Linux allows you to control the upload and download speed on specific network ports. This post is a follow-up on the wireless access point setup of a Raspberry Pi. When serving a guest Wifi setup, you may want to limit the bandwidth used by clients on the Raspberry Pi access point so that they won’t use up all Internet bandwidth of your main network. Whatever you case maybe I’ll show you how to throttle the eth0 bandwidth of the Raspberry Pi 3B+.
Continue reading “Control Network port bandwidth on Linux”Category: CentOS
CentOS
RAID Types – Explained
All hardware eventually fails. This is one of the painful side effects of entropy in our universe. For most of the types of hardware used in modern infrastructure, the loss of a single component usually incurs some amount of downtime. Other than the time taken to swap out something like a bad CPU or stick of RAM, sysadmins or users rarely see many long term ill-effects. But unless an admin takes particular care with storage, data loss from disk failures can have immediate and lasting consequences.
Continue reading “RAID Types – Explained”Linux file Permission – Oversimplified
Here’s a quick and dirty example to demonstrate Linux file permissions and how to read them.
Continue reading “Linux file Permission – Oversimplified”Manipulating text with sed
The sed utility can be used to print the contents of a
file, substitute a line (or multiple lines), and then save the file. In
contrast to grep, sed can substitute a line or multiple lines in a file and perform an in-place update of that file.
The simplest sed invocation when substituting foo for bar is:
$ sed 's/foo/bar/' inputfileThe /etc/passwd File
There are several different authentication schemes that can be used on Linux systems. The most commonly used and standard scheme is to perform authentication against the /etc/passwd and /etc/shadow files.
/etc/passwd is a plain text-based database that contains information for all user accounts on the system. It is owned by root and has 644 permissions. The file can only be modified by root or users with sudo privileges and readable by all system users.
Modifying the /etc/passwd file by hand should be avoided unless you know what you are doing. Always use a command that is designed for the purpose. For example, to modify a user account, use the usermod command, and to add a new user account use the useradd command.
How To Simulate Linux Commands
Every Linux command has one or more options and flags to perform different operations. One of the useful and important option allow us to simulate Linux commands but do not actually change the system. For instance, we can simulate the process of installation or removal of a package or program, but without actually installing or removing the intended package from a Linux system.
Continue reading “How To Simulate Linux Commands”The /etc/shadow File
There are several different authentication schemes that can be used on Linux systems. The most commonly used and standard scheme is to perform authentication against the /etc/passwd and /etc/shadow files.
/etc/shadow is a text file that contains information about the system’s users’ passwords. It is owned by user root and group shadow, and has 640 permissions.
Replacing rc.local in systemd Linux systems
Missing rc.local for adding commands to run on startup? Here’s how to set up similar functionality with today’s systemd.
The rc.local file was—and in some cases still is—the place for Linux sysadmins to put commands that need to be run at startup. Use of the rc.local
file is not only deprecated but after a couple of hours worth of
attempts, was not working in any event. This despite the fact that the systemd documentation mentions the use of a “generator” that generates systemd services from an rc.local file if one exists.