New Linux Kernel Introduced

Outside, it was a cold and rainy day. Inside, though, the convention center was bustling with warm bodies and even warmer servers. Tucked away in the .org pavilion was the Linux.com booth. The staff was rushing around, making sure all of the final details were ready, to the theme of "2001: A Space Odyssey."

The "2.4: A Kernel Odyssey" presentation at LinuxWorld 2001 New York was an overview of the 2.4.0 kernel and its various features. This live presentation by Brian Richardson introduced the audience to the new Linux kernel by stepping through the kernel configuration process.

This Linux.com Live! presentation demonstrated how to upgrade an existing Linux system to use the 2.4 kernel. Our demonstration machine was a VA Linux workstation (PIII 850 MHz, 384 MB RAM, 20 GB IDE disk) running Storm Linux ('Hail' version 2.06).

Sit back, relax, and enjoy this retelling of Linux.com's epic kernel presentation.

Precompile
Before an unsuspecting victim was selected from the audience, Brian explained a few things that you have to do to prepare for recompiling your kernel. One of the most important things to do is check to see exactly what type of hardware you have on your computer. When you configure the kernel for your system, you have to be able to tell it what hardware you have on your system, so that it knows how to communicate with your specific system. Take a look at all of the files in /proc. This will have all of the information about your system, just make sure you know how to interpret it. Also, you can find out exactly what you have if you keep all of the paperwork that companies send you with your computer or with the different components. If you have any other questions about preparing your computer for a recompile, take a look at Brian Richardson's article Before downloading the kernel source code, it is also a good idea to upgrade modutils. The modutils package contains utilities used to load modules for the Linux kernel. Since the 2.4 kernel changed the location of some modules, certain devices may not work unless a newer version is installed. This software can be downloaded from rpmfind, freshmeat, or kernel.org.

Downloading the Kernel
Once you have finished preparing for the recompile, you will need to download the kernel source code. There are two places you can go for this. You can go to the Linux Kernel Archives or you can go to one of the mirrors of this site. You will need to download either linux-2.4.x.tar.gz or linux-2.4.x.tar.bz2. For our demonstration, we downloaded linux-2.4.0.tar.gz and for the rest of this event we will refer to this file.

Note: The kernel is distribution independent. It does not matter which distribution you are running on your computer, you will need the same kernel for all of them.

For the sake of time constraints, we completed all of these above tasks before the event. As soon as Brian finished going through these events, we asked the audience for a volunteer. A few people hesitantly raised their hands, unsure of what they were volunteering for. Our volunteer had never actually compiled a kernel before, the perfect victim for our plans. The participant sat down in front of the computer and began the kernel configuration process.

Prepping for the New Kernel
One of the most important things that you must remember when you are preparing to compile the kernel is that you must be root on your system. If you are not currently root, then type in su and the system will prompt you for the root password. Once you are root, type in cd /usr/src. This will move you to the source directory. You will then need to copy linux-2.4.0.tar.gz into this directory. When this is copied, look at the contents of this directory. Make sure there are no symbolic links called 'linux'. If there are, remove them by typing rm /usr/src/linux.

Unpacking the Kernel
Once the symbolic link is removed, we then needed to unpack the kernel source. When it is downloaded, it is packed into a tarball. For Windows users, this is the same thing as zipping a file. In order to unpack the kernel source, type tar xvzf linux-2.4.0.tar.gz. This will unpack the kernel source into the directory you are in, so make sure that you are in the /usr/src directory. This creates the directory /usr/src/linux, which contains the 2.4.0 kernel source tree.

The /usr/src/linux directory should be renamed to refer to the kernel version; type mv /usr/src/linux /usr/src/linux-2.4.0. This keeps the kernel source organized, in case you keep more than one version available. Now create a symbolic link to the 2.4.0 kernel tree. In order to create the symbolic link, type ln -s /usr/src/linux-2.4.0 /usr/src/linux. You will now need to change to the new directory; type cd /usr/src/linux.

Running Config You are now in the new directory. Now comes the long, but necessary process of configuring the kernel. You will need to run one of the configuration tools so that the computer knows what parts of the kernel to compile, what to keep as modules or what to not worry about. There are three different configuration tools that a user can run.

• A text based config tool is make config. This is very primitive, so if you like something that is a little bit more graphically oriented, this is not the tool for you to run.

• The make menuconfig is also text based, but it is menu driven. In order to run this, you will need to have the ncurses library installed.

• The make xconfig tool requires the X Window System, but it is menu driven and has a graphical interface. We used this one for our demonstration.

Once xconfig is started, the kernel options are presented as a series of menus. We will list all of these categories in italics. If you don't know what something does, click on the help button. This will explain the option. If you are still stumped, read the last line of the help description ... this will usually tell you if you need the option or not.

Every kernel option has one of three selectable states:

• 'y' (yes) - include this support in the kernel

• 'n' (no) - do not include this support

• 'm' (module) - include this as a module, which is only loaded on demand

Note: If an option is 'greyed out', it is dependent on another options which has been turned off.

• Code Maturity Level Options
  This gives the user the chance to automatically disable any experimental code in the kernel. Enable this at your own discretion.

• Loadable Module Support
  Loadable module support allows parts of the kernel to be loaded only when needed. You will want to turn all of these options on, as this will allow you to select the option 'module' or 'm' later on in the configuration process.

  

• Processor Type and Features
  This section allows for optimization of specific processor types. In this kernel, support was added for AMD Athlon and Duron, P4, WinChip, Via/Cyrix and Crusoe. If your motherboard supports more than one CPU, enable SMP here. Support for large memory systems (1GB RAM or larger) is also an option here. Users will want to enable MTRR and MSR if they have a K6, PPro, PII, PIII, P4, Celeron, Duron or Athlon. MTRR is used by most AGP drivers. Users will also want to enable cpuid support for any CPU except a 384 or 486.
  
  Note: This menu will look different if you are on a non-x86 machine.
  Note: The kernel may not boot if you compile for the wrong CPU, so make sure you select the correct processor.

• General Setup
  General setup includes support for networking, expansion bus, module format and power management. You will want to enable 'Support for hot-pluggable devices' if you want to use FireWire, USB or PCMCIA with your computer. You will also want to enable PCI support. We disabled MCA, EISA and PCMCIA for our machine. If you are running a notebook, enable PCMCIA. If you have PCI bus, then enable 'PCI Device Name Database' and leave 'PCI Access Mode' as Any. Advanced Power Management (APM) support is only necessary for notebook power management.

• Memory Technology Devices
  This is new to Kernel 2.4. 'Disk on chip' style storage is supported here. This section is useful for embedded platforms. We will not enable this for our system.

• Parallel Port Support
  If you have an parallel devices, such as printers or other hardware that plugs into your parallel port, then you will want to enable this support. We will not enable this option, as we don't have any devices for it.

• Plug and Play
  This is for, you guessed it, plug and play devices. You will want to turn this on as a module. It will then load if needed.

• Block Devices
  Standard floppy support is in this section. ATAPI/IDE drive options were listed here in 2.2.x kernels, but they were moved to a new section. Options for some 'antique' storage devices are also located here.

• Multi-Device Support (RAID and LVM)
  RAID and clustering storage device support can be found here. Most people will not need to worry about this.

  

• Networking Options
  If you have your computer set up on any network, LAN, modem or otherwise, then you will need to pay attention to this section. You will need to turn on 'Packet Socket,' 'TCP/IP' and 'UNIX Domain Sockets' for any network cards or standard Internet access . If you are curious about using 'network packet filtering' instead of ipchains for firewall configurations, please consult additional documentation.

• Telephony Support
  This is not for modems. This support is used for voice mail, fax and other multimedia devices that interface with modems. No telephony ... no need for the support.

  

• ATA/IDE/MFM/RLL Support
  This support is compiled directly into the kernel, rather than as a module, because we will be booting off of an IDE hard drive. If you are using an ATAPI CD-RW, then you will need to turn 'SCSI Emulation' on in this section (see our CD-RW article for details). ATAPI/IDE devices that had been moved from the Block Devices section are listed in a submenu here.

  If you have an IDE hard drive, then you will need to select support for the proper IDE hard disk controller (this was part of the information you should have gathered in the precompile section). We turned on support for an Intel PIIX4 (also directly part of the kernel, not as a module). Turn off support for controllers that you don't need, as this will optimize your kernel.

• SCSI Support
  Support for a SCSI controller needs to be enabled here if you have one or if you enabled SCSI emulation earlier. If you are booting from a SCSI card, you will need to enable the proper one here in the 'SCSI Low-level Drivers' sub menu. SCSI support is a lso required for 'USB Mass Storage' ... but that's another article.

• IEEE 1394 (Fire Wire) Support
  This is still experimental, so most users will want to leave this alone.

• I2O Device Support
  If you have this, you paid quite a lot of money for it. You know if you have this and you should know what to do with it (or can afford somebody who does). Most people will leave this alone.

• Network Device Support
  Users will want to select the type(s) of network adapters that are present on their systems. For our system, we just want to select 'Ethernet 10/100' as that is the only type of adapter that we have present. In the submenu, we will select the Intel EtherExpress 100. If your ISP requires PPP, then you will want to enable this. This is also valid for DSL services that use PPPoE.

• Amateur Radio Support
  This section deals with transmitting data using a HAM radio. This is not new to Kernel 2.4. If you want more information, you can go to this site.

• IrDA Support
  IrDA are infrared devices. Users who own notebooks will mainly be concerned with this. There is a great web site for the Linux/IrDA Project, if you would like some more information on this topic.

• ISDN Subsystem
  We sincerely hope that you have better bandwidth than this. If you do not, you have our sincerest apologies. Contact your ISP if you have any questions about this.

• Old CD-ROM Drivers
  This section is for old CD-ROMs that attach to the sound card. Most people will not need to worry about this.

• Input Core Support
  Input core support is for USB input devices. This includes everything from USB mice to USB keyboards and joysticks. In this section, we turned on support for a USB keyboard, as this is one of the items that we demonstrated at the end of the event.

• Character Devices
  Character devices include everything from serial ports and TTY devices to speech synthesizer cards. At the end of our demonstration, we also set up a speech synthesizer card so that people could listen to the computer talk to them. Although speech synthesizer support is not new to Linux, it is new to the kernel itself. Kernel 2.4 has finally integrated speech synthesizer support into the source. In this section, we also enabled standard serial support and support for a PS/2 mouse. If you want X terminals to work, you will need to enable Unix98 PTY support. Vmware needs enhanced real time clock support enabled as well. Under Character Devices, there is AGP support. We enabled this for our chipset. If you do not know what your chipset is, this should be in the information you obtained during the precompile process.

• Multimedia Devices
  Video for Linux support is in this menu. This includes TV tuner cards, video capture and FM radio cards. We do not have any of these, so we left this section alone.

  

• File Systems
  This section determines what types of file systems can be mounted. Users will always want to include 'ext2' support. Also, if you would like to read files from a Windows partition on your computer, then enable 'DOS FAT fs' support, as well as 'VFAT fs' support. In order to read CD-ROM and ISO formats, you will need to include 'ISO 9660' and Joliet support.
  Note: Always include '/proc file system' support.
  

• Console Drivers
  For this section, the user will always want to include 'VGA text console' support. Also the user might want to select 'Video mode selection' support in order to take advantage of higher resolutions for text mode.

  

• Sound
  If your computer has a sound card or on-board sound (the sound card is built into the motherboard) you will at least want to enable sound support. Once you have enabled it, find your sound card in the list and enable that as well. Remember how we told you to upgrade your modutils? If you didn't, then your sound is not going to work (trust us, we learned that lesson the hard way).

  

• USB Support
  This support is new to Kernel 2.4. Remember to always turn on 'USB verbose debug messages' as well as 'Preliminary USB device file system.' You will then need to select the appropriate USB support. This is an important time to determine if you have a 'UHCI' or 'OHCI' USB controller ... Intel and VIA chipsets use UHCI, everybody else uses OHCI.
  Our Intel motherboard has an Intel PIIX4 USB controller, so the 'UHCI (Intel PIIX4, VIA, ...) support' option was selected (not as a module, but directly into the kernel). We also selected 'USB Human Interface Device (HID) support' to enable our USB keyboard and trackball.
  

• Kernel Hacking
  Congratulations! You've gotten to the very end of the config tool. This last option is mainly for hackers. Go ahead and enable it, though. If something breaks, then you can invite your kernel hacker friend to fix your system (with the proper bribe of pizza and caffeine).

Once you have gotten through all of these options, you will be returned to the main menu. Please click 'Save & Exit' ... that's 'Save & Exit', not just 'Exit'. If you exit without saving, you will have lost all of the information that you had and you'll have to go through the process of running the config tool all over again.

Compiling the Kernel
We finally got through the whole xconfig tool. Since we still had an audience, we figured we were doing something right. We had also gotten to the really important part. It was time to compile the kernel. Before we actually compiled it, though, we needed to quickly modify LILO so that if something went wrong, we could still boot into the stable version that was still in the computer.

In order to do this, we had our victim ... er, volunteer change to the /boot directory. We then found the symbolic link 'vmlinuz.' Our older kernel version was 2.2.15, so we created a link from /boot/vmlinuz-2.2.15 to stable (ln-s vmlinuz-2.2.15 stable). Once this link is created, you will need to edit /etc/lilo.conf using your preferred text editor. You will create a new set of instructions, to create /boot/stable as well as the /boot/linux. Save the changes, exit the editor and then type 'lilo' to reconfigure the boot loader.

Don't worry folks ... almost finished. It is now time to type the commands that will compile the kernel on your system. You have a couple choices in how you type these commands. You can either type them one at a time, or you can put them together, separating each part with just a space. Listed below are both ways of doing this.

make dep
make clean
make install
make modules
make modules_install

OR

make dep clean install modules modules_install

Note: you can also create a boot floppy using the make bzfloppy command

After these commands finished running their course, we were done (kernel compile time is dependent on system speed ... this took about 7 minutes on our computer). The computer was rebooted and 'linux' was selected from lilo at boot.

The 2.4.0 kernel compile was a success! The demonstration machine booted straight to Linux ... we were even able to use the USB keyboard. Thanks to our willing victim and the help of our audience members (and remote audience on IRC), we were able to get through the entire compiling process.

Out presentation had the support of a trained presenter and several hard-core Linux geeks. But you don't need an entire Linux convention to compile a kernel. If you ever run into any kernel problems and can not find the solution on your own, there are channels that you can go to on IRC that have people who can help. Both #kernelnewbies and #linuxhelp on irc.openprojects.net are good places to go searching for help. Even if they can not answer your question directly, these folks will be able to give you a web page to that will help.