Troubleshooting — Diskover on RHEL / Rocky / CentOS

Overview

RHEL, Rocky Linux, and CentOS hosts can run the full Diskover stack or act as dedicated indexer nodes. This guide covers the most common issues across all Diskover services on these distributions.

Full stack services:

Indexer-only nodes (remote workers) run only celery and diskoverd.

Quick Status Check

for svc in elasticsearch nginx php-fpm rabbitmq-server celery diskover-admin diskoverd; do
  printf "%-20s %s\n" "$svc" "$(systemctl is-active $svc 2>/dev/null || echo 'not-found')"
done

Service Startup Order

Services have dependencies. The correct startup sequence is:

1. elasticsearch

2. rabbitmq-server

3. diskover-admin

4. nginx

5. php-fpm

6. celery

7. diskoverd

Always confirm earlier services are healthy before investigating later ones.

Log Locations Reference

Troubleshooting

Diskover Web UI Not Loading

Check nginx:

sudo systemctl status nginx
sudo tail -20 /var/log/nginx/error.log

Check PHP-FPM:

sudo systemctl status php-fpm
sudo tail -50 /var/log/nginx/error.log | grep fastcgi

If nginx is up but returns a 502 on /diskover_admin routes, diskover-admin is likely down — see below.

Check file ownership — the nginx worker user on RHEL/Rocky is nginx:

ls -la /var/www/diskover-web/public
sudo chown -R nginx:nginx /var/www/diskover-web

diskover-admin Not Responding (502 on /diskover_admin)

sudo systemctl status diskover-admin
sudo journalctl -u diskover-admin -n 100 --no-pager

Check the Unix socket:

ls -la /var/www/diskover-admin/run/diskover-admin.sock

If missing, start diskover-admin:

sudo systemctl start diskover-admin

If the socket exists but 502 persists, fix permissions:

sudo chown nginx:nginx /var/www/diskover-admin/run/diskover-admin.sock
sudo chmod 777 /var/www/diskover-admin/run/diskover-admin.sock

Common startup failure causes:

• SQLite database not accessible: ls -la /var/www/diskover-web/diskoverdb.sqlite3

• Task Worker not installed at /opt/diskover: ls /opt/diskover/models/

• Python dependency missing — test manually:

  cd /var/www/diskover-admin && uvicorn --interface wsgi --workers 1 wsgi:app
  

Tasks Not Running / Crawls Not Starting

1. Confirm diskoverd is running:

   sudo systemctl status diskoverd
   sudo tail -50 /var/log/diskover/diskoverd.log
   

2. Confirm the task is assigned to the correct worker name:

   1. Edit the task

   2. Check Assigned Worker has the correct worker selected

Crawl Task Fails

sudo tail -100 /var/log/diskover/diskoverd_subproc.log

For more detail, set log level to DEBUG in Diskover Admin > Configuration > DiskoverD, restart diskoverd, and retry.

Common causes:

• Elasticsearch unreachable: curl -s http://<es-host>:9200/_cluster/health

• Path not accessible to the user running diskoverd

• NFS/CIFS mount failure:

  showmount -e <nfs-server>   # NFS
  mount | grep diskover
  

  Install packages if missing: sudo dnf install nfs-utils cifs-utils Or start diskoverd with --assumemountingenabled to skip mount capability checks

Elasticsearch Issues

Cluster health:

curl -s http://localhost:9200/_cluster/health?pretty

yellow is normal for single-node clusters. red means a primary shard is missing — check the log:

sudo tail -100 /var/log/elasticsearch/diskover.log

Disk space — most common cause of ES going read-only:

df -h /var/lib/elasticsearch

Elasticsearch stops writing at 90% disk usage. After freeing space, clear the watermark block:

curl -X PUT "http://localhost:9200/*/_settings" \
  -H 'Content-Type: application/json' \
  -d '{"index.blocks.read_only_allow_delete": null}'

See the Elasticsearch doc for more.

SELinux Blocking Services

SELinux is a common source of silent permission failures on RHEL/Rocky.

Check for recent AVC denials:

sudo ausearch -m avc -ts recent | grep -E 'nginx|diskover|php'

Common fixes:

# Allow nginx to serve files from the web root
sudo chcon -Rt httpd_sys_content_t /var/www/diskover-web

# Allow nginx to proxy to upstream sockets and ports
sudo setsebool -P httpd_can_network_connect 1
sudo setsebool -P httpd_can_network_relay 1

Firewall — Ports Reference

sudo firewall-cmd --list-all
sudo firewall-cmd --add-port=<port>/tcp --permanent && sudo firewall-cmd --reload

Disk Space / Log Rotation

df -h /var/log /var/lib/elasticsearch /opt/diskover

Log rotation is configurable in Diskover Admin > Configuration > Diskoverd. For Elasticsearch index cleanup, see the Kibana doc.

Reinstalling Python Dependencies

If Diskover services fail to start with ModuleNotFoundError or similar import errors, reinstalling the Python dependencies can resolve the issue. This is also required after a Diskover upgrade that introduces new package requirements.

Diskover on RHEL/Rocky uses a virtual environment at /opt/python-venv-diskover/:

# Reinstall all dependencies
sudo /opt/python-venv-diskover/bin/python3 -m pip install -r /opt/diskover/requirements.txt

# For diskover-admin
sudo /opt/python-venv-diskover/bin/python3 -m pip install -r /var/www/diskover-admin/etc/requirements.txt

After reinstalling, restart the affected services:

sudo systemctl restart diskover-admin diskoverd celery

License Failure

An expired or missing license causes diskoverd and Celery to exit at startup:

sudo tail -50 /var/log/diskover/diskoverd.log
sudo tail -50 /opt/diskover/diskover_celery/log/<nodename>.log

Contact Diskover support to obtain or renew a license.