Is an Operating System for all sort of things. In this database, I refer to Unix via Linux

Please note: I mainly use Ubuntu Server or Debian, so your mileage may vary with other distros.

Setup

• On a laptop: disable standby on lid close: in /etc/systemd/logind.conf, uncomment and change HandleLidSwitch=ignore

Related

• SSH
• ufw

Install FTP server

1. sudo apt install vsftpd
2. sudo nano /etc/vsftpd.conf to edit configuration
3. sudo ufw allow 21
4. sudo systemctl restart vsftpd

Related softwares

• Cron: Job scheduler

Cockpit - Remote administration of server

1. sudo apt-get install cockpit and with:
   • cockpit-machines for KVM
   • cockpit-docker for Docker
2. sudo ufw allow 9090
3. sudo systemctl restart cockpit.socket
4. If you cannot update packages, network manager may be in use, check with nmcli d
   • sudo systemctl disable network-manager.service
   • sudo systemctl stop network-manager.service

Advanced configuration

• See this guide to change port. Create file and directory if needed.
• Configuration file is /etc/cockpit/cockpit.conf, not created by default - see reference

• Setup with Cloudflare Tunnel - Based on this blog post.

  1. Setup a Let's Encrypt certificate below

  2. Setup a copy script - See example in Nextcloud

     ```sh

     !/bin/sh

     FQDN="DOMAIN.COM"

     echo "SSL certificates renewed" cp /etc/letsencrypt/live/$FQDN/fullchain.pem /etc/cockpit/ws-certs.d/$FQDN.crt cp /etc/letsencrypt/live/$FQDN/privkey.pem /etc/cockpit/ws-certs.d/$FQDN.key chown cockpit-ws:cockpit-ws /etc/cockpit/ws-certs.d/$FQDN.crt /etc/cockpit/ws-certs.d/$FQDN.key

     echo "Restarting Cockpit" systemctl restart cockpit ```

  3. Setup /etc/cockpit/cockpit.conf

     ```conf [WebService] Origins = https://URL:PORT

     ProtocolHeader = X-Forwarded-Proto

     AllowUnencrypted = false

     [Session] IdleTimeout = 10 ```

  4. Setup Cloudflare Tunnel and Access

  Install on VirtualBox

  See VirtualBox page.

  Tips & Tricks

  • Date & Time
  • timedatectl to check
  • sudo timedatectl set-timezone TZ
  • See also
  • Screen terminal multiplexer

  Command-line kung-fu

  • less to redirect output to a pager
  • watch to watch regularly an output
  • | grep x to pipe to grep which is going to select lines with x ^a163bc
  • clear to clear the command line
  • Check this Ars introduction about redirection, grep, sed, awk.
  • echo $? to inspect program exit code
  • du -h like disk usage to check size of directory
  • which abc to check where the abc binary is stored
  • See also:
  • Vi - text editor

  Install a software on system

wget the latest release of the chosen software
sudo apt-get install # dependencies
sudo mkdir -p /opt/software_name
mv # move the app to /opt/software_name
sudo chmod +x /opt/software_name/executable # make the executable executable
sudo ln -s /opt/software_name/executable /usr/bin/executable # create a simlink

CPU & Processes

• Check system stats
  • htop for processes
  • nmon for the whole system
• Health
  • Check CPU frequency cat /proc/cpuinfo
• System information dmidecode
• Do a stress test with full CPU utilization: for i in $(seq $(getconf _NPROCESSORS_ONLN)); do yes > /dev/null & done

Services with systemctl

• Service management
  • sudo systemctl restart SERVICE
  • sudo systemctl start SERVICE
  • sudo systemctl stop SERVICE
  • sudo systemctl kill SERVICE
• Service enable/disable
  • sudo systemctl enable SERVICE
  • sudo systemctl disable SERVICE
  • sudo systemctl is-enabled SERVICE
• Services mask/unmask
  • sudo systemctl unmask SERVICE
  • sudo systemctl mask SERVICE
• Service status
  • sudo systemctl list-timers
  • sudo systemctl status SERVICE

Disk & Data

• Current working directory: pwd
• Check free disk space df -h
• Tree file & folder with space taken ncdu
• Check for partition corruption fsck /dev/sdaXX00
• Stop a (USB) disk
  1. Unmount sudo umount /dev/sdXX
  2. Spin down sudo hdparm -Y /dev/sdXX
• Erase a disk sudo dd if=/dev/urandom of=/dev/sdXX bs=10M - Source
• Check what is mounted where: findmnt
• List all block devices: lsblk
• TRIM a SSD: sudo /sbin/fstrim -av

View SMART disk data

Source 1. Install smartmontools 1. View SMART data & status sudo smartctl -i /dev/sdXX 1. Find estimate & current SMART test sudo smartctl -a /dev/sdXX 1. Launch a test: sudo smartctl -t short /dev/sdXX * Possible options instead of short: * long * conveyance (after transport) for ATA disks * If the HDD go to sleep (especially true for USB ones), try the following:

    ```bash
    while true; do
        dd if=/dev/sdXX iflag=direct count=1 of=/dev/null
        sleep 60
    done
    ```

1. Read the result sudo smartctl -l selftest /dev/sdXX

Test read/write speed

Source 1. sync; dd if=/dev/zero of=tempfile bs=1M count=256; sync: write to tempfile 256 Mb 1. sudo /sbin/sysctl -w vm.drop_caches=3: clear the cache 1. dd if=tempfile of=/dev/null bs=1M count=256: read tempfile

Format & mount a USB stick

Files

• zip -r directoryname.zip ./ to zip current directory
  • unzip ./file.zip to unzip
  • unzip -l ./file.zip to list files in the zip (and the validity of the zip)
• tar -xvf file.tar.gz to extract tarball and zip (x for extract, v for verbose, f for file)
• bunzip2 filename.bz2 to extract a bz2 file
• find / -name filename to find filename in entire system (/) or active folder (.), and sudo to avoid permissions problems
• cp -a to copy everything (-Archive)
• find /path/to/folder -name "thing to search" to find something
• Edit a text file on GUI: mousepad

Virtual Systems: Mount QCoW2

1. sudo apt install libguestfs-tools to install required tool
2. sudo guestmount -a /var/lib/libvirt/images/IMAGE.qcow2 -m DEVICE --ro /mnt/FOLDER
   • DEVICE being the partition within this image. Make it bogus so a list will be shown
   • --ro if you only want read-only
3. sudo guestunmount /mnt

Network & Internet

• View current information (IP, netmask, ...) ifconfig
  • Assign an IP to a network sudo ifconfig wlan0 192.168.65.1 netmask 255.255.255.0 up for instance
• Edit network configuration
  • with netplan /etc/netplan/00-installer-config.yaml
• Check Wi-Fi adapter status:
  • rfkill list wlan to list status
  • rfkill unblock wlan to unblock
• Check used ports: ss -tunlp

Activate IPv6

• Edit /etc/network/interfaces
• Add iface eth0 inet6 dhcp - more options here
• Apply changes service networking restart

Disable IPv6

• ip a to list network adapters
• sudo sysctl -w net.ipv6.conf.ADAPTER.disable_ipv6=1 to disable (temporary) IPv6, with ADAPTER like br6
• Add the above to /etc/sysctl.conf and apply with sudo sysctl -p

Set up Let's Encrypt with Cloudflare DNS

• Source
• See this documentation on Cloudflare certbot
  • cloudflare.ini can be placed in /etc/cloudflared
  • Define proper permission with chmod 400
• Steps
  1. sudo snap install --classic certbot certbot-dns-cloudflare You may need to proceed with additional commands as explained in the console
  2. sudo ln -s /snap/bin/certbot /usr/bin/certbot
  3. sudo certbot certonly --dns-cloudflare --dns-cloudflare-credentials /etc/letsencrypt/cloudflare.ini -d <EXAMPLE.COM>
  4. Automated renewal should be set up by the snap, check systemctl list-timers

Users & Groups

• Users
  • useradd USERNAME add a new user
    • With a Home directory: -m
    • Remove shell access: --shell /bin/false
  • usermod -L USERNANE to lock access
  • passwd USERNAME define a password
  • id $user to get user PUID & GUID
• Groups
  • usermod -a -G GROUP $USER to add self to GROUP
  • cat /etc/group to list all groups
• Setup SFTP for without Shell: nice tutorial from Digital Ocean
• Act as a user: sudo -u USERNAME command
• Mails are stored in /var/mail/

Scripts execution

• Can be stored in /usr/sbin/user_scripts/
• visudo can help defining a script that can be run as sudo
  • <user> ALL=(ALL) NOPASSWD: /path/to/script.sh
• Don't forget to
  • Set the script as executable with sudo chmod +x /path/to/script.sh
  • Prevent edition with chmod u-w,g-w /path/to/script.sh (here we remove user and group write)

OS-related

• Know which OS, flavor, distro, distribution or version you are running cat /etc/os-release
• Install fonts, check package fonts-liberation - can help you to fix Fontconfig error: Cannot load default config file
• Change host name: hostnamectl set-hostname NEWHOSTNAME and update /etc/hosts
• Check all installed packages, sorted by size: dpkg-query -W -f='${Installed-Size;8} ${Package}\n' | sort -n

Hardware-related

• Sometime reboot is not accessible ... then use systemctl reboot
• Test RAM with sysbench --test=memory --memory-block-size=1M --memory-total-size=1000G
• Check PCIe speed: lspci -vvvv
• Reset an USB device: usbreset

Power & Battery

• Check system temperature
  1. sudo apt install lm-sensors
  2. sudo apt-get install lm-sensors
  3. sudo /etc/init.d/kmod start
  4. sensors
• Check status & stats about battery
  1. List paths upower -e
  2. Get status upower -i <path>
• Plan a reboot: shutdown -r 0:00 to restart at midnight for instance

BIOS

• Check BIOS version sudo dmidecode | less

Display, Media & Sound

• Instead of changing the DPI to 125% which makes things weird, enable Large Text in Accessability

Security

• Source: OVH, DigitalOcean, DigitalOcean
• Change all account passwords
• Regarding SSH
  • Disable all unnecessary users logins, like root - Example
  • Change default port (between 49152 and 65535) - Generator
  • Use SSH Keys instead of passwords
• Regarding network
  • Configure firewall like ufw
  • Configure fail2ban
  • Configure an Intrusion Detection System - Example
• Disable unneeded services - Example, sudo ss -atpu
• Implement unattended/automated upgrades and livepatch - Example
• Regularly
  • Update software
  • Check logs
  • Check for malware - Example: maldet
  • Make backups

Recover

Check logs

• System messages: cat /var/log/messages | tail -n 50

Bootloader

Try Super Grub2 Disk

KVM - Virtual Machines

Related

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