Tag: linux

Unstage the last local commit on git

This can be done using the git reset command to move the HEAD pointer back one commit while keeping the changes in your working directory.

git reset HEAD~1

The command has successfully unstaged your last commit. The changes from that commit are now back in your working directory, but they are not staged or committed. You can now:

  1. Review the changes
  2. Make additional modifications if needed
  3. Stage and commit the changes again when you’re ready

Revert the last local changes

This will discard all uncommitted changes in your working directory and staging area. Since this is a destructive operation, I’ll use git reset –hard to revert to the last commit.

git reset --hard HEAD

What Happens

  • All uncommitted changes are discarded
  • Working directory returns to the state of the last commit
  • Staging area is cleared
  • ⚠️ Warning: This operation cannot be undone

Shell script to create a new user and add their SSH public key to an Ubuntu VM

Below is a shell script that creates a new user and adds their SSH public key to an Ubuntu VM:

#!/bin/bash

# Function to create a new user and add SSH public key
create_user_and_add_ssh_key() {
    username=$1
    ssh_key_path=$2

    # Create user
    sudo adduser --disabled-password --gecos "" $username

    # Create .ssh directory if not exists
    sudo -u $username mkdir -p /home/$username/.ssh

    # Copy SSH public key to authorized_keys file
    cat $ssh_key_path >> /home/$username/.ssh/authorized_keys

    # Set proper permissions
    sudo chown -R $username:$username /home/$username/.ssh
    sudo chmod 700 /home/$username/.ssh
    sudo chmod 600 /home/$username/.ssh/authorized_keys
}

# Example usage
new_username="newuser"
ssh_key_path="/path/to/public_key.pub"

create_user_and_add_ssh_key $new_username $ssh_key_path

Make sure to replace newuser with the desired username and /path/to/public_key.pub with the path to the SSH public key file you want to add.

Save this script to a file (e.g., create_user_and_add_ssh_key.sh), make it executable (chmod +x create_user_and_add_ssh_key.sh), and then run it (./create_user_and_add_ssh_key.sh).

This script will create a new user without a password prompt and add their SSH public key to the authorized_keys file.

Screen Fix

The screen utility is not included on some server builds. You *have* to have screen or tmux as a DBA or long-running scripts and DML will timeout and the ssh daemon will boot you off the server.

As a workaround, I copy the “screen” binary from /usr/bin/screen on a server that does have it installed and put it in my ~/bin directory.  Ordinarily, screen requires write access to /var/run/screen — but there’s a workaround.

Copy the screen binary from a compatible system to your personal bin directory.

Fortunately, screen reads a environment variable SCREENDIR to utilize an alternative socket directory.

So to work around it, you can create a directory, such as ~/.screen:

mkdir ~/.screen && chmod 700 ~/.screen

and export the SCREENDIR to point to that directory:

export SCREENDIR=$HOME/.screen

You can also put this line into you ~/.bashrc or ~./profile so that it will also take effect afterwards.