Cgroup v2 combability with sysvinit (WARNING: No swap limit support)

[niksparte]

Hello,

We are trying to implement cgroup2 without systemd, we still have sysvinit on the system.

We are able to mount cgroup2 on /sys/fs/cgroup by adding below line in /etc/fstab
cgroup2 /sys/fs/cgroup cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot 0 0

But in the output of the "docker info" command, we have observered the below WARNING message
**WARNING: No swap limit support**

Also Cgroup Version is set to 2.

Below is the complete output of the command

Client: Docker Engine - Community
 Version:    27.5.1
 Context:    default
 Debug Mode: false

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 27.5.1
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: syslog
 **Cgroup Driver: cgroupfs
 Cgroup Version: 2**
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: active
  NodeID: kqca97hmz96ccio13j0e5kmrb
  Is Manager: true
  ClusterID: vm5lp8nd6cp80tgagpsr1mopo
  Managers: 1
  Nodes: 1
  Default Address Pool: 10.0.0.0/8
  SubnetSize: 24
  Data Path Port: 4789
  Orchestration:
   Task History Retention Limit: 5
  Raft:
   Snapshot Interval: 10000
   Number of Old Snapshots to Retain: 0
   Heartbeat Tick: 1
   Election Tick: 10
  Dispatcher:
   Heartbeat Period: 2 minutes
  CA Configuration:
   Expiry Duration: 3 months
   Force Rotate: 0
  Autolock Managers: true
  Root Rotation In Progress: false
  Node Address: 192.168.29.181
  Manager Addresses:
   192.168.29.181:2377
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: bcc810d6b9066471b0b6fa75f557a15a1cbf31bb
 runc version: v1.2.4-0-g6c52b3f
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  cgroupns
  no-new-privileges
 Kernel Version: 6.12.10generic
 Operating System: Debian GNU/Linux 12 (bookworm)
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 3.834GiB
 Name: test
 ID: dcad18b5-096f-4da4-ae01-a8852f9cb040
 Docker Root Dir: /opt/docker/lib
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No swap limit support

We tried below steps to move docker process to the cgroup2 manually

1. Set "cgroup-parent" to /sys/fs/cgroup/docker.slice in /etc/docker/daemon.json
2. mkdir -p /sys/fs/cgroup/docker.slice
3. echo "+cpuset +cpu +io +memory +pids" > /sys/fs/cgroup/cgroup.subtree_control
4. Start the docker service
5. echo {docker_process_id} > /sys/fs/cgroup/docker.slice/cgroup.procs
6. echo {docker_process_id} > /sys/fs/cgroup/docker.slice/cgroup.threads

But still the same WARNING message is observed in output of the "docker info" command.

Is systemd mandatory for docker process?

As per https://github.com/opencontainers/runc/blob/main/docs/cgroup-v2.md,
On cgroup v2 hosts, it is highly recommended to run runc with the systemd cgroup driver (runc --systemd-cgroup), though not mandatory.

As per above comment, it appears that systemd is not mandatory and can be run with sysvinit.
Please provide steps to make it compatible with sysvinit.

Environment:

• Debian 12 without systemd
• Kernel 6.12.10

[niksparte]

Hi,

We are able to sort this issue using cgroup-tools (cgcreate and cgexec).

Required packages

1. cgroup-tools
2. libcgroup2

Below steps are followed

1. Mounted cgroup2 using below command
   mount -t cgroup2 cgroup2 /sys/fs/cgroup -o rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot

2. Create docker group using cgcreate command
   cgcreate -g cpuset,cpu,io,memory,pids:/docker

   Contents of "/sys/fs/cgroup/docker/"

   root@test:/home/test# ls /sys/fs/cgroup/docker/
   cgroup.controllers      cgroup.type                      cpuset.mems.effective     hugetlb.2MB.rsvd.current  memory.min           
   memory.swap.peak
   cgroup.events           cpu.idle                         cpu.stat                  hugetlb.2MB.rsvd.max      memory.numa_stat     pids.current
   cgroup.freeze           cpu.max                          cpu.stat.local            io.max                    memory.oom.group     pids.events
   cgroup.kill             cpu.max.burst                    cpu.weight                io.stat                   memory.peak          pids.events.local
   cgroup.max.depth        cpuset.cpus                      cpu.weight.nice           memory.current            memory.reclaim       pids.max
   cgroup.max.descendants  cpuset.cpus.effective            hugetlb.2MB.current       memory.events             memory.stat          pids.peak
   cgroup.procs            cpuset.cpus.exclusive            hugetlb.2MB.events        memory.events.local       memory.swap.current  rdma.current
   cgroup.stat             cpuset.cpus.exclusive.effective  hugetlb.2MB.events.local  memory.high               memory.swap.events   rdma.max
   cgroup.subtree_control  cpuset.cpus.partition            hugetlb.2MB.max           memory.low                memory.swap.high
   cgroup.threads          cpuset.mems                      hugetlb.2MB.numa_stat     memory.max                memory.swap.max
   

3. Start docker using cgexec command
   cgexec -g cpuset,cpu,io,memory,pids:/docker /etc/init.d/docker <start/restart>

Docker version

Client: Docker Engine - Community
 Version:           27.5.1
 API version:       1.47
 Go version:        go1.22.11
 Git commit:        9f9e405
 Built:             Wed Jan 22 13:41:17 2025
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Engine - Community
 Engine:
  Version:          27.5.1
  API version:      1.47 (minimum version 1.24)
  Go version:       go1.22.11
  Git commit:       4c9b3b0
  Built:            Wed Jan 22 13:41:17 2025
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.25
  GitCommit:        bcc810d6b9066471b0b6fa75f557a15a1cbf31bb
 runc:
  Version:          1.2.4
  GitCommit:        v1.2.4-0-g6c52b3f
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

Docker Info

Client: Docker Engine - Community
 Version:    27.5.1
 Context:    default
 Debug Mode: false

Server:
 Containers: 1
  Running: 1
  Paused: 0
  Stopped: 0
 Images: 1
 Server Version: 27.5.1
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: syslog
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: runc io.containerd.runc.v2
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: bcc810d6b9066471b0b6fa75f557a15a1cbf31bb
 runc version: v1.2.4-0-g6c52b3f
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  cgroupns
  no-new-privileges
 Kernel Version: 6.12.10generic
 Operating System: Debian GNU/Linux 12 (bookworm)
 OSType: linux
 Architecture: x86_64
 CPUs: 8
 Total Memory: 31.09GiB
 Name: test
 ID: 2df631b2-fc8f-48fa-b932-ecca397d4ce9
 Docker Root Dir: /opt/docker/lib
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false