To boot the partition into the Linux rescue environment, refer to Starting a Linux Partition Image in Rescue Mode.

In the rescue environment, the partition boot disk is accessible via /dev/sda. Use the following command to list the partitions:

parted /dev/sda p

You can make repairs to the boot disk by mounting the required partition, and then create or modify files. For example, if the bootloader was damaged, you can mount the boot partition, and then copy a good bootloader to it.

If you need access to the network to read files from another machine or partition, refer to Configuring the Network Adapter in the Rescue Environment.