Opterius uses a different domain model than cPanel. In cPanel, a single account can have a main domain plus multiple "addon domains" — completely separate domains with their own document roots, all owned by the same account. Opterius deliberately does not work this way.
The Model: One Account, One Domain
In Opterius, each hosting account has exactly one main domain. That domain gets unlimited subdomains, but there's no concept of an "addon domain."
account: acmecorp (Linux user: acmecorp)
└── main domain: acmecorp.com
├── /home/acmecorp/acmecorp.com/public_html/ ← main site
├── subdomain: shop.acmecorp.com ← nested
├── subdomain: blog.acmecorp.com ← nested
└── subdomain: staging.acmecorp.com ← nested
If a client needs a second, unrelated domain (say, personal-site.com), they get a second account.
Why This Model
The 1-account-1-domain model is intentional and has advantages:
Security isolation. Each account is a separate Linux user. Files under acmecorp.com/ cannot be read by the user running otherclient.com/ — Linux DAC and ACLs enforce this at the OS level. With addon domains, both domains run as the same user, so a compromised site can read all other domains in the same account.
Clear resource attribution. Disk, bandwidth, and email quotas belong to exactly one domain. There's no ambiguity about which addon domain consumed the quota.
Simpler mental model. For a hosting company managing dozens of clients, one-account-one-domain maps cleanly to one-client-one-invoice. You never have to think about which of a client's five addon domains is on which server.
Easier migrations. A cPanel pkgacct backup for an addon-domain account is complex to parse correctly. Opterius accounts are simpler to back up and restore.
Subdomains vs Addon Domains
In Opterius, a subdomain (shop.acmecorp.com) is:
- Nested under the main domain of the account
- Its document root is inside the main domain's home tree
- It shares the account's resource quotas
A cPanel addon domain (personal-site.com) is a separate domain with its own document root, but running under the same Linux user as the main domain.
Opterius has no addon domain concept. If your clients regularly need multiple unrelated domains per account, use separate accounts — or use Opterius's collaborators feature so one person can access multiple accounts.
What Each Account Gets
| Resource | Notes |
|---|---|
| Linux system user | Created with useradd, home at /home/{username}/ |
| Home directory | /home/{username}/{domain.com}/ |
| PHP-FPM pool | Isolated socket, runs as the account user |
| Nginx vhost | Serves {domain.com} and www.{domain.com} |
| DNS zone | SOA, NS, A, MX, TXT/SPF records auto-created |
| Webmail access | Via Roundcube at port 8080 |
| phpMyAdmin access | Via phpMyAdmin at port 8081 |