You can try the administrator password recovery procedure:
This procedure can only be performed through the security console, and only within the first five minutes of rebooting the ACOS device.
1. Find and record the serial number on the back of the A10
2. Reboot the ACOS device.
3. Connect to the serial console.
4. When prompted for the user name and password, enter the following:
User Name: reset
Password: serial number for your device
Use the serial number recorded in step 1.
5. After logging in, the CLI presents the following questions:
a. Do you want to reset admin password to default?[y/n]:
Answering y to this question resets the admin user name and password to the factory default admin
and a10.
b. Do you want to reset enable password to default?[y/n]:
Answering y to this question resets the enable password to the factory default, which is no password.
c. Do you want to erase startup config?[y/n]:
Answering y to this question clears the startup config, thus returning the device to its factory default
settings.
6. Answer y to the first question so that you can log on to the device; answer the other two questions as
desired for your needs.
7. After you log on to the device, change the admin password for security purposes.