Unsupported packages architecture warning

This solution is specific for Ubuntu Bionic Beaver (18.xx)

In case if the repository contains unsupported platform packages (in this case 32bit packages), during `apt update` you will see a warning message:

N: Skipping acquire of configured file 'nginx/binary-i386/Packages' as repository 'http://nginx.org/packages/mainline/ubuntu bionic InRelease' doesn't support architecture 'i386'

To fix the warning edit the source list file by adding `[arch=amd64]` to it:

deb [arch=amd64] http://nginx.org/packages/mainline/ubuntu bionic nginx

Calculate space consumed by files

du -hc 2020-0[1-3]-*.txt | awk '{ L=$1 } END { print L }'

tmux - sessions client

List active sessions:

tmux list-clients

It sometimes happens, when the session stops responding to key presses, but `Ctrl+B` actions affects. To resolve this issue, type:

tmux detach-client

and attach the client again.

See the progress while archiving many/large files

tar cf - /usr/www -P | pv -s $(du -sb /usr/www | awk '{print $1}') | gzip > usr_www.tar.gz

will show output like this:

2.82GiB 0:02:01 [23.9MiB/s] [=====>                          ] 16% ETA 0:10:17