OpenWrt for Arduino Yun cheat sheet

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Revision as of 14:30, 7 April 2016 by Nxhack (talk | contribs) (→‎TO DO)
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OpenWrt running on Atheros AR9331 of Arduino Yun, LLC edition OpenWrt-Yun also Linino, is in obsolete (and has security issues) at kernel and various packages. I will try to investigate the upgrade to the latest version of OpenWrt. (With Absolutely NO Warranty)


Prepare for the Security update of OpenWrt-Yun, Arduino Yun Operating System (YunOS). In the IoT ERA, I think it is a very important thing.

OpenWrt-Yun Chaos Calmer 15.05

RedSnake64's implementation found at Arduino Yun forum.

RedSnake64 edition OpenWrt-Yun: 

https://github.com/RedSnake64/openwrt-yun/tree/15.05
ChaosCalmer_v1.3
I tried it. 'mDNS' is not active, so I could not be accessed in '.local'.
Grasp that implementation. I decided to make Arduino Yun package that can be used in OpenWrt trunk Bleeding Edge.

Investigate the Yun Profile of the OpenWrt Project

The OpenWrt Project, already there is a Arduino Yun Profile. 

target/linux/ar71xx/generic/profiles/arduino.mk
ar71xx: add Arduino Yun

https://github.com/openwrt/packages/tree/master/utils/yunbridge
yunbridge
Arduino Yun bridge library has been implemented.

OpenWrt snapshot images: 

https://downloads.openwrt.org/snapshots/trunk/ar71xx/generic/
https://downloads.openwrt.org/snapshots/trunk/ar71xx/generic/packages/
openwrt-ar71xx-generic-yun-16M-squashfs-sysupgrade.bin
This System Image is corresponding Arduino Yun Hardware. but, of course Arduino Yun own software is not implemented.
Mirror site: http://ftp.stw-bonn.de/pub/openwrt/snapshots/trunk/ar71xx/generic/

OpenWrt Core: 

git.openwrt.org Git - openwrt trunk tree
shortlog

OpenWrt Packages: 

https://github.com/openwrt/packages
https://github.com/openwrt/luci
https://github.com/openwrt-routing/packages
https://github.com/openwrt/telephony
https://github.com/openwrt/targets
https://github.com/openwrt-management/packages
Optional package of OpenWrt Project is managed on github.

Investigate the OpenWrt-Yun

OpenWrt-Yun arduino packages

LLC edition arduino package: 

https://github.com/arduino/openwrt-packages-yun/tree/master/arduino

RedSnake64 edition arduino package: 

https://github.com/RedSnake64/openwrt-arduino-packages/tree/for-15.05

Arduino OpenWrt Yún packages: 

(y) avrdude *
(y) cpu-mcu-bridge *
(m) cwiid *
(y) luci-app-arduino-webpanel
(m) node *
(m) node-bleno *
(m) node-noble *
(m) node-serialport *
(m) node-socket.io *
(m) node-socket.io-legacy *
(m) node-socket.io-client *
(m) node-socket.io-client-legacy *
(m) node-sqlite3 *
(m) node-ws *
(y) rng-tools *
(y) spacebrew
(y) temboo
(y) uSDaemon
(m) v8m-rb *
(y) yun-conf
(y) yun-scripts
  1. avrdude: use a OpenWrt package. Configuration for the Arduino Yun should be placed in /etc/avrdude.conf.
  2. cpu-mcu-bridge: overlaps with OpenWrt yunbridge package. For compatibility use a Arduino package.
  3. cwiid: only RedSnake64 edition. cwiid is Nintendo Wii remote interface package, so should delete.
  4. node, node-*: OpenWrt node package has a fpu problem. under checking update to v4.4.2.
  5. "-legacy" mean that the 0.9.x version.
  6. rng-tools: OpenWrt package has a problem. Should be changed START=98 to START=48.
  7. v8m-rb: node v4.4.2 not depend, so should delete.

My new arduino packages here: 

https://github.com/nxhack/openwrt-arduino-packages

Arturo Rinaldi edition linino packages: 

https://github.com/artynet/openwrt/tree/gcc5-07/package/linino

Important concept of OpenWrt

The Minimized (smaller footprint) is Highest Priority. This is the large difference in policy between PC GNU/Linux and OpenWrt.

Trunk Bleeding Edge version of OpenWrt-Yun package and build environment

https://git.openwrt.org/?p=openwrt.git
https://github.com/nxhack/openwrt-yun-build-extra
https://github.com/nxhack/openwrt-arduino-packages

Setup repos: 

mkdir Build_Path_Some_Where
cd Build_Path_Some_Where
git clone --depth=1 https://git.openwrt.org/openwrt.git
git clone --depth=1 --branch master --single-branch https://github.com/nxhack/openwrt-yun-build-extra.git
cd openwrt
ln -s ../openwrt-yun-build-extra/* .

Please modify ./files/etc/opkg/distfeeds.conf

First Time, Setup cross compile build environment (ubuntu 14.04): 

./FIRST_SETUP_ubuntu_Trusty_Tahr.sh

Build: 

./build.sh

When build succeed, You find openwrt-ar71xx-generic-yun-16M-squashfs-sysupgrade.bin in ./bin/ar71xx directory.

In order to using the packages, You must placed kernel packages and arduino packages to server (or SD card).

Essential items in the kernel configuration

CONFIG_TARGET_ar71xx=y
CONFIG_TARGET_ar71xx_generic=y
CONFIG_TARGET_ar71xx_generic_Yun=y

CONFIG_IMAGEOPT=y
# CONFIG_PREINITOPT is not set
CONFIG_TARGET_PREINIT_SUPPRESS_STDERR=y
CONFIG_TARGET_PREINIT_TIMEOUT=2
# CONFIG_TARGET_PREINIT_SHOW_NETMSG is not set
# CONFIG_TARGET_PREINIT_SUPPRESS_FAILSAFE_NETMSG is not set
CONFIG_TARGET_PREINIT_IFNAME=""
CONFIG_TARGET_PREINIT_IP="192.168.1.1"
CONFIG_TARGET_PREINIT_NETMASK="255.255.255.0"
CONFIG_TARGET_PREINIT_BROADCAST="192.168.1.255"
# CONFIG_INITOPT is not set
CONFIG_TARGET_INIT_PATH="/usr/sbin:/usr/bin:/sbin:/bin"
CONFIG_TARGET_INIT_ENV=""
CONFIG_TARGET_INIT_CMD="/sbin/init"
CONFIG_TARGET_INIT_SUPPRESS_STDERR=y
CONFIG_VERSIONOPT=y
CONFIG_VERSION_DIST="OpenWrt"
CONFIG_VERSION_NICK="Bleeding Edge"
CONFIG_VERSION_NUMBER=""
CONFIG_VERSION_REPO="http://downloads.openwrt.org/snapshots/trunk/%S/packages"
CONFIG_VERSION_MANUFACTURER="Arduino"
CONFIG_VERSION_MANUFACTURER_URL=""
CONFIG_VERSION_PRODUCT="Arduino Yun"
CONFIG_VERSION_HWREV="1.0"
# CONFIG_VERSION_FILENAMES is not set

CONFIG_PER_FEED_REPO=y
CONFIG_PER_FEED_REPO_ADD_DISABLED=y
CONFIG_PER_FEED_REPO_ADD_COMMENTED=y
CONFIG_FEED_packages=y
CONFIG_FEED_luci=y
CONFIG_FEED_routing=y
CONFIG_FEED_telephony=y
CONFIG_FEED_management=y
CONFIG_FEED_targets=y
CONFIG_FEED_arduino=y
# CONFIG_SMIMEOPT is not set
CONFIG_OPKGSMIME_PASSPHRASE=y

CONFIG_DEFAULT_base-files=y
CONFIG_DEFAULT_busybox=y
CONFIG_DEFAULT_dnsmasq=y
CONFIG_DEFAULT_dropbear=y
CONFIG_DEFAULT_firewall=y
CONFIG_DEFAULT_fstools=y
CONFIG_DEFAULT_ip6tables=y
CONFIG_DEFAULT_iptables=y
CONFIG_DEFAULT_iwinfo=y
CONFIG_DEFAULT_kmod-ath9k=y
CONFIG_DEFAULT_kmod-gpio-button-hotplug=y
CONFIG_DEFAULT_kmod-usb-core=y
CONFIG_DEFAULT_kmod-usb2=y
CONFIG_DEFAULT_libc=y
CONFIG_DEFAULT_libgcc=y
CONFIG_DEFAULT_mtd=y
CONFIG_DEFAULT_netifd=y
CONFIG_DEFAULT_odhcp6c=y
CONFIG_DEFAULT_odhcpd=y
CONFIG_DEFAULT_opkg=y
CONFIG_DEFAULT_ppp=y
CONFIG_DEFAULT_ppp-mod-pppoe=y
CONFIG_DEFAULT_swconfig=y
CONFIG_DEFAULT_uboot-envtools=y
CONFIG_DEFAULT_uci=y
CONFIG_DEFAULT_uclient-fetch=y
CONFIG_DEFAULT_wpad-mini=y

CONFIG_PACKAGE_python-base=y
CONFIG_PACKAGE_python-light=y

CONFIG_PACKAGE_avrdude=y
CONFIG_PACKAGE_cpu-mcu-bridge=y
CONFIG_PACKAGE_luci-app-arduino-webpanel=y
CONFIG_PACKAGE_node=m
CONFIG_PACKAGE_node-bleno=m
CONFIG_PACKAGE_node-noble=m
# CONFIG_PACKAGE_node-serialport is not set
CONFIG_PACKAGE_node-socket.io=m
CONFIG_PACKAGE_node-socket.io-client=m
CONFIG_PACKAGE_node-socket.io-client-legacy=m
CONFIG_PACKAGE_node-socket.io-legacy=m
CONFIG_PACKAGE_node-sqlite3=m
CONFIG_PACKAGE_node-ws=m
CONFIG_PACKAGE_rng-tools=y
CONFIG_PACKAGE_spacebrew=y
CONFIG_PACKAGE_temboo=y
CONFIG_PACKAGE_uSDaemon=y
CONFIG_PACKAGE_v8m-rb=m
CONFIG_PACKAGE_yun-conf=y
CONFIG_PACKAGE_yun-scripts=y

CONFIG_PACKAGE_luci=y
CONFIG_PACKAGE_luci-base=y
CONFIG_LUCI_LANG_en=y
CONFIG_PACKAGE_luci-mod-admin-full=y
CONFIG_PACKAGE_luci-app-arduino-webpanel=y
CONFIG_PACKAGE_luci-app-firewall=y
CONFIG_PACKAGE_luci-theme-bootstrap=y
CONFIG_PACKAGE_luci-theme-openwrt=y
CONFIG_PACKAGE_luci-proto-ipv6=y
CONFIG_PACKAGE_luci-proto-ppp=y
CONFIG_PACKAGE_luci-lib-ip=y
CONFIG_PACKAGE_luci-lib-json=y
CONFIG_PACKAGE_luci-lib-jsonc=y
CONFIG_PACKAGE_luci-lib-nixio=y
CONFIG_PACKAGE_luci-i18n-base-en=y
CONFIG_PACKAGE_luci-i18n-firewall-en=y

CONFIG_PACKAGE_kmod-nls-base=y
CONFIG_PACKAGE_kmod-nls-cp437=y
CONFIG_PACKAGE_kmod-nls-iso8859-1=y
CONFIG_PACKAGE_kmod-nls-utf8=y

# CONFIG_PACKAGE_triggerhappy is not set
CONFIG_PACKAGE_kmod-gpio-button-hotplug=y
CONFIG_PACKAGE_kmod-input-core=m
CONFIG_PACKAGE_kmod-input-evdev=m
CONFIG_PACKAGE_kmod-input-gpio-encoder=m
CONFIG_PACKAGE_kmod-input-gpio-keys=m
CONFIG_PACKAGE_kmod-input-gpio-keys-polled=m
CONFIG_PACKAGE_kmod-input-joydev=m
CONFIG_PACKAGE_kmod-input-matrixkmap=m
CONFIG_PACKAGE_kmod-input-polldev=m
CONFIG_PACKAGE_kmod-input-uinput=m

# CONFIG_PACKAGE_odhcp6c is not set
# CONFIG_PACKAGE_odhcpd is not set
# CONFIG_PACKAGE_dnsmasq is not set
CONFIG_PACKAGE_dnsmasq-dhcpv6=y

# CONFIG_PACKAGE_libavahi-client is not set
# CONFIG_PACKAGE_libavahi-compat-libdnssd is not set
# CONFIG_PACKAGE_libavahi-dbus-support is not set
CONFIG_PACKAGE_libavahi-nodbus-support=y

# CONFIG_PACKAGE_avahi-autoipd is not set
# CONFIG_PACKAGE_avahi-daemon-service-http is not set
# CONFIG_PACKAGE_avahi-daemon-service-ssh is not set
# CONFIG_PACKAGE_avahi-dbus-daemon is not set
CONFIG_PACKAGE_avahi-dnsconfd=y
CONFIG_PACKAGE_avahi-nodbus-daemon=y

CONFIG_PACKAGE_gnupg=y
CONFIG_PACKAGE_libgpg-error=y

CONFIG_PACKAGE_nano=y
CONFIG_PACKAGE_curl=y
CONFIG_PACKAGE_wget=y

openwrt-yun-minimum.config

Difference between the LLC edition

IPv6 stack is enabled.

Device name of the leds has been changed.
ds:green:wlan -> arduino:blue:wlan
ds:green:usb -> arduino:white:usb
target/linux/ar71xx/base-files/etc/uci-defaults/01_leds
https://github.com/nxhack/openwrt-arduino-packages/commit/eb7130ac331ce491765f27372d987d9d7415f6c0

In the original rng-tools has a problem. Should match the init script of the LLC version.
Should be started before the Yun original startup script "S49generate_new_gpg_key".
S98rngd -> S48rngd : START=98 -> START=48

 sed -i -e s/^START=98/START=48/ ./feeds/packages/utils/rng-tools/files/rngd.init

BUSYBOX ASH BANNER The date disappear.
https://git.openwrt.org/?p=openwrt.git;a=commit;h=39fabb5068e95ab9c0901dd4f37129111d88ae00

+# don't create a version string containing the actual timestamp
+export KCONFIG_NOTIMESTAMP=1
+

BUSYBOX ASH HELP Banner disappear.
CONFIG_ASH_HELP The default has been changed to 'n'.
https://github.com/openwrt/openwrt/blob/master/package/utils/busybox/Config-defaults.in#L2617

Add a configuration of the AR9331 as AVR writer to the original package.
/etc/avrdude.conf

/etc/avrdude.conf: 

programmer
  id    = "linuxgpio";
  desc  = "Use the Linux sysfs interface to bitbang GPIO lines";
  type  = "linuxgpio";
  reset = ~18;
  sck   = 11;
  mosi  = 27;
  miso  = 8;
;

BUSYBOX: telnet is disabled.
nc localhost 6571

PATH has changed.
CONFIG_TARGET_INIT_PATH="/bin:/sbin:/usr/bin:/usr/sbin" to CONFIG_TARGET_INIT_PATH="/usr/sbin:/usr/bin:/sbin:/bin"

uhttpd: SSL is forced.
option redirect_https '1'
/etc/config/uhttpd

uhttpd: Use URL alias handle. Do not apply alias patch.
/etc/config/uhttpd
Add to /etc/config/uhttpd
	list alias '/arduino=/cgi-bin/luci'
	list alias '/data=/cgi-bin/luci'
	list alias '/mailbox=/cgi-bin/luci'

Procd button mechanism exists. triggerhappy is not required.
(triggerhappy use HID button mechanism, It depends on kmod-input-*)
(kmod-gpio-button-hotplug + procd buttons, Of course, smaller footprint)
I was send PR, adding ath79_register_gpio_keys_polled.
https://git.openwrt.org/?p=openwrt.git;a=commit;h=10ae130265302c717b1580514ada28d9a48a2484
/etc/hotplug.d/button/00-button
/etc/config/system
Add button section to /etc/config/system.
config button
        option button 'wps'
        option action 'pressed'
        option handler '/usr/bin/wifi-reset-button-pressed'

config button
        option button 'wps'
        option action 'released'
        option handler '/usr/bin/wifi-reset-button-released'

TO DO

  1. uboot-linino 検証する。
    ブートローダの書き換え失敗したら完全に文鎮になるので検証はこわくてできない。うぅ
  2. SD card の automount 方法調査する。(uSDaemon がいまいちすぎるので)
    OpenWrt (e)udev まだ試していないが。
    /etc/udev/rules.d/11-sd-cards-auto-mount.rules
    KERNEL!="sda[0-9]", GOTO="sd_cards_auto_mount_end"
# Global mount options
ACTION=="add", ENV{mount_options}="relatime"
# Filesystem specific options
ACTION=="add", IMPORT{program}="/sbin/blkid -o udev -p %N"
ACTION=="add", ENV{ID_FS_TYPE}=="vfat|ntfs", ENV{mount_options}="$env{mount_options},utf8,gid=100,umask=002"
ACTION=="add", RUN+="/bin/mkdir -p /mnt/%k", RUN+="/bin/mount -o $env{mount_options} /dev/%k /media/%k"
ACTION=="remove", RUN+="/bin/umount -l /mnt/%k", RUN+="/bin/rmdir /mnt/%k"
# exit
LABEL="sd_cards_auto_mount_end"

    udevadm control --reload-rules
    なるほど、(e)udev を使わないのはサイズの問題だね。system image はできるだけ小さくするのが最優先になっている。なのでこの実装はしない。
  3. opkg packages
    procps -> procps-ng procps-ng-ps procps-ng-w procps-ng-top
    CPU Usage がバグってる様子...
    mg, logrotate がないので作った。
    python-pip があった
  4. local build packages の BUILD_KEY (Local build key)
    /etc/opkg/keys/ にストアされる。
    まちがって $(TOPDIR)/key-build と $(TOPDIR)/key-build.pub を消して再生成してしまったら、 その環境で作った base-files パッケージで入れ替える。
    $(CP) $(BUILD_KEY).pub $(1)/etc/opkg/keys/`$(STAGING_DIR_HOST)/bin/usign -F -p $(BUILD_KEY).pub`
  5. fstools, block-mount, fstab
    https://wiki.openwrt.org/doc/uci/fstab
    Sun Mar  6 19:54:35 2016 user.notice : this file has been obsoleted. please call "/sbin/block mount" directly
Sun Mar  6 19:54:36 2016 daemon.err block: /dev/sda2 is already mounted
    block-mount は /etc/config/fstab に automount って書けば boot 時によしなに mount するようだ。hotplug 的な挙動はまだこれからっぽい。
    block info and DISK_MEDIA_CHANGE events
    メディア挿入後 /sbin/block mount ってやればよいのだが、とりあえず今は uSDaemon は有効にする。
  6. extroot
    https://wiki.openwrt.org/doc/howto/extroot
    この作業を前提でパーティションとフォーマット済みのメディアがあるとして、
    cd /mnt/sda2
rm -rf *
rm -rf .??*
cd /
tar -C /overlay -cvf - . | tar -C /mnt/sda2 -xf -
block detect > /etc/config/fstab ; vi /etc/config/fstab
# edit /etc/config/fstab : Set all enabled '0' → enabled '1'
#      option target '/mnt/sda2' ->  option target '/overlay'
reboot
    戻す場合は、poweroff して SD card を取り出し 'YUN RST' を押し再起動。その後 /etc/config/fstab を修正。
    config global 'automount'
	option from_fstab '1'
	option anon_mount '1'
  7. /etc/opkg.conf と /etc/opkg/distfeeds.conf や /etc/opkg/customfeeds.conf の切り分けを調査する。
    なんか変なメッセージがでたので根元の　distfeeds.conf を書き換えたのだが、opkg.conf をユーザが書き換えるのが本筋。調査する。
    • opkg_conf_parse_file: Duplicate src declaration
    https://wiki.openwrt.org/doc/techref/opkg
    https://wiki.openwrt.org/doc/packages
    仕様がまだ定まってないようだ。
  8. OOM
    (もちろん extroot 環境で)
    python supervisor + beaver とかうごかすと OOM が発生する。
    メモリー減らすために、いらないモジュールがあるか再調査する。
    IPv6 support はさすがにこのご時世外せない。
    odhcpd はなくても大丈夫だった。そのかわりdnsmasq を dnsmasq-dhcpv6 に置き換える。
    dbus はなくても大丈夫だった。avahi を nodbus で。
    echo -1000 > /proc/`cat /var/run/dropbear.1.pid`/oom_score_adj
sysctl -w vm.swappiness=0
sysctl -w kernel.panic_on_oops=1
sysctl -w kernel.panic=3
    python supervisor + beaver の条件下で opkg でも Out of memory のエラー
    /etc/opkg/distfeeds.conf で本当に必要なレポジトリのみにする。
    /etc/opkg.conf の lists_dir ext /var/opkg-lists を tmpfs 以外の場所にする ex. lists_dir ext /usr/local/var/opkg-lists
    /etc/opkg.conf に option force_space を追加する
    lists_dir ext /usr/local/var/opkg-lists
option tmp_dir /usr/local/var/tmp
option force_space
    とにかく /tmp や /var (/tmp の symlink) には物を置かない事。これ大事。
  9. nodeが動かない
    trunk 版では "Illegal instruction"
    v4.4.2 は --with-mips-float-abi=soft が復活してるのでなんとかなるかな...
    kernelを素直に build すると CONFIG_MIPS_FPU_EMULATOR=y になってない。
    math-emu enable の場合に sysupgrade image できない? 16MB 超える?
    LLC版では swap 張っていない場合はメモリーを制限するオプション付きで起動させている。
    #!/bin/sh

SWAPS=`swapon -s | grep -c "file\|partition"`

if [ $SWAPS -gt 0 ]
then
	NODE_PATH=/usr/lib/node_modules /usr/bin/nodejs $@
else
	NODE_PATH=/usr/lib/node_modules /usr/bin/nodejs --optimize_for_size --stack_size=1024 --max_old_space_size=20 --max_executable_size=5 --gc_global --gc_interval=100 $@
fi
  10. led
    echo none > trigger すると、ちゃんと brightness が 0 になる。前のロジックがつかえない。

memo

Arduino IDE Bridge Library

Must apply this patch. 

--- a/Bridge/src/Bridge.cpp
+++ b/Bridge/src/Bridge.cpp
@@ -52,7 +52,7 @@
     // Wait for OpenWRT message
     // "Press enter to activate console"
     stream.print(F("run-bridge\n"));
-    delay(500);
+    delay(5000);
     dropAll();

     // Reset the brigde to check if it is running

refresh fstab : uci

uci delete fstab.@mount[0]
uci delete fstab.@mount[0]
uci commit

uci set fstab.automount=global
uci set fstab.automount.from_fstab='1'
uci set fstab.automount.anon_mount='1'
uci commit

extroot

cd /mnt/sda2
rm -rf *
rm -rf .??*
cd /
tar -C /overlay -cvf - . | tar -C /mnt/sda2 -xf -
block detect > /etc/config/fstab ; vi /etc/config/fstab
# edit /etc/config/fstab : Set all enabled '0' → enabled '1'
#      option target '/mnt/sda2' ->  option target '/overlay'
reboot

basic tools setup : opkg

# edit /etc/opkg.conf for extroot
opkg update
opkg list-upgradable
opkg install ca-certificates
opkg install unzip
opkg install screen
opkg install procps-ng procps-ng-ps procps-ng-w procps-ng-vmstat procps-ng-watch
opkg install procps-ng-top --force-overwrite
opkg install coreutils-ls coreutils-stty
opkg install dropbearconvert
opkg install e2fsprogs mkdosfs fdisk dosfsck
opkg install rsync
opkg install diffutils
opkg install logrotate
opkg install mg
opkg install openssh-client --force-overwrite
procps-ng has bug, CPU usage fail.
mkdir -p -m 1777 /usr/local/var/tmp
export TMPDIR=/usr/local/var/tmp
opkg install python-pip
opkg install python-six
# Edit /etc/pip.conf
#   cache-dir=/usr/local/var/tmp/.cache
# pip install --upgrade pip
pip install beaver==36.1.0
pip install supervisor
If OOM occurs, re-run pip.

dosfsck

cd /
umount /mnt/sda1
dosfsck -t -a -w /dev/sda1
# dosfsck -t -a /dev/sda1
mount /dev/sda1 /mnt/sda1

drop caches

echo 3 > /proc/sys/vm/drop_caches

network

eth1 -> wan
wlan0 -> lan

/etc/config/network
/etc/config/firewall
/etc/config/dhcp

Secure

Secure your router's access

Dropbear Security

Bricked

My Yún doesn't boot anymore! How can I restore it?

YunSerialTerminal をロードしてシリアルコンソールを有効にする。SDカードは抜いておく事。YUN RST ボタンをおす。

  1. YunSerialTerminal で prompt が出て OS の操作ができる場合。
    1. なんとかして network を生かす。 
      ifconfig インターフェース IPアドレス
route add default gw どこか
      /etc/resolv.conf を編集。
    2. SD card で正常な sysupgrade のイメージをもってくる。 
      mkdir /mnt/sda1
mount -t vfat /dev/sda1 /mnt/sda1
  2. YunSerialTerminal で u-boot を操作できる場合。
    1. https://www.arduino.cc/en/Tutorial/YunUBootReflash
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