int device_path_make_canonical(mode_t mode, dev_t devno, char **ret) {
_cleanup_free_ char *p = NULL;
int r;
/* Finds the canonical path for a device, i.e. resolves the /dev/{char|block}/MAJOR:MINOR path to the end. */
assert(ret);
if (major(devno) == 0 && minor(devno) == 0) {
char *s;
/* A special hack to make sure our 'inaccessible' device nodes work. They won't have symlinks in
* /dev/block/ and /dev/char/, hence we handle them specially here. */
if (S_ISCHR(mode))
s = strdup("/run/systemd/inaccessible/chr");
else if (S_ISBLK(mode))
s = strdup("/run/systemd/inaccessible/blk");
else
return -ENODEV;
if (!s)
return -ENOMEM;
*ret = s;
return 0;
}
r = device_path_make_major_minor(mode, devno, &p);
if (r < 0)
return r;
return chase_symlinks(p, NULL, 0, ret);
}
static int run(int argc, char *argv[]) {
VolatileMode m = _VOLATILE_MODE_INVALID;
const char *path;
dev_t devt;
int r;
log_setup_service();
if (argc > 3)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Too many arguments. Expected directory and mode.");
r = query_volatile_mode(&m);
if (r < 0)
return log_error_errno(r, "Failed to determine volatile mode from kernel command line.");
if (r == 0 && argc >= 2) {
/* The kernel command line always wins. However if nothing was set there, the argument passed here wins instead. */
m = volatile_mode_from_string(argv[1]);
if (m < 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Couldn't parse volatile mode: %s", argv[1]);
}
if (argc < 3)
path = "/sysroot";
else {
path = argv[2];
if (isempty(path))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory name cannot be empty.");
if (!path_is_absolute(path))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory must be specified as absolute path.");
if (path_equal(path, "/"))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"Directory cannot be the root directory.");
}
if (!IN_SET(m, VOLATILE_YES, VOLATILE_OVERLAY))
return 0;
r = path_is_mount_point(path, NULL, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a mount point: %m", path);
if (r == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "%s is not a mount point.", path);
r = path_is_temporary_fs(path);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a temporary file system: %m", path);
if (r > 0) {
log_info("%s already is a temporary file system.", path);
return 0;
}
/* We are about to replace the root directory with something else. Later code might want to know what we
* replaced here, hence let's save that information as a symlink we can later use. (This is particularly
* relevant for the overlayfs case where we'll fully obstruct the view onto the underlying device, hence
* querying the backing device node from the file system directly is no longer possible. */
r = get_block_device_harder(path, &devt);
if (r < 0)
return log_error_errno(r, "Failed to determine device major/minor of %s: %m", path);
else if (r > 0) {
_cleanup_free_ char *dn = NULL;
r = device_path_make_major_minor(S_IFBLK, devt, &dn);
if (r < 0)
return log_error_errno(r, "Failed to format device node path: %m");
if (symlink(dn, "/run/systemd/volatile-root") < 0)
log_warning_errno(errno, "Failed to create symlink /run/systemd/volatile-root: %m");
}
if (m == VOLATILE_YES)
return make_volatile(path);
else {
assert(m == VOLATILE_OVERLAY);
return make_overlay(path);
}
}
