CompTIA Exam Prep - ITF+, A+, Network+, Security+, CySA+

ifconfig — interface configuration — was the standard command for viewing and changing network settings on Unix-like systems for decades. It still works on macOS and on plenty of older Linux installations, but on modern Linux it has been deprecated in favour of the ip command , and that fact is itself an exam point. Learn ifconfig because you will meet it. Learn ip because it is what you should be using. On most current distributions ifconfig is not installed by default at all. It lives in the net-tools package, which is no longer maintained, and running it produces "command not found" on a clean Debian, Ubuntu, Fedora, or RHEL system. Reading the Output Running ifconfig with no arguments shows every active interface. The fields that matter: Interface name — eth0 or enp0s3 for wired, wlan0 or wlp2s0 for wireless, lo for loopback. Modern systems use predictable naming based on bus position rather than the old sequential names, which is why you see enp0s3 ...

APT — the Advanced Package Tool — is the package manager on Debian, Ubuntu, and their derivatives. It installs software, resolves dependencies, and keeps systems patched, and it is examinable territory on Linux+. A naming warning worth getting out of the way: in Linux, APT is a package manager. In security, APT means advanced persistent threat. They share nothing but three letters, and exam questions occasionally exploit the ambiguity. What APT Actually Does Underneath sits dpkg , the low-level tool that installs and removes individual .deb files. dpkg does exactly what it is told and nothing more — hand it a package whose dependencies are missing and it fails. APT is the layer above. It reads configured repositories, works out the full dependency tree, downloads everything required, and hands the packages to dpkg in the right order. Dependency resolution is the entire reason APT exists. The Commands Command What it does apt update Refreshes the package lists from the ...

Linux permissions look cryptic until you see the pattern, and then they are genuinely simple. Every file and directory has an owner, a group, and a set of three permissions applied to three categories of user. That is the whole model. Three permissions — read, write, execute — applied to three audiences: the owner, the group, and everyone else. Reading the Output of ls -l A listing line begins with something like -rwxr-xr-- . Ten characters, and each position means something specific. Position 1: the file type. - is a regular file, d a directory, l a symbolic link, c a character device, b a block device. Positions 2–4: the owner's permissions. Positions 5–7: the group's permissions. Positions 8–10: everyone else — "other". So -rwxr-xr-- is a regular file where the owner can read, write and execute; the group can read and execute; and everyone else can only read. The Numeric Shorthand Each permission has a value, and you add them. Permissio...