In the following table you see a collection of commands which can come handy. For some you need installed tools like jq, grep, aws or something. Should work in bash on Ubuntu or equivalent.

Command Comment
iperf3 -s Start network performance tool as server
iperf3 -c serverIP Connect client to server and do network performance test
iperf3 -R -c serverIP Do the above but reverse traffic flow
cat /proc/mdstat Check software raid status
du -hs /path/ Get folder size. Last / is for filtering on directory.
df -hT Get all filesystems and their utilizations
netstat -tnpa | grep ‘ESTABLISHED.*sshd’ Display all established ssh connections
docker-compose pull
docker-compose down
docker-compose up –remove-orphans -d
Update docker containers using docker-compose
aws s3 sync s3://bucketname/ ./ –delete –endpoint-url=https://s3.eu-central-1.wasabisys.com One-way sync objects in a bucket on Wasabi to ./
cat secret.txt | age -r a_public_key -a > secret.txt.age  PKI encrypt secret.txt using age
age –decrypt -i your_private_key secret.txt.age > secret.txt.age.txt PKI decrypt secret.txt.age using age
curl -s https://matrix.org/_matrix/federation/v1/version | jq -r .server.version Get the installed Matrix/Synapse Versions of a host.
curl -s https://demo1.nextcloud.com/status.php | jq -r .versionstring Get the installed Nextcloud Versions of a host.
curl wttr.in/Berlin Get weather forcast for a location for command line output