Difference between pages "GUID Booting Guide" and "Hostname"

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== Introduction ==
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w.i.p
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==Introduction==
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A hostname is a unique name created to identify a machine on a network. In computer networking, a hostname  is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, e-mail or Usenet. Hostnames may be simple names consisting of a single word or phrase, or they may be structured.
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==Configuration==
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In Funtoo Linux <code>/etc/conf.d/hostname</code> is the only configuration file for setting a hostname. In OpenRC framework <code>/etc/conf.d/foo</code> is the configuration file for a corresponding Init script <code>/etc/init.d/foo</code>.  With the case of hostname, default value in <code>/etc/conf.d/hostname</code> is set to ''localhost'', means when system boots and OpenRC's <code>/etc/init.d/hostname</code> script started a hostname getting only ''localhost'' name.  How it looks?  In your shell promt this will look in following way, an example for root:
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<console>
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localhost ~ # ##i## Hello :)
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</console>
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Let's play a bit with a configuration. Open <code>/etc/conf.d/hostname</code> with your favorite editor and set a hostname of your choice.  Below, I will use a real examples  from one of my working test boxes.
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<console>
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localhost ~ # ##i## nano /etc/conf.d/hostname
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</console>
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Let's set it to hostname="oleg-stable.host.funtoo.org". Save the file and restart  a hostname service:
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<console>
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localhost ~ # ##i## service hostname restart
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</console>
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Now, let's examine our changes, after a restarting a hostname
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<console>
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oleg-stable ~ # ##i## Hello :)
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</console>
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== Diving deeper==
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Notice, that in above output we seeing a shortened hostname and not a FQDN (Fully Qualified Domain Name). Don't be frustrated. This is  how  default bash promt <code>PS1</code> set. To get nice promts, please, consult http://www.ibm.com/developerworks/library/l-tip-prompt/ <-- this one should be on Funtoo wiki :)
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Another way to test our settings is using a '''hostname''' command. Here we will show only  some of it's features. Let's try to execute '''hostname''' command:
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<console>
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oleg-stable ~ # ##i## hostname
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oleg-stable.host.funtoo.org
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</console>
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Now we see our fully qualified domain name hostname just how we configured it in <code>/etc/conf.d/hostname</code> in above paragraph. To get a short hostname we need to set '''-s ''' (short) argument to hostname command.
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<console>
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oleg-stable ~ # ##i## hostname -s
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oleg-stable
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</console>
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Good! Hostname offers more then just displaying a system host name but can also set one. Let's try:
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<console>
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oleg-stable ~ # ##i## hostname foo.bar.baz
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oleg-stable ~ # ##i## hostname
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foo.bar.baz
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</console>
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As you can see, we changed a hostname on-the-fly. This is not recommended way.
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{{fancywarning|Please, notice that using '''hostname''' command to configure will work temporary for a current session and will be reverted back to a value set in <code>/etc/conf.d/hostname</code> file with next system restart.}}
  
GPT, which stands for GUID Partition Table, is a disk partitioning scheme that was introduced by Intel for Itanium architecture systems, as part of EFI, the Extensible Firmware Interface. While you are probably not using an Itanium architecture computer, and you are likely using a BIOS-based rather than an EFI-based system, you still may want to use GPT partitioning. Why? Because the standard MBR-based partitioning scheme only supports system disks that are less than 2TiB in size. On modern systems, especially systems with hardware RAID logical volumes, it is very easy to go beyond the 2TiB limit. GUID partition tables support disks that are larger than 2TiB in size.
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Now that we got a brief description of a hostname and basic configuration steps its time to reflect another important case, which is directly related to a Funtoo Linux hostname generation, a hosts.
  
=== GPT Technology Overview ===
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==Hosts case==
 
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As per man page <code>hosts</code> stands for static table lookup for hostnames and it's configuration file is <code>/etc/hosts</code>.
This section contains a technical overview of GPT technology.
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GUID partition tables support up to 512 partitions. GPT data structures are stored in the first sectors of the drive with a secondary copy stored at the end of the drive. This allows the partitioning scheme of your disk to be recovered in situations where the primary partition table has been corrupted.
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For compatibility with legacy partitioning tools, GPT partitioning tools typically rewrite the MBR partition table (generally located in the first sector of the disk) in a way those tools will interpret it like ''"This disk has only one partition (of an unknown type) covering the whole disk".''
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It is possible to convert an existing MBR-partitioned disk to GPT format using the <tt>gdisk</tt> command. Please carefully read the <tt>gdisk</tt> man page before using this capability, as it is potentially dangerous, particularly if you are performing it on your boot disk.
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{{ fancyimportant|Funtoo Linux fully supports GPT on x86-32bit and x86-64-bit systems. GPT is supported on SPARC systems, but currently only for non-boot disks.
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}}
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=== Booting GPT ===
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If you decide to use a GPT-based partitioning scheme for your system disk, either out of necessity due to a 2TiB+ disk, or because you want to try GPT out, then the question arises -- how do you get the darn thing to boot? This is where the new <tt>GRUB</tt> boot loader comes in. The new <tt>GRUB</tt> (version 1.9x, found at <tt>sys-boot/grub</tt>) is a redesign of the original <tt>GRUB</tt> (version 0.9x, now called <tt>sys-boot/grub-legacy</tt> in Funtoo) boot-loader that includes very mature support for booting from GPT-based disks.
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Now, let's take a look at how to get GPT-based booting working under Funtoo Linux.
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== Getting Started ==
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The first thing you'll need to do is to use a LiveCD. I recommend [http://www.sysresccd.org/Main_Page System Rescue CD] for this task as it is Gentoo-based and includes all the proper tools. Go ahead and boot the LiveCD, and then get to the point where you are ready to partition your system disk.
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At this point, you have two choices as to what partitioning tool to use. You can use either <tt>gdisk</tt> or <tt>parted</tt>. <tt>gdisk</tt> is a very nice <tt>fdisk</tt>-like partitioning tool that supports GPT partitioning. It is rather new software but seems to work quite well. The other tool you can use, GNU <tt>parted</tt>, has been around for a while and is more mature, but is harder to use.
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We'll take a look at how to create partitions using <tt>gdisk</tt>. Alternatively, <code>cgdisk</code>, curses-based gdisk for users familiar with cfdisk or <code>sgdisk</code>, command-line tool can be used for creating and managing GPT partitions.
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== Partitioning Using Gdisk ==
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OK, the first step is using <tt>gdisk</tt> is to start it up, specifying the disk you want to modify:
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<pre># gdisk /dev/sda</pre>
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You should find <tt>gdisk</tt> very familiar to <tt>fdisk</tt>. Here is the partition table we want to end up with:
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<pre>Command (? for help): p
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Disk /dev/sda: 312581808 sectors, 149.1 GiB
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Disk identifier (GUID): 17
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Partition table holds up to 128 entries
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First usable sector is 34, last usable sector is 312581774
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Total free space is 0 sectors (0 bytes)
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Number  Start (sector)    End (sector)  Size      Code  Name
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  1              34          204833  100.0 MiB  0700  Linux/Windows data
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  2          204834          270369  512.0 kiB  EF02  BIOS boot partition
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  3          270370        1318945  512.0 MiB  8200  Linux swap
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  4        1318946      312581774  148.4 GiB  0700  Linux/Windows data
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Command (? for help): </pre>
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Above, you'll see that we have a 100 MiB boot partition, a 512 kiB &quot;BIOS boot partition&quot;, 512 MiB of swap, and the remaining disk used by a 148.4 GiB root partition.
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The one new thing here is the &quot;BIOS boot partition.&quot; What is it? In GRUB-speak, this BIOS boot partition is basically the location of the meat of GRUB's boot loading code - the quivalent of the <tt>stage1_5</tt> and <tt>stage2</tt> files in legacy GRUB. Since GPT-based partition tables have less &quot;bonus&quot; space than their MBR equivalents, and explicit partition of code <tt>EF02</tt> is required to hold the guts of the boot loader.
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In all other respects, the partition table is similar to that of an MBR-based disk. We have a boot and root partition with code <tt>0700</tt>, and a Linux swap partition with code <tt>8200</tt>. One this partition table has been written to disk and appropriate <tt>mkfs</tt> and <tt>mkswap</tt> commands are issued, <tt>/dev/sda1</tt> will be used to hold <tt>/boot</tt>, <tt>/dev/sda2</tt> will be used by the new GRUB directly, <tt>/dev/sda3</tt> will house our swap and <tt>/dev/sda4</tt> will hold our root filesystem.
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Go ahead and create filesystems on these partitions, and then mount the root and boot filesystems to <tt>/mnt/gentoo</tt> and <tt>/mnt/gentoo/boot</tt> respectively. Now go ahead and unpack a stage3 tarball to <tt>/mnt/gentoo</tt> and chroot in as you normally do.
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== Configuring The Kernel ==
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Your kernel will need a couple of extra GPT-related options enabled in order for it to make sense of your GPT partitions and find your filesystems. These options can be found under <tt>Enable the block layer ---&gt; Partition Types</tt>:
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<pre>[*] Advanced Partition Selection (PARTITION_ADVANCED)
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[*] EFI GUID Partition Support (EFI_PARTITION)</pre>
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If you are using a non-Funtoo distribution then you may need to append a proper <tt>rootfstype=</tt> option to your kernel boot options to allow Linux to properly mount the root filesystem when <tt>Advanced Partition Selection</tt> is enabled. [[Boot-Update]] does this for you automatically.
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Now just go ahead and compile and install your kernel, and copy it to <tt>/boot/bzImage</tt>.
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== Booting The System ==
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To get the system booted, you will want to first edit <tt>/etc/fstab</tt> inside the chroot so that it reflects the partitions and filesystems you just created. Then, emerge <tt>boot-update</tt> version 1.4_beta2 or later:
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<pre># emerge boot-update</pre>
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[[Boot-Update]] is a front-end for the GRUB 1.9x boot loader and provides a necessary simplified configuration interface. <tt>boot-update</tt> is used to generate boot loader configuration files. But before we get to <tt>boot-update</tt>, we first need to install GRUB to your hard disk. This is done as follows:
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<pre># grub-install /dev/sda</pre>
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<tt>grub-install</tt> will detect and use <tt>/dev/sda2</tt> and use it to store its boot loader logic.
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Now it's time to create an <tt>/etc/boot.conf</tt> file. For more information on all available options, consult the [[Boot-Update]] guide -- I'll show you a sample configuration for the sample GPT partition scheme above:
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<pre>boot {
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        generate grub
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        default bzImage
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}
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&quot;Funtoo Linux&quot; {
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        kernel bzImage
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}</pre>
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Once <tt>/etc/boot.conf</tt> has been created, then type:
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<pre># boot-update</pre>
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This will auto-generate a <tt>/boot/grub/grub.cfg</tt> file for you, and you will now be able to reboot into Funtoo Linux using a GPT partitioning scheme.
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For more information on all the options available for <tt>/etc/boot.conf</tt>, please consult the [[Boot-Update]] guide.
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[[Category:Article]]
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Revision as of 16:38, February 20, 2015

w.i.p

Introduction

A hostname is a unique name created to identify a machine on a network. In computer networking, a hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, e-mail or Usenet. Hostnames may be simple names consisting of a single word or phrase, or they may be structured.

Configuration

In Funtoo Linux /etc/conf.d/hostname is the only configuration file for setting a hostname. In OpenRC framework /etc/conf.d/foo is the configuration file for a corresponding Init script /etc/init.d/foo. With the case of hostname, default value in /etc/conf.d/hostname is set to localhost, means when system boots and OpenRC's /etc/init.d/hostname script started a hostname getting only localhost name. How it looks? In your shell promt this will look in following way, an example for root:

localhost ~ #  Hello :)

Let's play a bit with a configuration. Open /etc/conf.d/hostname with your favorite editor and set a hostname of your choice. Below, I will use a real examples from one of my working test boxes.

localhost ~ #  nano /etc/conf.d/hostname

Let's set it to hostname="oleg-stable.host.funtoo.org". Save the file and restart a hostname service:

localhost ~ #  service hostname restart

Now, let's examine our changes, after a restarting a hostname

oleg-stable ~ #  Hello :)

Diving deeper

Notice, that in above output we seeing a shortened hostname and not a FQDN (Fully Qualified Domain Name). Don't be frustrated. This is how default bash promt PS1 set. To get nice promts, please, consult http://www.ibm.com/developerworks/library/l-tip-prompt/ <-- this one should be on Funtoo wiki :) Another way to test our settings is using a hostname command. Here we will show only some of it's features. Let's try to execute hostname command:

oleg-stable ~ #  hostname
oleg-stable.host.funtoo.org

Now we see our fully qualified domain name hostname just how we configured it in /etc/conf.d/hostname in above paragraph. To get a short hostname we need to set -s (short) argument to hostname command.

oleg-stable ~ #  hostname -s
oleg-stable

Good! Hostname offers more then just displaying a system host name but can also set one. Let's try:

oleg-stable ~ #  hostname foo.bar.baz
oleg-stable ~ #  hostname 
foo.bar.baz

As you can see, we changed a hostname on-the-fly. This is not recommended way.

Warning

Please, notice that using hostname command to configure will work temporary for a current session and will be reverted back to a value set in /etc/conf.d/hostname file with next system restart.

Now that we got a brief description of a hostname and basic configuration steps its time to reflect another important case, which is directly related to a Funtoo Linux hostname generation, a hosts.

Hosts case

As per man page hosts stands for static table lookup for hostnames and it's configuration file is /etc/hosts.