I have bought two second hand EX2200 units, one was factory reset the other does not seem so.
The instructions at the below URL state to boot into single-user mode and perform the recovery from there. The problem is that the switch does not pause for a few seconds for me to press the space bar key to get to the prompt to enter boot -s command.
This is what I am seeing at start up. The moment I see Hit [Enter] to boot immediately, or space bar for command prompt, it shows a countdown from 1 but it goes away faster than a second and no matter how fast I press on my space bar I cannot get it to stop and give me a prompt to enter single-user mode.
U-Boot 1.1.6 (Jul 26 2011 - 03:19:50)
Board: EX2200-24T-4G 4.18
EPLD: Version 04.100311 (0x10)
DRAM: Initializing (512MB)
Flash: 8 MB
USB: scanning bus for devices... 3 USB Device(s) found
scanning bus for storage devices... 1 Storage Device(s) found
ELF file is 32 bit
Consoles: U-Boot console
FreeBSD/arm U-Boot loader, Revision 1.1
(email@example.com, Tue Jul 26 01:25:53 UTC 2011)
bootsequencing is enabled
bootsuccess is set
new boot device = disk0s1:
/kernel data=0x889590+0xdd8ac syms=[0x4+0xf0f80+0x4+0xc89d0]
Hit [Enter] to boot immediately, or space bar for command prompt.
Kernel entry at 0x1400100 ...
GDB: debug ports: uart
GDB: current port: uart
KDB: debugger backends: ddb gdb
KDB: current backend: ddb
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JUNOS 12.3R12.4 #0: 2016-01-20 04:27:03 UTC#factoryreset#Passwordreset#ex2200