105 lines
3.1 KiB
Markdown
105 lines
3.1 KiB
Markdown
# Docker Log Rotation
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Prevents unbounded container log growth across all homelab hosts.
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Docker's default is no limit — a single chatty container can fill a disk.
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## Target Config
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```json
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{
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"log-driver": "json-file",
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"log-opts": {
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"max-size": "10m",
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"max-file": "3"
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}
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}
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```
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10 MB × 3 files = max 30 MB per container.
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---
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## Linux Hosts (Ansible)
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Covers: **homelab-vm**, **concord-nuc**, **pi-5**, **matrix-ubuntu**
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```bash
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cd ansible/automation
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ansible-playbook -i hosts.ini playbooks/configure_docker_logging.yml
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```
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Dry-run first:
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```bash
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ansible-playbook -i hosts.ini playbooks/configure_docker_logging.yml --check
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```
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Single host:
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```bash
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ansible-playbook -i hosts.ini playbooks/configure_docker_logging.yml -e "host_target=homelab"
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```
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The playbook:
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1. Reads existing `daemon.json` (preserves existing keys)
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2. Merges in the log config
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3. Validates JSON
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4. Restarts the Docker daemon
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5. Verifies the logging driver is active
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### After running — recreate existing containers
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The daemon default only applies to **new** containers. Existing ones keep their old (unlimited) config until recreated:
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```bash
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# On each host, per stack:
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docker compose -f <compose-file> up --force-recreate -d
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```
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Or verify a specific container has the limit:
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```bash
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docker inspect <container> | jq '.[0].HostConfig.LogConfig'
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# Should show: {"Type":"json-file","Config":{"max-file":"3","max-size":"10m"}}
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```
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---
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## Synology Hosts (Not Applicable)
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**atlantis**, **calypso**, and **setillo** all use DSM's native `db` log driver (Synology Container Manager default). This driver stores container logs in an internal database managed by DSM — it does not produce json-file logs and does not support `max-size`/`max-file` options.
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**Do not change the log driver on Synology hosts.** Switching to `json-file` would break the Container Manager log viewer in DSM, and the `db` driver already handles log retention internally.
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To verify:
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```bash
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ssh atlantis "/var/packages/REDACTED_APP_PASSWORD/target/usr/bin/docker info 2>&1 | grep -i 'logging driver'"
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# Logging Driver: db ← expected
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```
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---
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## Guava (TrueNAS SCALE)
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TrueNAS SCALE uses K3s (Kubernetes) as its primary app runtime — standard Docker daemon log limits don't apply to apps deployed through the UI. If you have standalone Docker containers on guava, apply the Linux procedure above via Ansible (`truenas-scale` host in inventory).
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---
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## Verification
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```bash
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# Check largest existing logs before rotation
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ssh <host> "sudo find /var/lib/docker/containers -name '*-json.log' -exec du -sh {} \; 2>/dev/null | sort -h | tail -10"
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# Check a container's effective log config
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docker inspect <name> | jq '.[0].HostConfig.LogConfig'
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# Check daemon logging driver
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docker info --format '{{.LoggingDriver}}'
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```
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---
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## What This Doesn't Do
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- **Does not truncate existing log files** — those are handled by the reactive `log_rotation.yml` playbook
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- **Does not apply to containers started before the daemon restart** — recreate them
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- **Does not configure per-container overrides** — individual services can still override in their compose with `logging:` if needed
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