sha256sum Command
Beginner Firewall & Security man(1)Compute and verify SHA-256 message digests
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📅 Updated: Mar 15, 2026
SYNTAX
sha256sum [OPTION]... [FILE]...
What Does sha256sum Do?
sha256sum calculates and verifies SHA-256 cryptographic hashes (256-bit). SHA-256 is part of the SHA-2 family and is currently the recommended standard for file integrity verification and security.
sha256sum produces a unique 64-character hexadecimal fingerprint. It is computationally infeasible to find two different files with the same hash, making it suitable for security-critical verification.
sha256sum is the standard for verifying software downloads, checking backup integrity, and detecting file tampering.
sha256sum produces a unique 64-character hexadecimal fingerprint. It is computationally infeasible to find two different files with the same hash, making it suitable for security-critical verification.
sha256sum is the standard for verifying software downloads, checking backup integrity, and detecting file tampering.
Options & Flags
| Option | Description | Example |
|---|---|---|
| file | Calculate SHA-256 hash | sha256sum file.iso |
| -c | Check hashes from file | sha256sum -c SHA256SUMS |
| -b | Binary mode | sha256sum -b file.bin |
| --quiet | Only show failures | sha256sum --quiet -c SHA256SUMS |
Practical Examples
#1 Calculate hash
Computes the SHA-256 hash of a file.
$ sha256sum ubuntu.iso
Output:
a1b2c3d4e5f6... ubuntu.iso
#2 Verify download
Checks files against their expected SHA-256 hashes.
$ sha256sum -c SHA256SUMS
Output:
ubuntu.iso: OK
#3 Hash a string
Calculates SHA-256 of a string.
$ echo -n "password123" | sha256sum
Output:
ef92b778bafe... -
#4 Create checksums
Generates a checksum file for all archives.
$ sha256sum *.tar.gz > SHA256SUMS#5 Multiple files
Calculates hashes for all backup files.
$ sha256sum backup_*.tar.gzTips & Best Practices
Always use SHA-256 over MD5: SHA-256 is the current standard for file verification. MD5 is broken for security. sha256sum should be your default.
Verify Linux downloads: Linux distributions provide SHA256SUMS files. Download both the ISO and SHA256SUMS, then run sha256sum -c SHA256SUMS.
Use -n with echo: echo "text" | sha256sum includes a trailing newline. Use echo -n "text" | sha256sum for the exact string hash.
Frequently Asked Questions
How do I verify a download with SHA-256?
Download the SHA256SUMS file, then run sha256sum -c SHA256SUMS in the same directory as the downloaded file.
What is the difference between MD5 and SHA-256?
SHA-256 is cryptographically secure (256-bit). MD5 is broken (128-bit, collisions possible). Always prefer SHA-256.
How do I hash a password?
echo -n "password" | sha256sum. Note: for actual password hashing in applications, use bcrypt or argon2, not raw SHA-256.
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