Linux Distribution: Kernel Configuration

Size: px

Start display at page:

Download "Linux Distribution: Kernel Configuration"

Leo Wilson
5 years ago
Views:

1 Instituto Superior de Engenharia do Porto Mestrado em Engenharia Eletrotécnica e de Computadores Arquitetura de Computadores Linux Distribution: Kernel Configuration The central element of a GNU/Linux distribution is the kernel of the operating system, "Linux" itself. The purpose of this tutorial is to configure, build and test a Linux kernel to be used in a dedicated distribution for a x86 machine. Note: this task will take about 1 GB of disk space for the kernel source code and object files created during compilation Obtaining kernel source 1) If you have not done this in previous classes, create a directory named with you student number (mkdir student_number) and use it as a working directory (cd student_number). 2) Get the kernel source code from Get the archive corresponding to the most recent stable version. 3) Extract the files from the archive: tar xvf ARCHIVE_PATHNAME where ARCHIVE_PATHNAME is the name of the downloaded file, including the path to it (e.g., ~/Downloads/Linux.tar.bz2). Run the ls command. You should see a new directory (e.g., linux ). Change to that directory. Configuration 4) Create a new configuration without any selected item: make allnoconfig 5) Go to the setup menu (for i386 architecture): make xconfig ARCH=i386 Note: You may have to install the qt-devel, qt-config and gcc-c++ packages. Linux Distribution: kernel configuration 1/6

2 6) You should go through the following main options (explained in more detail below): General setup Enable the block layer Processor type and features Bus options Executable file formats / Emulators Device drivers File systems Under General setup : Uncheck the Embedded system and Configure standard kernel features (expert users) options. Fill out the "Local version - append to kernel release" with a string that identifies the group (e.g., student numbers). Check "Initial RAM filesystem and Ram disk". This necessary if you plan to use of an initrd later. The ".config kernel support" allows for configuring the kernel in the / proc. It is an essential option, but allows you to recover the configuration of the kernel in case the original configuration file is lost. Select the "Enable block Layer" option. Under Processor type and features : The target system used in these classes is based on a Pentium MMX processor (i586). Select that family of processors. The target systems of this kernel will have less than 1 GiB of RAM. In this situation, the best setting for the "High memory support" option is "off". For multimedia applications, and in general, when you want to minimize the response time, you should select the "Preemptible Kernel (Low-Latency Desktop)" option and a high "Timer frequency". Under Bus options, select the support for the PCI bus. Under Executable file formats / Emulators, select the support for the format of executable commonly used in Linux distributions (ELF). Select also "Kernel support for scripts starting with #!". Under Device Drivers : Under Generic Driver Options, select Maintain a devtmpfs filesystem to mount at /dev as also the respective Automount sub-option. Under Block devices, select Loopback device support and RAM block device support. The last option is essential to the initrd mechanism. Linux Distribution: kernel configuration 2/6

3 Select "SCSI disk support" under SCSI device support. This is required to enable support for USB storage devices (in usb_storage option, you can find the following note "NOTE: usb_storage depends on SCSI but BLK_DEV_SD may also be needed"). Uncheck SCSI low-level drivers. The ATA support will be required in order to use disk emulation in QEMU, as also to support physical SATA/PATA on the final target. Check Serial ATA and Parallel ATA drivers and, under this group, Intel ESB, ICH, PIIX3, PIIX4 PATA/SATA support. Check USB support, Support for Host-side USB and select the USB controller driver corresponding to the one in the target PC (USB 1.1, "OHCI HCD support"). Select also "USB Mass Storage support". Under File systems : Check the support for The Extended 4 (ext4) filesystem. Under Pseudo filesystems o Check /proc file system support. o Check Tmpfs virtual memory file system support Compilation and test (static version) 7) Compile the kernel for the i386 processor architecture (the -j option lets you choose the number of tasks that will be run in parallel, in order to take advantage of multiple processor cores): make ARCH=i386 -j 8 After this, you should find the bzimage file under arch/x86/boot/. This is the resulting kernel image. Create a copy of this file, named bzimage-static, in the build directory: mkdir -p../build cp.config../build/config-static cp arch/x86/boot/bzimage../build/bzimage-static The expected directory structure is the following: ~/student_number/build ~/student_number/linux-xxx 8) Test the created kernel using the QEMU emulator. In order to do that, download the system image available at the course web site, rootfs.ext4.gz, into the ~/student_number directory and decompress it (gunzip../rootfs-x86.ext4.gz). Finally, test your kernel with the following command line: qemu-system-i386 -kernel arch/x86/boot/bzimage -append "root=800"../rootfs-x86.ext4 Linux Distribution: kernel configuration 3/6

4 Upload your work 9) Log in to your account on ave.dee.isep.ipp.pt and create the following directory: WWW/arcom. This will create a new directory in your web area, which should be accessible as 10) Upload the kernel image and configuration to the arcom directory in your web area on ave.dee.isep.ipp.pt. The kernel configuration is stored in the hidden file ".config", located in the kernel source directory. Append the suffix -static to the copies of both files and remove the dot from the.config file. Assuming the current directory is student_number/linux-xxx: scp.config student_number@ave.dee.isep.ipp.pt:www/arcom/config-static scp arch/x86/boot/bzimage student_number@ave.dee.isep.ipp.pt:www/arcom/bzimage-static Confirm the files are accessible by HTTP ( Loadable kernel modules (LKM) The next objective is to create a new version of the kernel with some components selected as "loadable kernel module." 11) Start by enabling the support for loadable modules ("Enable loadable Module support"). 12) Under File Systems => DOS/FAT/NT Filesystems : Select the VFAT option as a loadable module. Enter the value 860 as Default codepage for FAT. In "Native language support", select the NLS ISO , codepage 860 and NLS UTF-8 options as static modules (check mark). Set the Default NLS Option to utf8. 13) Check Network support. Select the Packet socket, Unix domain sockets and TCP/IP networking options. Under Device Drivers and Network device support, select Ethernet driver support. Next, you should select, as loadable kernel modules, the device drivers for two different ethernet controllers: Under Intel devices, select the Intel PRO/1000 Gigabit Ethernet driver. This will be used for the QEMU network controller. under Realterk devices, select the RealTek RTL-8129/8130/8139 PCI Fast Ethernet Adapter support driver. This will be used for the test PC network controller. Linux Distribution: kernel configuration 4/6

5 Compilation and test (LKM version) 14) Build the kernel using the new configuration 15) Create a copy of the generated modules in../build/modules: mkdir -p../build/modules cp $(find. -name *.ko)../build/modules/ 16) Copy all modules to the file system contained in rootfs-x86.ext4: mkdir -p m mount../rootfs-x86.ext4 m cp -a../build/modules m/ umount m 17) Test the new kernel using QEMU, the changed rootfs-x86.ext4 file system image and your USB disk from the previous classes: su qemu-system-i386 -kernel arch/x86/boot/bzimage -append "root=800" \ -hda../rootfs-x86.ext4 -hdb /dev/sdb1 -net nic,model=e1000 -net user After logging in, in the emulator, load every LKM, using the insmod command. Recall that the modules should be found in /modules. Mount the first partition of your USB disk on /mnt. Notice that this partition is identified as the second disk of the emulated machine: o mount /dev/sdb /mnt o ls /mnt Restart the network configuration 1 and test the network access using the wget command (note that the ping utility does not work on QEMU): o udhcpc o wget 18) Create a copy of the bzimage and.config in../build, adding the suffix "-lkm" to the name of the original files. Check the increment in the kernel image size. cp arch/x86/boot/bzimage../build/bzimage-lkm cp.config../build/config-lkm du -k../build 1 udhcpc is a DHCP client, part of the busybox package. Linux Distribution: kernel configuration 5/6

6 Support for graphics modes through frame buffer Still following the previous configuration, build a new kernel with Support for frame buffer devices (under Device drivers, Graphics support ). Under Frame buffer devices, select VESA VGA graphics support. Additionally, select the Framebuffer Console support and Bootup logo options. All previous options should be selected as static (check mark). Compile the kernel and test it on QEMU: qemu-system-i386 -kernel arch/x86/boot/bzimage \ -append "root=800 vga=0x311" -hda../rootfs-x86.ext4 The boot screen should present a picture of Tux, the mascot of the Linux kernel. Create a copy of the bzimage and.config in../build, adding the suffix "-fb" to the name of the original files. Upload your final work The following commands assume the current directory is ~/student_number/build: sftp student_number@ave.dee.isep.ipp.pt cd WWW/arcom pwd (check the remote directory) lpwd (check the local directory mkdir modules put * cd modules put modules/* quit Linux Distribution: kernel configuration 6/6

Cross-compilation with Buildroot

Instituto Superior de Engenharia do Porto Mestrado em Engenharia Eletrotécnica e de Computadores Arquitetura de Computadores Cross-compilation with Buildroot Introduction Buildroot is a tool that can be