Unable to acquire the dpkg frontend lock (/var/lib/dpkg/l code example

Example 1: 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/

Example 3: why upgrade ubuntu then frequently shows this message "It iwating for cache lock: Could not get lock /var/lib/dpkg/lock.frontend.

It iwating for cache lock: Could not get lock /var/lib/dpkg/lock.frontend.