Sign in Subscribe
Concepts

Keycloak Linux Terminal Bug Freezes Shell Under Heavy Logging

Andrios Robert

• 1 min read

The terminal froze. Commands stacked in memory, but nothing moved. Keycloak had stopped responding, and you were deep in the Linux shell with no GUI to escape.

A recent Keycloak Linux terminal bug has been disrupting workflows for developers running the open-source identity and access management tool entirely from the command line. The issue appears most often when running Keycloak 21.x and above in development mode, but reports show it can also occur in production-like setups on certain Linux distributions.

The bug triggers when the terminal input buffer locks under heavy logging or when specific CLI admin commands overlap with active runtime processes. Once it happens, the terminal session becomes unresponsive. The only workaround in some cases is killing the process or starting a new shell.

Common factors linked to the Keycloak Linux terminal bug include:

  • Running kc.sh start-dev with verbose logging enabled
  • Using embedded H2 with large datasets
  • Executing concurrent kcadm.sh commands over a slow container volume
  • Misconfigured JAVA_OPTS leading to excessive GC pauses

Debugging steps that help isolate the bug:

  1. Reproduce the issue with minimal configuration and logging on.
  2. Run Keycloak in a dedicated TTY separate from other heavy processes.
  3. Use strace on the Java process to detect blocked syscalls.
  4. Check the JDK version. Some OpenJDK builds for Linux ship with known bugs affecting non-blocking I/O.

Mitigation strategies until a permanent fix is issued:

  • Redirect STDOUT and STDERR to log files instead of streaming to the terminal.
  • Use screen or tmux to preserve the session when the terminal freezes.
  • Reduce log verbosity with --log-level=info or lower.
  • Run Keycloak inside Docker with a mounted log directory for cleaner output handling.

The Keycloak Linux terminal bug is a sharp reminder that identity services must be stable under all runtime conditions. Keep your environment minimal, log responsibly, and monitor known issues in the Keycloak Jira and GitHub repositories.

Deploying smooth and predictable developer environments is faster when you start from a clean, portable foundation. See how hoop.dev can get you there—live in minutes.