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volatile-root: add overlay mode for host boots, too

This commit is contained in:
Lennart Poettering 2018-12-19 17:30:13 +01:00
parent 26945d18ac
commit 1de7f825d3
2 changed files with 72 additions and 19 deletions
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7
src/fstab-generator/fstab-generator.c
View File

@ -722,10 +722,11 @@ static int add_sysroot_usr_mount(void) {
}
static int add_volatile_root(void) {
/* Let's add in systemd-remount-volatile.service which will remount the root device to tmpfs if this is
* requested, leaving only /usr from the root mount inside. */
if (arg_volatile_mode != VOLATILE_YES)
/* Let's add in systemd-remount-volatile.service which will remount the root device to tmpfs if this is
* requested (or as an overlayfs), leaving only /usr from the root mount inside. */
if (!IN_SET(arg_volatile_mode, VOLATILE_YES, VOLATILE_OVERLAY))
return 0;
return generator_add_symlink(arg_dest, SPECIAL_INITRD_ROOT_FS_TARGET, "requires",

84
src/volatile-root/volatile-root.c
View File

@ -3,6 +3,7 @@
#include <sys/mount.h>
#include "alloc-util.h"
#include "escape.h"
#include "fs-util.h"
#include "main-func.h"
#include "mkdir.h"
@ -17,20 +18,7 @@ static int make_volatile(const char *path) {
_cleanup_free_ char *old_usr = NULL;
int r;
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;
}
assert(path);
r = chase_symlinks("/usr", path, CHASE_PREFIX_ROOT, &old_usr);
if (r < 0)
@ -79,6 +67,51 @@ finish_rmdir:
return r;
}
static int make_overlay(const char *path) {
_cleanup_free_ char *escaped_path = NULL;
bool tmpfs_mounted = false;
const char *options = NULL;
int r;
assert(path);
r = mkdir_p("/run/systemd/overlay-sysroot", 0700);
if (r < 0)
return log_error_errno(r, "Couldn't create overlay sysroot directory: %m");
r = mount_verbose(LOG_ERR, "tmpfs", "/run/systemd/overlay-sysroot", "tmpfs", MS_STRICTATIME, "mode=755");
if (r < 0)
goto finish;
tmpfs_mounted = true;
if (mkdir("/run/systemd/overlay-sysroot/upper", 0755) < 0) {
r = log_error_errno(errno, "Failed to create /run/systemd/overlay-sysroot/upper: %m");
goto finish;
}
if (mkdir("/run/systemd/overlay-sysroot/work", 0755) < 0) {
r = log_error_errno(errno, "Failed to create /run/systemd/overlay-sysroot/work: %m");
goto finish;
}
escaped_path = shell_escape(path, ",:");
if (!escaped_path) {
r = log_oom();
goto finish;
}
options = strjoina("lowerdir=", escaped_path, ",upperdir=/run/systemd/overlay-sysroot/upper,workdir=/run/systemd/overlay-sysroot/work");
r = mount_verbose(LOG_ERR, "overlay", path, "overlay", 0, options);
finish:
if (tmpfs_mounted)
(void) umount_verbose("/run/systemd/overlay-sysroot");
(void) rmdir("/run/systemd/overlay-sysroot");
return r;
}
static int run(int argc, char *argv[]) {
VolatileMode m = _VOLATILE_MODE_INVALID;
const char *path;
@ -116,10 +149,29 @@ static int run(int argc, char *argv[]) {
"Directory cannot be the root directory.");
}
if (m != VOLATILE_YES)
if (!IN_SET(m, VOLATILE_YES, VOLATILE_OVERLAY))
return 0;
return make_volatile(path);
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;
}
if (m == VOLATILE_YES)
return make_volatile(path);
else {
assert(m == VOLATILE_OVERLAY);
return make_overlay(path);
}
}
DEFINE_MAIN_FUNCTION(run);