From df00ca1e4fe43ed9b487ed0fef8ed7dad9811ef4 Mon Sep 17 00:00:00 2001 From: Stijn Segers Date: Thu, 26 May 2016 22:09:41 +0200 Subject: [PATCH] Add new page explaining failsafe mode --- docs/failsafe.txt | 72 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 docs/failsafe.txt diff --git a/docs/failsafe.txt b/docs/failsafe.txt new file mode 100644 index 0000000..e1a4747 --- /dev/null +++ b/docs/failsafe.txt @@ -0,0 +1,72 @@ +--- +--- +Failsafe mode +============= + +== Failsafe mode + +**Caveat:** This functionality only applies to SquashFS images, since they come +with a read-only root partition. To verify whether your device uses SquashFS, +check for "SquashFS" either in the _LEDE_ image name or perform the following +check on your device: + + # grep squash /proc/mount + +_LEDE_ allows you to boot into failsafe mode and override the configuration saved +on the JFFS2 overlay. It will revert to a few hard coded defaults stored in the +SquashFS image. If your device becomes inaccessible, e.g. after a configuration +error, then failsafe mode is there to help you out; it *cannot*, however, fix +more deeply rooted problems like faulty hardware or a broken kernel. It is +comparable to a reset, but not entirely the same - you will still be able to +access your settings and restore them if desired, whereas a reset would just +wipe everything. + +=== Entering failsafe mode + +Make sure you use a wired connection, since the failsafe will disable your +wireless connectivity. + +To enter failsafe mode, follow one of the procedures listed below: + +* Wait for a flashing LED and press a button; +* Wait (with a packet sniffer) for a special broadcast packet and press a button; +* Watch for a boot message (on the serial port) and press a key ("f") on the serial keyboard. + +Usually, the first procedure is the easiest one. However, do consult the available +documentation for your device, as there is no default button assigned as a reset +button and not all procedures work on every device. Whichever trigger you use, +the device will enter failsafe mode and you can access the command line with SSH +(always possible) or a serial keyboard. OpenWrt releases (15.05 and before) offer +a telnet connection in this state but no SSH. + +=== Fixing or wiping your settings + +Once failsafe mode is triggered, the router will boot with a network address +of 192.168.1.1/24, usually on the 'eth0' network interface, with only essential +services running. Using SSH or a serial connection, you can then mount the +JFFS2 partition with the following command: + + # mount_root + +After that, you can start looking around and fix what's broken. The JFFS2 +partition will be mounted to '/overlay', as under normal operation. + +If you want a clean slate, there's no need to flash again; just enter the +following command and your device will be reset. + + # firstboot + +=== Settings not being saved + +When your device seems to save settings but loses them upon every reboot, +this could mean that overlayfs is corrupted. You can fix this by SSH-ing into the +device and issuing the following command to reset your JFSS2 partition: + + # jffs2reset + +While essentially doing the same thing as 'firstboot', this rewrites the flash +area of the JFFS2 file system instead of formatting it. + +More specific instructions will be provided in the wiki. + +**WIP** -- 2.30.2