Troubleshooting

Systemd Notify

If you want to use systemd to start your node and be notified, you can use NotifyAccess=all, it will accept notifications from a different pid than the one launched by the unit.

notify vs cgroup

When systemd daemon receives a message through the socket, it searches the unit matching the cgroup of the process, so if you use cgroup with redpak, redpak cgroup should be a child of the systemd unit cgroup.

For that, you can just remove the cgrouproot option in configuration files.

See https://www.freedesktop.org/software/systemd/man/latest/systemd.service.html#NotifyAccess=

SMACK

Labels with vim

When you open a file with vim and save it, vim creates a copy of it and replaces the original by the copy, and the label on the file can be lost.

Use chsmack command to relabel the file.

cgroups

You can visit a specific chapter for correctly configuring and using cgroup

V2 Issue

Redpak handles cgroups only in pure version 2. If you are in cgroup version 1, or hybrid, you need to reboot after appending to the command line:

systemd.unified_cgroup_hierarchy=1

After reboot, you can check that `/sys/fs/cgroup’ is in version 2 with:

mount -l | grep /sys/fs/cgroup
cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)

User issue

If you don’t have the rights to create a sub cgroup into your current parent cgroup, it may be due to the fact that you’re not in a user cgroup session.

You can try to start one with:

# rp-owner
export XDG_RUNTIME_DIR=/run/user/$(id -u)
export DBUS_SESSION_BUS_ADDRESS=unix:path=${XDG_RUNTIME_DIR}/bus
systemd-run --user -p "Delegate=yes" --slice redpak --shell

Controller issue

If you can’t write into some controllers, it may be due to an issue in delegation. For that, you need to verify:

• /sys/fs/cgroup from your parent cgroup (cat /proc/self/cgroup),
• the available controllers cat cgroup.controllers,
• the controllers delegated to the children cgroup.subtree_control.

A temporary way to test it, is to append the missing ones at each level, for example:

echo "+cpuset +cpu +memory +io +pids" > cgroup.subtree_control

Then you can check in the child that you can see the controllers:

# in child
cat cgroup.controllers

All of the elements of redpak configuration file respects kernel definitions, please have a look at https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html.