First of all, using this command to check what's the shell type right now:
$ls -al /bin/sh
There will be the symbol link of sh to bash or dash.
There are ways to change it:
1. using this command, and select NO when in the pop-up window.
$sudo dpkg-reconfigure dash
2. just update the symbol link to bash:
$sudo ln -sf /bin/bash /bin/sh
3. change the line of file : /etc/passwd, while line contains the "user" of yours.
sqwu:x:1000:1000:EDA,,,:/home/sqwu:/bin/bash