The Certified Open Source Systems Administrator (COSA) is an intermediate, vendor-neutral certification for the people who administer Linux and open-source systems. It validates that you know the Linux foundations, can manage users, storage and filesystems, can configure networking and services, can script and automate, can secure and harden a system, and can operate and troubleshoot it. The exam is computer adaptive and performance-based, and the credential is kept current through continuing education.
| Level | Intermediate. A practitioner credential: it goes deep on running Linux and open-source systems and assumes some hands-on experience. |
|---|---|
| Delivery model | Computer adaptive, three stages. Your score on each stage selects the difficulty of the next, so no two candidates sit the same paper. |
| Format | 80 questions. A performance-based exam that includes performance-based questions and multiple-choice questions. Concepts transfer across every distribution. |
| Time | 120 minutes for the whole exam, timed. Autosaves every answer. |
| Scoring | You need a score of 700 out of 900 to pass. Results are reported on a scale of 100 to 900, and 700 corresponds to answering 72% of the exam correctly. Harder questions carry more weight, so a score means the same thing on any route. Multiple-response items and PBQs are all or nothing. |
| Retakes | No waiting period after a failed first attempt. Every attempt is paid for at the exam price. See the CertLabz Certification Retake Policy. |
| Voucher validity | 12 months from purchase, for one sitting. |
| Certification validity | 3 years. Renew with 50 CEUs per cycle and the $35 annual CE fee, or pass the current exam. Renewal details. |
| Language | English. |
| Credential | PDF certificate with QR code, public verification page, LinkedIn-ready credential ID. Issuer: CertLabz Certification Board. |
| Free resources | The exam objectives PDF and the ten sample questions PDF. |
| Workforce mapping | NICE Framework work roles: Systems Administration (IO-WRL-005). O*NET occupations: Network and Computer Systems Administrators (15-1244.00). Self-declared by CertLabz, not reviewed by NIST or CISA. See the full mapping. |
A signed, verifiable:
The COSA is a performance-based exam: it includes performance-based questions alongside multiple-choice questions. Instead of only picking A, B, C or D, you match commands to their effect, order a setup task, fix a permission or service problem, and choose the right approach. It is computer adaptive, is proctored and timed, needs no mandatory course, and tests administering Linux rather than reciting man pages.
The filesystem, shell, permissions, processes, packages, users, disks and LVM.
Network configuration, SSH, DNS, web and database services and firewalls.
Shell scripting, cron, configuration management and text processing.
Sudo, mandatory access control, hardening, systemd, monitoring and backups.
Linux runs the internet and the cloud, so open-source administration skills are broadly and durably in demand. Every route is shown here at once, so nothing is hidden behind a control you have to find.
United States pay reported by Glassdoor, checked September 2026. Pay varies by location, employer and experience. No certification guarantees a salary or a job.
| CertLabz COSA | Linux Foundation LFCS | |
|---|---|---|
| What it is | Certification exam | Certification exam |
| Computer adaptive | Yes | No |
| Hands-on PBQs | Yes | Yes |
| Scope | Open-source administration | Linux administration |
| Vendor neutral | Yes | Yes |
| Proctored | Yes | Yes |
| Questions | 80 | Practical tasks |
| Time | 120 min | 120 min |
| Pass mark | 700 of 900 | 67% |
| Course required | No | No |
| Exam voucher | $149 | $445 |
Compiled September 2026 from the Linux Foundation LFCS pages. The LFCS is a respected, fully hands-on command-line exam; the COSA is computer adaptive, blends scenario multiple choice with performance-based questions, and costs less. Product names and trademarks belong to their owners; CertLabz is not affiliated with any of them. Confirm current details with each provider.
Six reasons this credential is worth your time, and worth an employer's attention.
One price for the exam, set by its level. Bundles add the study guide and hands-on practice at a saving.
Secure checkout by Stripe. Prices in USD. Sign in or create a free CertLabz account at checkout.
Every form is drawn from a bank of more than 90 items to these exact weights, whichever adaptive route you take. Filter by the area you want to study.
The exam runs in three stages. Your score on each stage selects the difficulty of the next, so a strong candidate is stretched and a struggling one is measured fairly rather than swamped. No two candidates sit the same paper. Harder questions carry more weight, so a scaled score means the same thing whichever route you took.
Each exam can have up to 5 to 12 performance-based questions, drawn fresh on every attempt, alongside the multiple-choice questions. A PBQ is a task rather than a list: you match commands to their effect, order a setup task, fix a permission or service problem, or choose the right approach. They are scored all or nothing, so partial guesses do not pass.
The COSA is vendor neutral and distribution-agnostic, focused on standard Linux and open-source concepts. It tests the administration judgement that transfers across distributions.
Yes. Where a tool such as a firewall or a service manager is involved, it is described by what it does, not tied to one distribution.
700 out of 900. Results are reported on a scale of 100 to 900, and 700 corresponds to answering 72% of the exam correctly.
There is no waiting period between a failed first attempt and a second attempt. Buy another voucher and sit the exam again when you are ready, and it will draw a fresh adaptive form from the bank. See the CertLabz Certification Retake Policy.
Yes, after three years. Keep it current by logging 50 CEUs during the cycle and paying the $35 annual CE fee before expiry, or by passing the current exam again.
The exam objectives PDF and the ten sample questions PDF. The COSA Official Study Guide is a $50 ebook, included in two of the bundles. Hands-on practice comes with the All Access plan, included in the Complete bundle.
A laptop or desktop with a webcam and microphone, Chrome, Edge or Firefox, a stable connection, and a quiet private room for two hours. Phones and tablets are not supported.
COSA is a continuing-education certification, like the CE credentials from CompTIA and ISC2. It is valid for three years from the day you pass. To keep it, log 50 continuing-education units during the cycle and pay the $35 annual CE fee before your expiry date. Or pass the current version of the exam again. Earning a higher-level CertLabz certification renews it too, the way CompTIA certifications stack.
CEUs are logged from your CertLabz dashboard with supporting evidence. A certification that lapses can be reinstated only by passing the current exam.
Buy a voucher, study the objectives, sit the exam when you are ready. Your credential is issued the moment you pass.