Reverting back to OpenWrt from DD-WRT

Hi,

I am a newbie in the world of router customized firmware, so please excuse my question.
I have been given an old TP Link TL-WR710N router from my friend with DD-WRT installed. I have seen that this router supports OpenWRT too. I tried to "upgrade the firmware through the admin console to install OpenWRT, but the router, upon rebooting, still shows up DD-WRT.

Would anyone be able to help out?

Thank you!

~Lorenzo

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Which version is it?
https://openwrt.org/toh/tp-link/tl-wr710n#openwrt_images
Did you try the factory or sysupgrade image?

Worst case scenario is to revert back to stock firmware from TP-Link and then try to install OpenWrt.

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Take care: Only 32MB RAM.

https://openwrt.org/supported_devices/432_warning

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I switch between OpenWrt and DDWrt often with my wr841nd v7 and wdr4900v2.

From DDwrt to OpenWrt:

  1. Enable SSH in services tab of ddwrt.
  2. scp (winscp) openwrt-your-router-FACTORY.bin (factory not upgrade) to /tmp
  3. ssh login to ddwrt, cd /tmp
    mtd -f write openwrt-your-router-factory.bin linux
    reboot

From Openwrt to DDwrt:
mtd write /tmp/factory-to-ddwrt.bin firmware

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@zen1932 , for this particular case:

mtd -f write openwrt-your-router-factory.bin linux

I have compared those two images using hexdump, and I think probably either of them should work if flashed directly to firmware partition. sysupgrade one is probably preferable, because it doesn't have 4325372 unused 0xff bytes at the end.

In general, OpenWrt sysupgrade image is flashed directly to partition by sysupgrade script, while factory image is flashed via vendor web interface and can contain different/additional headers.

But the original poster does not have openwrt installed yet, hence no sysupgrade script, that's why I insisted on factory image.

But the original poster does not have openwrt installed yet, hence no sysupgrade script

My point is that script is not necessary. It does verification and backs config up, but mainly it does is writing directly to mtd which can be done by mtd write without sysupgrade, from factory or dd-wrt. For this router both images work, but for other routers attempt to write factory directly to flash will brick the device, while writing openwrt-sysupgrade to correct flash offset/partition should work for majority of devices.

Hi all,

Just thought I'd report back my own experience with trying to move from DD WRT to OpenWrt on my TP-Link Archer C7 AC1750 v5.

  1. I tried using the DD WRT firmware upgrade to install openwrt-21.02.1-ath79-generic-tplink_archer-c7-v5-squashfs-factory.bin. After reboot, back to DD-WRT without any effect.
  2. Next did an scp to /tmp of the above OpenWRT binary. Copy was good - exactly the same byte count.
  3. Finally did a "mtd -f write <openwrt-your-router-factory.bin> linux" as suggested above. Here's the result:
root@DD-WRT:/tmp# mtd -f write openwrt-21.02.1-ath79-generic-tplink_archer-c7-v5-squashfs-factory.bin linux
Unlocking linux ...
[flash] : Could not unlock MTD device: linux
linux: No such file or directory
Writing from openwrt-21.02.1-ath79-generic-tplink_archer-c7-v5-squashfs-factory.bin to linux ...  [w]
Warning unaligned data, we use manual padding to avoid errors. size was 24939!!!

Sensing a reboot would brick the router I reflashed, using the DD-WRT GUI, firmware DD-WRT v3.0-r47942 std (12/30/21) and thankfully everything came up.

Any explanation of what went wrong with the "mtd -f write" approach?
Is reverting back to the OEM factory firmware the only way to get to OpenWrt?

This is the recommended approach. The OpenWrt factory images / methods are designed to work from the OEM factory state (or from a TFTP or similar 'recovery' mechanism). When the device is running an alternative firmware, the firmware flashing functions may not understand what to do with an OpenWrt image, and it is possible that things will be written to the wrong places in memory. Flashing directly from DD-WRT to OpenWrt has never been recommended. Always revert to the factory firmware and then flash to OpenWrt from there.

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Thanks. I'll give that a try.

Be careful factory images usually consist of the mtd image with some headers containing magic numbers or checksums. Those are required by the stock updater to prevent flashing an image incompatible to your device. But those headers will get stripped before being written on the flash.

Depending on the type of router there is no image that can directly been written by mtd, see here for a rather interesting thread regarding a Linksys:

DD-WRT has a list of "revert to stock" images for quite a few devices.

In the past, I've used the one for the C7 v2, and it worked.

https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=85237&postdays=0&postorder=asc&start=0&sid=642108c3975004eb255c4de83242697c

Final update: Using the TFTP method I was able to flash directly to the openwrt-...-factory.bin image. That is, I did not need to revert to the stock TP-Link factory firmware beforehand.

Specifics of the process (as laid out in https://openwrt.org/toh/tp-link/archer_c7):

  1. Read documentation about five times.
  2. sudo apt-get install tftp
  3. Manual IP change to 192.168.0.66/24 on my desktop (i.e. the TFTP server)
  4. Copy openwrt-...-factory.bin to /var/lib/tftpboot/ArcherC7v5_tp_recovery.bin
  5. Power-off router. Power-on with reset pressed (requires paperclip or like). Wait for the 'swirly arrow' LED to start flashing orange.
  6. After the port 1 LED goes green, reset desktop network interface to use DHCP.
  7. Point browser to 192.168.1.1.

Thanks for all the input from everyone.

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