Speaker 1: Welcome back to the deep dive. Today, we're jumping into
Speaker 1: something really essential, getting a handle on red Hat Enterprise
Speaker 1: Lenox nine rh A nine. We're basically mining the Enterprise
Speaker 1: Lenox nine Certification Study Guide, the RHGSA one from twenty
Speaker 1: twenty four for the absolute core stuff.
Speaker 2: Exactly. The mission really is to pull out those key
Speaker 2: ideas about RHGL nine administration, make it clear maybe even
Speaker 2: you know, engaging, avoid just drowning you in information.
Speaker 1: Yeah, think of it as a shortcut. We're not replacing
Speaker 1: the guide obviously, No, no, definitely not.
Speaker 2: But it's like a focused look at the must nose.
Speaker 2: So whether you're just kind of RHL curious or you're
Speaker 2: actually you know, needing to work with.
Speaker 1: It, right, we hope this helps you nail down those
Speaker 1: fundamentals and maybe you uncover a few surprising bits along
Speaker 1: the way. So useful. Okay, let's kick off part one,
Speaker 1: getting started setting things up, and then the command line itself.
Speaker 1: So groundwork first, hardware. Now, the actual RHCSA exam. It
Speaker 1: doesn't test hardware.
Speaker 2: Knowledge, but you need something to run it on, obviously,
Speaker 2: Exactly it.
Speaker 1: Has to be a six to four bit system. That's
Speaker 1: a must. And if you're using virtual machines for practice, which,
Speaker 1: let's be honest, is probably how most people learn this stuff.
Speaker 2: Yeah, highly recommended.
Speaker 1: The guide suggests aiming for at least eight GB of RAM.
Speaker 1: That's if you want to run a couple of vms comfortably, right, like.
Speaker 2: A server and maybe a client, or just two practice machines.
Speaker 1: It mentions VMware workstation players specifically, which is a solid choice.
Speaker 2: Yeah, but KVM is another great one, especially if you're
Speaker 2: already comfortable in a Linux environment.
Speaker 1: They're just different ways to get that virtual sandbox set up,
Speaker 1: you know.
Speaker 2: Yeah, and having that good practice setup is key. It
Speaker 2: just avoids a lot of frustration down the line if
Speaker 2: your base system can actually handle it.
Speaker 1: Okay, so installation itself. You've got your boot, media, DBD, maybe.
Speaker 2: USB, uh huh, the usual suspects.
Speaker 1: Then you hit partitioning. This is where you're dividing up
Speaker 1: your disc.
Speaker 2: Think of it like setting up drawers in a filing
Speaker 2: cabinet before you put files in. Create the partitions, assign
Speaker 2: mount points like the main slash for the root directory
Speaker 2: or home for user files exactly, and the way richil
Speaker 2: nine organizes files within those partitions. The default file system
Speaker 2: is excess. That gets the main focus in.
Speaker 1: The guide, right, So you set up your partitions, choose
Speaker 1: your software, and for learning, the guide points towards server
Speaker 1: with uy. Yeah.
Speaker 2: That gives you both the command line and a graphical desktop,
Speaker 2: which can be handy when you're starting.
Speaker 1: You set the root passwords super important, that's the master key.
Speaker 2: Don't lose that, huh.
Speaker 1: Yeah, and then there's a little initial setup after the
Speaker 1: first boot.
Speaker 2: Pretty straightforward stuff.
Speaker 1: Okay, So you're logged in now the command line that's
Speaker 1: where the action.
Speaker 2: Is pretty much, and the default language the shell you're
Speaker 2: talking to is.
Speaker 1: Bash, right BSh. Yeah.
Speaker 2: There are others like KSh, tcs ZISH, yeah, you might
Speaker 2: see them, but Bash is the default you'll find yourself in.
Speaker 1: You can have multiple command lines open these virtual consoles.
Speaker 2: Oh yeah, like having different text based screens. You can
Speaker 2: flip between them seatrawl alt F three, seatrawl alt f four,
Speaker 2: things like that. Each one can be a separate log
Speaker 2: in session.
Speaker 1: Handy. Okay, course skills finding your way around.
Speaker 2: First up PWD print working directory tells you where you
Speaker 2: are right now.
Speaker 1: And CD to move change directory.
Speaker 2: Exactly, and you need to get the difference between absolute paths.
Speaker 2: Starting from the root like a full.
Speaker 1: Address all major documents.
Speaker 2: Yeah, and relative paths which are based on your current location,
Speaker 2: like go up one level CD, or go into this
Speaker 2: directory here's CD, durnet, we.
Speaker 1: Got it, and this path variable ah path.
Speaker 2: That's basically a list of directories the system checks whenever
Speaker 2: you just type of command name like l's or p doud.
Speaker 2: It's how it finds the program.
Speaker 1: Okay, and the tilled.
Speaker 2: Oh, the tildy that's just a shortcut always takes you
Speaker 2: back to your own home directory. Super useful.
Speaker 1: Nice okay. Dealing with files and directories.
Speaker 2: Listing them l's that's your basic listing command, but the
Speaker 2: real power is in the options like.
Speaker 1: Aero for the long listing, shows missions, size, date, right.
Speaker 2: And a to see all files, including the hidden ones
Speaker 2: that start with a dot. Then you've got at to
Speaker 2: sort by time. It shows the inn number like a
Speaker 2: unique id for the file on the disc. R R
Speaker 2: reverses the sort order, and MSR capital r that lists
Speaker 2: everything recursively like all the subdirectories too.
Speaker 3: Wow.
Speaker 1: Okay, so l's is pretty powerful.
Speaker 2: Definitely worth learning those options. Creating directories mm deer make
Speaker 2: directory and the optic option is great. It creates parent
Speaker 2: directories if they don't already exist. So mm ear MmpD one,
Speaker 2: deer two, deer three works even if deer one and
Speaker 2: deer two aren't there yet.
Speaker 1: Saves time and empty files.
Speaker 2: Touch just touch file name, or you can update the
Speaker 2: timestamp of an existing file.
Speaker 1: With it too. Okay, Copying, moving, removing.
Speaker 2: CP for copy, MV for move, which also renames files
Speaker 2: by the way, and RM for remove.
Speaker 1: And this is the one to be careful with, right, No.
Speaker 2: Trash bin exactly. Once you arm something, it's generally gone.
Speaker 2: So yeah, double check before you hit enter.
Speaker 1: Good advice. What about links? Hard link soft links?
Speaker 2: Right, So MMn file name link name creates a hard link.
Speaker 2: Think of it as two directory entries pointing to the
Speaker 2: exact same data block on the disc. If you delete
Speaker 2: one name, the data is still there under the other name.
Speaker 2: Soft links or symbolic links are made with LNNSS. That's
Speaker 2: more like a shortcut. It just points to the name
Speaker 2: of the original file. If the original file moves or
Speaker 2: gets deleted, the soft link breaks.
Speaker 1: Gotcha. So hard links point to the data. Soft links
Speaker 1: point to the name.
Speaker 2: Pretty much.
Speaker 1: Yeah, all right, permissions, This looks important.
Speaker 2: Chwud very important schmad changes the mode the permissions. You
Speaker 2: can use numbers like schmod six forty file.
Speaker 1: Six four zero. What does that mean?
Speaker 2: It's octal. Each number represents permissions for user, group and others.
Speaker 2: Six is read and write, four plus two four is
Speaker 2: read only. Zero is no permissions.
Speaker 1: Ah. Okay, r as four w is two.
Speaker 2: X is one exactly. Or you can use the symbolic
Speaker 2: mode you gore x like schmod g plus w file
Speaker 2: adds right permission for the group g com for user
Speaker 2: G group oh others.
Speaker 1: Okay, that seems more intuitive, Maybe it can be.
Speaker 2: The guide also mentions special dits sgid G plus s
Speaker 2: on a director means new files created inside it get
Speaker 2: the directory's group, not the user's primary group, and the
Speaker 2: sticky bit O plus T on a shared directory like
Speaker 2: tm tem it means only the owner of a file
Speaker 2: can delete it, even if others have right permission to
Speaker 2: the directory.
Speaker 1: Ah. Useful for shared spaces.
Speaker 2: Yeah. Then chound changes the owner th hg RP changes
Speaker 2: the group pretty straightforward, and the ooh mask that sets
Speaker 2: the default permissions. When you create a new file or directory,
Speaker 2: the system starts with full permissions and then subtracts whatever
Speaker 2: the mask specifies, so it controls how things are created initially.
Speaker 1: Okay, kind of like a template for new file permissions
Speaker 1: sort of.
Speaker 2: Yeah, it masks off permissions.
Speaker 1: Then chatter file attributes.
Speaker 2: Yeah, that's another layer chatter. Let's you say, attributes like
Speaker 2: immutable plus I. If a file is immutable, nobody can
Speaker 2: change or delete it, not even root.
Speaker 1: Seriously, not even root.
Speaker 2: Nope, you have to remove the immutable flag first. With
Speaker 2: chat r, there's also a pend only plus a where
Speaker 2: you can add to the end of a file but
Speaker 2: can't delete or change existing content.
Speaker 1: Interesting, okay. Working with text dot redirection super useful.
Speaker 2: The greater then sign redirects output to a file overwriting
Speaker 2: it double greater than a pens to the file. Less
Speaker 2: then feeds a file as input to a command, and
Speaker 2: the pipe sends the output of one command directly as
Speaker 2: input to.
Speaker 1: The next, Say chaining commands together.
Speaker 2: Exactly and two redirects error messages.
Speaker 1: Specifically, good to know searching text dot rep rep.
Speaker 2: Is your best friend for searching dot GP pattern file name,
Speaker 2: and it gets really powerful with regular expressions. Those special
Speaker 2: characters like dot for any character, square brackets for set
Speaker 2: of characters, question mark plus plus star for matching repetitions.
Speaker 1: Let's you do really complex pattern matching.
Speaker 2: Absolutely, and if you just need to compare two files,
Speaker 2: see what's different, use diff.
Speaker 1: Defall one file two simple enough YEP editing files. Okay, VI,
Speaker 1: this one has a reputation.
Speaker 2: It does, it's powerful, it's everywhere. But yeah, it had
Speaker 2: a learning curve. The key is understanding its modes, especially
Speaker 2: command mode.
Speaker 1: Right, we're not typing text directly exactly.
Speaker 2: You use keys like to search forward, to search backward right,
Speaker 2: followed by commands like W to wright, save, q to quit,
Speaker 2: or to buq to save and quit.
Speaker 1: Okay. And these special versions VBO, VG pseudo.
Speaker 2: Ah, yeah, those are wrappers around V, specifically for editing
Speaker 2: critical system files like et cetubas, food, et cetera, group
Speaker 2: and etcetera. Pseudos they add safeguards like file locking to
Speaker 2: prevent multiple people editing at once or messing things up
Speaker 2: too badly. Definitely use those when editing those specific files.
Speaker 2: But if V is just too much at first, well,
Speaker 2: you can actually change your default editor. You set the
Speaker 2: editor environment variable and the guide mentions NANO, which is
Speaker 2: much simpler and more like a standard notepad style editor,
Speaker 2: and you at the bottom pretty intuitive.
Speaker 1: Good alternative to know about definitely. Lastly, for this section,
Speaker 1: getting help documentation crucial.
Speaker 2: Man pages are the first stop man command name read
Speaker 2: the manual.
Speaker 1: People always say that.
Speaker 2: Because it's true, especially check the example section at the
Speaker 2: end of many men pages. Super helpful.
Speaker 1: Okay, what is an apropos?
Speaker 2: What shared as gives you just a quick one line
Speaker 2: summary of what a command does. Apropos keyword searches those summaries,
Speaker 2: so if you can't remember the command name but know
Speaker 2: what it does, apropos can help you find it.
Speaker 3: Nice and infodocs oser doc Info is another documentation system,
Speaker 3: sometimes more detailed than man pages, but maybe less used
Speaker 3: now and yeah, asha doc often has rehabiens examples, extra
Speaker 3: docs provided by the software package itself always worth a look.
Speaker 2: If you're stuck.
Speaker 1: Lots of places to find help, then for sure. Okay,
Speaker 1: let's shift gears part two, Managing the system itself. Starting
Speaker 1: with software right.
Speaker 2: So RHL uses RPM packages. That's the underlying format, But
Speaker 2: the main tool you'll use to install, update remove software
Speaker 2: is DNF.
Speaker 1: DNF okay you replace YM right.
Speaker 2: Yeah. DNF is the modern version. It talks to repositories
Speaker 2: basically online collections of software packages. These are configured in
Speaker 2: files under ETCM, DOT Repo, dot D and.
Speaker 1: Red Hat subscription management.
Speaker 2: That's how your system proves it's allowed to access the
Speaker 2: official red Hat repositories and get updates in software. And
Speaker 2: DNF handles dependencies automatically.
Speaker 1: Meaning if you install program A and needs library B
Speaker 1: to work, DNF figures that out and installs library B
Speaker 1: too exactly.
Speaker 2: Saves a ton of.
Speaker 1: Hassle so common DNF commands.
Speaker 2: DNF List shows available or installed packages. DNF install package name,
Speaker 2: DNF update updates everything or just one package. DNF remove package.
Speaker 1: Name, okay, install update, remove what else.
Speaker 2: DNF info package name gives you details about a package.
Speaker 2: DNF repolist shows you which repositories your system is actually using,
Speaker 2: and DNF provides file name as useful, it tells you
Speaker 2: which package owns a specific file like a SERB and.
Speaker 1: Mash ah handy for tracking things down.
Speaker 2: And While DNF is the main tool, you can sometimes
Speaker 2: interact with RPM files.
Speaker 1: Directly using the RPM command.
Speaker 2: Right rpmdshis package dot RPM installs a specific RPM file,
Speaker 2: I install viver bose h hash marks for progress. RPM
Speaker 2: dosh qa lists all installed packages, rpmdsh QL package name
Speaker 2: lists all the files inside and installed package okay, and
Speaker 2: RPM dash K package dot RPM verifies the package's digital
Speaker 2: signature using gpgkeys usually stored in et cetera, KERPM, DOUSHDPG
Speaker 2: to make sure it's legitimate and hasn't been tampered with.
Speaker 1: Security check good. What about module streams ah modules?
Speaker 2: There a way? Our HL offers different versions of software
Speaker 2: like maybe Python three point nine and Python three point
Speaker 2: one one on the same system without conflicts. You can
Speaker 2: use DNF module list and DNF module infotasy what's available? Okay.
Speaker 1: It provides flexibility exactly right. System startup the boot process.
Speaker 1: How does that work?
Speaker 2: It's a sequence. First, the bios or UA five firmware
Speaker 2: initializes the hardware. Then and it hands off to the bootloader.
Speaker 1: Which is GRB two and RHL nine correct.
Speaker 2: GRB two then loads the Linux kernel into memory. The
Speaker 2: kernel starts up, mounts a temporary initial filesystem called the
Speaker 2: INNA tramps, and finally the kernel starts the very first
Speaker 2: real process, which is systemed. System gets process ID one
Speaker 2: and it takes over managing the rest of the system.
Speaker 1: Startup system does the big boss.
Speaker 2: Then pretty much the conductor, As the guide.
Speaker 1: Says, what about GRB two itself? Anything we need to know?
Speaker 2: You'll see its menu at boot. You can choose different
Speaker 2: kernels if you have them. Pressing E lets you temporarily
Speaker 2: edit the kernel boot parameters useful for troubleshooting. Sometimes its
Speaker 2: main config file is etc default grub a key setting.
Speaker 2: There is jur rub time out how long the menu
Speaker 2: waits before booting the default entry?
Speaker 1: Right. So, systemed you said it manages everything.
Speaker 2: It manages services, devices, mount points, almost everything using units.
Speaker 2: These are just configuration files telling a system to how
Speaker 2: to manage something.
Speaker 1: Where are these unit files?
Speaker 2: System Wide defaults are in e U solob systemed system
Speaker 2: and your customizations or locally installed ones go in its
Speaker 2: systems system Targets. Targets are special units that group other units.
Speaker 2: Think of them like run levels in the old days.
Speaker 2: Multi user dot target is your typical command line server state.
Speaker 2: Graphical dot target adds the graphical desktop on top of that.
Speaker 1: How do you control these units and.
Speaker 2: Targets with the system's statle command?
Speaker 1: It's central, okay, What can I do?
Speaker 2: System statle start service name stop, restart, reload to reread
Speaker 2: config without a full restart status to see if it's
Speaker 2: running and get recent logs.
Speaker 1: Basic service control Yeah.
Speaker 2: Then system tell'll enable service name makes it start automatically
Speaker 2: at boot disabled, stops that is enabled, checks the current setting,
Speaker 2: and list units shows everything system is currently managing.
Speaker 1: Can you change the default state like boot to command
Speaker 1: line instead of graphical Yep.
Speaker 2: You can set the default target using system teleset default.
Speaker 1: Okay, what if things go wrong during boot? How do
Speaker 1: you see messages journal?
Speaker 2: Telll that's the command to view the system journal, which
Speaker 2: collects logs from pretty much everywhere.
Speaker 1: So system lugs are centralized now largely.
Speaker 2: Yes, And for troubleshooting, you can manually boot to a
Speaker 2: specific target by adding like system d dot unit multi
Speaker 2: user dot target to the kernel line in grub. Okay,
Speaker 2: and there's dart dot break. You can add two, which
Speaker 2: interrupts the boot process very early, drops you into a shell.
Speaker 2: Useful for things like receiving a lost root password. Power
Speaker 2: for stuff can be a lifesaver. Oh and interestingly, commands
Speaker 2: like shut down, reboot, halt they're mostly just links pointing
Speaker 2: back to system.
Speaker 1: Techle Now, system really took over?
Speaker 2: It really did. And for time management, time detectal shows
Speaker 2: and sets the system time and time zone, and cronid
Speaker 2: is the service that sinks your clock over the network
Speaker 2: using NTP.
Speaker 1: Got it? Okay? Users in groups.
Speaker 2: Right, You generally don't want to be logged in as
Speaker 2: route all the time, bad practice. So you create regular
Speaker 2: user accounts.
Speaker 1: Where is user info store?
Speaker 2: It's mainly in Etcetera's user info etc. Shadow, Secure password info, etc.
Speaker 2: Group info and etcetera Shadow secure group info. Defaults for
Speaker 2: new users come from at clog in dot DEFs.
Speaker 1: And the commands to manage them.
Speaker 2: User AD creates a user, User MOD modifies an existing user.
Speaker 2: You can use options like EDES to change their shell
Speaker 2: AOD for home directory, DAD them to supplementary groups. User
Speaker 2: at deletes a user. Use ther option with user del
Speaker 2: to remove their.
Speaker 1: Home directory too important detail.
Speaker 2: Yeah, Password username changes the user's password. You can also
Speaker 2: use password batstin to pipe a password in maybe from
Speaker 2: a script. Password atch l username locks an account, you
Speaker 2: unlocks it ato E sets and expiration date.
Speaker 1: Lots of control their end groups plant.
Speaker 2: Group, AD, group, mod, group del. Simple enough. Users have
Speaker 2: one primary group but can be members of many supplementary groups.
Speaker 2: That's all defined in et cetera.
Speaker 1: Group. Okay, what about getting root privileges when you need them.
Speaker 2: Well, they're sue switch user. You can sue to become
Speaker 2: root if you know the root password. But the more
Speaker 2: common and generally better way.
Speaker 1: Is pseudo right super rousers do Yeah.
Speaker 2: It lets specific users run specific commands as route without
Speaker 2: needing the root password. It's configured in et ceter Suitors
Speaker 2: use the pseudo command to edit this safely, or by
Speaker 2: adding files in et cetera suters dot and.
Speaker 1: You can grant permissions to groups like the Wheel group exactly.
Speaker 2: Often admins are just added to the Wheel group and
Speaker 2: that group is given pseudo access in the configuration. You
Speaker 2: can also allow passwordless pseudo for certain commands with the
Speaker 2: no pay SSWD tag okay.
Speaker 1: Flexible user environment files like Bash RCI.
Speaker 2: Yeah, those control your shell environment, et Cetera profile and
Speaker 2: etceterashard are system wide. Then each user has their own
Speaker 2: Bash profile for login shells and augershar for interactive shells.
Speaker 2: There's also etceeter profile dot d, which contains scripts run
Speaker 2: at log in good place for system wide customizations.
Speaker 1: Setting aliases, environment variables, that kind of thing exactly, okay,
Speaker 1: storty deep dive partitions again.
Speaker 2: Tools you've got f disc, which is older works well
Speaker 2: for MBR discs. Then gie disc is for modern GPT
Speaker 2: partition discs, and parted is another powerful tool works with
Speaker 2: Both can be used interactively or scripted.
Speaker 1: What can you do with them?
Speaker 2: The basics Print the partition table, P create new partitions
Speaker 2: and delete them D change the partition type to use
Speaker 2: LDC the type codes like a E for Linux, LBM
Speaker 2: eighty two for swap, write changes to disc w or
Speaker 2: quit without saving Q.
Speaker 1: And you mentioned needing to tell the kernel about changes.
Speaker 2: Yes, crucial step after using f disc or g disc
Speaker 2: or parted to change partitions on a disc that's in use,
Speaker 2: the kunnel might not see the changes. Immediately, run part
Speaker 2: probe to ask the kernel to reread the partition table
Speaker 2: or just reboot.
Speaker 1: Okay, reboot, got it. Formatting.
Speaker 2: Once you have a partition, you need a filesystem. Use mkfs,
Speaker 2: mkfs dot, XFS dev's day one formats that partition with
Speaker 2: XFS or mkfs dot, ext fours dB two for.
Speaker 1: EXT four and mounting making it usable.
Speaker 2: Right, you mount the filesystem onto a directory a mount point.
Speaker 2: For permanent mounts that happen at boot, you can figure
Speaker 2: them in etcetera.
Speaker 1: Snet what's in there?
Speaker 2: Each line defines a mount the device, often by UUID,
Speaker 2: the mount point directory, the filesystem type like x SpaceX
Speaker 2: to four, NFS mount options, and then two numbers for
Speaker 2: backup dump and filesystem check.
Speaker 1: Order pass okay, and you find the UIDs with ball kid.
Speaker 2: Great command shows uoids and filesystem types for all your
Speaker 2: block devices. Using UIDs and haf STAB is better than
Speaker 2: device names like devs to one because the device names
Speaker 2: can sometimes change, but uaeds don't.
Speaker 1: Good. Tip and manual mounting.
Speaker 2: Mount device, mount point and mount mountpoint or device simple okay.
Speaker 1: Now, LVM Logical Volume Manager sounds complicated.
Speaker 2: It adds a layer, but it's incredibly flexible. The ideas
Speaker 2: you take your physical desks or petitions and designate them
Speaker 2: as physical volumes or pvs using PV create IPS. Then
Speaker 2: you group one or more pvs together into a volume
Speaker 2: group or VG using VG create. Think of the VG
Speaker 2: as a pool of storage.
Speaker 1: Space coolest space. Got it.
Speaker 2: Finally, you carve out logical volumes or lvs from that
Speaker 2: v G pool using lv create. These lvs are what
Speaker 2: you actually format with a filesystem MKFS, dot XSS, div,
Speaker 2: MYVGMLLV and.
Speaker 1: Mount O so PV MIDG MELV miile V filesystem exactly.
Speaker 2: You've got commands to display and manage each layer PB display, VV,
Speaker 2: display V display VJE extend at PV to VG, lvextend
Speaker 2: grow in LV, and the big benefit is resizing. You
Speaker 2: can add another desk, make it a PV, add it
Speaker 2: to the VG with VEG extend, and then grow an
Speaker 2: existing LV within that VG using lvextend. After extending the LV,
Speaker 2: you just need to resize the filesystem inside it.
Speaker 1: How do you do that?
Speaker 2: For XFS, it's XFS growths mount point. For x four
Speaker 2: it's re sized two SVGLV. You can often do this
Speaker 2: online without unmounting. That's huge flexibility.
Speaker 1: Yeah, that sounds real useful. What's the autom mount ad off.
Speaker 2: It's a service that automatically mounts filesystems, often network shares
Speaker 2: like NFS, only when someone tries to access them and
Speaker 2: unmounts them after a period of inactivity. Configured it in
Speaker 2: at COUTO, dot master and related files.
Speaker 1: Okay, handy for on demand access YEP networking time basics.
Speaker 2: First, it addresses your systems address subnetmasks, defining the network size,
Speaker 2: often in CIDR like twenty four and the default gateway
Speaker 2: the router to reach other networks standard.
Speaker 1: Stuff, and the main command now is IP.
Speaker 2: Yes, the IP command is the modern tool. IP address
Speaker 2: show replaces if configure that IP route show replaces Route I,
Speaker 2: neighbor replaces ARP. It does a lot, so learn IP definitely.
Speaker 2: You'll still use ping to test connectivity, trace route to
Speaker 2: see the path packets take, and hostnamechial to view or
Speaker 2: set the system's host name.
Speaker 1: Where network settings stored.
Speaker 2: RHBL nine uses Network Manager heavily. Connection profiles are stored
Speaker 2: as files in Acceta Network Manager System connections.
Speaker 1: How do you configure Network Manager several ways?
Speaker 2: NMTI is the command line tool very powerful. Nmto me
Speaker 2: gives you a text based menu interface simpler for some tasks,
Speaker 2: and if you have a GUI, there's NM connection editor.
Speaker 1: Choose your weapon.
Speaker 2: DNS configued usually handled by Network Manager too, but the
Speaker 2: resulting DNS server list ends up in ecresol dot com.
Speaker 2: You can test DNS lookups with tools like dig or hosts.
Speaker 1: Okay, secure remote access, SSH.
Speaker 2: Absolutely essential s s username at host name, connects you securely,
Speaker 2: SEP securely copies files, sepfil user at host dot path
Speaker 2: and SFTP gives you an interactive secure FTP like session.
Speaker 1: Secure alternatives to older tools like telnet and FTP exactly.
Speaker 2: Don't use those anymore if you can avoid it. Firewall
Speaker 2: RHTL uses Fireworld by default. It uses zones like public,
Speaker 2: internal DMZ to apply different levels of trust and rules,
Speaker 2: and it manages access using pre defined services like HTTP,
Speaker 2: SEEPR specific port numbers.
Speaker 1: How do you troll it?
Speaker 2: Check status with system s system status Fireworld check if
Speaker 2: enabled with system is enabled fireworld. The main command is
Speaker 2: firewall cmd.
Speaker 1: What can firewall cmd do?
Speaker 2: Lots AD service remove servicesh AD port ADYADATCP remove port ADADTCP.
Speaker 2: Use permanent to make changes stick after a reboot, but
Speaker 2: then you need reload to apply them to the running
Speaker 2: canfig list all shows the current rules.
Speaker 1: For his zone. There's a guy too, yeah, firewall can
Speaker 1: fig okay and making assets even more secure with.
Speaker 2: Keys highly recommended. Generate a keypair on your client machine
Speaker 2: with shosh keygen, then copy the public key IDRSA dot
Speaker 2: pub or similar to the server using a shock of
Speaker 2: eyed user at host.
Speaker 1: What does spage copid do?
Speaker 2: It automatically appends your public key to the sumprovised keys
Speaker 2: file in the user's home directory on the server. Once
Speaker 2: that's done, you can staution from your client without needing
Speaker 2: a password because it verifies using your private key much
Speaker 2: more secure.
Speaker 1: Definitely sounds better than passwords. It is all right, broader
Speaker 1: security topic.
Speaker 2: Sell Linux Security Enhanced Linux. It's a mandatory access control
Speaker 2: MAC system standard Linux permissions should I or not are
Speaker 2: discretionary access control DAC. The user owns the file, they
Speaker 2: decide permissions. SELinux adds another layer where policy decides what's allowed,
Speaker 2: regardless of ownership.
Speaker 1: How does it work modes?
Speaker 2: It runs in one of three modes. Enforcing actively blocks violations,
Speaker 2: permissive logs violations, but doesn't block or disabled off completely.
Speaker 2: You check with get and force change temporarily with set
Speaker 2: and force zero, permissive or set and force one. Enforcing
Speaker 2: permanent change is in ETCeteras configure.
Speaker 1: Okay, what does it actually control? Contexts?
Speaker 2: Yeah? Everything, files, processes, ports, gets, and SELinux security context
Speaker 2: It's like a labeled user, dot role, dot type That
Speaker 2: level policy rules say things like a process with the
Speaker 2: HTPDT type context can only write to files with the
Speaker 2: HTPPD size content type context.
Speaker 1: So it restricts what processes can do even if running
Speaker 1: is root.
Speaker 2: Especially if running is root or if a service gets compromised.
Speaker 2: You manage file contexts with some manage f context to
Speaker 2: set defaults and restore senecon to apply those defaults. J
Speaker 2: con changes a context manually for a specific file, but
Speaker 2: that might not survive.
Speaker 1: A relabel okay and boollians.
Speaker 2: Celinicx buollions are like on off switches for specific policies
Speaker 2: like allow hggpd to connect to the network. Use getspool
Speaker 2: a to list them and sets the boolean name on
Speaker 2: or sets po bully name off to change them. Use
Speaker 2: jash p with setspool to make the change persistent across reboots.
Speaker 1: How do you troubleshoot Selenix issues?
Speaker 2: Check the audit log usually var logatitatt it dot log.
Speaker 2: The audit service lawns denials. The sealer tool part of
Speaker 2: set tools can analyze these logs and often suggest restore
Speaker 2: con or sets bool commands to fix the issue.
Speaker 1: So first claub odd, then Selenics on top.
Speaker 2: That's the idea. Layers of security.
Speaker 1: Managing resources processes.
Speaker 2: This is the classic command. Pso shows all processes in detail.
Speaker 2: Ps axle shows even more. P s e Z is
Speaker 2: useful to see the Sylenux context of processes, and TOP
Speaker 2: gives you that. Real time interactive view shows cpu usage, memory,
Speaker 2: running processes. Let's you sort kill processes.
Speaker 1: Right there, very hand delid processes.
Speaker 2: Kill pid sends a signal, usually sigterm terminate politely by
Speaker 2: default kill naff nine pid sends sigkill force kill uses
Speaker 2: last resort, kill process name kills all processes with that name.
Speaker 1: Signal SIGTERMI yeah.
Speaker 2: Sig up often tells a demon to reload its configuration.
Speaker 2: Sigin is what cool plus c sends. Sigteruramasks nicely sick
Speaker 2: kill forces it.
Speaker 1: Controlling priority nice re nice.
Speaker 2: Nice starts to command with a specific scheduling priority. Higher
Speaker 2: number means lower priority, more nice to others. Re nice
Speaker 2: changes the priority of an already running process. Okay.
Speaker 1: Monitoring over time.
Speaker 2: The system package provides SAR, System Activity Reporter and IOSTAT.
Speaker 2: SAR collects historical data on CPU memory, IO, network, et cetera.
Speaker 2: IOSTAT focuses on disc iostats great for tracking performance.
Speaker 1: Trends, scheduling future tasks. Contron yep chron.
Speaker 2: Is for recurring tasks users edit their own schedules with crontab.
Speaker 2: The format specifies minute, our day of month, month, day
Speaker 2: of week, and then.
Speaker 1: The command system wide chron jobs.
Speaker 2: Those go in at cedacron or as separate files and
Speaker 2: etceteracron dot D. There are also directories like etcetercron dot hourly,
Speaker 2: etceteracron dot daily, et cetera, where you just drop scripts
Speaker 2: you want run at those intervals.
Speaker 1: Simple enough. What about one off tasks.
Speaker 2: At schedules A command to run once at a specific time,
Speaker 2: like at ten thirty pm tomorrow. You type the commands
Speaker 2: press crash all plus d at Q list pending jobs
Speaker 2: at scheckblurm removes them.
Speaker 1: Handy for delayed tasks. Yeah. Basic scripting BASH scripts.
Speaker 2: Super common for automation. Starts with the shebang line hashtag
Speaker 2: dot bin. Bash use variables, command, substitution, command, or backticks
Speaker 2: to capture output control structures like if conditioned then and
Speaker 2: down fire or four I in list at ton testing
Speaker 2: conditions with test or ton right, and scripts can take
Speaker 2: arguments one two dollars, et cetera. The exit command sets
Speaker 2: the exit status zero usually means success.
Speaker 1: Logging where do messages go?
Speaker 2: Traditionally cislog handles it config and as she can. Ra
Speaker 2: sizelog dot com defines rules based on facility like kernel mail,
Speaker 2: user and priority info warning error to send messages to files,
Speaker 2: usually under varlog like varlog messages varlog secure.
Speaker 1: But systems has its own journal yes.
Speaker 2: And journal lichells the tool to read it. It captures
Speaker 2: syslog messages plus output from services managed by system. By default,
Speaker 2: it might only store logs in memory, but you can
Speaker 2: configure you're persistent logging to varlog journal.
Speaker 1: So check both varlog files and journal ductel good idea. Yeah. Finally,
Speaker 1: containers big topic now huge.
Speaker 2: The guide gives an intro. Containers are like lightweight isolated
Speaker 2: environments for apps. They share the host OS kernel, unlike vms,
Speaker 2: which emulate whole hardware stacks.
Speaker 1: So they're faster, use fewer resources.
Speaker 2: Generally yes, much faster startup, lower overhead. Great for developers
Speaker 2: packaging apps and dependencies, and for operations deploying them consistently
Speaker 2: drives DevOps well.
Speaker 1: What makes them work? Names basis true groups.
Speaker 2: Those are key Linux kernel features. Name spaces isolate things
Speaker 2: like process IDs, network stacks, user IDs, C groups limit
Speaker 2: and manage resource usage, CPU memory and c Linux helps
Speaker 2: provide security separation between containers.
Speaker 1: And the hosts, and the tool in RHL nine is Podman.
Speaker 2: Yes, Podman is the main command line tool for working
Speaker 2: with containers and container images. It's designed to be compatible
Speaker 2: with Docker commands, which helps.
Speaker 1: So containers aren't just lighter vms about packaging and portability too.
Speaker 2: Absolutely package your app and all its libraries, dependencies, everything
Speaker 2: into an image. That image runs the same way on
Speaker 2: your laptop on a test server in the cloud. That
Speaker 2: consistency is a massive.
Speaker 1: Benefit, game changer. As the guide says, Okay, Podman commands.
Speaker 2: A lot overlap with Docker. If you know that. Podman
Speaker 2: run imagine name creates and starts a container. Podman tuss
Speaker 2: list running containers a forall, pod Men Stop Container aid,
Speaker 2: Podman start Container aide, podmn.
Speaker 1: Restart Managing container life cycle.
Speaker 2: Right, Podman pom and canterrad removes a stop container. Podman
Speaker 2: Images lists images you have locally. Podman vian image.
Speaker 1: Removes an image getting images.
Speaker 2: Podman pull imagine name downloads from a registry. Podman push
Speaker 2: uploads your own images. Podman's search term looks for images
Speaker 2: in registries.
Speaker 1: What about running commands inside or copying files?
Speaker 2: Podman exec it containered command runs a command inside a
Speaker 2: running container like Bash to get a shell. Podman sipe
Speaker 2: copies files between the host and container. Podman logs shows
Speaker 2: contains output inspecting things, Podman inspect container it or image
Speaker 2: eyed gives you tons of detailed Jason info. Podman tag
Speaker 2: lets you give an image an alias or new name,
Speaker 2: and Podman version shows versions.
Speaker 1: Can you run containers like system services? Yes.
Speaker 2: Podman can generate system unit files for containers using Podman
Speaker 2: generate system then you can manage them with system sucleshall
Speaker 2: user often run as non root user services.
Speaker 1: Persistent data containers are ephemeral by default.
Speaker 2: Right. If you want data to survive container restarts, you
Speaker 2: need to mount host directories into the container using the
Speaker 2: ACV option with Podman run like defvpathon hoost dot pathing
Speaker 2: container Okay.
Speaker 1: And registries where do images come from?
Speaker 2: They're like app stores for container images. Docker hub is
Speaker 2: the big public one. Red Hat has its own registry
Speaker 2: registrate dot red hat dot Io. Companies often run private
Speaker 2: ones too.
Speaker 1: Phew, Okay, that was a lot.
Speaker 2: It really is a broad landscape, isn't it. RHL nine
Speaker 2: administration covers so much from the absolute basics right up
Speaker 2: to containers.
Speaker 1: But you start to see how it connects. Right. Yeah,
Speaker 1: command line skills are fundamental for almost everything.
Speaker 2: Absolutely, managing files, users, services, even containers often comes back
Speaker 2: to the command line.
Speaker 1: And maybe things clicked a bit more like how trim
Speaker 1: new permissions and Cylenix contexts work together for security, or how.
Speaker 2: System changed the whole boot and service management game compared
Speaker 2: to older systems.
Speaker 1: Yeah, or the flexibility LVM gives you for storage.
Speaker 2: Hopefully some of those aha moments happened.
Speaker 1: But this deep dive, it's really just scratching the surface.
Speaker 2: Oh for sure, the guide lays it all out, but
Speaker 2: you really learn by doing getting those vms set up,
Speaker 2: trying the commands, breaking things, fixing things. That's where mastery
Speaker 2: comes from.
Speaker 1: So definitely encourage you, the listener, to get hands on experiment.
Speaker 1: Focus on the areas you need most, maybe storage, maybe networking,
Speaker 1: maybe containers.
Speaker 2: Whatever fits your goals.
Speaker 1: So here's a final thought, today's one. With containers becoming
Speaker 1: so dominant, how do you see these fundamental OS admin
Speaker 1: skills evolving? Hmmm, will mastery of the command line and
Speaker 1: deep system knowledge still be as crucial, or will higher
Speaker 1: level tools and automation, abstract, more of it away. Where's
Speaker 1: that balance heading.
Speaker 2: That's a really interesting question. The tools change, but understanding
Speaker 2: what's happening underneath that seems like it will always be valuable.
Speaker 2: Definitely something to think about as you keep learning. RGL
Speaker 2: nine