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<v Speaker 1>Welcome to the deep dive today. We're really cutting through

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<v Speaker 1>the noise to get right to the core of Linux.

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<v Speaker 2>Yeah, the foundations exactly.

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<v Speaker 1>Think of this as your essential guide, you know, understanding

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<v Speaker 1>what makes a Linux system tick, right from power on

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<v Speaker 1>to keeping your data safe. We're pulling insights from Steven

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<v Speaker 1>Surring's LPIC one practice test, kind of a shortcut to

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<v Speaker 1>those aha moments, but you know, without getting totally overwhelmed.

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<v Speaker 2>And that's key, isn't it, Because whether you're just curious

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<v Speaker 2>or you actually manage Linux systems day to day, these

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<v Speaker 2>concepts are well, they're fundamental to so much tech out there,

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<v Speaker 2>ensuring i mean, twenty years in the field engineering Sissigmin

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<v Speaker 2>Architecture author, Linux World editor. He's packaged up that.

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<v Speaker 1>Real world knowledge, but practical stuff.

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<v Speaker 2>Absolutely. Our mission here is to demystify Linux admin, give

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<v Speaker 2>you a clear, solid understanding of how it all fits together,

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<v Speaker 2>more than just definitions.

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<v Speaker 1>Okay, let's dive in. Then the machine's off, cold, silent.

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<v Speaker 1>What's that very first spart? How does it even begin

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<v Speaker 1>to wake up and become you know, Linux?

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<v Speaker 2>It's a really precise sequence, actually, almost like choreography. It

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<v Speaker 2>starts way down low, with the BIOS or more commonly

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<v Speaker 2>now UEFI firmware.

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<v Speaker 1>Right, the basic hardware stuff exactly.

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<v Speaker 2>That's the very first code that runs. It does its

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<v Speaker 2>initial checks, then it hands control.

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<v Speaker 1>Over to the bootloader like GRUB.

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<v Speaker 2>Yeah, GRB legacy or GRB two are the most common examples.

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<v Speaker 2>The bootloader's job is basically to find the operating system

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<v Speaker 2>kernel and get it ready to launch.

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<v Speaker 1>Okay, so the bootloader finds the kernel, the heart of

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<v Speaker 1>the OS. What's next? Does a kernel just take over?

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<v Speaker 2>It does, but there's another clever step. First, the kernel

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<v Speaker 2>starts loading, but then it often relies on something called

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<v Speaker 2>the intotramps in initial RAM file system. Yeah, it's a

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<v Speaker 2>it's quite ingenious. It's a tiny temporary root filesystem loaded

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<v Speaker 2>into memory, okay, because it contains just the essential drivers

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<v Speaker 2>like for your discontroller needed to mount the actual root

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<v Speaker 2>filesystem from your hard drive or ssd ah.

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<v Speaker 1>So it's like a temporary toolkit to access the main storage.

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<v Speaker 2>Exactly. It lets Linux boot on tons of different hardware

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<v Speaker 2>before it can even fully see the main disc Super flexible.

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<v Speaker 1>That makes sense. Okay, kernels loaded, we've used the innatrams

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<v Speaker 1>to find the real file system. How does it get

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<v Speaker 1>ready for us? You know, start services, let us log.

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<v Speaker 2>In, right, that's the system initialization phase. The kernel. Once

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<v Speaker 2>it's up, hands off control to the very first userspace process.

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<v Speaker 2>Traditionally this was CISSV in it the old way, the

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<v Speaker 2>older classic way. Most modern distries now use systems both

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<v Speaker 2>fundamentally do the same thing though. Start all the necessary

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<v Speaker 2>background services, mount file systems, listened in, et cetera. Get

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<v Speaker 2>the network going, and bring the system up to a

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<v Speaker 2>usable state.

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<v Speaker 1>Yeah, that first process, that's PID one.

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<v Speaker 2>That's the one process, ID one, whether it's sissv in

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<v Speaker 2>it or systemed, it's the ancestor of pretty much everything

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<v Speaker 2>else running on the system. A critical process.

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<v Speaker 1>Got it. So these in its systems bring things up?

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<v Speaker 1>Can you tell Linux how to come up? Like different modes?

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<v Speaker 1>Sometimes I just need a command line for fixing things.

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<v Speaker 2>Absolutely. That's where run levels in cissp in it or

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<v Speaker 2>boot targets in systems come in. They define different operational states.

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<v Speaker 1>Like safe mode and Windows sort of.

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<v Speaker 2>Kind of analogous. Yeah, you have single user mode that's

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<v Speaker 2>often run level one or rescue dot target. It's minimal,

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<v Speaker 2>usually no networking, just a rootshell, perfect for maintenance. Okay,

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<v Speaker 2>then you've got your typical states like a multi user

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<v Speaker 2>command line environment run level three or multi user dot

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<v Speaker 2>target or the full multi user graphical desktop run level

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<v Speaker 2>five or graphical dot target.

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<v Speaker 1>And if things go wrong during boot where I want

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<v Speaker 1>to change the default state, what tools do I use?

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<v Speaker 2>Good question? For diagnosing boot issues, DMEs is invaluable. It

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<v Speaker 2>shows you the kernel's messages right from startup. You can

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<v Speaker 2>see hardware detection, driver loading errors.

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<v Speaker 1>Okay.

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<v Speaker 2>On system systems general, pizerl is your main log viewing tool.

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<v Speaker 2>It's incredibly powerful for seeing what happened during boot, checking

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<v Speaker 2>service status everything.

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<v Speaker 1>Right, systems journal YEP, and to.

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<v Speaker 2>Manage services and targe gets use system tail like system taitl.

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<v Speaker 2>Set default graphical dot target makes it boot to the

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<v Speaker 2>desktop by default.

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<v Speaker 1>And rebooting is it just pulling the plug?

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<v Speaker 2>Haha? Please don't. The class command is in its six

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<v Speaker 2>or with systemed system tel to reboot is the standard

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<v Speaker 2>way graceful shut down and restart and.

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<v Speaker 1>A quick troubleshooting tip from the source. Ah yes.

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<v Speaker 2>If a hard disk isn't even showing up in Linux

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<v Speaker 2>like DMAs doesn't see it, the first place to check

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<v Speaker 2>is often the system bios or UF five setup. Linux

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<v Speaker 2>can't see hardware. The firmware doesn't recognize first.

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<v Speaker 1>Makes sense, starts the lowest level. Okay, so the system's alive.

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<v Speaker 1>But how does Linux organize everything? It feels very structured

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<v Speaker 1>compared to say, Windows drive letters.

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<v Speaker 2>It is, and that structure is key. It's largely governed

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<v Speaker 2>by the Filesystem Hierarchy Standard, the FHS FAHS. Yeah, it's

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<v Speaker 2>a standard that defines where specific types of files and

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<v Speaker 2>directories should live. It provides consistency across different Linux distributions.

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<v Speaker 1>So it's at or always means configuration.

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<v Speaker 2>Files more or less exactly. That predictability is a huge

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<v Speaker 2>advantage for anyone managing Linux systems. You know where to

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<v Speaker 2>look for things.

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<v Speaker 1>So walk us through some of the big ones. The

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<v Speaker 1>really critical directories defined by the FAHS.

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<v Speaker 2>Heay top level is bull the root file system. Everything absolutely,

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<v Speaker 2>everything stems.

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<v Speaker 1>From there, the single slash YEP.

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<v Speaker 2>Then boot is crucial. It holds the kernel itself. The

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<v Speaker 2>any tramps we talked about, bootloader can figs like grub

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<v Speaker 2>dot cfg. You don't want to mess that up, definitely.

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<v Speaker 2>Not et cetera is where system wide configuration files live,

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<v Speaker 2>things like etcetera, STAB, for filesystem mounts at tetcresolve dot

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<v Speaker 2>com for DNS network settings, service can figs it's the

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<v Speaker 2>control center.

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<v Speaker 1>Got it can figs and ACCA.

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<v Speaker 2>Home is where user directories are typically created, so you'd

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<v Speaker 2>have homilis home Bob containing their personal.

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<v Speaker 1>File and stuff that changes a lot, like logs.

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<v Speaker 2>That goes in VAR for variable data. Varlog is the

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<v Speaker 2>standard place for system logs. You also find things like

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<v Speaker 2>mailspools and varspool temporary files used by services, database files

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<v Speaker 2>sometimes okay var.

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<v Speaker 1>For variable stuff. What about US? I see that everywhere?

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<v Speaker 2>S tor often pronounced user, though historically it's good for

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<v Speaker 2>Unix system resources. Holds most user installed applications and shared libraries, documentation, etc.

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<v Speaker 2>It's usually one of the largest directories.

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<v Speaker 1>And USB drives. Where do they pop up?

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<v Speaker 2>The FHS designates media as the standard mount point for

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<v Speaker 2>removable media. Some systems might also use run media or

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<v Speaker 2>other locations, but media is the traditional FAHS spot.

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<v Speaker 1>This structure feels really logical. Now thinking about the actual discs,

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<v Speaker 1>How does Linux lay them out? Partitions and such?

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<v Speaker 2>Yeah, good disc layout is important. You typically partition your

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<v Speaker 2>drive to create separate filesystems for different parts of.

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<v Speaker 1>The hierarchy, like a separate partition for home.

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<v Speaker 2>Exactly or for VAR or t pay. It helps with

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<v Speaker 2>organizations security and performance. If VAR fills up with logs,

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<v Speaker 2>it won't crash the whole system by filling the root

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<v Speaker 2>file systems Smart end swap space AH swap space essential.

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<v Speaker 2>It's disc space that Linux uses as virtual memory when

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<v Speaker 2>your physical ram gets full. It's slower than obviously, but

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<v Speaker 2>it prevents the system from crashing due to lack of memory.

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<v Speaker 2>Usually it's on its own partition okay.

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<v Speaker 1>And for booting with UEFI you.

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<v Speaker 2>Need an EFI system Partition or ESP is usually formatted

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<v Speaker 2>as FA thirty two, surprisingly not a native Linux file system.

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<v Speaker 2>That's where the bootloader lives.

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<v Speaker 1>For UAFI systems, FAT thirty two. Interesting and partitioning schemes

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<v Speaker 1>MBR versus GPT.

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<v Speaker 2>Right MBR Masterboot Record is the older style. It has limitations,

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<v Speaker 2>most notably a two terabyte limit on perkission size. GPT

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<v Speaker 2>Goid Partition Table is the modern standard. Supports much larger

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<v Speaker 2>disks and more partitions. You'll use GPT on almost any

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<v Speaker 2>modern system.

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<v Speaker 1>Good to know, especially with big drives now okay, shifting

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<v Speaker 1>gears slightly hard links versus symbolic links. This trips people up,

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<v Speaker 1>it can.

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<v Speaker 2>Yeah, they're both ways to refer to files, but they

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<v Speaker 2>work differently. A hard link is essentially another name for

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<v Speaker 2>the exact same file data another name.

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<v Speaker 1>Yeah.

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<v Speaker 2>Imagine if files data has an ID number on the

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<v Speaker 2>disc an eNode number. A hard link is just another

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<v Speaker 2>directory entry pointing to that same inode.

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<v Speaker 1>So deleting one hard link doesn't delete the file.

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<v Speaker 2>Not if other hard links to that inode still exist.

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<v Speaker 2>The data only gets removed when the last link pointing

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<v Speaker 2>to it is gone. And crucially, hard links must be

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<v Speaker 2>on the same filesystem because inode numbers are filesystems specific.

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<v Speaker 1>Okay, So what's a symbolic link.

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<v Speaker 2>Then, symbolic link or simlink or soft link. It's more

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<v Speaker 2>like a pointer or a shortcut. It's a small file

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<v Speaker 2>that simply contains the path to another file or directory.

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<v Speaker 1>Huh, like a window shortcut.

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<v Speaker 2>Exactly like that. It has its own inode number. It

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<v Speaker 2>just points somewhere else. This means sim links can cross filesystems,

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<v Speaker 2>but if you delete the original file, the sim link

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<v Speaker 2>becomes broken. It points to.

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<v Speaker 1>Nothing, and you create those with ln ns.

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<v Speaker 2>Yep LNS target link name very useful.

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<v Speaker 1>Okay, and tools for managing disk space.

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<v Speaker 2>DF shows DISC free space on mounted filesystems. D estimates

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<v Speaker 2>DISC usage for files and directories. Very handy for finding

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<v Speaker 2>what's eating up space, DPN.

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<v Speaker 1>Do got it? And creating filesystems.

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<v Speaker 2>Use MKFS commands like nkfs dot e st four to

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<v Speaker 2>create an XT four filesystem, or mk swap to prepare

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<v Speaker 2>a partition for swap space.

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<v Speaker 1>And making sure they mount automatically.

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<v Speaker 2>That's etc. F STAB. That file lists all the file

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<v Speaker 2>systems the system should mount at boot time, where to

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<v Speaker 2>mount them, and with what options critical canfig file?

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<v Speaker 1>All right, we understand the layout. Now how do we

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<v Speaker 1>actually talk to the machine? The command line right?

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<v Speaker 2>Absolutely, the command line interface or a CLI is where

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<v Speaker 2>the real power lies in Linux administration. It's not just

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<v Speaker 2>an afterthought, it's central.

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<v Speaker 1>So the basics moving around listing files.

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<v Speaker 2>Your bread and butter. Dot LS to list files, CD

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<v Speaker 2>to change directory, MV to move a rename, CP to copy,

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<v Speaker 2>RM to remove. You'll use these constantly. PWGAWD prince your

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<v Speaker 2>present working directory tells you where you are, and history

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<v Speaker 2>is amazing shows you your previous commands. Let's you reuse

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<v Speaker 2>them easily. Huge time saver.

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<v Speaker 1>Yeah, history is great, but the real magic happens when

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<v Speaker 1>you chain commands, doesn't it. Pipes and redirects.

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<v Speaker 2>Oh absolutely, that's where the CLI really shines. Streams, pipes

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<v Speaker 2>and redirects let you build complex workflows from simple tools.

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<v Speaker 1>Okay, break down redirects first.

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<v Speaker 2>The symbol right redirection controls where output goes. By default,

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<v Speaker 2>commands send output to your screen, st doo et and

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<v Speaker 2>errors to your screen too. Std err redirects stdu to

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<v Speaker 2>a file. Overwriting it appends stdog to a file and errors.

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<v Speaker 2>You can redirect sddoo using two for example, command to

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<v Speaker 2>error dot log. A common trick is command output dot

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<v Speaker 2>log two on one, which sends both stdou and st

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<v Speaker 2>r to the same file.

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<v Speaker 1>Okay, two in one for combined output. Now, pipes, the vertical.

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<v Speaker 2>Of art pipes are incredibly powerful. They takes the standard

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<v Speaker 2>output of the command on its left and feeds it

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<v Speaker 2>directly as standard input to the command on its right.

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<v Speaker 2>It lets you chain commands together.

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<v Speaker 1>Can you give that example from the source again? The

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<v Speaker 1>password file one?

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<v Speaker 2>Sure. Let's say you want a sorted list of just

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<v Speaker 2>the user names from etcter password. You could do cat

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<v Speaker 2>et cetera. Password a SF print one.

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<v Speaker 1>Dollars, Sort okay, walk me through.

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<v Speaker 2>It, kat, etc. Password displays the file content stdo ut right.

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<v Speaker 2>That output is piped into oc ocdash xcdof tells OC

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<v Speaker 2>to use a colon as the field separator. Print one

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<v Speaker 2>dollar tells OC to print only the first field the

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<v Speaker 2>username from each line.

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<v Speaker 1>Okay, so now we have just user names exactly.

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<v Speaker 2>And that list of user names ox stdout is piped

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<v Speaker 2>into the sort command, which sorts them alphabetically. The final

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<v Speaker 2>sordid list appears on your screen.

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<v Speaker 1>Wow, simple commands, complex result. That's cool.

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<v Speaker 2>It really is. That composibility is a core Linux philosophy.

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<v Speaker 2>Oh and T is useful too. It reads from standard

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<v Speaker 2>input and writes to both standard output and one or

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<v Speaker 2>more files like a T junction for data streams.

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<v Speaker 1>Handy for seeing output while also logging in. Okay, command

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<v Speaker 1>line basics covered. What about installing software? It's different on

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<v Speaker 1>different Linux types, right, it is.

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<v Speaker 2>That's a major distinction. You generally have two main families

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<v Speaker 2>or ecosystems for package management. Family one Debian based systems

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<v Speaker 2>think Debian, Oupa to Mint. They use dot deb package files.

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<v Speaker 2>The low level tool is dpkg gpeg, but you usually

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<v Speaker 2>interact with higher level tools like app get or the

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<v Speaker 2>newer often preferred app. They handle dependencies automatically fetching packages

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<v Speaker 2>from repositories defined and at capsources dot list.

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<v Speaker 1>You're right apped update first.

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<v Speaker 2>Usually Yeah, app update or act get update refreshes the

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<v Speaker 2>list of available packages from the repositories before you install

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<v Speaker 2>or upgrade anything.

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<v Speaker 1>Okay, Debianfamily, dot, DPKG, app dot deb files at caapsources

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<v Speaker 1>dot list.

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<v Speaker 2>What's the other big one, the red Hat based systems.

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<v Speaker 2>It's RedHat Enterprise Linux, r h e L, Fedora, Sentos,

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<v Speaker 2>sec Linux uses it to They use dot rpm package files.

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<v Speaker 2>The low level tool is RPM. The higher level tools

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<v Speaker 2>are typically YUM older or its successor, d n F,

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<v Speaker 2>s U s C and opencus use zipper like APPED.

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<v Speaker 2>These handle dependencies and use repositories configured in places like

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<v Speaker 2>at CHAM dot COF or files in at CM dot, rebos, dot.

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<v Speaker 1>D SO, yum in package or DNF info.

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<v Speaker 2>Package exactly to get information about a package before installing it.

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<v Speaker 2>Understanding which system you're on, Debian based or red Hat

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<v Speaker 2>based is crucial for managing software effectively.

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<v Speaker 1>Makes sense and other useful command line tools for finding

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<v Speaker 1>things or searching. Oh, yeah.

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<v Speaker 2>Find is incredibly powerful for locating files based on name, type, size, modification, time, permissions,

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<v Speaker 2>anything you can think of. And REP is essential for

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<v Speaker 2>searching inside text files for specific patterns using regular expressions.

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<v Speaker 1>Find and GP got them.

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<v Speaker 2>Yeah.

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<v Speaker 1>Okay. Let's shift to system administration and crucially security.

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<v Speaker 2>Very important topics. Let's start with user and group management.

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<v Speaker 2>Linux is multi user from the ground up. Commands like

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<v Speaker 2>user rat right, user red, user mod, modify, user BETL delete,

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<v Speaker 2>same for groups, group head, group mod group doll managing

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<v Speaker 2>who can access the system and what they.

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<v Speaker 1>Can do, and the key files here it's set our

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<v Speaker 1>pass group.

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<v Speaker 2>Yes, it's setter pass roots stores basic user info username,

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<v Speaker 2>user id, UID, group id GID, home directory path default show.

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<v Speaker 2>Well it's readable by.

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<v Speaker 1>Everyone, but not the passwords.

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<v Speaker 2>Critically no, the encrypted passwords are an et ceter shadow.

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<v Speaker 2>This file is only readable by the root user. That's

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<v Speaker 2>a fundamental security features shadow passwords.

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<v Speaker 1>Oh okay, shadow for passwords.

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<v Speaker 2>What else, ETCETERA group defines the groups and their members,

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<v Speaker 2>and it setuskool is neat. It's a skeleton directory. When

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<v Speaker 2>you create a new user with USAD, the files in

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<v Speaker 2>its siscle are copied into their new home directory, providing

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<v Speaker 2>default canfigs or files.

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<v Speaker 1>Like default that bashshack maybe.

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<v Speaker 2>Exactly insures consistency. And if you want to check password

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<v Speaker 2>policies like explanation dates, the change command change h L

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<v Speaker 2>username shows password, aging info, last change, expiry date, et

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<v Speaker 2>cetera very.

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<v Speaker 1>Useful, good one. What about automating task running backups every night?

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<v Speaker 2>That's where scheduling comes in. The classic tool is krawn.

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<v Speaker 2>It runs commands or scripts on a schedule a minute, hour,

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<v Speaker 2>day of month, month, day.

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<v Speaker 1>Of week, defined in crontab files yep.

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<v Speaker 2>Each user can have their own cron tab and there

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<v Speaker 2>are system wide chron jobs defined in et cetera cantab

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<v Speaker 2>or files within et ceter used for log rotation, backup

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<v Speaker 2>system checks all sorts of things.

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<v Speaker 1>And if I just want to run something once.

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<v Speaker 2>That's the job for AT. You can say at now

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<v Speaker 2>plus one hour and then type the commands you want

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<v Speaker 2>or run in an hour. Simple but effective for one off.

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<v Speaker 1>Delayed tasks and the system's way.

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<v Speaker 2>System timer units. They're the modern approach, more flexible than kron,

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<v Speaker 2>integrated with system services offer finer control. They're becoming the

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<v Speaker 2>standard way to schedule tasks on systems systems.

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<v Speaker 1>Okay, let's talk host security. What are the absolute must knows?

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<v Speaker 2>Well, we mentioned shadow passwords, keep et cetera, shadow secure,

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<v Speaker 2>that's number one. Number two, use pseudo. Don't log in

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<v Speaker 2>as route directly unless absolutely necessary. Pseudo lets authorized users

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<v Speaker 2>run specific commands as route or another user temporarily.

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<v Speaker 1>And editing the pseudo rules.

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<v Speaker 2>Always use vesudo, Never edit et cetera, seriers directly with

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<v Speaker 2>the text editor. Pisudo locks the file and performs syntax

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<v Speaker 2>checking before saving. This prevents you from making a mistake

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<v Speaker 2>that locks you out of Pseudo entirely. Tip the pseudo

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<v Speaker 2>absolutely critical another useful security measure, especially during maintenance. Touch

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<v Speaker 2>its knowledge in this knowlogy Yeah, if that file exists,

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<v Speaker 2>only root can log in. It displays the contents of

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<v Speaker 2>the file to users trying to log in non route.

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<v Speaker 2>It's a simple way to keep users off while you're

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<v Speaker 2>doing major work. Just remember to remove it when you're done.

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<v Speaker 2>Good temporary lockout and generally minimize your attack surface. Turn

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<v Speaker 2>off any network services you don't absolutely need. Every listening

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<v Speaker 2>service is a potential entry point.

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<v Speaker 1>Solid advice. How about securing data and communications?

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<v Speaker 2>Encryption SSH secure shell that's the standard for secure remote logins,

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<v Speaker 2>command execution, and file transfers like cit AP or.

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<v Speaker 1>SFTP uses key pairs right.

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<v Speaker 2>Yes, public private key pairs. You generate them with shurch keysen.

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<v Speaker 2>Put your public key in the dotch authorized keys file

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<v Speaker 2>on the server, keep your private key safe, and you

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<v Speaker 2>get secure often passwordless.

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<v Speaker 1>Access and graphical apps remotely.

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<v Speaker 2>SSH can do x eleven forwarding on a graphical program

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<v Speaker 2>on a remote server, but have its window displayed securely

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<v Speaker 2>on your local desktop.

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<v Speaker 1>Very handy, cool and for encrypting files themselves.

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<v Speaker 2>Et IPG or GPG. It's the standard tool for encrypting, decrypting, signing,

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<v Speaker 2>and verifying files and messages using public key cryptography. Essential

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<v Speaker 2>for data confidentiality and integrity.

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<v Speaker 1>GPG Yeah, got it? Any other useful DMin security tools.

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<v Speaker 2>To end attention wallets, you send a quick message to

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<v Speaker 2>the terminals of all logged in users. Good for broadcasting systems,

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<v Speaker 2>shut down warnings, okay, and end map. It's a powerful

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<v Speaker 2>network scanner used to discover hosts on a network, see

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<v Speaker 2>which ports are open, identify services running. It's essential for

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<v Speaker 2>security auditing, understanding what's exposed.

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<v Speaker 1>Network mapping makes sense. Wow, we've covered a lot of ground.

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<v Speaker 1>We really have from the boot process, the file system,

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<v Speaker 1>structure of the command line, power package management, user admin security. Oh,

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<v Speaker 1>it's a pretty comprehensive.

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<v Speaker 2>Look under the hood, it is, and like you said,

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<v Speaker 2>drawing from that LPIC one material gives a really solid

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<v Speaker 2>press pactical foundation. But you know, this deep dive, it's

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<v Speaker 2>really just scratching the surface. Linux is vast, but hopefully

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<v Speaker 2>this gives you a much better framework for understanding how

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<v Speaker 2>these core pieces work together. The key is to keep exploring,

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<v Speaker 2>keep asking questions.

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<v Speaker 1>Definitely, and as you do, maybe consider this, how do

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<v Speaker 1>those fundamental Linux principles like modularity, you know, six v

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<v Speaker 1>in it versus system or using separate partitions. How does

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<v Speaker 1>that and the reliance on plaintext canfig files we saw

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<v Speaker 1>on etc and the FHS contribute to its incredible longevity

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<v Speaker 1>and adaptability.

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<v Speaker 2>Right from tiny embedded systems to massive cloud exactly.

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<v Speaker 1>So, what other sort of hidden design ideas might be

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<v Speaker 1>shaping the tech you use every day and how can

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<v Speaker 1>understanding them empower you? Something to think about