Lesser Known Bash Shell Commands for Ubuntu/Debian GNU/Linux: Discover Hidden Gems for Faster System Administration

Ubuntu and Debian GNU/Linux are popular choices for those who seek a robust and flexible operating system. As they are based on the Linux kernel, they offer a variety of powerful tools, many of which can be made even more potent with the Bash Shell. This article delves into some lesser-known Bash commands that experienced users recommend, providing insights into their capabilities and efficiency.

Understanding Bash Shell in Ubuntu/Debian

The Bash Shell is a widely used command-line interface in the Unix/Linux environment. It is pre-installed with both Ubuntu and Debian and serves as a powerful tool for system administration and scripting. However, its full potential is often underutilized due to the availability of more prominent, commonly used commands. This article aims to highlight some of the lesser-known commands that can help system administrators and power users work more efficiently.

Lesser-Known Bash Shell Commands

1. dd

dd is a versatile command-line utility that can be used for data conversion and replication. It is less frequently used due to its complicated syntax, but when utilized correctly, it offers immense power.

One of the most common uses of dd is for copying and converting blocks of data. For example, you can use dd to copy a hard drive, create a bootable USB drive, or even clone a system.

dd if/dev/sdA of/dev/sdB

In the command above, /dev/sdA is the source device, and /dev/sdB is the destination device. This command can be incredibly useful for system backups and deployments.

2. fsck

fsck is a tool for checking and repairing errors in the file system. Unlike some other commands, fsck is straightforward to use and essential for maintaining the health of your Linux system.

Execute fsck on a filesystem

sudo fsck /dev/sdX

In the above example, /dev/sdX is the device you want to check. The sudo command is used to run the command with superuser privileges, as fsck requires root access.

Experience with fsck helps in identifying and resolving file system issues, such as damaged sectors, corrupted inode tables, and others. Regular use of fsck ensures that your system remains stable and responsive, reducing the risk of data loss or system crashes.

3. fsdb

fsdb stands for File System Database. It provides a simple way to create, modify, and read the superblock and other critical structures of a file system. While not as commonly used as some other commands, fsdb can be indispensable in certain scenarios.

fsdb is particularly useful when you need to modify the inodes or superblock information of a file system, for example, when you need to change the file type or reclaim unused space.

fsdb -r /dev/sdX

This command opens the file system database for the specified device. Once you are in the fsdb shell, you can navigate through the file system and make changes.

4. rsync

rsync is a powerful command-line utility designed to maintain file systems and data synchronization. It works not only on Linux systems but also on other Unix-like operating systems. While rsync is well-known for data synchronization and remote file operations, there are some lesser-known features that can enhance its functionality.

One such feature is the ability to preserve file attributes and permissions using the -a option. This comes in handy during long-term backups and system migrations, ensuring that all file properties are maintained.

rsync -avz /source/ /destination/

This command synchronizes the contents of the /source/ directory with the /destination/ directory. The -a option preserves the archive mode, which includes permissions, ownership, timestamps, and more, and -vz provide verbose output and compression to make the transfer efficient.

5. scp/ssh

scp (secure copy) and ssh (secure shell) are vital for remote file operations and access to remote systems. However, there are a few lesser-known options that can enhance their functionality.

For instance, when copying files to a remote system, you can use the -p option in scp to preserve the file permissions, and the -t option to specify the target directory. Additionally, ssh itself can be used to execute commands on the remote system, which can be very handy for complex tasks.

scp -p :/path/to/file /local/path/

Similarly, to execute a command on a remote system:

ssh  'command'

These functions can be particularly useful for system administrators who need to manage multiple systems efficiently. scp and ssh are included in the Bash Shell, making them available for a wide range of tasks from simple file transfers to remote system management.

6. update-alternatives

update-alternatives is a command often overlooked due to its complexity and the security concerns it can address. This command helps in managing a set of alternatives for different software packages, allowing users to switch between different versions seamlessly.

Using update-alternatives, you can change the default version of an installed software package, ensuring that you can work with the most stable or preferred version. This is particularly useful when dealing with packages that have multiple versions available, such as BIND (domain name system server) or debuggers like GDB.

sudo update-alternatives --config java

The above command provides you with a list of available versions of Java, and you can select the preferred version.

In conclusion, while the Bash Shell in Ubuntu and Debian provides a wide range of powerful commands, there are lesser-known tools like dd, fsck, fsdb, rsync, scp/ssh, and update-alternatives that can significantly boost your system administration and development efficiency. By mastering these commands, you can streamline your workflows, reduce the time spent on common tasks, and ensure that your system remains stable and secure.