ext2 and ext3 are not natively supported on Mac so you need to install third party software.
- Install OSXFuse and select the MacFuse compatibility layer
- Install the it's Ext2 FUSE module
- Make a mount point for mounting:
- Mount the disk read/write using the 'force' option:
fuse-ext2 /dev/disk2s1 /Volumes/mountpoint1 -o force
- Edit a file on the system e.g.