What is CloudLinux and how it protects hosting
CloudLinux is the OS used on UnderHost shared hosting servers. It isolates each account with resource limits so one account cannot slow down or crash the ent...
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CloudLinux is a specialized Linux operating system designed for shared web hosting servers. Unlike standard Linux where all accounts share server resources freely, CloudLinux enforces per-account resource limits and isolates each account from the others. UnderHost shared hosting servers run CloudLinux.
What is CloudLinux?
On a standard shared server, one account running a heavy script can consume all available CPU or RAM, causing every other site on the server to slow down or fail. CloudLinux prevents this through a technology called LVE (Lightweight Virtual Environment) that enforces per-account resource limits.
Every account on an UnderHost shared server runs in its own LVE container with dedicated limits for CPU, RAM, Entry Processes (concurrent PHP requests), I/O, and more. When you hit a limit, only your account is affected-others continue normally.
Account isolation
CloudLinux isolation provides several security and stability benefits:
- Resource isolation: Your account's CPU/RAM usage cannot exceed allocated limits
- Process isolation: Processes running in one account cannot see or affect processes in another account
- File system isolation: Each account has a restricted view of the file system-you cannot browse to other accounts' files
- Malware containment: If your account is compromised, the attacker cannot easily pivot to other accounts on the same server
How limits work
| Resource | What it controls | When exceeded |
|---|---|---|
| CPU | Processing power allocation (in percentage of a CPU core) | PHP processes run slower; page loads increase |
| RAM (PMEM) | Physical memory allowed for PHP processes | PHP processes are killed; 500 errors or blank pages |
| Entry Processes (EP) | Maximum concurrent PHP processes | New requests see 508 Resource Limit Is Reached |
| I/O | Disk read/write throughput (MB/s) | File access slows down; database queries take longer |
| IOPS | Number of disk operations per second | Similar to I/O throttle-performance degrades |
| Nproc | Maximum number of total processes | Cannot launch new processes; errors on script start |
Checking your usage
- Log in to cPanel
- Go to Metrics → Resource Usage
- View 24-hour history graphs for CPU, RAM, EP, and I/O
- If any resource shows consistent usage near 100%, your account is being throttled
Benefits for shared hosting users
- Consistent performance: Other tenants on the server cannot affect your site's speed
- Predictable limits: Your allocated resources are always available to you
- Clear diagnostics: Resource Usage graphs show exactly what's happening with your account
- Better security: Account isolation limits the blast radius of any compromise
Related: Resource limits | CloudLinux resource limit | Shared hosting overview | How to choose the right hosting plan
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