1. lock locked:
root@bbb:~# dpkg -i /var/cache/apt/archives/dpkg_1.19.0.5ubuntu2.1_amd64.deb
dpkg: error: dpkg status database is locked by another process
2. Frontend locked
root@bbb:~# dpkg -i /var/cache/apt/archives/dpkg_1.19.0.5ubuntu2.1_amd64.deb
dpkg: error: dpkg frontend is locked by another process
3. Frontend locked, but overriden by env:
root@bbb:~# DPKG_FRONTEND_LOCKED=1 dpkg -i /var/cache/apt/archives/dpkg_1.19.0.5ubuntu2.1_amd64.deb
(Reading database ... 28496 files and directories currently installed.)
Preparing to unpack .../dpkg_1.19.0.5ubuntu2.1_amd64.deb ...
Unpacking dpkg (1.19.0.5ubuntu2.1) over (1.19.0.5ubuntu2.1) ...
Setting up dpkg (1.19.0.5ubuntu2.1) ...
Processing triggers for man-db (2.8.3-2) ...
Same with bionic (1.19.0.5ubuntu2.1)
1. lock locked: apt/archives/ dpkg_1. 19.0.5ubuntu2. 1_amd64. deb
root@bbb:~# dpkg -i /var/cache/
dpkg: error: dpkg status database is locked by another process
2. Frontend locked apt/archives/ dpkg_1. 19.0.5ubuntu2. 1_amd64. deb
root@bbb:~# dpkg -i /var/cache/
dpkg: error: dpkg frontend is locked by another process
3. Frontend locked, but overriden by env:
root@bbb:~# DPKG_FRONTEND_ LOCKED= 1 dpkg -i /var/cache/ apt/archives/ dpkg_1. 19.0.5ubuntu2. 1_amd64. deb 1.19.0. 5ubuntu2. 1_amd64. deb ...
(Reading database ... 28496 files and directories currently installed.)
Preparing to unpack .../dpkg_
Unpacking dpkg (1.19.0.5ubuntu2.1) over (1.19.0.5ubuntu2.1) ...
Setting up dpkg (1.19.0.5ubuntu2.1) ...
Processing triggers for man-db (2.8.3-2) ...
=> verified