Quick reference for md5sum, a tool to compute and verify MD5 checksums. MD5 is considered cryptographically broken; use it only for legacy integrity checks, not for security.

Basic usage

• md5sum file.iso – print MD5 hash and filename.
• md5sum file1 file2 file3 – hash multiple files.
• echo -n "test" | md5sum – hash data from stdin.

Common options

• -b – read files in binary mode (default on Linux).
• -t – read files in text mode (mainly for non-Unix systems).
• -c – check MD5 sums from a file.
• --tag – create BSD-style output (MD5 (file) = hash).

Creating and verifying checksum files

• md5sum file.iso > file.iso.md5 – save checksum.
• md5sum file1 file2 > checksums.md5 – create checksum list.
• md5sum -c file.iso.md5 – verify a single file.
• md5sum -c checksums.md5 – verify multiple files.

Tips

• Use sha256sum or sha512sum for security-sensitive integrity checks.
• When hashing from echo, remember -n to avoid including the newline.
• Checksum files are just text; you can version them in git or share them alongside downloads.