250 lines
7.1 KiB
C
250 lines
7.1 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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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program 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
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*/
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#define _GNU_SOURCE
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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 <assert.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 <dirent.h>
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static int
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perrorv (const char *format, ...) __attribute__ ((format (printf, 1, 2)));
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static int
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perrorv (const char *format, ...)
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{
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va_list args;
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char buf[PATH_MAX];
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char *p;
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p = strerror_r (errno, buf, sizeof (buf));
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va_start (args, format);
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vfprintf (stderr, format, args);
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fprintf (stderr, ": %s\n", p);
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fflush (stderr);
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va_end (args);
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sleep (3);
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return 0;
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}
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static void
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parse_ostree_cmdline (char **out_osname,
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char **out_tree)
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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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size_t len;
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if (!f)
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return;
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if (getline (&cmdline, &len, f) < 0)
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return;
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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 *slash = strchr (iter, '/');
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if (slash)
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{
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const char *start = iter + strlen ("ostree=");
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*out_osname = strndup (start, slash - start);
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if (next)
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*out_tree = strndup (slash + 1, next - slash - 1);
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else
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*out_tree = strdup (slash + 1);
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break;
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}
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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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}
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int
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main(int argc, char *argv[])
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{
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const char *toproot_bind_mounts[] = { "/home", "/root", "/tmp", NULL };
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const char *ostree_bind_mounts[] = { "/var", NULL };
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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_osname = NULL;
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char *ostree_target = NULL;
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char ostree_target_path[PATH_MAX];
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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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struct stat stbuf;
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size_t len;
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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 (1);
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}
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root_mountpoint = argv[1];
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parse_ostree_cmdline (&ostree_osname, &ostree_target);
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if (!ostree_osname)
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{
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fprintf (stderr, "No OSTree target; expected ostree=OSNAME/TREENAME\n");
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exit (1);
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}
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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 (1);
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}
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snprintf (destpath, sizeof(destpath), "%s/ostree/deploy/%s/%s",
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root_mountpoint, ostree_osname, ostree_target);
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fprintf (stderr, "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 (1);
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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 (1);
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}
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if (readlink (destpath, ostree_target_path, PATH_MAX) < 0)
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{
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perrorv ("readlink(%s) failed: ", destpath);
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exit (1);
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}
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len = strlen (ostree_target_path);
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if (ostree_target_path[len-1] == '/')
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ostree_target_path[len-1] = '\0';
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fprintf (stderr, "Resolved OSTree target to: %s\n", ostree_target_path);
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(void) asprintf (&deploy_path, "%s/ostree/deploy/%s/%s", root_mountpoint,
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ostree_osname, ostree_target_path);
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/* Make deploy_path a bind mount, so we can move it later */
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if (mount (deploy_path, deploy_path, 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 (1);
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}
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snprintf (destpath, sizeof(destpath), "%s/sysroot", deploy_path);
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if (mount (root_mountpoint, destpath, NULL, MS_BIND, NULL) < 0)
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{
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perrorv ("Failed to bind mount %s to '%s'", root_mountpoint, destpath);
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exit (1);
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}
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snprintf (srcpath, sizeof(srcpath), "%s-etc", deploy_path);
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snprintf (destpath, sizeof(destpath), "%s/etc", deploy_path);
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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 (1);
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}
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for (i = 0; toproot_bind_mounts[i] != NULL; i++)
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{
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snprintf (srcpath, sizeof(srcpath), "%s%s", root_mountpoint, toproot_bind_mounts[i]);
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snprintf (destpath, sizeof(destpath), "%s%s", deploy_path, toproot_bind_mounts[i]);
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if (mount (srcpath, destpath, NULL, MS_BIND & ~MS_RDONLY, NULL) < 0)
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{
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perrorv ("failed to bind mount (class:toproot) %s to %s", toproot_bind_mounts[i], destpath);
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exit (1);
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}
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}
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for (i = 0; ostree_bind_mounts[i] != NULL; i++)
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{
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snprintf (srcpath, sizeof(srcpath), "%s/ostree/deploy/%s%s", root_mountpoint,
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ostree_osname, ostree_bind_mounts[i]);
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snprintf (destpath, sizeof(destpath), "%s%s", deploy_path, ostree_bind_mounts[i]);
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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 (class:bind) %s to %s", srcpath, destpath);
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exit (1);
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}
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}
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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", deploy_path, 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 (1);
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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 (1);
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}
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}
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/* This is a bit hacky - move our deployment to /sysroot, since
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* systemd's initrd-switch-root target hardcodes looking for it
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* there.
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*/
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if (mount (deploy_path, 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 (1);
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}
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exit (0);
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}
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