Difference between pages "Extlinux" and "IPv4 calculations"

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(GPT)
 
(The Internet layer)
 
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= What is ExtLinux? =
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WARNING: Work in progress. Do not edit this article unless you are the original author.
  
ExtLinux is a pretty simple and modern systemloader, bundled with the syslinux tools, installation is really simple for it and fast, and thanks to our CoreTeam member Slashbeast the configuration runs automated in an awesome way.
 
  
= Installing ExtLinux for funtoo =
+
= Refresh on TCP/IP model =  
  
Installing ExtLinux for funtoo is known to work and supported too. If you like to try it just emerge syslinux
+
When the ARPANet (a packet oriented network) was born in those good old seventies, engineers had to solve the problem of making computers being able to exchange packets of information over the network and they invented in 1974 something you are now using to view this page: TCP/IP! TCP/IP is a collection of various network protocols, being organized as a stack. Just like your boss does not do everything in the company and delegates at lower levels which in turn delegates at an even more lower level, no protocol in the TCP/IP suite takes all responsibilities, they are working together in a hierarchical and cooperative manner.  A level of the TCP/IP stack knows what its immediate lower subordinate can do for it and whatever it will do will be done the right way and will not worry about the manner the job will be done.  Also the only problem for a given level of the stack is to fulfill its own duties and deliver the service requested  by the upper layer, it does not have to worry about the ultimate goal of what upper levels do.
 +
 
 +
<illustration goes here TCP/IP model>
  
<console>
+
The above illustration sounds horribly familiar : yes, it is sounds like this good old OSI model. Indeed it is a tailored view of the original OSI model and it works the exact same way: so the data sent by an application A1 (residing on computer C1) to another application A2 (residing on computer C2) goes through C1's TCP/IP stack (from top to bottom), reach the C1's lower layers that will take the responsibility to move the bits from C1 to C2 over a physical link (electrical or lights pulses, radio waves...sorry no quantum mechanism yet) . C2's lower layers will receive the bits sent by C1 and pass  what has been received to the C2's TCP/IP  stack (bottom to top) which will pass the data to A2. If C1 and C2 are not on the same network the process is a bit more complex because it involves relays (routers) but the global idea remains the same. Also there is no shortcuts in the process : both TCP/IP stacks are crossed in their whole, either from top to bottom for the sender or  bottom to top for the receiver. The transportation process in itself is also absolutely transparent from an application's point of view:  A1 knows it can rely on the TCP/IP stack to transmits some data to A2, ''how'' the data is transmitted is not its problem, A1 just assumes the data can be transmitted by some means. The TCP/IP stack is also loosely coupled to a particular network technology because its frontier is precisely the physical transportation of bits over a medium and so the physical network's technology,  just the same way A1 does not care about how the TCP/IP stack will move the data from one computer to another. The TCP/IP stack itself does not care about the details about how the bits are physically moved and thus it can work with any network technology no matter the technology is Ethernet, Token Ring or FDDI for example.
# ##i##emerge syslinux
+
</console>
+
  
with that you have the complete syslinux tools installed. Another helpful tool you should merge with syslinux is slashbeast's lazykernel tool, so let us merge it too:
+
= The Internet layer =
  
<console>
+
The goal of this article being more focused on calculation of addresses used at the ''Internet layer'' so  let's forget the gory details of the TCP/IP stack works (you can find an extremely detailed discussion in [[How the TCP/IP stack works]]...  to be written...). From here, we assume you have a good general understanding of its functionalities and how a network transmission works. As you know the ''Internet'' layer is responsible to handle logical addressing issues of a TCP segment (or UDP datagram) that has either to be transmitted over the network to a remote computer or that has been received from the network from a remote computer. That layer is governed by a set of strict set rules called the ''Internet Protocol'' or ''IP'' originally specified by [RFC 791] in september 1981. What is pretty amazing with IP is that, although its original RFC has been amended by several others since 1981, its specification remains absolutely valid! If have a look at [RFC 791] you won't see "obsoleted". Sure IPv4 reached its limits in this first half the XXIst century but will remains in the IT landscape for probably several years to not say decades (you know, the COBOL language....). To finish on historical details, you might find interesting know that TCP/IP was not the original protocol suite used on the ARAPANet, it superseded in 1983 another protocol suite the [http://en.wikipedia.org/wiki/Network_Control_Program Network Control Program]. NCP looks like, from our point of view, quite prehistoric but it is of big importance as it established a lot of concepts still in use today : PDU, splitting an address in various components, connection management and so on comes from NCP. Historical reward  for those who are still reading this long paragraph: first, even a computer user was addressable in NCP messages second even in 1970 the engineers were concerned by network congestions issues ([http://www.cs.utexas.edu/users/chris/think/ARPANET/Timeline this page]).
# ##i##emerge lazykernel
+
</console>
+
  
== Installing extlinux ==
+
Let's go back to those good old seventies: the engineers who designed the Internet Protocol retained a 32 bits addressing scheme for IP and, afterall, the ARAPnet will never have the need to be able to address  billions of hosts! If you look at some ARAPANet diagrams it counted less than 100 hosts in
  
to install extlinux just follow these steps:
+
who would ''ever'' need millions of addresses afterall?  So in theory with those 32 bits we can have around 4 billions of computers within that network and arbitrarily retain that the very first connected computer must be given the number "0", the second one "1", the third one "2" and so on until we exhaust the address pool at number 4294967295 giving no more than 4294967296 (2^32) computers on that network because no number can be a duplicate.
  
<console>
+
= Classful and classless networks =
# ##i##install -d /boot/extlinux
+
# ##i##extlinux --install /boot/extlinux
+
# ##i##cd /boot
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# ##i##ln -s . boot
+
</console>
+
  
the next steps are different depending if you use an MBR or GPT setup and the HDD you installed on and want to boot from. Let us now for general take /dev/sda as your boot device.
+
Those addresses follows the thereafter logic:
  
=== MBR ===
+
{| class="wikitable"
 +
|-
 +
| colspan="2" | '''32 bits (fixed length)'''
 +
|-
 +
| '''Network''' part (variable length of N bits ) || '''Host''' part (length : 32 - N bits)
 +
|}
  
If you set up your disk with MBR partition scheme just do the next steps:
+
* The network address : this part is uniquely assigned amongst all of the organizations in the world (i.e. No one in the world can hold the same network part) 
 +
* The host address : unique within a given network part
  
<console>
+
So in theory we can have something like this (remember the network nature is not to be unique, it hs to be be a collection of networks  :
# ##i##dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/mbr.bin of=/dev/sda
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# ##i##cp /usr/share/syslinux/menu.c32 /boot/extlinux/
+
# ##i##cp /usr/share/syslinux/libutil.c32 /boot/extlinux/
+
# ##i##touch /boot/extlinux/extlinux.conf
+
</console>
+
  
=== GPT ===
+
* Network 1 Host 1
 +
*
  
<console>
 
# ##i##sgdisk /dev/sda --attributes=1:set:2
 
# ##i##sgdisk /dev/sda --attributes=1:show
 
1:2:1 (legacy BIOS bootable)
 
# ##i##dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sda
 
# ##i##cp /usr/share/syslinux/menu.c32 /boot/extlinux/
 
# ##i##cp /usr/share/syslinux/libutil.c32 /boot/extlinux/
 
# ##i##touch /boot/extlinux/extlinux.conf
 
</console>
 
  
== Setting up the Kernel ==
+
Just like your birthday cake is divided in more or less smaller parts depending on how guests' appetite, the IPv4 address space has also been divided into more or less smaller parts just because organizations needs more or less computers on their networks. How to make this possible? Simply by dedicating a variable number of bits to the network part! Do you see the consequence? An IPv4 address being '''always''' 32 bits wide, the more bits you dedicate to the network part the lesser you have for the host part and vice-versa, this is a tradeoff, always. Basically, having more bits in :
 +
* the network part : means more networks possible at the cost of having less hosts per network 
 +
* the host part : means less networks but more hosts per network
  
Now if you followed our advice to install lazykernel we have a pretty nice way to solve all the setup with a bit of prework and finish it then. If not you should go to the manual part. :)
+
It might sounds a bit abstract but let's take an example : imagine we dedicate only 8 bits for the network part and the remaining 24 for the hosts part. What happens?  First if we only
  
=== lazykernel way ===
+
  
As you setup lazykernel, we now need to edit /etc/lazykernel.conf
+
Is the network part assigned by each organization to itself? Of course not! Assignment are coordinated at the worldwide level by what we call Regional Internet Registries or RIRs which, in turn, can delegate assignments to third-parties located within their geographic jurisdiction. Those latter are called Local Internet Registries or LIRs (the system is detailed in RFC 7020). All of those RIRs are themselves put under the responsibility of now now well-known Internet Assigned Numbers Authority or [http://www.iana.org IANA]. As of 2014 five RIR exists :
 
+
make it to look like somethink like that:
+
* ARIN (American Registry for Internet Numbers) : covers North America
 
+
* LACNIC (Latin America and Caribbean Network Information Centre): covers South America and the Caribbean
<pre>
+
* RIPE-NCC (Réseaux IP Européens / or RIPE Network Coordination Centre): covers Europe, Russia and middle east
# After configuring, hash or remove line below.
+
* Afrinic (Africa Network Information Center) : covers the whole Africa
#CONFIGUREFIRST
+
* APNIC (Asian and Pacific Network Information Centre) : covers oceania and far east.
 
+
# Number of the kernels to keep so `lazykernel clean` will not propose to remove them. Default: 3
+
keep_kernels=5
+
 
+
# Sort kernels by 'version' (biggest version first) or by 'mtime' (latest images first). Default: mtime
+
# Sorting by version may fail and 3.3.0-rc2 will be marked as newer than 3.3.0.
+
#sort_by='version'
+
sort_by=mtime
+
 
+
# The name for menu entry.
+
menu_entry_name="Funtoo Linux"
+
 
+
# Specify what initramfs image to use, if any. (Optional)
+
initramfs='initramfs.cpio.gz'
+
 
+
# Append kernel params, usualy you use it to specify rootfs device, but you can use it to pass switches to initramfs as well. (Optional)
+
#kernel_params='root=/dev/sda2'
+
#kernel_params="rootfstype=ext4 luks enc_root=/dev/sda2 lvm root=/dev/mapper/vg-rootfs uswsusp resume=/dev/mapper/vg-swap"
+
kernel_params="rootfstype=ext4 luks enc_root=/dev/sdb3 lvm root=/dev/mapper/vg-root uswsusp resume=/dev/mapper/vg-swap"
+
</pre>
+
 
+
please make sure to comment out or delete the second line of the config file, else it will spit out an error for you... :)
+
 
+
Now let us setup our kernel with lazykernel if you have a manual kernel just run:
+
 
+
<console>
+
# ##i##cd <kernel build dir>
+
# ##i##lazykernel auto
+
</console>
+
 
+
that will generate the modules for you, copy your kernel form /usr/src/linux over to /boot and generate the /boot/extlinux/extlinux.conf for you. The manual kernel will be the only supported one by lazykernel.
+
 
+
That's all you are ready to boot. :)
+
 
+
=== manual extlinux.conf ===
+
 
+
For other kernels, like those created by genkernel or by the binary USE-flag you need to edit your config by yourself. Just open /boot/extlinux/extlinux.conf in your favorite editor and setup something like the following:
+
 
+
<pre>
+
TIMEOUT 30
+
UI menu.c32
+
 
+
MENU TITLE Boot Menu
+
MENU COLOR title        1;37;40
+
MENU COLOR border      30;40
+
MENU COLOR unsel        37;40
+
 
+
LABEL funtoo1
+
        MENU LABEL Funtoo Linux KERNEL-VERSION
+
        LINUX /<kernel>
+
        INITRD /<initramfs>
+
        APPEND rootfstype=ext4 luks enc_root=/dev/sdb3 lvm root=/dev/mapper/vg-root uswsusp resume=/dev/mapper/vg-swap
+
</pre>
+
 
+
That's all again you are ready for boot. You can also define several LABELs in that list to have multiple kernels been booted... :)
+
 
+
[[Category:HOWTO]]
+

Revision as of 17:52, January 16, 2014

WARNING: Work in progress. Do not edit this article unless you are the original author.


Refresh on TCP/IP model

When the ARPANet (a packet oriented network) was born in those good old seventies, engineers had to solve the problem of making computers being able to exchange packets of information over the network and they invented in 1974 something you are now using to view this page: TCP/IP! TCP/IP is a collection of various network protocols, being organized as a stack. Just like your boss does not do everything in the company and delegates at lower levels which in turn delegates at an even more lower level, no protocol in the TCP/IP suite takes all responsibilities, they are working together in a hierarchical and cooperative manner. A level of the TCP/IP stack knows what its immediate lower subordinate can do for it and whatever it will do will be done the right way and will not worry about the manner the job will be done. Also the only problem for a given level of the stack is to fulfill its own duties and deliver the service requested by the upper layer, it does not have to worry about the ultimate goal of what upper levels do.

<illustration goes here TCP/IP model>

The above illustration sounds horribly familiar : yes, it is sounds like this good old OSI model. Indeed it is a tailored view of the original OSI model and it works the exact same way: so the data sent by an application A1 (residing on computer C1) to another application A2 (residing on computer C2) goes through C1's TCP/IP stack (from top to bottom), reach the C1's lower layers that will take the responsibility to move the bits from C1 to C2 over a physical link (electrical or lights pulses, radio waves...sorry no quantum mechanism yet) . C2's lower layers will receive the bits sent by C1 and pass what has been received to the C2's TCP/IP stack (bottom to top) which will pass the data to A2. If C1 and C2 are not on the same network the process is a bit more complex because it involves relays (routers) but the global idea remains the same. Also there is no shortcuts in the process : both TCP/IP stacks are crossed in their whole, either from top to bottom for the sender or bottom to top for the receiver. The transportation process in itself is also absolutely transparent from an application's point of view: A1 knows it can rely on the TCP/IP stack to transmits some data to A2, how the data is transmitted is not its problem, A1 just assumes the data can be transmitted by some means. The TCP/IP stack is also loosely coupled to a particular network technology because its frontier is precisely the physical transportation of bits over a medium and so the physical network's technology, just the same way A1 does not care about how the TCP/IP stack will move the data from one computer to another. The TCP/IP stack itself does not care about the details about how the bits are physically moved and thus it can work with any network technology no matter the technology is Ethernet, Token Ring or FDDI for example.

The Internet layer

The goal of this article being more focused on calculation of addresses used at the Internet layer so let's forget the gory details of the TCP/IP stack works (you can find an extremely detailed discussion in How the TCP/IP stack works... to be written...). From here, we assume you have a good general understanding of its functionalities and how a network transmission works. As you know the Internet layer is responsible to handle logical addressing issues of a TCP segment (or UDP datagram) that has either to be transmitted over the network to a remote computer or that has been received from the network from a remote computer. That layer is governed by a set of strict set rules called the Internet Protocol or IP originally specified by [RFC 791] in september 1981. What is pretty amazing with IP is that, although its original RFC has been amended by several others since 1981, its specification remains absolutely valid! If have a look at [RFC 791] you won't see "obsoleted". Sure IPv4 reached its limits in this first half the XXIst century but will remains in the IT landscape for probably several years to not say decades (you know, the COBOL language....). To finish on historical details, you might find interesting know that TCP/IP was not the original protocol suite used on the ARAPANet, it superseded in 1983 another protocol suite the Network Control Program. NCP looks like, from our point of view, quite prehistoric but it is of big importance as it established a lot of concepts still in use today : PDU, splitting an address in various components, connection management and so on comes from NCP. Historical reward for those who are still reading this long paragraph: first, even a computer user was addressable in NCP messages second even in 1970 the engineers were concerned by network congestions issues (this page).

Let's go back to those good old seventies: the engineers who designed the Internet Protocol retained a 32 bits addressing scheme for IP and, afterall, the ARAPnet will never have the need to be able to address billions of hosts! If you look at some ARAPANet diagrams it counted less than 100 hosts in

who would ever need millions of addresses afterall? So in theory with those 32 bits we can have around 4 billions of computers within that network and arbitrarily retain that the very first connected computer must be given the number "0", the second one "1", the third one "2" and so on until we exhaust the address pool at number 4294967295 giving no more than 4294967296 (2^32) computers on that network because no number can be a duplicate.

Classful and classless networks

Those addresses follows the thereafter logic:

32 bits (fixed length)
Network part (variable length of N bits ) Host part (length : 32 - N bits)
  • The network address : this part is uniquely assigned amongst all of the organizations in the world (i.e. No one in the world can hold the same network part)
  • The host address : unique within a given network part

So in theory we can have something like this (remember the network nature is not to be unique, it hs to be be a collection of networks  :

  • Network 1 Host 1


Just like your birthday cake is divided in more or less smaller parts depending on how guests' appetite, the IPv4 address space has also been divided into more or less smaller parts just because organizations needs more or less computers on their networks. How to make this possible? Simply by dedicating a variable number of bits to the network part! Do you see the consequence? An IPv4 address being always 32 bits wide, the more bits you dedicate to the network part the lesser you have for the host part and vice-versa, this is a tradeoff, always. Basically, having more bits in :

  • the network part : means more networks possible at the cost of having less hosts per network
  • the host part : means less networks but more hosts per network

It might sounds a bit abstract but let's take an example : imagine we dedicate only 8 bits for the network part and the remaining 24 for the hosts part. What happens? First if we only


Is the network part assigned by each organization to itself? Of course not! Assignment are coordinated at the worldwide level by what we call Regional Internet Registries or RIRs which, in turn, can delegate assignments to third-parties located within their geographic jurisdiction. Those latter are called Local Internet Registries or LIRs (the system is detailed in RFC 7020). All of those RIRs are themselves put under the responsibility of now now well-known Internet Assigned Numbers Authority or IANA. As of 2014 five RIR exists :

  • ARIN (American Registry for Internet Numbers) : covers North America
  • LACNIC (Latin America and Caribbean Network Information Centre): covers South America and the Caribbean
  • RIPE-NCC (Réseaux IP Européens / or RIPE Network Coordination Centre): covers Europe, Russia and middle east
  • Afrinic (Africa Network Information Center) : covers the whole Africa
  • APNIC (Asian and Pacific Network Information Centre) : covers oceania and far east.