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Ergonomics

Model of how systems work

Directories

Debian install with UTC as timezone

Script development

Install your own SSH key

S="${HOME}/.ssh";mkdir --mode 0700"$S";editor"${S}/authorized_keys"ssh-keygen -v -l -f"${S}/authorized_keys"

# restrict == no-port-forwarding,no-agent-forwarding,no-X11-forwarding,no-pty,no-user-rcrestrict,command="echo 'Please login as the user \"debian\" rather than the user \"root\".';echo;sleep 10" ssh-rsa AAAA...

Install a user's SSH key

u bash -c'S="${HOME}/.ssh";mkdir --mode 0700 "$S";editor "${S}/authorized_keys"'U="$(stat -c %U .)";S="$(getent passwd$U|cut -d: -f6)/.ssh";mkdir -m 0700"$S";editor"${S}/authorized_keys";chown -R$U:$U"$S"

Retrieve public key from private key

ssh-keygen -y -f~/.ssh/id_ecdsa

Display SSH access details

printf'host: %s\nport: %s\nuser: %s\n'"$(hostname)""$(/usr/sbin/sshd -T -C user=root -C host=localhost -C addr=localhost|sed -n -e's/^port \([0-9]\+\)$/\1/p')""$(ls -tr /home/|tail -n1)"

List sshd host keys

ls /etc/ssh/ssh_host_*_key.pub| xargs -n 1 ssh-keygen -l -f

Record terminal session

script --timing=NAME.time --append NAME.scriptscriptreplay --maxdelay 1 NAME.time NAME.script

Fast and safe transit of scripts (or any data) via copy&paste

Pack

cat$SCRIPT|xz -9|base64 -w$((COLUMNS-1))# alias: cat $SCRIPT | transit

Unpack

cat$PASTED_FILE|base64 -d|xz -d>$SCRIPT# alias: cat $PASTED_FILE | transit-receive

Moving away git-dir

git init --separate-git-dir=/home/user/gitdir

Rescan the SCSI Bus to Add SCSI Devices

echo"- - -"> /sys/class/scsi_host/host0/scan

Flush Google public DNS cache

Whois servers

AS information

ROA validation, RPKI status

Crontab format

.---------------- minute (0 - 59)| .-------------- hour (0 - 23)| |  .----------- day of month (1 - 31)| |  | .--------- month (1 - 12)| |  | | .------- day of week (0 - 6)| |  | | |* *  * * *  USER  COMMAND

crontab -e -u USER.---------------- minute (0 - 59)| .-------------- hour (0 - 23)| |  .----------- day of month (1 - 31)| |  | .--------- month (1 - 12)| |  | | .------- day of week (0 - 6)| |  | | |* *  * * *  COMMAND

Cron scheduling with timezone

# Well before the actual execution time!0006***echo "/bin/ls -l" | at "$(date --date='TZ="Europe/Budapest" 10:30' "+\%H:\%M")" 2>/dev/null

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