Add general admin docs

Author: meganschanz

docs/general.md

@@ -0,0 +1,54 @@
+# General
+
+This page provides general administrative help and troubleshooting
+tips.
+
+## Docker
+
+### Host resolution errors
+
+Sometimes Docker can have seemingly mysterious network issues, where
+you might see errors like this in the logs:
+
+<!-- markdownlint-disable MD013 MD031 -->
+```bash
+*5 monitoring could not be resolved (3: Host not found), client: 192.168.0.66, server: proxysolr
+```
+<!-- markdownlint-enable MD013 MD031 -->
+
+With a multi-node cluster, sometimes the overlay network can start having
+issues and needs to be recreated for that service. This can be done, by
+removing the service (or stack) and then redeploying it.
+
+For example, to redeploy just `proxysolr` (since we don't want to remove
+the whole Solr stack):
+
+```bash
+docker service rm catalog-preview-solr_proxysolr
+sudo pc-deploy catalog-preview solr-cloud
+```
+
+But if it was the Monitoring application having issues, we'd be ok temporarily removing
+all those services and could just do this:
+
+```bash
+docker stack rm catalog-preview-monitoring
+sudo pc-deploy catalog-preview monitoring
+```
+
+### Upgrade errors
+
+If you find you're having issues with a newer version of `docker.io`,
+(like we did with 28.2.2) you can revert it to your last working version,
+found in `/var/log/apt/history.log` using:
+
+```bash
+# 27.5.1-0ubuntu3~22.04.2 was the version
+# from /var/log/apt/history.log that was running previously
+sudo apt install docker.io=27.5.1-0ubuntu3~22.04.2
+sudo apt-mark hold docker.io
+```
+
+You can also review the [release notes](https://docs.docker.com/engine/release-notes/28/)
+to identify if there are known issues in the release that are fixed in newer releases,
+so you can safely remove the `apt-mark hold`.

docs/index.md

@@ -16,6 +16,7 @@ questions or suggestions you have!
 
 ## Administration
 
+* [General](general.md)
 * [Backup & Restore](backup-and-restore.md)
 * [Upgrading](upgrading.md)
 * [VuFind](vufind.md)

mkdocs.yml

@@ -37,6 +37,7 @@ nav:
     - Harvesting & Importing: harvesting-and-importing.md
     - CI/CD: CICD.md
 - Administration:
+    - General: general.md
     - Backup & Restore: backup-and-restore.md
     - Upgrading: upgrading.md
     - VuFind: vufind.md