How to use an external sdcard as internal in Android Lolipop 5.1.1? I have seen option of making external sd card to internal in android 6 mobile phones but i have  android lolipop  5.1.1 how can i  make it adoptable or get that option is it feasable to get that option i found  some commands  but that command is not found in my /system/bin even after rooting to 

sm has-adoptable 

sm set -force- adoptable true



  /sbin/sh: sm: not found


can i find some sm binary and use it ..i tried but my  phone got problem
sm is actually not a binary, it is a shell script for java program which does not exist/work on 5.1-lollipop  

# Script to start "sm" on the device, which has a very rudimentary
# shell.
#
base=/system
export CLASSPATH=$base/framework/sm.jar
exec app_process $base/bin com.android.commands.sm.Sm "$@"


to answer the headline  

a completely another solution for rooted devices only:  

you can mount ext4 disk image (or ext4 partition) with same permissions like /data
(mount script example)  

/su/su.d/40sdextimg start-up script with executable permissions  

#!/system/bin/sh
until grep -qw /data/sdext2 /proc/mounts
  do
    mount -t ext4 -o loop,rw,nosuid,nodev,noatime /storage/31D1-1308/data.sdext2.img /data/sdext2
    sleep 1
done &amp;


then you can move apps and create symbolic links
(that's what Link2SD does)  

mkdir /data/sdext2/com.textra-1
mv /data/app/com.textra-1/base.apk /data/sdext2/com.textra-1/
ln -s /data/sdext2/com.textra-1/base.apk /data/app/com.textra-1/base.apk


or bind mount whole folder
(assuming 2nd partition is mounted /data/sdext2)

mkdir /data/sdext2/media
chmod 0770 /data/sdext2/media
chown 1023.1023 /data/sdext2/media
chcon u:object_r:media_rw_data_file:s0 /data/sdext2/media
mv /data/media/. /data/sdext2/media
mount -o bind /data/sdext2/media /data/media