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cache_check(8) System Manager's Manual cache_check(8)

📛 NAME

cache_check — validates cache metadata on a device or file.

🚀 Quick Reference

Use Case	Command	Description
Validate cache metadata on a device	cache_check /dev/vg/metadata	Checks cache metadata for errors
Check only the superblock	cache_check --super-block-only /dev/vg/metadata	Validates only the superblock, skipping other metadata
Skip hints check	cache_check --skip-hints /dev/vg/metadata	Bypass checking of policy hint values
Clear needs-check flag after successful check	cache_check --clear-needs-check-flag /dev/vg/metadata	Clears the kernel’s ‘needs_check’ flag if check passes

📖 SYNOPSIS

cache_check [options] {device|file}

📝 DESCRIPTION

cache_check checks cache metadata created by the device-mapper cache target on a device or file.

⚠️ This tool cannot be run on live metadata.

⚙️ OPTIONS

-h, --help 🔍 Print help and exit. -V, --version ℹ️ Output version information and exit. -q, --quiet 🔇 Suppress output messages, return only exit code. --super-block-only 🛡️ Only check the superblock. --skip-hints ⏭️ Skip checking of the policy hint values metadata. --skip-discards ⏭️ Skip checking of the discard bits in the metadata. --clear-needs-check-flag ✅ Clears the 'needs_check' flag in the superblock.

The kernel may set a flag to force the pool to be checked before it's next activated. Set this switch to clear the flag if the check is successful. If the metadata check failed, the flag is not cleared and a cache_repair run is needed to fix any issues. After cache_repair succeeded, you may run cache_check again.

💡 EXAMPLE

Analyses and repairs cache metadata on logical volume /dev/vg/metadata:

$ cache_check /dev/vg/metadata

The device may not be actively used by the target when running.

🔬 DIAGNOSTICS

cache_check returns an exit code of 0 for success or 1 for error.

🚪 Exit Codes

Code	Meaning
0	✅ Success – metadata is valid
1	❌ Error – metadata corruption or other failure

🔗 SEE ALSO

cache_dump(8), cache_repair(8), cache_restore(8)

👤 AUTHOR

Joe Thornber <ejt AT redhat.com>, Heinz Mauelshagen <HeinzM AT RedHat.com>

📛 NAME 🚀 Quick Reference 📖 SYNOPSIS 📝 DESCRIPTION ⚙️ OPTIONS 💡 EXAMPLE 🔬 DIAGNOSTICS 🚪 Exit Codes 🔗 SEE ALSO 👤 AUTHOR