How can I check if cgroups are available on my Linux host?

Question

Is there a command to check if the container services are running on a Linux system? Someone suggested unshare but I am not sure if that is the best way to do it.

Answer 1

UPDATE: Upon re-reading your question, I realized that I had answered a slightly different one. You want to know whether a service is running, and I had originally answered how to tell if a package was installed. To answer your actual question, it depends upon your init system.

1. systemd - the basic command is systemctl, which will list all services and their states, so you could either manually browse it manually or pipe it through a grep command, like so: systemctl | grep -e cgmanager -e cgproxy -e cgroupfs-mount. Or, as user muru suggests in the comments, simply systemctl status 'cg*'.

2. sysVinit - the basic command is service --status-all and the grep command would be service --status-all 2>&1 | grep -e cgmanager -e cgproxy -e cgroupfs-mount. Note that in this case, running services are denoted with a [+] prefix symbol. Also note that for the grep to work, the redirect 2>&1 must be made for the service command.

ORIGINAL ANSWER:

1. Maybe the simplest thing to do is try man cgroups. If that brings up a documentation page, then your host has the package installed. However, some installs are 'stingy' and don't install man pages.

2. You could try cgm and see if that produces output. Most installs of cgroups will include that command, but not necessarily.

3. You could look up the package list of your host distribution. On debian derivatives, that would be dpkg -l |grep cgroup, but occasionally a system will restrict access to root or sudo for dpkg.

There will be a lot of other ways.

Answer 2

You can check which cgroup features are enabled in kernel config with:

# zcat /proc/config.gz | grep CGROUP
CONFIG_CGROUPS=y
CONFIG_BLK_CGROUP=y
# CONFIG_DEBUG_BLK_CGROUP is not set
CONFIG_CGROUP_WRITEBACK=y
CONFIG_CGROUP_SCHED=y
CONFIG_CGROUP_PIDS=y
# CONFIG_CGROUP_RDMA is not set
# CONFIG_CGROUP_FREEZER is not set
CONFIG_CGROUP_HUGETLB=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
CONFIG_CGROUP_PERF=y
# CONFIG_CGROUP_DEBUG is not set
# CONFIG_SOCK_CGROUP_DATA is not set
# CONFIG_NETFILTER_XT_MATCH_CGROUP is not set
# CONFIG_CGROUP_NET_PRIO is not set
# CONFIG_CGROUP_NET_CLASSID is not set

(note: in order for /proc/config.gz to show up

CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y

need to be set)