To use copy flash_image and recovery-RA-GNM-thunderc-s-1.1.0.img to the root of your sdcard.

To flash: via adb shell or terminal type this from root # shell

PHP Code:
# mount -o remount,rw -t yaffs2 /dev/block/mtdblock5 /system

# cat /sdcard/flash_image > /system/bin/flash_image

# chmod 755 /system/bin/flash_image

# mv /system/etc/ /system/etc/

# mount -o remount,ro -t yaffs2 /dev/block/mtdblock5 /system

# flash_image recovery /sdcard/recovery-RA-GNM-thunderc-s-1.1.0.img

# reboot recovery 
Key combo to boot custom recovery from powered off is vol_down + home + power and release keys at LG splash.

Recovery Features:

ADB as root user

USB-MS Toggle :mounts sdcard as mass storage

Nand Backup : runs a nandroid backup of data, cache, boot, system
Nand Backup + .android secure : backs up above plus .android_secure on sdcard (froyo native apps on sd)
Nand + ext backup : data, cache, system, boot, plus apps2sd on ext partition (old style apps2sd)
Nand Restore : browse to and select nandroid backup to restore

Flash Zip From Sdcard: must be in root of sdcard

Wipe Menu:
Wipe data/factory reset: wipes data & cache
Wipe cache
Wipe Dalvik cache : Wipes Dalvik cache in all possible locations if moved by apps2sd
Wipe SD:ext : Wipes Apps2sd ext partition
Wipe Battery Stats
Wipe rotate settings
Wipe .android secure : Wipes froyo native .android_secure on sdcard

Partition Sdcard:
Partition SD: Partition's sdcard for apps2sd (this formats card so all non backed-up data is lost)
Repair Sd:ext
SD:ext2 to ext3 : coverts apps2sd ext2 partition to ext3 (requires kernel support for ext3)
SD:ext3 to ext4 : same as above but ext3 to ext4 (requires kernel support for ext4)

Gui mounts to avoid typing in terminal to mount and cd into a dir to mount system, data, cache, sd-ext (if exists), sdcard

Fix apk uid mismatches
Move recovery log to SD
Toggle Signature Verify : Turn of signature checking on flashing zips
Key Test : Output keycodes for debugging recovery

Recovery Key mapping:
Up & down : vol-up and vol-down
Select : Menu
Backup : Back

Orginally posted by drellisdee @