252 lines
7.3 KiB
C
252 lines
7.3 KiB
C
/* -*- c-file-style: "gnu" -*-
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* Switch to new root directory and start init.
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*
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* Copyright 2011,2012,2013 Colin Walters <walters@verbum.org>
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*
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* Based on code from util-linux/sys-utils/switch_root.c,
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* Copyright 2002-2009 Red Hat, Inc. All rights reserved.
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* Authors:
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* Peter Jones <pjones@redhat.com>
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* Jeremy Katz <katzj@redhat.com>
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*
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* Relicensed with permission to LGPLv2+.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#include "config.h"
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#include <sys/mount.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/param.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdarg.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <ctype.h>
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#include "ostree-mount-util.h"
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static char *
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parse_ostree_cmdline (void)
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{
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FILE *f = fopen("/proc/cmdline", "r");
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char *cmdline = NULL;
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const char *iter;
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char *ret = NULL;
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size_t len;
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if (!f)
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return NULL;
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/* Note that /proc/cmdline will not end in a newline, so getline
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* will fail unelss we provide a length.
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*/
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if (getline (&cmdline, &len, f) < 0)
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return NULL;
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/* ... but the length will be the size of the malloc buffer, not
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* strlen(). Fix that.
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*/
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len = strlen (cmdline);
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if (cmdline[len-1] == '\n')
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cmdline[len-1] = '\0';
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iter = cmdline;
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while (iter != NULL)
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{
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const char *next = strchr (iter, ' ');
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const char *next_nonspc = next;
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while (next_nonspc && *next_nonspc == ' ')
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next_nonspc += 1;
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if (strncmp (iter, "ostree=", strlen ("ostree=")) == 0)
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{
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const char *start = iter + strlen ("ostree=");
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if (next)
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ret = strndup (start, next - start);
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else
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ret = strdup (start);
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break;
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}
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iter = next_nonspc;
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}
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free (cmdline);
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return ret;
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}
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/* This is an API for other projects to determine whether or not the
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* currently running system is ostree-controlled.
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*/
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static void
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touch_run_ostree (void)
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{
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int fd;
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fd = open ("/run/ostree-booted", O_CREAT | O_WRONLY | O_NOCTTY, 0640);
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/* We ignore failures here in case /run isn't mounted...not much we
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* can do about that, but we don't want to fail.
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*/
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if (fd == -1)
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return;
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(void) close (fd);
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}
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int
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main(int argc, char *argv[])
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{
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const char *readonly_bind_mounts[] = { "/usr", NULL };
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const char *root_mountpoint = NULL;
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char *ostree_target = NULL;
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char *deploy_path = NULL;
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char srcpath[PATH_MAX];
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char destpath[PATH_MAX];
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char newroot[PATH_MAX];
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struct stat stbuf;
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int i;
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if (argc < 2)
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{
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fprintf (stderr, "usage: ostree-prepare-root SYSROOT\n");
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exit (EXIT_FAILURE);
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}
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root_mountpoint = argv[1];
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ostree_target = parse_ostree_cmdline ();
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if (!ostree_target)
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{
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fprintf (stderr, "No OSTree target; expected ostree=/ostree/boot.N/...\n");
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exit (EXIT_FAILURE);
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}
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/* Create a temporary target for our mounts in the initramfs; this will
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* be moved to the new system root below.
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*/
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snprintf (newroot, sizeof(newroot), "%s.tmp", root_mountpoint);
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if (mkdir (newroot, 0755) < 0)
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{
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perrorv ("Couldn't create temporary sysroot '%s': ", newroot);
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exit (EXIT_FAILURE);
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}
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snprintf (destpath, sizeof(destpath), "%s/%s", root_mountpoint, ostree_target);
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printf ("Examining %s\n", destpath);
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if (lstat (destpath, &stbuf) < 0)
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{
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perrorv ("Couldn't find specified OSTree root '%s': ", destpath);
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exit (EXIT_FAILURE);
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}
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if (!S_ISLNK (stbuf.st_mode))
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{
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fprintf (stderr, "OSTree target is not a symbolic link: %s\n", destpath);
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exit (EXIT_FAILURE);
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}
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deploy_path = realpath (destpath, NULL);
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if (deploy_path == NULL)
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{
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perrorv ("realpath(%s) failed: ", destpath);
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exit (EXIT_FAILURE);
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}
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printf ("Resolved OSTree target to: %s\n", deploy_path);
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/* Work-around for a kernel bug: for some reason the kernel
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* refuses switching root if any file systems are mounted
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* MS_SHARED. Hence remount them MS_PRIVATE here as a
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* work-around.
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*
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* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
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if (mount (NULL, "/", NULL, MS_REC|MS_PRIVATE, NULL) < 0)
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{
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perrorv ("Failed to make \"/\" private mount: %m");
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exit (EXIT_FAILURE);
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}
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/* Make deploy_path a bind mount, so we can move it later */
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if (mount (deploy_path, newroot, NULL, MS_BIND, NULL) < 0)
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{
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perrorv ("failed to initial bind mount %s", deploy_path);
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exit (EXIT_FAILURE);
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}
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/* Link to the deployment's /var */
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snprintf (srcpath, sizeof(srcpath), "%s/../../var", deploy_path);
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snprintf (destpath, sizeof(destpath), "%s/var", newroot);
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if (mount (srcpath, destpath, NULL, MS_MGC_VAL|MS_BIND, NULL) < 0)
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{
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perrorv ("failed to bind mount %s to %s", srcpath, destpath);
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exit (EXIT_FAILURE);
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}
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/* If /boot is on the same partition, use a bind mount to make it visible
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* at /boot inside the deployment. */
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snprintf (srcpath, sizeof(srcpath), "%s/boot/loader", root_mountpoint);
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if (lstat (srcpath, &stbuf) == 0 && S_ISLNK (stbuf.st_mode))
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{
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snprintf (destpath, sizeof(destpath), "%s/boot", newroot);
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if (lstat (destpath, &stbuf) == 0 && S_ISDIR (stbuf.st_mode))
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{
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snprintf (srcpath, sizeof(srcpath), "%s/boot", root_mountpoint);
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if (mount (srcpath, destpath, NULL, MS_BIND, NULL) < 0)
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{
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perrorv ("failed to bind mount %s to %s", srcpath, destpath);
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exit (EXIT_FAILURE);
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}
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}
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}
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/* Set up any read-only bind mounts (notably /usr) */
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for (i = 0; readonly_bind_mounts[i] != NULL; i++)
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{
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snprintf (destpath, sizeof(destpath), "%s%s", newroot, readonly_bind_mounts[i]);
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if (mount (destpath, destpath, NULL, MS_BIND, NULL) < 0)
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{
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perrorv ("failed to bind mount (class:readonly) %s", destpath);
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exit (EXIT_FAILURE);
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}
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if (mount (destpath, destpath, NULL, MS_BIND | MS_REMOUNT | MS_RDONLY, NULL) < 0)
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{
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perrorv ("failed to bind mount (class:readonly) %s", destpath);
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exit (EXIT_FAILURE);
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}
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}
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touch_run_ostree ();
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/* Move physical root to $deployment/sysroot */
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snprintf (destpath, sizeof(destpath), "%s/sysroot", newroot);
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if (mount (root_mountpoint, destpath, NULL, MS_MOVE, NULL) < 0)
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{
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perrorv ("Failed to MS_MOVE %s to '%s'", root_mountpoint, destpath);
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exit (EXIT_FAILURE);
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}
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/* Now that we've set up all the bind mounts in /sysroot.tmp which
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* points to the deployment, move it /sysroot. From there,
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* systemd's initrd-switch-root.target will take over.
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*/
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if (mount (newroot, root_mountpoint, NULL, MS_MOVE, NULL) < 0)
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{
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perrorv ("failed to MS_MOVE %s to %s", deploy_path, root_mountpoint);
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exit (EXIT_FAILURE);
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}
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exit (EXIT_SUCCESS);
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}
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