When you have MySQL's physical data files but no dump backups, you're essentially working with the raw database storage. The key files you'll typically find in a MySQL data directory include:

ibdata1          # InnoDB system tablespace
ib_logfile0      # InnoDB log files
ib_logfile1
database_name/   # Directory for each database
  table_name.frm # Table structure
  table_name.ibd # InnoDB table data

Before proceeding, ensure you have:

• MySQL server installed (same or compatible version)
• File system permissions to access the old data files
• Enough disk space for the recovery process
• Stopped the MySQL service during the operation

1. Prepare the Environment

First, locate your current MySQL data directory. You can find it by running:

SHOW VARIABLES LIKE 'datadir';

Create a backup of your current data directory before proceeding:

sudo systemctl stop mysql
sudo cp -R /var/lib/mysql /var/lib/mysql_backup

2. Transfer the Old Database Files

Copy the files from your old installation to the new data directory:

sudo cp -R /path/to/old/mysql/data /var/lib/mysql
sudo chown -R mysql:mysql /var/lib/mysql

3. Handle InnoDB Recovery

If you're using InnoDB, add these lines to your my.cnf/my.ini file:

[mysqld]
innodb_force_recovery = 6
innodb_purge_threads = 0

Then start MySQL in recovery mode:

sudo systemctl start mysql

4. Verify and Repair Tables

After MySQL starts, check for corrupted tables:

mysqlcheck --all-databases --check --extended

Repair any corrupted tables:

mysqlcheck --all-databases --repair --extended

If the direct file copy method fails, you can try extracting data using mysqlfrm:

# Install mysql-utilities
sudo apt-get install mysql-utilities

# Recreate CREATE TABLE statements from .frm files
mysqlfrm --server=user:pass@localhost:3306 /path/to/old/data/database/table.frm

Then import the generated SQL to recreate tables and use ALTER TABLE to attach the .ibd files:

ALTER TABLE table_name IMPORT TABLESPACE;

• Version compatibility is crucial - MySQL 5.7 files won't work with MySQL 8.0
• Mixed storage engines (MyISAM and InnoDB) require different handling
• Always test recovered databases thoroughly before putting them into production
• Consider setting up proper backup routines after recovery

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When you have MySQL's physical data files but no SQL dump, you're working with the raw database structure. MySQL stores data in several critical files:

/var/lib/mysql/
├── ibdata1          # Shared tablespace data
├── ib_logfile0      # Transaction logs
├── ib_logfile1
├── database_name/   # Per-database directory (for file-per-table)
│   ├── table_name.frm
│   ├── table_name.ibd
│   └── db.opt

Here's how to restore from physical files after system reinstallation:

1. Stop MySQL Service

sudo systemctl stop mysql

2. Backup Current Data Directory

sudo mv /var/lib/mysql /var/lib/mysql_backup

3. Copy Old Data Files

sudo cp -R /path/to/old/mysql/data /var/lib/mysql
sudo chown -R mysql:mysql /var/lib/mysql

4. Handle InnoDB Configuration

Add these to your my.cnf if using InnoDB files from different MySQL version:

[mysqld]
innodb_force_recovery = 1
innodb_file_per_table = 1

When Table Files Are Corrupted

Try extracting data using mysqlfrm (for .frm files):

mysqlfrm --diagnostic /path/to/table.frm > table_definition.sql

Recovering Specific Tables Only

For file-per-table storage:

CREATE DATABASE recovered_db;
USE recovered_db;
# Create empty tables first
# Then discard tablespace and copy .ibd files
ALTER TABLE table_name DISCARD TABLESPACE;
cp old_table.ibd /var/lib/mysql/recovered_db/
chown mysql:mysql /var/lib/mysql/recovered_db/old_table.ibd
ALTER TABLE table_name IMPORT TABLESPACE;

• Run mysql_upgrade if moving between major versions
• Check for errors in MySQL error log
• Consider running REPAIR TABLE on problematic tables