Erigon Mdbx Compact

Verify that <datadir>/chaindata/mdbx.dat exists. Abort if it does not.

2. Report Size and Check Disk Space

1. Run du -sh <datadir>/chaindata/mdbx.dat and report the size to the user.
2. Run df -h <datadir>/chaindata and check available space. If available space is less than the mdbx.dat size, abort and tell the user there is not enough disk space.

3. Diagnose (Optional)

If the user wants to see whether compaction is worthwhile before proceeding:

make db-tools
./build/bin/mdbx_stat -ef <datadir>/chaindata

Look at the Reclaimable line in the output to estimate space savings.

4. Build mdbx_copy

make db-tools

This places mdbx_copy at ./build/bin/mdbx_copy.

5. Run Compaction

Create a sibling directory for the compacted output. The destination argument to mdbx_copy must be a file path, not a directory.

mkdir -p <datadir>/chaindata-compacted
./build/bin/mdbx_copy -c <datadir>/chaindata <datadir>/chaindata-compacted/mdbx.dat

• Source is the directory <datadir>/chaindata
• Destination is a file <datadir>/chaindata-compacted/mdbx.dat

This can take hours to days for large databases. Run in background.

6. Replace the Original

After mdbx_copy completes successfully:

1. Delete the old files:

   rm <datadir>/chaindata/mdbx.dat <datadir>/chaindata/mdbx.lck
   

2. Move the compacted file in:

   mv <datadir>/chaindata-compacted/mdbx.dat <datadir>/chaindata/mdbx.dat
   

3. Clean up:

   rmdir <datadir>/chaindata-compacted
   

7. Verify

Run du -sh <datadir>/chaindata/mdbx.dat and report the new size compared to the original.

The user can now restart erigon.