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Computer System Laboratory

Computer System Laboratory. Lab6 - Root Filesystem. Experimental Goal. Learn how to build your own root filesystem for PXA270. Environment. Host System Windows XP Build System VirtualBox + Ubuntu 8.04 Target System Creator XScale PXA270 Software BusyBox Compiled toolchain

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Computer System Laboratory

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  1. Computer System Laboratory Lab6 - Root Filesystem

  2. Experimental Goal • Learn how to build your own root filesystem for PXA270. / 22

  3. Environment • Host System • Windows XP • Build System • VirtualBox + Ubuntu 8.04 • Target System • Creator XScale PXA270 • Software • BusyBox • Compiled toolchain • mkfs.jffs2 & genext2fs utility • You can download all software from RSWiki CSL Course Software / 22

  4. Introduction to Root Filesystem • A file system is a method of storing and organizing computer files and their data. • A root filesystem is the file system that is contained on the same partition on which the root directory, i.e., / in Linux, is located. • The exact contents of the root filesystem will vary according to the computer, but they will include the files that are necessary for booting the system. reference: linfo: root filesystem, http://www.linfo.org/root_filesystem.html / 22

  5. Memory Layout of PXA270 • 32MB Flash ROM • Addressing from 0x00000000 • 64MB SDRAM • Addressing from 0xa0000000 / 22

  6. Basic Root Filesystem Structure • Root filesystem follows FHS (Filesystem Hierarchy Standard). • FHS has the guideline of your filesystem. / 22

  7. Types of Filesystems • Some well-known filesystems • Windows : FAT, NTFS • Mac OS X : HFS Plus, UFS • Linux : ext*, XFS, JFS, ReiserFS • We will use JFFS2 & ext2 in this lab. • JFFS2 (Journaling Flash File System Version 2) • A journaling file system. • Writable, compressed, power-down-reliable file system. • ext2 (The second extended filesystem) • A non-journaling file system. • Writable. / 22

  8. Create Root Filesystem Skeleton • Step1: create a folder for placing root filesystem content. • % mkdir $HOME/<root filesystem folder’s name> • Step2: create the essential directories. • % cd <the path in step1> • % mkdiretc lib varprocmntdevtmp / 22

  9. Compiled Toolchain Installation • To compile BusyBox, we need to install another cross-compiler. • Step1: download cross-compiler (cross-2.95.3.tar.bz2). • Step2: extract the compiler. • % tar jxvf cross-2.95.3.tar.bz2 • Step3: move files to specified location. • % sudomkdir –p /usr/local/arm • % sudo mv 2.95.3 /usr/local/arm • Step4: append installation directory (bin) to PATH. • Test new cross-compiler. • % arm-linux-gcc -v / 22

  10. Build BusyBox (1/3) • BusyBox contains a collection of stripped-down Unix utilities into a single executable. • Why BusyBox? • You don’t have to configure and build the sources of each utility. • Step1: download BusyBox (busybox-1.00.tar.gz). • Step2: extract the source codes. • Step3: copy header from kernel source codes of Lab5. • % cd busybox-1.00 • % cp –R <creator mt-linux path>/pxa270/linux/include/linuxinclude / 22

  11. Build BusyBox (2/3) • Step3: download Linux verison.h. • % wgethttp://eraser.csie.ntu.edu.tw/courses/csl/10201/lab6/software/version.h • % cpversion.h include/linux • Step4: configure BusyBox. • % make menuconfig • Build Options  • Networking Utilities  / 22

  12. Build BusyBox (3/3) • Step5: compile BusyBox. • % make -j4 • Step6: install BusyBox. • % make -j4 install • Step7: move files to your root filesystem folder (slide8). • % mv _install/* <root filesystem folder’s path> / 22

  13. Create Essential Device Files (1/3) • Device files allow user programs to access hardware devices on the system through the kernel. • The kernel just relies on device file’s type and major number to find which driver manages this device. / 22

  14. Create Essential Device Files (2/3) • The official information for device major and minor numbers can be found in Documentation/devices.txt under the kernel source codes. • We can use mknod command to create device files in Linux, e.g., if we want to create a character ttyS0 device with major number 4 and minor number 64: • % mknod ttyS0 c 4 64 / 22

  15. Create Essential Device Files (3/3) • For the convenience, we use a script to create related device files for our root filesystem: • % wget http://eraser.csie.ntu.edu.tw/courses/csl/10201/lab6/software/mknod.sh • % cp mknod.sh <root filesystem folder’s path>/dev • % cd <root filesystem folder’s path>/dev • % sudosh mknod.sh • % rmmknod.sh / 22

  16. Add Initialization Scripts (1/2) • Step1: add configuration file used by first user-space program (i.e. /sbin/init). • % wget http://eraser.csie.ntu.edu.tw/courses/csl/10201/lab6/software/inittab • % cpinittab<root filesystem folder’s path>/etc • inittab describes which processes are started during bootup. • The entry syntax of inittab. • id : runlevels : action : process ::sysinit:/etc/rcS ::askfirst:/bin/sh • sysinit: execute the process during system boot • askfirst : prompt “Please press Enter to activate this console.” before execution • Some other actions: respawn, ctrlaltdel / 22

  17. Add Initialization Scripts (2/2) • Step2: add system initialization script (rcS). • % wget http://eraser.csie.ntu.edu.tw/courses/csl/10201/lab6/software/rcS • % cprcS<root filesystem folder’s path>/etc • Step3: change permission. • % cd <root filesystem folder’s path>/etc • % chmod 777 inittabrcS • Please refer to the website below for more information. • http://linux.vbird.org/linux_basic/0510osloader.php#startup_init / 22

  18. Create Root Filesystem Image (1/2) • Step1: make a JFFS2 file system image. (Download mkfs.jffs2) • % chmod +x mkfs.jffs2 • % ./mkfs.jffs2 -v -e 0x20000 --pad=0xf00000 -r <root filesystem folder’s path> -o rootfs.jffs2 • You can see the mkfs.jffs2 usage by executing without arguments. • Step1: or a ext2 file system image. (Optional) • Install genext2fs package in Ubuntu 8.04. • % genext2fs -b 15360 -d <root filesystem folder’s path> -e 0 rootfs.ext2 • Please refer to the website below for the genext2fs usage. • http://csurs.csr.uky.edu/cgi-bin/man/man2html?genext2fs / 22

  19. Create Root Filesystem Image (2/2) • Step2: now, you can copy rootfs.* image to PXA270. • If you choose ext2 format for your root filesystem, you need to change rootfstype in bootargs environment variable in U-Boot. • u-boot$ setenvbootargs root=/dev/mtdblock3 rwrootfstype=ext2 console=ttyS0,9600n8 mem=64M ip=... • u-boot$ saveenv / 22

  20. Change Filesystem Image Size (1/2) • Recall Lab5, if we want to change the size of filesytem, we need to modify creator_pxa270_partitions[] in Linux kernel. • Also, the corresponding arguments are required to be set in mkfs.jffs2 and genext2fs commands, e.g. a 15M root filesystem. • % ./mkfs.jffs2 -v -e 0x20000 --pad=0xf00000 -r <root filesystem folder’s path> -o rootfs.jffs2 • % genext2fs -b 15360 -d <root filesystem folder’s path> -e 0 rootfs.ext2 / 22

  21. Change Filesystem Image Size (2/2) • Now, please refer to previous slides to increase the size of your root filesystem to 20M and add tftp client utility. • Please calculate new erased end address for root filesystem. • It will take about 8 minutes to copy new 20M root filesystem. • You can use “df -h” command to check the size. • You can add tftp client utility to BusyBox. / 22

  22. Lab Requirement & Bonus • Show that you can use tftp on your Linux kernel which has a 20M filesystem. • Bonus:Answer the question of lab6 on RSWiki CSL course website.Write it in your report. • Please send your report to both TAs. • csiedatou@gmail.com, meenchen79@gmail.com • Please use this title format: [CSL] G# Lab# Ver# • E.g., [CSL] G13 Lab6 Ver1 / 22

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