Troubleshooting sched_ext

Check the installation requirements first. Use the read-only commands below to identify the failure before changing configuration.

Read the current state

scxcli get
systemctl status scx.service
journalctl -u scx.service -b 0

In scxcli get, state identifies a scheduler when the service process and kernel agree. kernel shows the kernel observation, running describes the service process, and configured describes the resolved next-start configuration. They can differ after a manual edit, failed start or scheduler launched outside the service. scxcli get --json exposes the status for scripts.

Reading service logs requires permission to read the system journal. If your account cannot see the logs, ask an administrator to collect them; switching authorization does not grant journal access.

Tools or kernel support are missing

If scxcli or scxtui is not found, check the contents of your distribution’s package. The installation guide distinguishes the Devario tools from releases with a different management interface. Do not add a second scheduler manager to supply a missing command.

If the kernel check does not print sched_ext available, or the service is skipped, boot a kernel with sched_ext support. Installing tools alone does not add kernel support.

A scheduler fails to start

Read scxcli get and journalctl -u scx.service -b 0. Systemd limits the service to two start attempts within 30 seconds. It restarts on failure, not on a clean exit. An explicit start ID or no-ID resume attempts to reset the failed state and start counter before starting again. Select a known working entry or return to Default.

Switching asks for a password

Check that scxcli is installed at /usr/bin/scxcli and that /usr/share/polkit-1/actions/org.sched_ext.scxcli.policy is installed. A local policy or a non-console session can also require authentication.

Resume refuses custom options

Use pkexec scxcli start ID to select a listed entry, or repeat the administrator-authorized run command. Resume validates the saved command even when run as root; custom options must exactly match an installed catalog profile. See custom options and profiles.

A scheduler is missing from the list

Try scxcli list all. Some schedulers are deliberately hidden because they need their own configuration; use an administrator profile or run with the required options.

Commands refuse the custom catalog

Check both /etc/scx and /etc/scx/catalog.json: ownership, permissions, symlinks or invalid contents can make the override unusable. There is no automatic fallback to the shipped catalog. sudo scxcli catalog reset removes an override file, including a file symlink, but refuses a symlinked /etc/scx directory; correct that directory separately. See catalog ownership and overrides.

Configured and running schedulers differ

Check for active overrides, another scheduler manager, a failed start, or a scheduler launched manually. Do not start a second manager to fix the mismatch. To remove test overrides, follow temporary service overrides.

Default stops scx.service; it cannot stop a scheduler launched outside that service. Stop such a scheduler through the tool or process that launched it, then check the state again.

Ask for help

Include the package version, running kernel, scxcli get output and relevant service log when asking in the Fluxer community. Review logs for personal information before sharing them.