Faq

How to find symbolic links that point to a directory

Learn how to use the find command to discover symbolic links that refer to a directory.

Summary

Find symbolic links pointing to a directory

How to compare two directories and find the differences

Learn how to compare two directories and see their differences or what files they are having in common.

Summary

Compare two directories, find their differences and what they have in common

How to see the number of open connections on Linux

Show the number of open connections using the ss command on Linux.

Summary

Show number of open connections per protocol

How to see when a process was started

Show process details to learn more about when a process was started using the ps tool.

Summary

Show start time of a process

How to see when the system was started (uptime)

When did a system start? Learn how to query the boot time (uptime) of a system using commands like uptime and ps.

Summary

Show uptime of the system

Frequently Asked Questions

Frequently asked questions about system administration, system state, and how to perform common tasks.

Summary

How to see active connections and bandwidth usage on Linux

Show actual bandwidth usage and active connections using the iftop tool on Linux.

Summary

Show actual bandwidth usage

Show to clear the DNS cache with systemd

Learn how to inspect and clear the DNS cache when using the systemd resolver daemon.

Summary

Clear DNS cache using resolvectl

How to show network TCP statistics and counters

Show counters related to the TCP connections by using the nstat command. This small utility will quickly retrieve the related statistics and display them.

Summary

Show TCP connection statistics

How to see CPU details

Show CPU details such as architecture, vendor, caches, virtualization options, and even known CPU vulnerabilities such as Meltdown and Spectre.

Summary

Show CPU details

Methods to find the Linux distribution and version

Learn how to find the Linux distribution and version of a system. Use the right tool or file to find the relevant details.

Summary

Find the Linux distribution name and version

How to see memory information such as type and speed

Show memory information and details such as the number of banks in use, the memory type and speed.

Summary

Show memory details

How to securely delete a file and its contents

Need to delete the contents of a sensitive file? Instead of just deleting it with rm, look at this option first.

Summary

Learn how to purge data before deleting a file

How to see the creation date of a file

Learn how to use the stat command to find the initial creation time of a file, also known as its birth time.

Summary

Find out when a file was initially created

What is a tainted kernel

Learn what it means when the Linux kernel is marked as tainted, including finding the cause.

Summary

Learn what it means when the kernel is tainted

How to find the specific cause of a tainted kernel

Learn what it means when the Linux kernel is marked as tainted and in particular the underlying cause.

Summary

Learn about the specific cause that tainted the kernel

Frequently Asked Questions

Frequently asked questions about the Linux kernel and kernel security.

Summary

How to see errors on dropped packets on a network interface on Linux

Show the network link details using the ip command to find out if a network has errors or dropped packets on a Linux system.

Summary

Show network link statistics to discover errors or dropped packets

How to see the default gateway on Linux

Show the network routing table to discover the default gateway used on a Linux system.

Summary

Show network table to discover the default gateway

How to see which process is using a port

Show which process is already opened an UDP or TCP port on Linux by using the ss command.

Summary

Show which process is listening to a port

How to see open ports on Linux

Show which UDP/TCP ports are opened on a Linux system, including the related process. Use the ss tool to see more details about these sockets.

Summary

Show open network ports such as TCP and UDP

Frequently Asked Questions

Frequently asked questions about networking, such as DNS, IP configuration, TCP/UDP details, and more.

Summary

How to see the TTL value of a DNS record

Learn how to query the Time To Live (TTL) for a DNS record by using the dig tool.

Summary

Query DNS to reveal the TTL value of a DNS record.

How to show all installed packages on Ubuntu

Query the package manager to show installed packages on Ubuntu systems including version details.

Summary

Query tools like dpkg to show installed packages

Frequently Asked Questions

Frequently asked questions about software, such as package manager, package versions, and how to configure them.

Summary

How to list all USB devices

Retrieve device information from USB hubs and devices using the lsusb command.

Summary

Retrieve USB device information using lsusb

How to see the available hard disks

Show the available hard disks in a system by using the right Linux tool. There are multiple options to pick, so let's have a look.

Summary

Query the available hard disk(s)

How to see hard disk specifications and details

Show more detailed information about the available hard disks in the system. Specifications like speed, serial number, firmware, and other details.

Summary

More in-depth information about the available hard disks

How to see BIOS details

Show bios details from within a Linux system. Learn how to query these details and where to find more information.

Summary

Show BIOS information using dmidecode

Frequently Asked Questions

Frequently asked questions about hardware information such as bios, USB devices, memory, and other details.

Summary

How to find the biggest directories on disk

Find the biggest directories and files on disk by using the du command.

Summary

Leverage the du command to find the biggest directories

How to see the last X lines with journalctl

Limit the output from journalctl by defining the number of lines you want to see.

Summary

Perform smarter queries when requesting information from journalctl

How to disable a systemd unit with systemctl

Want to disable a service or specific systemd unit? Use systemctl to configure units and disable it on boot or completely.

Summary

Disable a service or specific unit with systemctl

How to start and enable a unit with systemctl

Combine the start and enable command when using systemctl to get a unit like a service started at boot and right away.

Summary

Start and enable a unit with one command

How to show failed units with systemctl

Want to check the system for failed systemd units? In this article we show how to do this with systemctl and query the units with a failure state.

Summary

Show failed systemd units with systemctl

Frequently Asked Questions

Frequently asked questions about systemd, systemctl, and journalctl. Learn by pratical examples how to use these tools.

Summary

Frequently Asked Questions

Frequently asked questions about file systems, file permissions, directories and files.

Summary