Lab 01-07 · Reinstall RouterOS with Netinstall¶

When a PC's operating system is so broken that it will not even start, you do not repair it: you boot from a USB stick and reinstall. The disk is formatted, a clean system goes on, and you copy your files back from your backup.

A router has no USB stick to boot from, but it can boot from the network. Your laptop plays the USB stick, and the tool that does it is Netinstall. It is the last resort when nothing else works: forgotten password with no backup, failed upgrade, a router that only blinks.

Reset button, reset configuration, or Netinstall?¶

The reset button of a RouterBOARD does more the longer you hold it while the router boots (course slide 66):

flowchart LR
    A["Hold reset<br>while powering on"] --> B["~5 s · LED <b>blinks</b><br>release: reset configuration"]
    B --> C["~10 s · LED <b>solid</b><br>release: CAP mode"]
    C --> D["~15 s · LED <b>off</b><br>release: look for a<br><b>Netinstall</b> server"]

How Netinstall works¶

Netinstall is a MikroTik program (Windows, and netinstall-cli for Linux) that installs RouterOS on a router booted from the network. It formats the router's storage and writes the packages you give it.

flowchart LR
    L["<b>Laptop</b><br>netinstall-cli<br>192.168.88.2/24<br>routeros + wifi-qcom .npk"] -- "Ethernet cable<br>to <b>ether1</b>" --- R["<b>hAP</b><br>in Netinstall mode<br>(boots from the network,<br>gets 192.168.88.3)"]

1. The router, in Netinstall mode, asks the network "who can give me a system?" (a BOOTP request).
2. Netinstall answers, gives it a temporary address (the client IP, here 192.168.88.3) and a tiny boot program.
3. The router formats its storage and receives the .npk packages.
4. It reboots into a clean RouterOS.

What survives: the license key and RouterBOOT settings. What is lost: configuration and all files (your backups on the router too!). If you give neither -r nor -e, netinstall-cli downloads the old configuration database and puts it back after the install (files are still lost); in this lab we start clean on purpose.

Important rules (slide 88 and the MikroTik manual):

• The cable goes to ether1 (on some models, a port labelled BOOT; on a few models, such as the RB1100 series, the last port). The hAP ax² uses ether1.
• The laptop needs a fixed IP address on its wired interface, and only one active network interface.
• The packages must match the router's architecture (arm64 for the hAP ax²) and the system package goes first.

The scenario¶

Start the lab¶

Download the lab files and unzip them: 01-07-netinstall.zip. Open a terminal inside the 01-07-netinstall folder.

Prepare before touching the router:

1. Download from mikrotik.com/download, all for the same version and ARM64:
   • Netinstall (CLI Linux) (netinstall-<version>.tar.gz)
   • the main package routeros-7.23.8-arm64.npk
   • the extra packages archive, to take wifi-qcom-7.23.8-arm64.npk from it

2. Unpack netinstall-cli:

   tar -xzf netinstall-*.tar.gz
   ls netinstall-cli
   

Step 1 · Save what you want to keep¶

Why: Netinstall formats the router. Anything only on the router is gone.

On the working hAP, run the commands of initial/r1.rsc (WinBox: Files → Backup, then New Terminal for the export):

/system backup save name=before-netinstall password=Lab-Pass-13
/export file=before-netinstall

Copy both files to the laptop (WinBox Files, drag and drop to your desktop). Also note the version and architecture (System → Resources).

Done when: both files are on your laptop.

Step 2 · Prepare the laptop's network¶

Why: the router in Netinstall mode cannot get its address from a DHCP server; Netinstall gives it one, and needs a fixed address itself.

Turn WiFi off. Find your wired interface name and give it a fixed address (Ubuntu):

ip link                                     # e.g. enp3s0 or enx1234567ee890
sudo ip addr add 192.168.88.2/24 dev enp3s0
sudo ip link set enp3s0 up

Plug the cable from the laptop into the hAP's ether1.

On Windows the equivalent is: static IP 192.168.88.2/24 on the Ethernet adapter, run Netinstall as administrator, allow it in the firewall, and in Net booting set the client IP 192.168.88.3.

Done when: ip addr show enp3s0 shows 192.168.88.2/24.

Step 3 · Start netinstall-cli¶

Why: Netinstall must be waiting before the router asks.

sudo ./netinstall-cli -r -s r1.rsc -a 192.168.88.3 \
    routeros-7.23.8-arm64.npk wifi-qcom-7.23.8-arm64.npk

(copy final/r1.rsc next to netinstall-cli as r1.rsc first). What each part means:

Expected: netinstall-cli starts and waits for a device to appear (leave the window open).

Done when: netinstall-cli is waiting.

Step 4 · Boot the router in Netinstall mode¶

1. Unplug the hAP's power.
2. Press and hold the reset button, plug the power back in while holding it.
3. Keep holding: the LED blinks (~5 s), goes solid (~10 s), then turns off (~15 s). Release it.
4. Watch the laptop: netinstall-cli shows the router's MAC address, the formatting, the packages being sent, and finally that the router is rebooting.

Alternative without the button, from a working RouterOS: /system routerboard settings set boot-device=try-ethernet-once-then-nand, then reboot (it applies to the next boot only).

Done when: netinstall-cli reports the installation finished.

Step 5 · Restore your configuration¶

Why: the course LAB ends by restoring the backup you saved in step 1.

1. Move the laptop's address to the LAN: remove the cable from ether1, plug it into ether2, and use DHCP or 192.168.88.2/24. The configure script gave the router 192.168.88.1 on its LAN bridge and the admin password Lab-Pass-13.
2. Log in (WinBox or ssh admin@192.168.88.1). The prompt shows 13_JohnDoe: your configure script ran.

3. Upload before-netinstall.backup (WinBox Files, drag and drop) and restore it: Files → Restore, or

   /system backup load name=before-netinstall.backup password=Lab-Pass-13
   

4. After the reboot, check that your configuration from the previous labs is back (identity, users, Internet access).

Done when: the router is back to how it was before step 1.

If something goes wrong¶

Key takeaways¶

• Netinstall reinstalls RouterOS over Ethernet: the last resort when RouterOS itself is broken.
• It formats the router: configuration and files are lost; the license and RouterBOOT settings survive. Save and copy your backup first.
• The router boots from the network when you hold the reset button at power-on until the LED goes off (~15 s); the cable goes to ether1 (or the BOOT port).
• The laptop needs a fixed IP, a single active interface, and packages for the right architecture, system package first.
• netinstall-cli options: -e empty config, -r default config, -s your own configure script, -b remove branding, -a the router's temporary IP.

Quick check¶

With Netinstall you can bring back any MikroTik router, no matter how broken. That closes Module 1: next, Module 2 and the world of DHCP, ARP and bridging.