src/volatile-root/volatile-root.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2016 Lennart Poettering
   4 ***/
   5
   6 #include <sys/mount.h>
   7
   8 #include "alloc-util.h"
   9 #include "fs-util.h"
  10 #include "mkdir.h"
  11 #include "mount-util.h"
  12 #include "stat-util.h"
  13 #include "volatile-util.h"
  14 #include "string-util.h"
  15 #include "path-util.h"
  16
  17 static int make_volatile(const char *path) {
  18         _cleanup_free_ char *old_usr = NULL;
  19         int r;
  20
  21         r = path_is_mount_point(path, NULL, AT_SYMLINK_FOLLOW);
  22         if (r < 0)
  23                 return log_error_errno(r, "Couldn't determine whether %s is a mount point: %m", path);
  24         if (r == 0) {
  25                 log_error("%s is not a mount point.", path);
  26                 return -EINVAL;
  27         }
  28
  29         r = path_is_temporary_fs(path);
  30         if (r < 0)
  31                 return log_error_errno(r, "Couldn't determine whether %s is a temporary file system: %m", path);
  32         if (r > 0) {
  33                 log_info("%s already is a temporary file system.", path);
  34                 return 0;
  35         }
  36
  37         r = chase_symlinks("/usr", path, CHASE_PREFIX_ROOT, &old_usr);
  38         if (r < 0)
  39                 return log_error_errno(r, "/usr not available in old root: %m");
  40
  41         r = mkdir_p("/run/systemd/volatile-sysroot", 0700);
  42         if (r < 0)
  43                 return log_error_errno(r, "Couldn't generate volatile sysroot directory: %m");
  44
  45         r = mount_verbose(LOG_ERR, "tmpfs", "/run/systemd/volatile-sysroot", "tmpfs", MS_STRICTATIME, "mode=755");
  46         if (r < 0)
  47                 goto finish_rmdir;
  48
  49         if (mkdir("/run/systemd/volatile-sysroot/usr", 0755) < 0) {
  50                 r = -errno;
  51                 goto finish_umount;
  52         }
  53
  54         r = mount_verbose(LOG_ERR, old_usr, "/run/systemd/volatile-sysroot/usr", NULL, MS_BIND|MS_REC, NULL);
  55         if (r < 0)
  56                 goto finish_umount;
  57
  58         r = bind_remount_recursive("/run/systemd/volatile-sysroot/usr", true, NULL);
  59         if (r < 0)
  60                 goto finish_umount;
  61
  62         r = umount_recursive(path, 0);
  63         if (r < 0) {
  64                 log_error_errno(r, "Failed to unmount %s: %m", path);
  65                 goto finish_umount;
  66         }
  67
  68         if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
  69                 log_warning_errno(errno, "Failed to remount %s MS_SLAVE|MS_REC: %m", path);
  70
  71         r = mount_verbose(LOG_ERR, "/run/systemd/volatile-sysroot", path, NULL, MS_MOVE, NULL);
  72
  73 finish_umount:
  74         (void) umount_recursive("/run/systemd/volatile-sysroot", 0);
  75
  76 finish_rmdir:
  77         (void) rmdir("/run/systemd/volatile-sysroot");
  78
  79         return r;
  80 }
  81
  82 int main(int argc, char *argv[]) {
  83         VolatileMode m = _VOLATILE_MODE_INVALID;
  84         const char *path;
  85         int r;
  86
  87         log_set_target(LOG_TARGET_AUTO);
  88         log_parse_environment();
  89         log_open();
  90
  91         if (argc > 3) {
  92                 log_error("Too many arguments. Expected directory and mode.");
  93                 r = -EINVAL;
  94                 goto finish;
  95         }
  96
  97         r = query_volatile_mode(&m);
  98         if (r < 0) {
  99                 log_error_errno(r, "Failed to determine volatile mode from kernel command line.");
 100                 goto finish;
 101         }
 102         if (r == 0 && argc >= 2) {
 103                 /* The kernel command line always wins. However if nothing was set there, the argument passed here wins instead. */
 104                 m = volatile_mode_from_string(argv[1]);
 105                 if (m < 0) {
 106                         log_error("Couldn't parse volatile mode: %s", argv[1]);
 107                         r = -EINVAL;
 108                         goto finish;
 109                 }
 110         }
 111
 112         if (argc < 3)
 113                 path = "/sysroot";
 114         else {
 115                 path = argv[2];
 116
 117                 if (isempty(path)) {
 118                         log_error("Directory name cannot be empty.");
 119                         r = -EINVAL;
 120                         goto finish;
 121                 }
 122                 if (!path_is_absolute(path)) {
 123                         log_error("Directory must be specified as absolute path.");
 124                         r = -EINVAL;
 125                         goto finish;
 126                 }
 127                 if (path_equal(path, "/")) {
 128                         log_error("Directory cannot be the root directory.");
 129                         r = -EINVAL;
 130                         goto finish;
 131                 }
 132         }
 133
 134         if (m != VOLATILE_YES) {
 135                 r = 0;
 136                 goto finish;
 137         }
 138
 139         r = make_volatile(path);
 140
 141 finish:
 142         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 143 }