ext4

http://h-wrt.com/en/doc/

https://openwrt.org/docs/guide-user/additional-software/extroot_configuration
http://dashohoxha.fs.al/recycle-tplink-router/

sudo mke2fs /dev/sdb1 -O ^metadata_csum

sudo fdisk /dev/sdb

kmod-usb-storage
kmod-fs-ext4 
kmod-fs-vfat 
block-mount 

abhinav@abhinavpc:~$ sudo mke2fs /dev/sdb1 -O ^metadata_csum
mke2fs 1.44.1 (24-Mar-2018)
/dev/sdb1 contains a ext2 filesystem
	last mounted on /media/abhinav/ef13b0d6-2e0d-43ae-9d7d-47fe472c0c5d on Wed Oct  7 15:05:26 2020
Proceed anyway? (y/N) y
/dev/sdb1 is mounted; will not make a filesystem here!
abhinav@abhinavpc:~$ sudo umount -fl /dev/sdb1
abhinav@abhinavpc:~$ sudo mke2fs /dev/sdb1 -O ^metadata_csum
mke2fs 1.44.1 (24-Mar-2018)
/dev/sdb1 contains a ext2 filesystem
	last mounted on /media/abhinav/ef13b0d6-2e0d-43ae-9d7d-47fe472c0c5d on Wed Oct  7 15:05:26 2020
Proceed anyway? (y/N) y
Creating filesystem with 3784064 4k blocks and 946560 inodes
Filesystem UUID: 6538f454-7984-4e73-b82c-66857a60351b
Superblock backups stored on blocks: 
	32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208

Allocating group tables: done                            
Writing inode tables: done                            
Writing superblocks and filesystem accounting information: done   

root@OpenWrt:~# mkdir -p /mnt/usb
root@OpenWrt:~# mount /dev/sda1 /mnt/usb
root@OpenWrt:~# mkdir -p /tmp/cproot
root@OpenWrt:~# mount --bind / /tmp/cproot
root@OpenWrt:~# tar -C /tmp/cproot -cvf - . | tar -C /mnt/usb -xf -
root@OpenWrt:~# umount /tmp/cproot
root@OpenWrt:~# umount /mnt/usb

root@OpenWrt:~# vim /etc/config/fstab

change
option target : /
option enabled: 1

root@OpenWrt:~# reboot


for > 17

use below in place of sudo mke2fs /dev/sdb1 -O ^metadata_csum
sudo mkfs.ext4 /dev/sdc1 

check this for update fstab
https://openwrt.org/docs/guide-user/storage/usb-drives


dmesg
......
[ 2008.400000] usb 1-1.3: new full-speed USB device number 4 using ehci-platform
[ 2029.920000] usb 1-1.3: USB disconnect, device number 4
[ 2038.090000] usb 1-1.1: new full-speed USB device number 5 using ehci-platform
[ 2049.770000] usbcore: registered new interface driver usbserial
[ 2049.780000] USB Serial support registered for generic
[ 2049.780000] usbcore: registered new interface driver usbserial_generic
[ 2049.790000] usbserial: USB Serial Driver core
[ 2049.850000] USB Serial support registered for FTDI USB Serial Device
[ 2049.860000] usbcore: registered new interface driver ftdi_sio
[ 2049.860000] ftdi_sio: v1.6.0:USB FTDI Serial Converters Driver

kmod-usb-serial-ftdi
kmod-usb-serial-pl2303
stty
openssl-util
wget
python
js


https://openwrt.org/docs/guide-user/storage/usb-installing
https://wiki.dragino.com/index.php?title=FTDI_%26_OpenWrt
https://openwrt.org/docs/guide-user/advanced/arduino
https://openwrt.org/docs/guide-user/hardware/bluetooth/usb.bluetooth

Installing openssl-util (1.0.2g-1) to root...
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/geode/packages/base/openssl-util_1.0.2g-1_x86.ipk.
Installing libopenssl (1.0.2g-1) to root...
Downloading http://downloads.openwrt.org/chaos_calmer/15.05/x86/geode/packages/base/libopenssl_1.0.2g-1_x86.ipk.
Configuring libopenssl.
Configuring openssl-util.