Linux command: du - disk usage

Where have all my storage gone? du summarize disk usage of the set of FILEs, recursively for directories.

du -sh : summary, human readable format (B,KB,MB,GB)
du -d 1 : 1 depth level

du / -h -d 1

Take a look at /usr and /var directories

du /usr -h -d 1
du /var -h -d 1

df -h

Notes while trying Wireguard VPN on some of my testbeds.

The default Creation of forwarding/redirect rule alert policy will be triggered when end-users create rule to forward or redirect mail

ssh-keygen — authentication key generation, management and conversion

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