Part 1 - Overview & Concepts

What ServersCTL hosting pools are
ServersCTL (serversctl.com) is the control plane for redundant server infrastructure: enrol Linux VMs with the ServersCTL agent, monitor heartbeats, cut over DNS between peers, run stack backups, and (on the cPanel preset) orchestrate account replication and live WHM transfers.
A server pool is one deployment in your dashboard — a set of members sharing failover DNS and pool-level settings. Members run what you actually install on each host. The dashboard exposes member tabs for OpenLiteSpeed, MariaDB/MySQL, Galera, and cPanel/WHM; each tab fills in when the agent detects that stack on that server.
ServersCTL does not host traffic. It moves DNS, queues remote jobs, and calls APIs where configured.
Pool Presets
Server pools are created using a preset template in the UI. This chapter is for the Generic Linux Server Preset. For HAProxy Server Pools, see the HAProxy chapter.
What runs on a member (stack compatibility)
Do not assume one VM runs every stack. Common deployments:
Deployment
Typical member stacks
Notes
cPanel / WHM hosting
cPanel tab + MariaDB tab (cPanel-managed MySQL)
Apache/httpd via cPanel — not OpenLiteSpeed
OpenLiteSpeed web farm
OpenLiteSpeed tab only
Standalone OLS
MariaDB / Galera nodes
MariaDB tab + Galera readout
DNS swing ≠ Galera quorum
Mixed pool
Different tabs per member
e.g. two cPanel standbys + one OLS edge — each member’s tabs reflect its OS
Core terminology
Term
Meaning
Pool
One ServersCTL Pool.
Member
One enrolled server (hostname, egress IP, enrollment secret)
Active member
Host whose IPv4 receives the pool failover A record.
Stack tab
Member workspace: OpenLiteSpeed, MariaDB, cPanel, etc.
Protected account
cPanel account with a replication job.
Agent
balctl_heartbeat.py on each member — heartbeats to 
serversctl.com
Architecture
Clients → DNS (Cloudflare / WHM) → A record → Active member IPv4
↑
ServersCTL Worker (serversctl.com)
↑
Standby members' ← agent heartbeats (+ WHM replication on cPanel preset)
Failover health: missed heartbeat beyond failover delay (10–120 s). No HAProxy systemd check on hosting presets.
All Linux Servers should use the Generic Server Preset when adding a pool. Only ever select the HAProxy Preset if HAProxy is installed on your server.
Create a Generic Linux pool
Sign in at serversctl.com → Pools → Create Pool.
Configuration preset: Generic Linux servers.
Name the Pool.
Now, go to the pool. Pool  Overview → Add server. Choose — RHEL/Ubuntu - Enter hostname, allowed egress IP.
Click Create Enrollment" and copy the install command.
On the VM: 
Paste the install command into the console to install the agent. 
If you have existing installs of cPanel, OpenLiteSpeed, MariaDB etc. The agent will report this to the UI. 
When 2+ members run cPanel: pool Protection and Managed DNS tabs appear (see Chapter 1).
Optional: Configure DNS on Managed DNS for account-level cutover.
Add further members to the Pool
From the pool overview tab click "Add Member".
Name the member and supply the member's egress IP.
Copy the install command into the console of the server being added to the pool.
Repeat the process to add further members. There are no limits to the number of pools or members you may have.
How pool navigation works
Two layers on one screen
The UI is split into two sections. The top tabs manage overall pool settings and the lower tabs manage member settings.
Layer
What it controls
Examples
Pool tabs
Settings and services that span all members or protected accounts across members
Overview fleet, Protection replication, Managed DNS catalogue, pool Monitoring presets, pool Settings
Member tabs
One enrolled Linux server — host OS, detected stacks, jobs, and backups
Control panel, Security, cPanel, MariaDB, Cron & Jobs
Protection and Managed DNS are pool settings. They float in the top tab bar above the member server tabs. They coordinate account replication, DNS cutover, and provider keys across the fleet — not operations on a single box.
Pool tab visibility (Generic Linux template)
Pool tab
Always?
When it appears
Overview
Yes
Default landing
Member tabs (one per server)
When enrolled
Subtitle Member on Generic pools (not Active/Standby)
Protection
No
2+ members with cPanel detected
Managed DNS
No
Same as Protection on Generic pools (2+ cPanel members)
Monitoring
Yes
Pool-wide alert presets
Settings
Yes
Pool name, API providers, delete pool
Tab: Overview (first pool tab).
Purpose: Fleet-wide health — are agents reporting, are backups and jobs healthy across Linux servers?
What you see
Section
Content
Fleet Status header
KPI widgets: member count, healthy agents, last check-in, backup count, cron jobs, running jobs, outdated agents
Fleet geography map
Members plotted when geo is set on each member’s Settings tab
Server tiles
One tile per enrolled member — click to open that member’s workspace
Actions
Add server, Pool settings
Operator actions
Add server — enroll another VM (see §18)
Click a server tile or member tab — jump to that member’s Control panel
Pool settings — shortcut to pool Settings tab
Tab: Protection (pool tab bar).
When visible: 2+ pool members where the agent reports cPanel.
Purpose: Account-level warm standby — scheduled WHM backup → Secure Storage → restore on a standby server, with optional DNS cutover per protected account.
What you see
Section
Content
Protection dashboard
KPIs: protected accounts, replication health, last sync
Server cards
Each cPanel-eligible member — readiness, WHM link, geography
Protected accounts
Per-account source → standby mapping, schedule, TTL, DNS provider
Replication log
Sync, DNS cut, transfer, and failure events
Geo map
Primary / standby geography when locations are set
Operator workflow
Ensure 2+ cPanel members and WHM API keys (Settings or Managed DNS → API providers).
Add protection — pick source account, target standby member, schedule (
1h … 
1mo), DNS TTL, DNS provider (Cloudflare or WHM).
Replicate now / Replicate protected (Pro) — on-demand sync.
Account Cut DNS — per-account A record swing to standby (coordinates with Managed DNS).
After DNS cut: post-failover hook on standby.
Relationship to member tabs
Task
Where
Bulk account replication, schedules, protection DNS
Pool Protection
Single-account migrate, live transfer sessions
Member cPanel → Migrate & Recovery
WHM account CRUD, suspend, AutoSSL
Member cPanel → Accounts
Protection is pool-wide orchestration; member cPanel is per-server WHM operations.
Replication Transfer
Replication can take anywhere from a few minutes to several hours, depending on the size of the account.
The source agent will package the account and split it into multiple chunks, which are securely stored temporarily in D2 storage. Once all chunks have been uploaded, the UI instructs the receiving agent to download them and begin the restore process.
After the restore has completed successfully, all stored chunks are automatically removed from S3. As a guide, a 1.8GB backup typically takes around 5 minutes to replicate. Please take replication time into account when configuring your schedule. If the account is large, you may need to replicate once per day or every few days to avoid overlap and ensure the process completes cleanly.
Tab: Managed DNS (pool tab bar).
When visible (Generic Linux): 2+ cPanel-detected members
Purpose: Pool-level DNS catalogue for protected accounts and optional dynamic DNS — WHM vs Cloudflare zones, record health, sync, import. The API keys listed here are for DNS only. Do not use your production WHM API key here. You must use Cloudflare or a cPanel DNS Cluster API Key.
What you see
Section
Content
DNS Health
Zone summary, provider linkage, drift, topology banner (DNS Provider → Primary → Standby) when Protection is active
Protected account records
Per-FQDN proxied/DNS-only, enabled, active IP, cut actions
API providers
Cloudflare account keys (one Global), per-member WHM keys
Dynamic DNS card
Failover hostname and sync toggle (Generic pools — primary place for DNS failover config)
Actions
Refresh DNS, Sync WHM→CF, Add record, Import from Cloudflare
Operator actions
Connect Cloudflare and/or cPanel DNS API credentials
Import existing Cloudflare records into the catalogue
Sync WHM→CF after account changes on WHM
Account Cut DNS from record rows (also available on Protection cards)
Set failover hostname and enable DNS sync (when using pool-level cutover)
Protected DNS
The UI treats WHM servers as the source of truth and replicates changes to any linked DNS provider, as long as the account is marked as Managed. By default, the only record that will cut over automatically is the domain’s A record.
Multiple DNS Record Cut Over
You can configure the UI to cut over additional DNS records from the Protected Account DNS list. From here, you can specify A, AAAA, MX, and SRV records that should automatically cut to a standby server when the primary becomes unavailable.
Actions
The three‑dot menu under the Action column provides additional fine‑tuning options:
Disable Managed DNS – When disabled, DNS records will not be updated or cut over during failover.
DNS Only – During cutover, Cloudflare proxying will be disabled (grey cloud), ensuring a direct DNS‑level switch without CDN caching or WAF interference.
Sync to Cloudflare – If you’ve added new DNS records in WHM’s DNS Manager, they will appear in the Protected DNS table and can be automatically pushed to Cloudflare.
Pool vs member DNS
Scope
Tab
Protected accounts, zone catalogue, provider keys, and failover FQDN
Pool Managed DNS
Per-member WHM key rotation
Pool Settings or Managed DNS API panel
Host TLS / Let’s Encrypt on a single VM
Member Control Panel or Recipes
Tab: Monitoring (pool tab bar).
Purpose: Pool-wide monitoring presets — distinct from per-member alerts on each server’s Monitoring tab.
Generic pool without Protection (0–1 cPanel members)
Infrastructure alerts section:
Heartbeat miss thresholds, CPU/disk/service alert toggles
Optional alert email recipients (account + team inboxes)
Generic pool with Protection (2+ cPanel members)
Protection DNS failover section (in addition to or instead of infrastructure, depending on layout):
Preset
Meaning
Failover banner
How long pool header shows Failover active after DNS cut (Community: 2 h max)
Failover email
Notify when DNS moves to standby
Failover alert recipients
Team inboxes for protection cutover
Operator note
Configure per-member heartbeat and resource alerts on each server’s member Monitoring tab. Pool Monitoring is for fleet-level and protection DNS behavior.
Tab: Settings (pool tab bar).
Purpose: Pool identity, shared API credentials, danger zone.
What you see (Generic Linux)
Card
Content
Pool name
Rename the pool
API providers
Cloudflare account keys (mark one Global). Each cPanel server needs its own WHM key (pool-level + per-member rows)
Danger zone
Delete pool
What is NOT on the Generic pool Settings
Feature
Where instead
Balancer failover (auto-failover delay, make-active hostname)
Managed DNS (when tab visible) or optional — Generic pools work without DNS
Protection jobs
Protection tab
DNS record catalog
Managed DNS tab
HAProxy pools include Balancer failover on Settings.