ssht라는 계정에 제한을 걸어서 쉘 접속은 가능하되 임의의 행동을 하지 못하도록 제한
mkdir /usr/ssht_rbin
ln /bin/ls /usr/ssht_rbin
ln /bin/date /usr/ssht_rbin
ln /usr/bin/vi /usr/ssht_rbin
ln /bin/cat /usr/ssht_rbin
ln /usr/bin/rz /usr/ssht_rbin
ln /usr/bin/sz /usr/ssht_rbin
ln /bin/mv /usr/ssht_rbin
ln /bin/cp /usr/ssht_rbin
ln /bin/rm /usr/ssht_rbin
chmod 555 /usr/ssht_rbin
echo "set -r" > /home/ssht/.bash_profile
echo 'PATH="/usr/ssht_rbin"' >> /home/ssht/.bash_profile
chmod 444 /home/ssht/.bash_profile
chown root.root /home/ssht/.bash_profile
usermod -s /bin/rbash ssht