# 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 + /` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://oviniciusfeitosa.gitbook.io/knowledge/technology/operational-systems/linux/how-to.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.