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November 2, 2025 01:06
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when openwrt after update does not load - broken config
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| yes I did backup configs before update | |
| I updated from openwrt 20 to 24 | |
| used squashfs-sysupgrade.bin | |
| ... and after update it boot and look like react as usual | |
| but - no internet - not even DHCP ip working | |
| can not get IP | |
| setting IP to static on PC like 192.168.1.153 | |
| can not ping 192.168.1.1 - ssh obviously also does not work | |
| ... lots of internet search | |
| ... nothing useful | |
| then I run Wireshark | |
| boot router (does not matter if you have IP or dhcp on PC) | |
| and noticed | |
| 192.168.1.1 send message to 192.168.1.255 | |
| "Please press button now to enter failsafe" | |
| I press(dont hold) reset-button on router load - after power up | |
| (I clicked many times till it started blinking fast one led) | |
| and set IP to static on PC 192.168.1.153 mask 255.255.255.0 | |
| I seasrch - "openwrt failsafe" | |
| https://openwrt.org/docs/guide-user/troubleshooting/failsafe_and_factory_reset | |
| - Failsafe mode starts the router with the IP address 192.168.1.1, | |
| - and disables DHCP and wireless connectivity | |
| - You will need to set your PC to a static address on the same subnet | |
| - (e.g., 192.168.1.10) and connect via Ethernet. | |
| - On most routers, OpenWrt will blink an LED (usually “Power”) during the boot process. | |
| - Early in the boot cycle, OpenWrt watches for a button press (any button) | |
| - inside a specific four second window to indicate that it should enter failsafe mode. | |
| finally I can ping 192.168.1.1 | |
| but ssh does not work | |
| Bad server host key: Invalid key length | |
| ... found | |
| https://forum.openwrt.org/t/cant-access-to-failsafe-mode-ssh/166791/ | |
| but this is solution | |
| https://forum.openwrt.org/t/23-05-snapshot-in-fallback-mode-ssh-fails-bad-server-host-key-invalid-key-length/166823/8 | |
| file | |
| ~/.ssh/config | |
| Host 192.168.1.1 | |
| User root | |
| UserKnownHostsFile /dev/null | |
| then ssh connect | |
| ssh [email protected] | |
| after connect (look openwrt failsafe wiki link above) | |
| firstboot | |
| or | |
| jffs2reset | |
| reboot | |
| and it works finally in normal boot | |
| I tried to load my "backup" config to new 24 openwrt after "failsafe restore" | |
| rebooted | |
| and it returned to "dead" state - no dhcp nothing - I repeated failsafe again | |
| il restore my configs manually without backup | |
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