Mount cgroups-v1

To use cgroup-v1 functionality for resource limitation, manually configure the system, as RHEL 10 mounts cgroup-v2 by default.

Before you begin

  • You have root permissions on the system.

About this task

Note

Both cgroup-v1 and cgroup-v2 are fully enabled in the kernel. There is no default control group version from the kernel point of view, and is decided by systemd to mount at startup.

Procedure

  1. Configure the system to mount cgroups-v1 by default during system boot by the systemd system and service manager: 
    # grubby --update-kernel=/boot/vmlinuz-$(uname -r) --args="systemd.unified_cgroup_hierarchy=0 systemd.legacy_systemd_cgroup_controller"

    This adds the necessary kernel command-line parameters to the current boot entry.

    1. To add the same parameters to all kernel boot entries: 
      # grubby --update-kernel=ALL --args="systemd.unified_cgroup_hierarchy=0 systemd.legacy_systemd_cgroup_controller"
  2. Reboot the system for the changes to take effect.

Results

  1. Verify that the cgroups-v1 filesystem was mounted: 
    # mount -l | grep cgroup
     
    tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,seclabel,size=4096k,nr_inodes=1024,mode=755,inode64)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,perf_event)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,cpu,cpuacct)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,pids)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,cpuset)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,net_cls,net_prio)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,hugetlb)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,memory)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,blkio)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,devices)
cgroup on /sys/fs/cgroup/misc type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,misc)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,freezer)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,seclabel,rdma)

    The cgroups-v1 filesystems that correspond to various cgroup-v1 controllers were successfully mounted on the /sys/fs/cgroup/ directory.

  2. Inspect the contents of the /sys/fs/cgroup/ directory: 
    # ll /sys/fs/cgroup/
     
    dr-xr-xr-x. 10 root root  0 Mar 16 09:34 blkio
lrwxrwxrwx.  1 root root 11 Mar 16 09:34 cpu -> cpu,cpuacct
lrwxrwxrwx.  1 root root 11 Mar 16 09:34 cpuacct -> cpu,cpuacct
dr-xr-xr-x. 10 root root  0 Mar 16 09:34 cpu,cpuacct
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 cpuset
dr-xr-xr-x. 10 root root  0 Mar 16 09:34 devices
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 freezer
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 hugetlb
dr-xr-xr-x. 10 root root  0 Mar 16 09:34 memory
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 misc
lrwxrwxrwx.  1 root root 16 Mar 16 09:34 net_cls -> net_cls,net_prio
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 net_cls,net_prio
lrwxrwxrwx.  1 root root 16 Mar 16 09:34 net_prio -> net_cls,net_prio
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 perf_event
dr-xr-xr-x. 10 root root  0 Mar 16 09:34 pids
dr-xr-xr-x.  2 root root  0 Mar 16 09:34 rdma
dr-xr-xr-x. 11 root root  0 Mar 16 09:34 systemd

    The /sys/fs/cgroup/ directory, also called the root control group, by default, contains controller-specific directories such as cpuset. In addition, there are some directories related to systemd.