I checked on other Edimax 6200n equipment that I managed to get. Overall the same problem.
On 19.07.4 version I set the password and turned on WiFi, on the next higher versions and 19.07.3 I only set the password for the router. Settings are always lost after restarting the router with LuCI network. I updated the software without keeping the settings from the previous version. Logs are added in order of update. In the logs you can see e.g. differences in the amount of memory depending on the version (they are small). Below are logs for commands
mount
df -h
free
on individual versions of OpenWrt. I executed the commands after setting the password and rebooting.
Powered by LuCI openwrt-19.07 branch (git-20.247.75781-0d0ab01) / OpenWrt 19.07.4 r11208-ce6496d796
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.4, r11208-ce6496d796
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28268 14128 5156 304 8984 11800
Swap: 0 0 0
root@OpenWrt:~#
Powered by LuCI openwrt-19.07 branch (git-20.341.57626-51f55b5) / OpenWrt 19.07.5 r11257-5090152ae3
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.5, r11257-5090152ae3
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28268 14088 5200 304 8980 11848
Swap: 0 0 0
root@OpenWrt:~#
Powered by LuCI openwrt-19.07 branch (git-21.018.57536-6ba9740) / OpenWrt 19.07.6 r11278-8055e38794
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.6, r11278-8055e38794
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 248.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28268 14168 5104 308 8996 11760
Swap: 0 0 0
root@OpenWrt:~#
Powered by LuCI openwrt-19.07 branch (git-21.044.30835-34e0d65) / OpenWrt 19.07.7 r11306-c4a6851c72
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.7, r11306-c4a6851c72
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 248.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28268 14176 5096 308 8996 11784
Swap: 0 0 0
root@OpenWrt:~#
Powered by LuCI openwrt-19.07 branch (git-21.189.23240-7b931da) / OpenWrt 19.07.8 r11364-ef56c85848
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.8, r11364-ef56c85848
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28260 14096 5172 304 8992 11820
Swap: 0 0 0
root@OpenWrt:~#
Powered by LuCI openwrt-19.07 branch (git-22.045.73925-36e5c1c) / OpenWrt 19.07.9 r11405-2a3558b0de
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.9, r11405-2a3558b0de
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28260 14108 5156 304 8996 11808
Swap: 0 0 0
root@OpenWrt:~#
Here, see that I go back to an older version from 19.07.9 to 19.07.3. Version 19.07.3 was not in firmware selector and I found the bin file with the firmware manually (https://downloads.openwrt.org/releases/17.01.3/targets/ramips/rt305x/).
Powered by LuCI openwrt-19.07 branch (git-20.136.49537-fb2f363) / OpenWrt 19.07.3 r11063-85e04e9f46
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.3, r11063-85e04e9f46
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28268 14096 5188 304 8984 11840
Swap: 0 0 0
root@OpenWrt:~#
And the newest firmware for this device currently:
Powered by LuCI openwrt-19.07 branch (git-22.099.58928-786ebc9) / OpenWrt 19.07.10 r11427-9ce6aa9d8d
login as: root
BusyBox v1.30.1 () built-in shell (ash)
_______ ________ __
| |.-----.-----.-----.| | | |.----.| |_
| - || _ | -__| || | | || _|| _|
|_______|| __|_____|__|__||________||__| |____|
|__| W I R E L E S S F R E E D O M
-----------------------------------------------------
OpenWrt 19.07.10, r11427-9ce6aa9d8d
-----------------------------------------------------
=== WARNING! =====================================
There is no root password defined on this device!
Use the "passwd" command to set up a new password
in order to prevent unauthorized SSH logins.
--------------------------------------------------
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# cls
-ash: cls: not found
root@OpenWrt:~# clear
root@OpenWrt:~# mount
/dev/root on /rom type squashfs (ro,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,noatime)
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,noatime)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,noatime)
tmpfs on /tmp/root type tmpfs (rw,noatime,mode=755)
overlayfs:/tmp/root on / type overlay (rw,noatime,lowerdir=/,upperdir=/tmp/root/upper,workdir=/tmp/root/work)
tmpfs on /dev type tmpfs (rw,nosuid,relatime,size=512k,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600,ptmxmode=000)
debugfs on /sys/kernel/debug type debugfs (rw,noatime)
root@OpenWrt:~# df -h
Filesystem Size Used Available Use% Mounted on
/dev/root 3.0M 3.0M 0 100% /rom
tmpfs 13.8M 244.0K 13.6M 2% /tmp
tmpfs 13.8M 60.0K 13.7M 0% /tmp/root
overlayfs:/tmp/root 13.8M 60.0K 13.7M 0% /
tmpfs 512.0K 0 512.0K 0% /dev
root@OpenWrt:~# free
total used free shared buff/cache available
Mem: 28252 14160 5088 304 9004 11752
Swap: 0 0 0
root@OpenWrt:~#