System Tools

Essential utilities for Unix/Linux system administration and DevOps

What's in this category

A grab-bag of utilities for the kind of work that fills a Linux admin's day: parsing certificates, decoding JWTs, building cron expressions, calculating IOPS for storage plans, generating credentials, and testing regex against real log lines. These aren't toys — each one was built because we needed it during real on-call work and wanted something that runs without a network connection.

Every tool processes everything locally in your browser. The Certificate Parser never sees your cert. The JWT Decoder never sees your token. The Passphrase Generator uses your browser's cryptographic random source, not a server-side word list. Cron expressions, chmod permissions, and IOPS numbers are all pure math — no reason for them to round-trip a server. Use the Regex Tester for PCRE-style patterns against sample text with live highlighting, and the Log Parser when you need to grep, filter, and analyze raw logs without piping them anywhere unsafe.

Chmod Calculator

Visual permission calculator with checkboxes for owner/group/other. Bidirectional conversion between octal (755) and symbolic (-rwxr-xr-x) notation. Includes umask calculator and special permission bits.

Open Calculator

Cron Builder

Build cron expressions visually or parse existing ones. Human-readable explanations, next 10 execution times, and common preset library. Essential for scheduling tasks on Linux systems.

Open Builder

DISK Tools

Comprehensive storage and RAID calculator. Calculate RAID capacity and rebuild times, convert disk space units, analyze disk usage percentages, and estimate IOPS performance for various disk types and RAID configurations.

Open Tools

Password Generator

Generate secure random passwords with configurable length and complexity. Supports multiple policies (Active Directory, Linux PAM, custom), XKCD-style passphrases, and batch generation. Uses Web Crypto API for secure randomness.

Open Generator

Regex Tester

Test regular expressions against multi-line text with real-time matching. Includes common network patterns for MAC addresses, IPs, VLANs, and interface names. View matches with highlighting or in list format.

Open Tester

Log Timestamp Converter

Parse and convert log timestamps in batch mode. Auto-detects ISO8601, RFC3339, syslog, Windows Event Log, Apache/Nginx, and Unix formats. Convert to multiple timezones with CSV export.

Open Converter

Certificate Parser

Parse and decode PEM certificates to view expiry dates, subject, issuer, and Subject Alternative Names (SANs). Parse existing CSRs or generate new Certificate Signing Requests with custom SANs.

Open Parser

Log Parser

Parse log lines into structured fields. Auto-detects syslog RFC 3164/5424, Apache/Nginx combined and common, JSON, Windows Event Log, and custom delimited formats. Export results to CSV or JSON.

Open Parser

IOPS Calculator

Calculate storage IOPS for on-premises RAID arrays, AWS EBS, Azure Managed Disks, and Google Cloud Persistent Disks. Estimate read/write performance with RAID penalties and cloud provider limits.

Open Calculator

JWT Decoder

Decode JSON Web Tokens entirely in your browser. View header, payload, and signature with human-readable timestamps for exp, iat, and nbf claims. Validation status at a glance — no server upload.

Open Decoder

Built for the on-call shift

Local-only by design. None of these tools log inputs, send analytics, or require an account. Bookmark them on a laptop or pin them to a tab — they all keep working when the corporate proxy is down or the VPN is being temperamental.

Useful next: Data Tools for hashing, encoding, and text comparison. Network Tools for subnet planning and bandwidth math. If you're managing finances on the side, Financial Tools has paycheck, loan, and retirement calculators.