{"id":216,"date":"2020-09-26T13:31:33","date_gmt":"2020-09-26T13:31:33","guid":{"rendered":"https:\/\/dft.wiki\/?p=216"},"modified":"2026-07-16T08:43:15","modified_gmt":"2026-07-16T12:43:15","slug":"useful-tricks-and-commands-linux","status":"publish","type":"post","link":"https:\/\/dft.wiki\/?p=216","title":{"rendered":"Random Linux Commands and Useful Tips"},"content":{"rendered":"

CATEGORIES<\/b><\/p>\n

    \n
  1. System and Environment<\/a><\/li>\n
  2. Network<\/a><\/li>\n
  3. Public IP<\/a><\/li>\n
  4. DNS Utilities<\/a><\/li>\n
  5. Mounting Volumes<\/a><\/li>\n
  6. General Linux Tips<\/a><\/li>\n
  7. Ubuntu Tips<\/a><\/li>\n
  8. Raspberry PI Tips<\/a><\/li>\n
  9. Kali Tips<\/a><\/li>\n
  10. Forensics Tools<\/a><\/li>\n
  11. Western Digital NAS<\/a><\/li>\n
  12. VMWare ESXi Tips<\/a><\/li>\n
  13. NVIDIA Drivers<\/a><\/li>\n
  14. AMD GPU Drivers<\/a><\/li>\n<\/ol>\n
    \n

    SYSTEM AND ENVIRONMENT<\/strong><\/p>\n

    sudo hostnamectl set-hostname newHostName<\/strong>\r\nid || (whoami && groups) 2>\/dev\/null\r\nid -un\r\nuname\r\nuname -a\r\nuname -r\r\nuname -m\r\nneofetch\r\ninxi -F\r\nw\r\nlast -aiF\r\nlastb -adF\r\nlast reboot\r\njournalctl --list-boots\r\narch\r\nlsb_release -rd\r\ncat \/proc\/version\r\n(cat \/proc\/version || uname -a) 2>\/dev\/null\r\nsystemctl show-environment\r\nenv\r\nset\r\nuptime\r\nlsblk\r\nlsblk -f\r\nlscpu\r\nlsusb\r\nlspci\r\nlspci -vvv\r\nlsmod\r\necho $SHELL\r\necho $HOME\r\nreset\r\nman commandName<\/strong>\r\ntldr commandName<\/strong>\r\napropos commandName<\/strong>\r\nsystemd-analyze\r\nsystemd-analyze blame\r\nsystemd-analyze critical-chain<\/pre>\n
    Manage physical (discrete) memory:<\/p>\n
    dmidecode -t memory\r\nlsmem\r\nlsmem -a\r\nchmem -d 0x0000000878000000-0x000000087fffffff\r\nchmem -e -b 271<\/pre>\n
    History of commands:<\/p>\n
    history -c\r\nhistory -r\r\nset +o history\r\n# history does not store this command\r\nset -o history\r\nhistory\r\n!123\r\nHISTTIMEFORMAT=\"%Y-%m-%d %T \"\r\ncat ~\/.bash_history | fzf -i<\/pre>\n
    Prevent a command from being saved to history by starting it with a space (~\/.bashrc):<\/p>\n
    HISTCONTROL=ignoreboth<\/pre>\n
    List all available commands, aliases, bash built-ins, bash keywords, and bash functions:<\/p>\n
    compgen -c\r\ncompgen -a\r\ncompgen -b\r\ncompgen -k\r\ncompgen -A function<\/pre>\n
    Display kernel ring buffer messages sent to syslog since the last boot (human-readable timestamp, watch live, filter content, and clear buffer):<\/p>\n
    sudo dmesg -T\r\nsudo dmesg -w\r\nsudo dmesg | grep error\r\nsudo dmesg | grep usb\r\nsudo dmesg -c<\/pre>\n
    List timers and services:<\/p>\n
    systemctl list-timers --all\r\nsystemctl list-units --type=service\r\nsystemctl --all<\/pre>\n
    Rootless services:<\/p>\n
    systemctl edit --force --full serviceName<\/strong> --user<\/strong>\r\nsystemctl start serviceName<\/strong> --user<\/strong><\/pre>\n
    Enable lingering (keep processes running after the user logs off):<\/p>\n
    loginctl show-user<\/strong> userName | grep Linger<\/strong>\r\nloginctl enable-linger<\/strong> userName<\/pre>\n
    Storage volume speed test:<\/p>\n
    sudo apt install hdparm -y\r\nhdparm -tv -direct \/dev\/sdc1<\/pre>\n
    Inodes:<\/p>\n
    ls -i\r\nstat fileName<\/strong>\r\ndf -i<\/pre>\n
    sudo apt install inotify-tools<\/strong> -y\r\ninotifywait -m -q -e modify \/var\/log\/applicationLogs<\/strong><\/pre>\n
    Note:<\/strong> there is a kernel module called fanotify<\/code> that can monitor and intercept filesystem events.<\/p>\n
    List users, superusers, logged-in users, login history, last login per user, and all users and groups:<\/p>\n
    cat \/etc\/passwd | cut -d: -f1\r\nawk -F: '($3 == \"0\") {print}' \/etc\/passwd\r\nw\r\nlast\r\nlastlog\r\nfor i in $(cut -d\":\" -f1 \/etc\/passwd 2>\/dev\/null);do id $i;done 2>\/dev\/null | sort\r\nid userName<\/strong><\/pre>\n
    Get password policy:<\/p>\n
    grep \"^PASS_MAX_DAYS\\|^PASS_MIN_DAYS\\|^PASS_WARN_AGE\\|^ENCRYPT_METHOD\" \/etc\/login.defs<\/pre>\n
    Find files writable by anyone or any group:<\/p>\n
    find \/ '(' -type f -or -type d ')' '(' '(' -user $USER ')' -or '(' -perm -o=w ')' ')' 2>\/dev\/null | grep -v '\/proc\/' | grep -v $HOME | sort | uniq\r\nfor g in `groups`; do find \\( -type f -or -type d \\) -group $g -perm -g=w 2>\/dev\/null | grep -v '\/proc\/' | grep -v $HOME; done\r\nfind . -mindepth 1 -type f -name \"*.zip\"\r\nfind . -mindepth 1 -type f -name \"*.zip\" -printf x | wc -c<\/pre>\n
    Read a specific line number from a file:<\/p>\n
    awk 'NR==50' fileName<\/strong>\r\nsed '50!d' fileName<\/strong><\/pre>\n
    Running processes:<\/p>\n
    ps aux\r\nps -ef\r\npgrep -l ssh\r\npgrep -u root\r\ntop -n 1<\/pre>\n
    Run a process with a given priority, or change the priority of a running process:<\/p>\n
    nice -n 3<\/strong><\/span> script.sh\r\nrenice +1<\/span><\/strong> -p PID<\/strong>\r\nrenice 5<\/strong><\/span> -p PID<\/strong><\/pre>\n
    Note: PID<\/strong> is the process ID, which can be found using the ps<\/code> command. The priority range is -20 (highest) to +19 (lowest)<\/strong><\/span>.<\/p>\n
    Reparent a running program to a new terminal:<\/p>\n
    sudo reptyr PID\r\nsudo reptyr -s PID<\/pre>\n
    List detailed information about all PCI buses and devices<\/strong>:<\/p>\n
    lspci<\/pre>\n
    Configure and update Grub<\/strong>:<\/p>\n
    sudo nano \/etc\/default\/grub\r\nsudo os-prober\r\nsudo update-grub<\/pre>\n
    See also the configuration files inside \/etc\/grub.d\/<\/strong>.<\/p>\n
    Adding net.ifnames=0<\/code> and biosdevname=0<\/code> to the Grub config makes the Linux kernel name interfaces like eth*<\/code>.<\/p>\n
    GRUB_CMDLINE_LINUX=\"net.ifnames=0 biosdevname=0\"<\/pre>\n
    Check out Clover<\/strong> [Link<\/a>] as an alternative to Grub. It is especially useful as a bootloader that runs from a thumb drive to boot from an NVMe drive on systems with older BIOS firmware that cannot do so directly.<\/p>\n
    Remove the welcome banner:<\/p>\n
    touch .hushlogin<\/pre>\n
    Command-line calendar:<\/p>\n
    cal<\/pre>\n
    Create a Linux password hash:<\/p>\n
    mkpasswd -m sha-512<\/pre>\n
    Refresh a cloned instance or virtual machine:<\/p>\n
    apt purge cloud-init -y\r\napt install cloud-init -y\r\nnano \/etc\/cloud\/cloud.cfg\r\ncloud-init clean\r\ncloud-init init<\/pre>\n
    Package managers by distribution:<\/p>\n