> For the complete documentation index, see [llms.txt](https://oviniciusfeitosa.gitbook.io/knowledge/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://oviniciusfeitosa.gitbook.io/knowledge/technology/operational-systems/linux/how-to.md). # How to ## Topics * [**Proxy**](/knowledge/technology/operational-systems/linux/how-to/proxy.md) * [**SSH**](/knowledge/technology/operational-systems/linux/how-to/ssh.md) * [**ZSH**](/knowledge/technology/operational-systems/linux/how-to/zsh.md) ## Download files from the cloud {% hint style="info" %} * Send content to WeTransfer cloud-like * Download using **wget** {% endhint %} ### Installing wget ``` sudo apt install wget ``` ### Download a single file ``` wget https://wordpress.org/latest.zip ``` ### Save the downloaded file under a different name To save the downloaded file under a different name, pass the `-O` option followed by the chosen name. ``` wget -O latest-wordpress.zip https://wordpress.org/latest.zip ``` ### How to download in the background mode with wget To download in the background, use the option `-b` . In the following example, we are downloading the OpenSuse iso file in the background. ``` wget -b https://download.opensuse.org/tumbleweed/iso/openSUSE-Tumbleweed-DVD-x86_64-Current.iso ``` ### Download all files from FTP ``` wget -r 'ftp://username:password@ip/directoryname' ``` ## Download / Upload Files ### Single file from remote to local ``` scp remoteuser@remoteserver:/remote/folder/myfile.txt myfile.txt ``` ### Multiple files from local to remote ``` scp myfile.txt myfile2.txt remoteuser@remoteserver:/remote/folder/ ``` ### All files from local to remote ``` scp * remoteuser@remoteserver:/remote/folder/ ``` ### All files and folders recursively from local to remote ``` scp -r * remoteuser@remoteserver:/remote/folder/ ``` #### References: [Simplified Guide](https://www.simplified.guide/ssh/copy-file) ## DNS ### Custom DNS ``` $ vim /etc/resolv.conf nameserver 8.8.8.8 nameserver 8.8.4.4 ``` ### Custom DNS servers for /etc/resolv.conf To define a custom DNS: * First, install **`resolvconf`** and follow the commands bellow ```bash sudo apt install resolvconf -y ``` * Put the nameservers from Google inside the file**`/etc/resolvconf/resolv.conf.d/head`** ```bash sudo sh -c "echo \"nameserver 8.8.8.8 nameserver 8.8.4.4\" >> /etc/resolvconf/resolv.conf.d/head" sudo sh -c "echo \"nameserver 8.8.8.8 nameserver 8.8.4.4\" >> /etc/resolvconf/resolv.conf.d/base" ``` * Update Resolvconf ``` sudo resolvconf -u ```
* Restart the resolvconf service ```bash sudo service resolvconf restart ``` ## Get current IP from the shell ```bash remoteHost=$(dig +short myip.opendns.com @resolver1.opendns.com) echo $remoteHost ``` ## Stream audio ```bash sudo apt install -y pulseaudio pavucontrol ``` * `Alt + F2` and type `pavucontrol` * Select `Recording` tab * Change to `Internal audio monitor` ## Search inside files recursively ``` grep -rli "my-name" ``` ## Display Usage in Megabytes and Gigabytes ``` df -h ``` ### Display a Specific File System ``` df –h /dev/sda2 ``` ## Show size of folders ``` sudo du -shc /var/* ``` ## Empty trash ``` rm -rf ~/.local/share/Trash/* ``` ## Search and replace inside the file ``` sed -i 's/SEARCH_REGEX/REPLACEMENT/g' INPUTFILE ``` ## Network ### Check network ports in use ``` sudo netstat -tlnp | grep 80 ``` ### Check opened network ports of the server ``` nmap HOST ## Example nmap google.com nmap 55.1.22.5.68 ``` ### Open network ports ``` # Openning 8080 port sudo iptables -A INPUT -p tcp --dport 8080 -j ACCEPT ``` ### Open Firewall ports To open ports on the firewall, using the **iptables** command is possible specifying the desired port. Using the example below, just replace port **8888** with the desired port. ``` $ iptables -I INPUT -p tcp --dport 8888 -j ACCEPT $ iptables -t filter -I FORWARD -i eth2 -o etho -m multiport --dport 8888 -j ACCEPT ``` ## Logs ### Show real-time logs from OS ``` tail -f /var/log/syslog # Or you can use journalctl # journalctl -f ``` ## Environment ### Set Global environment ``` sudo sh -c "echo MY_GLOBAL_ENV_TO_MY_CURRENT_DIR=$(pwd)" >> /etc/environment" ``` ### Set local environment ``` env MY_GLOBAL_ENV_TO_MY_CURRENT_DIR=$(pwd) ``` ### Unset local environment ``` unset MY_GLOBAL_ENV_TO_MY_CURRENT_DIR ``` ## Startup ### Show all service status ``` sudo service --status-all ``` ### Exec commands at startup ``` sudo vim /etc/init.d/rc.local #!/bin/bash #command1 #command2 exit 0; sudo chmod ugo+x /etc/init.d/rc.local update-rc.d rc.local defaults ``` ## PPA ### Remove installed PPA repository Use the "--remove" flag, similar to how the PPA was added: ``` sudo add-apt-repository --remove ppa:whatever/ppa ``` As a safer alternative, you can install "ppa-purge": ``` sudo apt-get install ppa-purge ``` And then remove the PPA, downgrading gracefully packages it provided to packages provided by official repositories: ``` sudo ppa-purge ppa:whatever/ppa ``` Note that this will uninstall packages provided by the PPA, but not those provided by the official repositories. If you want to remove them, you should tell it to apt: ``` sudo apt-get purge package_name ``` You can also remove PPAs by deleting the .list files from `/etc/apt/sources.list.d` directory. Last but not least, you can also disable or remove PPAs from the "Software Sources" section in Ubuntu Settings with a few clicks of your mouse (no terminal needed). ### **Execute "add-apt-repository" without press enter** {% hint style="info" %} **--force-yes** Force yes; this is a dangerous option that will cause apt to continue without prompting if it is doing something potentially harmful. It **should not** be used except in very special situations. Using force-yes can potentially destroy your system! Configuration Item: APT::Get::force-yes. {% endhint %} ``` # Example sudo add-apt-repository ppa:ondrej/php --force-yes ``` ## Create an alias for shell commands * Add the script below at end of the file **`~/.profile`** ``` alias hello_world="echo \"Hello World!\"" ``` * Then type your alias directly ``` hello_world # output: Hello World ``` ## Update packages less noisy ``` apt-get -qq update ``` ## Revalidade ca-certificates ``` sudo apt-get install -y --reinstall ca-certificates ``` ## ## Add multi-touch to your Linux distribution To do it, make sure to do the steps below: ``` sudo gpasswd -a $USER input sudo apt install xdotool wmctrl libinput-tools git clone https://github.com/bulletmark/libinput-gestures cd libinput-gestures sudo ./libinput-gestures-setup install touch ~/.config/libinput-gestures.conf ``` * Paste the content below inside **`~/.config/libinput-gestures.conf`**: ``` gesture swipe up 3 xdotool key super+Down gesture swipe left 3 xdotool key super+Right gesture swipe right 3 xdotool key super+Left ``` * `After that execute the commands below` ``` libinput-gestures-setup autostart libinput-gestures-setup start libinput-gestures-setup restart ``` ### References: * * ## Get SO information ``` sudo apt-get install screenfetch -y screenfetch ``` ## Know where the program was installed ``` which php ``` ## Show any configured swap ``` sudo swapon --show ``` ## Observe and monitor system memory usage {% hint style="info" %} * "-h" means Human Mode * Shows values in Mega or Giga {% endhint %} ``` free -h ``` ## Downgrade Ubuntu Linux system version {% hint style="info" %} This example will be used a downgrade from Ubuntu 20.10 to 20.04. * **From** * **Version**: Ubuntu 20.10 * **Name**: Gorilla Grovy * **Codename**: grovy * **To** * **Version**: Ubuntu 20.04 * **Name**: Focal Fossa * **Codename**: focal {% endhint %} ### **Downgrade sources.list** ``` sudo sed -i 's/groovy/focal/g' /etc/apt/sources.list ``` ### **Pin packages** {% hint style="info" %} Open **`/etc/apt/preferences`** file and enter the following content while replacing the codename of the system codename you aim to downgrade to. {% endhint %} {% code title="/etc/apt/preferences" %} ``` Package: * Pin: release a=focal v=20.04 Pin-Priority: 1001 ``` {% endcode %} ### **Downgrade Ubuntu system** ``` sudo apt update ; sudo apt upgrade ; sudo apt dist-upgrade ``` {% hint style="warning" %} If you found any errors try this: ``` sudo apt --fix-broken install sudo dpkg --configure -a sudo apt dist-upgrade sudo apt install ubuntu-desktop ``` {% endhint %} ## Find and remove folder recursively ``` # Example: node_modules sudo find . -type d -name node_modules -exec rm -r {} \; ``` ## Open Mac External Harddrive on Linux ``` - [x] sudo apt-get install hfsprogs - [x] Mount volume or - [x] chmod -R 777 /user/media/volumeX # df -h # sudo mount -t hfsplus -o remount,force,rw /dev/sdg1 ``` ## [Remote access using the xrdp package](https://serverspace.io/support/help/install-xrdp-server-on-ubuntu-20-04/) ``` apt install xrdp adduser xrdp ssl-cert systemctl restart xrdp # Allow firewall access on port 3389 ufw allow 3389 # Change "allowed_users" to anybody # like this: allowed_users=anybody vim /etc/X11/Xwrapper.config # Check your hostname cat /etc/hostname # Or get your ip address if config ``` ## Install Postman ``` sudo apt update sudo apt install snapd sudo snap install postman ``` ## Unzip with the destination folder Set **-d** parameter ``` unzip package.zip -d /opt ``` ## How to Install netstat Command in Linux ``` # [On CentOS/RHEL] yum install net-tools # [On Debian/Ubuntu] apt install net-tools # [On OpenSuse] zypper install net-tools # [On Arch Linux] pacman -S netstat-nat ``` ``` netstat -r -n ``` ## Show subnet ``` ip -o -f inet addr show | awk '/scope global/ {print $2, $4}' ``` ## Show gateway ``` ip route | grep default ``` ## User & Groups ### Create new user ``` sudo adduser newuser ``` ### Add an existing user to the Sudo group ``` sudo usermod -aG sudo newuser ``` ### Bluetooth device disconnects right after connect 1. Remove the device on Pulse Audio Bluetooth Devices 2. Kill pulse audio and restart the Bluetooth service ```bash sudo killall pulseaudio && sudo service bluetooth restart ``` ## Bash/Zsh undo (CTRL + Z) Type: `CTRL + /`