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You find all my knowledge on GitHub in form of Bash and PHP scripts and Markdown documents.
Updated daily as I work.

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Superior cloud hosting

Install Debian on UpCloud

How UpCloud was chosen? Read https://github.com/szepeviktor/wordpress-speedtest/blob/master/README.md#how-to-choose-vps-provider

Ergonomics

How to Set Up Your Desk

Model of how systems work

Richard Cook at Velocity NY 2013

Directories

Debian install with UTC as timezone

Select Expert install.

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"

authorized_keys parameters:

# restrict == no-port-forwarding,no-agent-forwarding,no-X11-forwarding,no-pty,no-user-rc
restrict,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.script
scriptreplay --maxdelay 1 NAME.time NAME.script

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

Use magic-wormhole

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

Produces:

/home/user/work-dir/.git: gitdir: /home/user/git

/home/user/gitdir/config: worktree = /home/user/work-dir

Rescan the SCSI Bus to Add SCSI Devices

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

Flush Google public DNS cache

https://google-public-dns.appspot.com/cache

Free CDN for GitHub

https://staticaly.com/ https://cdn.staticaly.com/gh/USER/REPO/TAG/FILE

Whois servers

AS information

whois -h whois.radb.net -- "-i origin AS202053"

ROA validation, RPKI status

whois -h whois.bgpmon.net 94.237.81.0

<!-- UNICODE owl domain name [﴾͡๏̯͡๏﴿.tk](http://xn--wta3hb403ica11187ama.tk/) -->

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!
00 06  * * *  echo "/bin/ls -l" | at "$(date --date='TZ="Europe/Budapest" 10:30' "+\%H:\%M")" 2>/dev/null

Looking for a dedicated team member running your application or website?

Contact me: viktor@szepe.net