [-o <opts>] -t <type> <device> <mntpoint>\n");
+ return 1;
+ }
+
+ while (cmd && *spec == '-') {
+ if (!strcmp(spec, "--ro")) {
+ flags |= MS_RDONLY;
+ } else if (!strcmp(spec, "--bind")) {
+ flags = MS_BIND;
+ fsType = "none";
+ } else if (!strcmp(spec, "--move")) {
+ flags = MS_MOVE;
+ fsType = "none";
+ } else if (!strcmp(spec, "-o")) {
+ cmd = getArg(cmd, end, &opts);
+ if (!cmd) {
+ printf("mount: -o requires arguments\n");
+ return 1;
+ }
+ } else if (!strcmp(spec, "-t")) {
+ if (!(cmd = getArg(cmd, end, &fsType))) {
+ printf("mount: missing filesystem type\n");
+ return 1;
+ }
+ }
+
+ cmd = getArg(cmd, end, &spec);
+ }
+
+ if (!cmd) {
+ printf("mount: missing device or mountpoint\n");
+ return 1;
+ }
+
+ if (!(cmd = getArg(cmd, end, &mntPoint))) {
+ struct mntent *mnt;
+ FILE *fstab;
+
+ fstab = fopen("/etc/fstab", "r");
+ if (!fstab) {
+ printf("mount: missing mount point\n");
+ return 1;
+ }
+ do {
+ if (!(mnt = getmntent(fstab))) {
+ printf("mount: missing mount point\n");
+ fclose(fstab);
+ return 1;
+ }
+ if (!strcmp(mnt->mnt_dir, spec)) {
+ spec = mnt->mnt_fsname;
+ mntPoint = mnt->mnt_dir;
+
+ if (!strcmp(mnt->mnt_type, "bind")) {
+ flags |= MS_BIND;
+ fsType = "none";
+ } else
+ fsType = mnt->mnt_type;
+
+ opts = mnt->mnt_opts;
+ break;
+ }
+ } while(1);
+
+ fclose(fstab);
+ }
+
+ if (!fsType) {
+ printf("mount: filesystem type expected\n");
+ return 1;
+ }
+
+ if (cmd && cmd < end) {
+ printf("mount: unexpected arguments\n");
+ return 1;
+ }
+
+ /* need to deal with options */
+ if (opts) {
+ char * end;
+ char * start = opts;
+
+ newOpts = alloca(strlen(opts) + 1);
+ *newOpts = '\0';
+
+ while (*start) {
+ end = strchr(start, ',');
+ if (!end) {
+ end = start + strlen(start);
+ } else {
+ *end = '\0';
+ end++;
+ }
+
+ if (!strcmp(start, "ro"))
+ flags |= MS_RDONLY;
+ else if (!strcmp(start, "rw"))
+ flags &= ~MS_RDONLY;
+ else if (!strcmp(start, "nosuid"))
+ flags |= MS_NOSUID;
+ else if (!strcmp(start, "suid"))
+ flags &= ~MS_NOSUID;
+ else if (!strcmp(start, "nodev"))
+ flags |= MS_NODEV;
+ else if (!strcmp(start, "dev"))
+ flags &= ~MS_NODEV;
+ else if (!strcmp(start, "noexec"))
+ flags |= MS_NOEXEC;
+ else if (!strcmp(start, "exec"))
+ flags &= ~MS_NOEXEC;
+ else if (!strcmp(start, "sync"))
+ flags |= MS_SYNCHRONOUS;
+ else if (!strcmp(start, "async"))
+ flags &= ~MS_SYNCHRONOUS;
+ else if (!strcmp(start, "nodiratime"))
+ flags |= MS_NODIRATIME;
+ else if (!strcmp(start, "diratime"))
+ flags &= ~MS_NODIRATIME;
+ else if (!strcmp(start, "noatime"))
+ flags |= MS_NOATIME;
+ else if (!strcmp(start, "atime"))
+ flags &= ~MS_NOATIME;
+ else if (!strcmp(start, "relatime"))
+ flags |= MS_RELATIME;
+ else if (!strcmp(start, "norelatime"))
+ flags &= ~MS_RELATIME;
+ else if (!strcmp(start, "remount"))
+ flags |= MS_REMOUNT;
+ else if (!strcmp(start, "bind"))
+ flags |= MS_BIND;
+ else if (!strcmp(start, "defaults"))
+ ;
+ else {
+ if (*newOpts)
+ strcat(newOpts, ",");
+ strcat(newOpts, start);
+ }
+
+ start = end;
+ }
+
+ opts = newOpts;
+ }
+
+ device = strdupa(spec);
+
+ if (!device) {
+ printf("mount: could not find filesystem '%s'\n", spec);
+ return 1;
+ }
+
+ {
+ char *mount_opts = NULL;
+ mount_opts = opts;
+ if (mount(device, mntPoint, fsType, flags, mount_opts) < 0) {
+ printf("mount: error mounting %s on %s as %s: %m\n",
+ device, mntPoint, fsType);
+ rc = 1;
+ }
+ }
+
+ return rc;
+}
+
+/* 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 void
+mountMntEnt(const struct mntent *mnt)
+{
+ char *start = NULL, *end;
+ char *target = NULL;
+ struct stat sb;
+
+ printf("mounting %s\n", mnt->mnt_dir);
+ if (asprintfa(&target, ".%s", mnt->mnt_dir) < 0) {
+ printf("setuproot: out of memory while mounting %s\n",
+ mnt->mnt_dir);
+ return;
+ }
+
+ if (stat(target, &sb) < 0)
+ return;
+
+ if (asprintf(&start, "-o %s -t %s %s .%s\n",
+ mnt->mnt_opts, mnt->mnt_type, mnt->mnt_fsname,
+ mnt->mnt_dir) < 0) {
+ printf("setuproot: out of memory while mounting %s\n",
+ mnt->mnt_dir);
+ return;
+ }
+
+ end = start + 1;
+ while (*end && (*end != '\n'))
+ end++;
+ /* end points to the \n at the end of the command */
+
+ if (mountCommand(start, end) != 0)
+ printf("setuproot: mount returned error\n");
+}
+
+static int
+setuprootCommand(char *new)
+{
+ FILE *fp;
+
+ printf("Setting up new root fs\n");
+
+ if (chdir(new)) {
+ printf("setuproot: chdir(%s) failed: %m\n", new);
+ return 1;
+ }
+
+ if (mount("/dev", "./dev", NULL, MS_BIND, NULL) < 0)
+ printf("setuproot: moving /dev failed: %m\n");
+
+ fp = setmntent("./etc/fstab.sys", "r");
+ if (fp)
+ printf("using fstab.sys from mounted FS\n");
+ else {
+ fp = setmntent("/etc/fstab.sys", "r");
+ if (fp)
+ printf("using fstab.sys from initrd\n");
+ }
+ if (fp) {
+ struct mntent *mnt;
+
+ while((mnt = getmntent(fp)))
+ mountMntEnt(mnt);
+ endmntent(fp);
+ } else {
+ struct {
+ char *source;
+ char *target;
+ char *type;
+ int flags;
+ void *data;
+ int raise;
+ } fstab[] = {
+ { "/proc", "./proc", "proc", 0, NULL },
+ { "/sys", "./sys", "sysfs", 0, NULL },
+#if 0
+ { "/dev/pts", "./dev/pts", "devpts", 0, "gid=5,mode=620" },
+ { "/dev/shm", "./dev/shm", "tmpfs", 0, NULL },
+ { "/selinux", "/selinux", "selinuxfs", 0, NULL },
+#endif
+ { NULL, }
+ };
+ int i = 0;
+
+ printf("no fstab.sys, mounting internal defaults\n");
+ for (; fstab[i].source != NULL; i++) {
+ if (mount(fstab[i].source, fstab[i].target, fstab[i].type,
+ fstab[i].flags, fstab[i].data) < 0)
+ printf("setuproot: error mounting %s: %m\n",
+ fstab[i].source);
+ }
+ }
+
+ chdir("/");
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ /* Don't try to unmount the old "/", there's no way to do it. */
+ const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
+ char *new = NULL;
+ int fd, i = 0;
+
+ argv++;
+ new = argv[0];
+ argv++;
+ printf("Switching to root: %s", new);
+
+ setuprootCommand(new);
+
+ fd = open("/", O_RDONLY);
+ for (; umounts[i] != NULL; i++) {
+ printf("unmounting old %s\n", umounts[i]);
+ if (umount2(umounts[i], MNT_DETACH) < 0) {
+ printf("ERROR unmounting old %s: %m\n",umounts[i]);
+ printf("forcing unmount of %s\n", umounts[i]);
+ umount2(umounts[i], MNT_FORCE);
+ }
+ }
+ i=0;
+
+ chdir(new);
+
+ recursiveRemove("/");
+
+ if (mount(new, "/", NULL, MS_MOVE, NULL) < 0) {
+ printf("switchroot: mount failed: %m\n");
+ close(fd);
+ return 1;
+ }
+
+ if (chroot(".")) {
+ printf("switchroot: chroot() failed: %m\n");
+ close(fd);
+ return 1;
+ }
+
+ /* release the old "/" */
+ close(fd);
+
+ close(3);
+ if ((fd = open("/dev/console", O_RDWR)) < 0) {
+ printf("ERROR opening /dev/console: %m\n");
+ printf("Trying to use fd 0 instead.\n");
+ fd = dup2(0, 3);
+ } else {
+ setFdCoe(fd, 0);
+ if (fd != 3) {
+ dup2(fd, 3);
+ close(fd);
+ fd = 3;
+ }
+ }
+ close(0);
+ dup2(fd, 0);
+ close(1);
+ dup2(fd, 1);
+ close(2);
+ dup2(fd, 2);
+ close(fd);
+
+ if (access(argv[0], X_OK)) {
+ printf("WARNING: can't access %s\n", argv[0]);
+ }
+
+ execv(argv[0], argv);
+
+ printf("exec of init (%s) failed!!!: %m\n", argv[0]);
+ return 1;
+}
--
1.6.0.6
