Hello,
I have a lot of things to say about the Yun rev 2.
And this is part of it. I will take advantage of this post.
First of all, for any readers and to answer your question afterwards,
I imagine that you have already searched the forum before opening this post and I therefore assume that your post is the most recent on this topic.
I also consider that, like me, you followed very carefully the instructions given on this page:
A link will take you to the download page of "Arduino Yun Linux openWrt 1.5.3 UpGrade image".
In theory, and for the "Yun rev 1", you download the binary:
openwrt-ar71xx-generic-yun-16M-squashfs-sysupgrade.bin
that you put directly to the root of the SD card.
The following is clearly explained in the page cited above.
By cons, I read correctly, the subject is the "Yun rev 2" and there arduino site does not offer a different binary ?! nor does it mention otherwise to its use on a rev 2 which is already ambiguous.
A clarification between Linino and OpenWrt would be welcome for users.
But since Rev 2 comes with OpenWrt / LEDE 17.x.x, it seems more consistent to use the Table of Hardware on the OpenWrt website:
Thus, the filter proposes us for the Yun
without specifying the revision ???
to download version
18.06.2
.
Incidentally, I recommend "strongly" to download the YunSerialTerminal in the arduino, before any operation! And display it in the foreground to monitor boot messages!
The firmware programming went well.
Unfortunately, this version does not work with the sketch "Yun Serial Terminal" and the boot is therefore silent.
So back to square one.
Good player, I still tried to install the
image 1.5.3
proposed on the arduino site.
The installation went well, but the card refuses to update!
opkg update
Downloading http://downloads.arduino.cc/openwrtyun/1/packages/Packages.gz.
Downloading http://downloads.arduino.cc/openwrtyun/1/packages/Packages.sig.
Signature check failed.
Remove wrong Signature file.
Collected errors:
* opkg_download: Failed to download http://downloads.arduino.cc/openwrtyun/1/packages/Packages.gz: Error.
* opkg_download: Failed to download http://downloads.arduino.cc/openwrtyun/1/packages/Packages.sig: Error.
Not wishing to debug an old version, so I undertook to reinstall a version close to that delivered on the map (17 then 18 without success!)
Result via the web interface:
Failed to execute call dispatcher target for entry '/webpanel/reset_board'.
The called action terminated with an exception:
bad argument #1 to 'gsub' (string expected, got nil)
stack traceback:
[C]: in function 'assert'
?: in function 'dispatch'
?: in function <?:194>
Result via the terminal (putty):
run-sysupgrade /mnt/sda1/lede-17.01.6-ar71xx-generic-yun-16M-squashfs-sysupgrade.bin
The first try did not work, but the second yes ???
Sending TERM to remaining processes ... sleep uhttpd dbus-daemon dnsmasq avahi-daemon thd ntpd uSDaemon rcS logger syslogd klogd hotplug2 ubusd netifd
Sending KILL to remaining processes ... uhttpd
Switching to ramdisk...
Performing system upgrade...
Unlocking firmware ...
Writing from <stdin> to firmware ...
Upgrade completed
Rebooting system...
And here I am with version LEDE 17.01.6 and the Yun Serial Terminal which works again!
but on the other hand: "opkg update" fails
opkg update
Downloading http://downloads.lede-project.org/releases/17.01.6/targets/ar71xx/generic/packages/Packages.gz
Failed to establish connection
*** Failed to download the package list from http://downloads.lede-project.org/releases/17.01.6/targets/ar71xx/generic/packages/Packages.gz
Blablabla….
Collected errors:
* opkg_download: Failed to download http://downloads.lede-project.org/releases/17.01.6/targets/ar71xx/generic/packages/Packages.gz, wget returned 4.
* opkg_download: Check your network settings and connectivity.
* opkg_download: Failed to download http://downloads.lede-project.org/releases/17.01.6/packages/mips_24kc/base/Packages.gz, wget returned 4.
* opkg_download: Check your network settings and connectivity.
Moreover, the command
run-sysupgrade
is not recognized and the assembly of SDA1 is not automatic
=> I go through the WEB interface, make a prayer, and especially touch nothing!
desperately white page ###!? $ #
no LED flashing... nothing!
Fortunately on the second try:
It's gone and a message appears on the web interface warning not to cut off the power,
the LED flashing for a moment until the Luci home page is refreshed: phew!
but ping always fails 
so no opkg update/install is possible!
So finally I advise against doing a firmware update!
And for me the first question would be:
where can we find the firmware that came with the Yun rev2
See also this post:
Arduino Yun Rev. 2 - Firmware file and package list - Arduino Yún - Arduino Forum
Arduino Yun Rev. 2 - Firmware file and package list
Thanks for your feedbacks!