Log FRR container output to docker logs#3541
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Jun 30, 2026
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I guess there's not much harm in doing this, so let's do it (with a few safeguards ;)
| # Redirect FRR's log to the container's stdout so 'docker logs' works | ||
| # | ||
| FRR_LOG_OUTPUT="/proc/$(pgrep -f '^/bin/bash /usr/lib/frr/docker-start$')/fd/1" | ||
| touch /var/log/frr/frr.log && chown frr:frr /var/log/frr/frr.log |
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Move the whole block after FRR configuration is already done, and you won't need this
| # | ||
| FRR_LOG_OUTPUT="/proc/$(pgrep -f '^/bin/bash /usr/lib/frr/docker-start$')/fd/1" | ||
| touch /var/log/frr/frr.log && chown frr:frr /var/log/frr/frr.log | ||
| tail -n 0 -F /var/log/frr/frr.log >${FRR_LOG_OUTPUT} 2>&1 & |
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You sure you don't need 'nohup' here?
Also, execute this at the very end of the initial configuration, preceded by set +e, so we won't get configuration errors if this concoction crashes.
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I left out the set +e, after removing the touch it's only a tail. I checked that nohup is not needed (bash has huponexit disabled by default)
Relay FRR file logging to the container stdout stream for clab nodes while keeping the regular file target for other providers. Co-authored-by: Cursor <cursoragent@cursor.com>
Use frr.logfile consistently, run tail after vtysh initial config, and forward to PID 1 stdout so docker logs captures FRR output. Co-authored-by: Cursor <cursoragent@cursor.com>
FRR creates the log file when logging is enabled; tail can follow it directly. Co-authored-by: Cursor <cursoragent@cursor.com>
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Relay FRR file logging to the container stdout stream for clab Docker nodes, enabling debugging when
frr.debugis setSample use case:
With this PR,
docker logs clab-bgpsession-dutshows the BFD events working for 10.6.1 but failing for 10.5.1