Can't start service or rc-service

Similar with https://github.com/gliderlabs/docker-alpine/issues/183 , but still not work.

```
/ # apk add openrc --no-cache
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/community/x86_64/APKINDEX.tar.gz
OK: 10 MiB in 20 packages/ # apk add openssh --no-cache
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.8/community/x86_64/APKINDEX.tar.gz
OK: 10 MiB in 20 packages/ # /etc/init.d/sshd start

/ # /etc/init.d/sshd start
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/blkio/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/cpu/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/cpu,cpuacct/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/cpuacct/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/cpuset/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/devices/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/freezer/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/hugetlb/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/memory/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/net_cls/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/net_cls,net_prio/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/net_prio/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/perf_event/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/pids/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/rdma/tasks: Read-only file system
/lib/rc/sh/openrc-run.sh: line 279: can't create /sys/fs/cgroup/systemd/tasks: Read-only file system
* You are attempting to run an openrc service on a
* system which openrc did not boot.
* You may be inside a chroot or you may have used
* another initialization system to boot this system.
* In this situation, you will get unpredictable results!
* If you really want to do this, issue the following command:
* touch /run/openrc/softlevel
* ERROR: sshd failed to start
```

Start by reproducing the Alpine v3.8 commands shown in the issue, then inspect /etc/init.d/sshd and the referenced /lib/rc/sh/openrc-run.sh behavior. Compare the result with gliderlabs/docker-alpine#183 and establish whether the service can start in this container setup; done means the failure is fixed or the supported limitation and required setup are documented.

Written by the indexing model from the issue text.