Debian server tools

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-setup - Debian installation scripts including debian-setup.sh
• /backup - Tools related to archiving
• /image - Tools related to image optimization
• /input - Tools related to the terminal
• /mail - Tools related to email account management
• /monitoring - Tools related to server monitoring, alert and statistics emails
• /mysql - Tools related to database management
• /package - Tools related to Debian packages and general packaging
• /security - Security and SSL certificate related tools
• /tools - Various small tools
• /virtualization - Docker containers
• /webserver - Tools related to building webservers

Debian install with UTC as timezone

Select Expert install.

Script development

• Check shell scripts: http://www.shellcheck.net/
• Code styling: https://github.com/git/git/blob/master/Documentation/CodingGuidelines
• Bashism: https://wiki.ubuntu.com/DashAsBinSh checkbashisms -f bash-script.sh

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|sed -ne '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

• whois -h whois.iana.org $TLD https://www.iana.org/domains/root/db
• dig _nicname._tcp.$TLD SRV https://tools.ietf.org/html/draft-sanz-whois-srv-01
• https://github.com/rfc1036/whois/blob/next/tld_serv_list

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

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

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