Docker cPanel

Technical summary

Infrastructure project to run a full cPanel/WHM instance inside Docker on AlmaLinux 8. The implementation targets development and integration scenarios and focuses on three practical failure points: reliable systemd behavior in containers, persistent cPanel core state, and lower bootstrap failure rate during installer execution.

Executed scope

• Built a Docker Compose runtime using privileged container mode for cPanel internal service compatibility.
• Applied required Linux capabilities (NET_ADMIN, SYS_ADMIN, SYS_RAWIO) to avoid low-level service failures.
• Implemented named-volume persistence to preserve installation state across container recreation.
• Added bootstrap strategy to inject required dependencies (wget, perl, network-scripts) before installer flow.
• Parameterized runtime through .env for hostname, ports, credentials, CPU, and memory limits.
• Enabled /usr/local/cpanel host-side mirroring for real-time plugin/core editing without docker cp loops.

Operational architecture

• Container base image: AlmaLinux 8.
• Orchestration layer: Docker Compose.
• Persistence:

- cpanel_core volume for /usr/local/cpanel; - auxiliary volumes for durable config/data.

• Access model:

- mapped cPanel/WHM ports; - dedicated SSH port for technical administration.

Initial configuration (.env)

CONTAINER_NAME=cpanel-server
HOSTNAME=srv.domain.com
ROOT_PASSWORD=YourStrongPasswordHere

SSH_PORT_HOST=22028
SSH_PORT_CONTAINER=22028
CPANEL_SSL_PORT=2083
CPANEL_NON_SSL_PORT=2082
WHM_SSL_PORT=2087
WHM_NON_SSL_PORT=2086
HTTP_PORT_HOST=8080
HTTPS_PORT_HOST=8443
HTTP_PORT_CONTAINER=80
HTTPS_PORT_CONTAINER=443

CPU_LIMIT=2.0
MEM_LIMIT=4G
MEM_RESERVATION=2G

TIMEZONE=America/Sao_Paulo
LANG=C.utf8

Practical execution

# start environment
docker-compose up -d

# manual cPanel reinstall when needed
docker exec -it cpanel-server bash -c "cd /home && curl -o latest -L https://securedownloads.cpanel.net/latest && sh latest"

Real-time development workflow

# local development workspace
mkdir -p /home/cpanel/dev

# symlink to cPanel core Docker volume
ln -s /var/lib/docker/volumes/NOME_DO_DIRETORIO_cpanel_core/_data /home/cpanel/dev/core

This setup reflects host-side edits directly inside the running container and shortens plugin integration cycles.

Security and hardening limits

• Runtime uses privileged: true; recommended scope is dev/lab/testing only.
• External exposure requires reverse proxy and additional host-level hardening.
• Immediate root password rotation after first WHM access is mandatory.

Stack and tooling

• Docker Compose
• AlmaLinux 8
• cPanel/WHM
• Containerized systemd
• Docker named volumes

Operational tags

• Docker
• cPanel
• AlmaLinux
• Systemd
• Dev Environment

Operational outcome

• Reproducible lab for cPanel plugin validation without dedicated physical server dependency.
• Reduced setup time for integration tests and installer troubleshooting.
• Higher change predictability with persistent core volume and real-time editing workflow.