CentOS Network Connection Files
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Video Transcription
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>> Hello, Cybrarians.
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>> Welcome back to
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>> the Linux plus course here at Cybrary.
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I'm your instructor, Rob Goelz.
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In today's lesson, we're going to discuss
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network connection files in CentOS.
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Now, upon completing today's lesson,
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you'll be able to understand
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the network configuration file syntax
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for CentOS interface files,
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and those are found in the etc/
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sysconfig/ network scripts directory.
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We're also going to touch briefly on the dhclient file.
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With that being said, let's go ahead and get right
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to it with some demo time.
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In today's demo, we're over here in our CentOS system,
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let's go ahead and navigate to
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that directory I had mentioned.
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We going to go to cd/etc/sysconfig network scripts.
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All right, and then if we do an ls
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dash al in this directory,
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we're going to see all of the interface files,
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the network connection files on the system.
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Now, on this particular VM,
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I only have a single interface file
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for this IF Config E&P 0, S3.
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Now that's the interface,
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the network connection that we're using for this system.
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It's a little bit weird.
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ENP 0S3, what does that mean?
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Well, that is actually gotten
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from something called predictable
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interface naming that takes into
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account the way that the system comes up,
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the settings in the bios,
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the order that the PCI bus boots in,
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lot of these things we'll cover later,
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but if you want to know a little bit more about why that
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has such a wacky interface name,
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take a look at predictable interface naming.
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Go ahead and Google that and
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you'll know all you need to know.
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Let's go ahead and take a look in this file,
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so if we do a less on IFCFG ENP 0S3, hit, Enter here.
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What we're going to see is all of the configuration that
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is specific to this interface.
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Now, it's not super interesting on this system and
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that's because I only have DHCP,
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I just added, just getting an IP address over DHCP.
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All we're really seeing here
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is that the type is Ethernet,
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we're running the boot protocol, DHCP.
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If we were using a static IP addressing,
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we would see some other settings in this file,
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so for instance our boot protocol,
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instead of saying DHCP,
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it would say static.
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If we were running a static system we would
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have an IP address line, IPADDR.
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We would also see a netmask line,
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we would see a gateway to specify
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the default gateway that the system is
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using with a static IP address that it has,
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and then finally, we would also
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definitely see a broadcast.
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We would see a broadcast line in that file that would
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indicate the broadcast network that the interface is on.
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That's pretty much it for the networks scripts directory
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and the network configuration files
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that we find in the network directory.
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Well that's pretty much it for
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etc/config/network scripts and the interface files
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that we see in that directory.
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Now, let's move over and take a look at the DH client.
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Now, the DH client on the system is used for DHCP.
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It's used to configure DHCP on
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this system to connect and talk to a DHCP server.
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The DH client file is found in, etc/DHCP/DH client.
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We're going to try and do a less on this if we can,
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let's see if it allows us to,
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we might actually need to become sudo, and we do,
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we need to elevate our privileges in order
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to view this file so let's just do a sudo edit.
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What I'll do here is I'll type in
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my user password to elevate
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my privileges in order to read that file.
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In CentOS, the only configuration
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is a single send command,
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and we can see that down here at the very bottom,
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send DHCP client identifier equals hardware.
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Now, what this specifies is that
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the DHCP client is going to send the MAC address,
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the hardware address of the interface to
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the DHCP server in order to
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get back it's DHCP information.
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With that, in today's lesson,
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we covered network connection configuration and CentOS,
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which is found in
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the /etc/sysconfig/ network-scripts directory,
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and we also talked a little bit about
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DHCP client configuration using the DH client file.
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Thank you so much for being here
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>> and I look forward to seeing you in the next lesson.
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