Recovering From a Corrupted Lease Database

The dhcpd service maintains lease information, such as IP addresses, MAC addresses, and lease expiry times, in the following flat-file databases:

For DHCPv4: /var/lib/dhcpd/dhcpd.leases.
For DHCPv6: /var/lib/dhcpd/dhcpd6.leases.

To prevent the lease database files from becoming too large with stale data, the dhcpd service periodically regenerates the files through the following mechanism:

The service renames the existing lease files:
- /var/lib/dhcpd/dhcpd.leases is renamed to /var/lib/dhcpd/dhcpd.leases~
- /var/lib/dhcpd/dhcpd6.leases is renamed to /var/lib/dhcpd/dhcpd6.leases~
The service re-creates brand new dhcpd.leases and dhcpd6.leases files.

If a lease database file is corrupted, you need to restore the lease database from the last known backup of the database.

Typically, the most recent backup of a lease database is the filename.leases~ file.

Note:

A backup instance is a snapshot taken at a particular point in time, and therefore might not reflect the latest state of the system.

Ensure that you have the required administrative privileges and complete the following steps:

For DHCPv4

Stop the dhcpd service:
```
sudo systemctl stop dhcpd
```

Rename the corrupt lease database:

sudo mv /var/lib/dhcpd/dhcpd.leases /var/lib/dhcpd/dhcpd.leases.corrupt

Restore the lease database from its corresponding filename.leases~ backup file.
```
sudo cp -p /var/lib/dhcpd/dhcpd.leases~ /var/lib/dhcpd/dhcpd.leases
```
Start the dhcpd service:
```
sudo systemctl start dhcpd
```

For DHCPv6

Stop the dhcpd service:
```
sudo systemctl stop dhcpd6
```

Rename the corrupt lease database:

sudo mv /var/lib/dhcpd/dhcpd6.leases /var/lib/dhcpd/dhcpd6.leases.corrupt

Restore the lease database from its corresponding filename.leases~ backup file.
```
sudo cp -p /var/lib/dhcpd/dhcpd6.leases~ /var/lib/dhcpd/dhcpd6.leases
```
Start the dhcpd6 service:
```
sudo systemctl start dhcpd6
```