Serial console server

I wanna build a serial console server. So i can access a Debian Server in my network if i locked myself out of SSH.

I was thinking for something like that:

            ttyd/picocom  ------->  screen /dev/ttyUSB0
+---------------+-------+          +-------+-----------+
|GL-AR300M16    |CP2102 |          |CP2102 |Debian     |
|OpenWRT 22.03.3|ttyUSB0+----------+ttyUSB0|11 Bullseye|
+------+-+------+-------+          +-------+----+-+----+
|WAN   | |LAN   |        +--------+        |LAN | |LAN |
|eth0.1| |eth0.0+--------+ SWITCH +--------+eth0| |ethX|
+------+ +------+        +---+----+        +----+ +----+
                         |Client   |
                         |SSH/22   |

So if the LAN Connection to the Debian Server fails, i still could get onto the console and fix /etc/network/interfaces to reach it again.

I have a bunch of WR703n/WR710n, but they are all restricted to 4MB Flash, or already used and modded too much and are EOL.

Question #1: Which device is at the moment the WR703n from 8 Years ago?

  • cheap
  • at least one 100Mbit Port
  • VLAN capable NIC is a plus
  • i do not care for WiFi
  • at least 1x USB 2.0
  • UART is a plus (soldering is OK)
  • µUSB is OK, Power through USB-C is a plus
  • 16MB Flash

Which device would you pick? GL-AR300M16 for example, any better?

Question #2: Which device would you pick for the USB-UART-USB NullModem Cable?
There is a USB-FTDI-USB Cable on the market, which is quite pricey.

I like the USB CP2102 devices. Atm they are at 5-8€ per item.
Any better?
OpenWRT and Debian Driver Support should be easily possible.

Question #3: On the Debian Host, i thought putting screen /dev/ttyUSB0 into the root crontab with @reboot should be sufficient.

Question #4: On the OpenWRT Host, i thought picocom(minicom?) Should be sufficient for the beginning or rare use.
ttyd would be nice. I guess for ttyd it's some effort to push it into a working https/443 setup without any mixed content warnings on the client.

Any thoughts about that one?

Seagate Dockstar or Pogoplug Series 4 (the one with the SATA connector on top),
you can easily find them used on ebay, for $10 + shipping.
Will run openwrt or plain Linux, boots from SD card, USB storage, or, in the Pogo case, SATA.

FYI, the USB3 ports will be capped by the bus/SoC, you won't get full speed.
No uUSB / USB-C power.

The Doozan forum is a gold mine for those interested in these devices.
They have Linux images, upgraded u-boots, and u-boot settings for multi boot.

I'd pick the same.

I'd add serial= param to the kernel command line in the boot loader.

that or screen, works too

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