NetAlertX/docs/FILE_PERMISSIONS.md

Managing File Permissions for NetAlertX on a Read-Only Container

Tip

NetAlertX runs in a secure, read-only Alpine-based container under a dedicated netalertx user (UID 20211, GID 20211). All writable paths are either mounted as persistent volumes or tmpfs filesystems. This ensures consistent file ownership and prevents privilege escalation.

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Writable Paths

NetAlertX requires certain paths to be writable at runtime. These paths should be mounted either as host volumes or tmpfs in your docker-compose.yml or docker run command:

Path	Purpose	Notes
/data/config	Application configuration	Persistent volume recommended
/data/db	Database files	Persistent volume recommended
/tmp/log	Logs	Lives under /tmp; optional host bind to retain logs
/tmp/api	API cache	Subdirectory of /tmp
/tmp/nginx/active-config	Active nginx configuration override	Mount /tmp (or override specific file)
/tmp/run	Runtime directories for nginx & PHP	Subdirectory of /tmp
/tmp	PHP session save directory	Backed by tmpfs for runtime writes

Mounting /tmp as tmpfs automatically covers all of its subdirectories (log, api, run, nginx/active-config, etc.).

All these paths will have UID 20211 / GID 20211 inside the container. Files on the host will appear owned by 20211:20211.

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Fixing Permission Problems

Sometimes, permission issues arise if your existing host directories were created by a previous container running as root or another UID. The container will fail to start with "Permission Denied" errors.

Solution

1. Run the container once as root (--user "0") to allow it to correct permissions automatically:

docker run -it --rm --name netalertx --user "0" \
  -v local/path/config:/data/config \
  -v local/path/db:/data/db \
  ghcr.io/jokob-sk/netalertx:latest

2. Wait for logs showing permissions being fixed. The container will then hang intentionally.
3. Press Ctrl+C to stop the container.
4. Start the container normally with your docker-compose.yml or docker run command.

The container startup script detects root and runs chown -R 20211:20211 on all volumes, fixing ownership for the secure netalertx user.

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Example: docker-compose.yml with tmpfs

services:
  netalertx:                                  
    container_name: netalertx                
    image: "ghcr.io/jokob-sk/netalertx"  
    network_mode: "host"       
    cap_add:
      - NET_RAW
      - NET_ADMIN
      - NET_BIND_SERVICE
    restart: unless-stopped
    volumes:
      - local/path/config:/data/config         
      - local/path/db:/data/db                 
    environment:
      - TZ=Europe/Berlin      
      - PORT=20211
    tmpfs:
      - "/tmp:uid=20211,gid=20211,mode=1700,rw,noexec,nosuid,nodev,async,noatime,nodiratime"

This setup ensures all writable paths are either in tmpfs or host-mounted, and the container never writes outside of controlled volumes.