Avoid warning messages when booting systemd-nspawn containers and using
hybrid or legacy cgroups. systemd-nspawn mounts the cgroups v1 controller
tree as read-only so these errors are expected and not problematic.
Partially fixes#17862.
Test plan:
- Before: `mkosi --default .mkosi/mkosi.fedora boot`
```
‣ Processing default...
Spawning container image on /home/daan/projects/systemd/image.raw.
Press ^] three times within 1s to kill container.
systemd 247 running in system mode. (+PAM +AUDIT +SELINUX -APPARMOR +IMA +SMACK +SECCOMP +GCRYPT +GNUTLS +OPENSSL +ACL +BLKID +CURL +ELFUTILS +FIDO2 +IDN2 -IDN +IPTC +KMOD +LIBCRYPTSETUP +LIBFDISK +PCRE2 +PWQUALITY +P11KIT +QRENCODE +BZIP2 +LZ4 +XZ +ZLIB +ZSTD +XKBCOMMON +UTMP +SYSVINIT default-hierarchy=unified)
Detected virtualization systemd-nspawn.
Detected architecture x86-64.
Welcome to Fedora 33 (Thirty Three)!
Queued start job for default target Graphical Interface.
-.slice: Failed to migrate controller cgroups from , ignoring: Read-only file system
system.slice: Failed to delete controller cgroups /system.slice, ignoring: Read-only file system
[ OK ] Created slice system-getty.slice.
[ OK ] Created slice system-modprobe.slice.
user.slice: Failed to delete controller cgroups /user.slice, ignoring: Read-only file system
[ OK ] Created slice User and Session Slice.
[ OK ] Started Dispatch Password Requests to Console Directory Watch.
[ OK ] Started Forward Password Requests to Wall Directory Watch.
[ OK ] Reached target Local Encrypted Volumes.
[ OK ] Reached target Paths.
[ OK ] Reached target Remote File Systems.
[ OK ] Reached target Slices.
[ OK ] Reached target Swap.
[ OK ] Listening on Process Core Dump Socket.
[ OK ] Listening on initctl Compatibility Named Pipe.
[ OK ] Listening on Journal Socket (/dev/log).
[ OK ] Listening on Journal Socket.
[ OK ] Listening on User Database Manager Socket.
dev-hugepages.mount: Failed to delete controller cgroups /dev-hugepages.mount, ignoring: Read-only file system
Mounting Huge Pages File System...
sys-fs-fuse-connections.mount: Failed to delete controller cgroups /sys-fs-fuse-connections.mount, ignoring: Read-only file system
Mounting FUSE Control File System...
Starting Journal Service...
Starting Remount Root and Kernel File Systems...
system.slice: Failed to delete controller cgroups /system.slice, ignoring: Read-only file system
```
After: `mkosi --default .mkosi/mkosi.fedora boot`
```
‣ Processing default...
Spawning container image on /home/daan/projects/systemd/mkosi.output/image.raw.
Press ^] three times within 1s to kill container.
systemd 247 running in system mode. (+PAM +AUDIT +SELINUX -APPARMOR +IMA +SMACK +SECCOMP +GCRYPT +GNUTLS +OPENSSL +ACL +BLKID +CURL +ELFUTILS +FIDO2 +IDN2 -IDN +IPTC +KMOD +LIBCRYPTSETUP +LIBFDISK +PCRE2 +PWQUALITY +P11KIT +QRENCODE +BZIP2 +LZ4 +XZ +ZLIB +ZSTD +XKBCOMMON +UTMP +SYSVINIT default-hierarchy=unified)
Detected virtualization systemd-nspawn.
Detected architecture x86-64.
Welcome to Fedora 33 (Thirty Three)!
Queued start job for default target Graphical Interface.
[ OK ] Created slice system-getty.slice.
[ OK ] Created slice system-modprobe.slice.
[ OK ] Created slice User and Session Slice.
[ OK ] Started Dispatch Password Requests to Console Directory Watch.
[ OK ] Started Forward Password Requests to Wall Directory Watch.
[ OK ] Reached target Local Encrypted Volumes.
[ OK ] Reached target Paths.
[ OK ] Reached target Remote File Systems.
[ OK ] Reached target Slices.
[ OK ] Reached target Swap.
[ OK ] Listening on Process Core Dump Socket.
[ OK ] Listening on initctl Compatibility Named Pipe.
[ OK ] Listening on Journal Socket (/dev/log).
[ OK ] Listening on Journal Socket.
[ OK ] Listening on User Database Manager Socket.
Mounting Huge Pages File System...
Mounting FUSE Control File System...
Starting Journal Service...
Starting Remount Root and Kernel File Systems...
[ OK ] Mounted Huge Pages File System.
[ OK ] Mounted FUSE Control File System.
[ OK ] Finished Remount Root and Kernel File Systems.
Starting Create Static Device Nodes in /dev...
[ OK ] Finished Create Static Device Nodes in /dev.
[ OK ] Reached target Local File Systems (Pre).
[ OK ] Reached target Local File Systems.
Starting Restore /run/initramfs on shutdown...
[ OK ] Finished Restore /run/initramfs on shutdown.
[ OK ] Started Journal Service.
Starting Flush Journal to Persistent Storage...
[ OK ] Finished Flush Journal to Persistent Storage.
Starting Create Volatile Files and Directories...
[ OK ] Finished Create Volatile Files and Directories.
Starting Network Name Resolution...
Starting Update UTMP about System Boot/Shutdown...
[ OK ] Finished Update UTMP about System Boot/Shutdown.
[ OK ] Reached target System Initialization.
[ OK ] Started Daily Cleanup of Temporary Directories.
[ OK ] Reached target Timers.
[ OK ] Listening on D-Bus System Message Bus Socket.
[ OK ] Reached target Sockets.
[ OK ] Reached target Basic System.
Starting Home Area Manager...
Starting User Login Management...
Starting Permit User Sessions...
[ OK ] Finished Permit User Sessions.
[ OK ] Started Console Getty.
[ OK ] Reached target Login Prompts.
Starting D-Bus System Message Bus...
[ OK ] Started D-Bus System Message Bus.
[ OK ] Started Home Area Manager.
[ OK ] Started User Login Management.
[ OK ] Reached target Multi-User System.
[ OK ] Reached target Graphical Interface.
Starting Update UTMP about System Runlevel Changes...
[ OK ] Finished Update UTMP about System Runlevel Changes.
[ OK ] Started Network Name Resolution.
[ OK ] Reached target Host and Network Name Lookups.
Fedora 33 (Thirty Three) (built from systemd tree)
Kernel 5.9.11-arch2-1 on an x86_64 (console)
```