Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 702 (apt-get) code example
Example 1: E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
ps aux | grep -i apt
Example 2: apt lock
rm -rf /var/cache/apt/* /var/lib/dpkg/lock /var/lib/dpkg/lock-frontend \
/var/cache/debconf/ /var/lib/apt/lists/* \
/var/lib/dpkg/lock /var/lib/dpkg/lock-frontend /var/cache/debconf/