【背景】
折腾：
【记录】尝试用QEMU模拟ARM开发板去加载并运行Uboot，kernel，rootfs
期间，折腾完毕，可以运行kernel：
后，接着再去参考那人的教程：
去弄rootfs。
【折腾过程】
1.先去交叉编译busybox：
【记录】Ubuntu下为QEMU的arm平台交叉编译BusyBox
2.再去用cpio创建压缩格式的rootfs：
crifan@ubuntu:busybox-1.16.0$ ls applets busybox.links console-tools editors _install loginutils Makefile.help procps shell util-linux arch busybox_unstripped coreutils examples INSTALL mailutils miscutils README sysklogd archival busybox_unstripped.map debianutils findutils libbb Makefile modutils runit testsuite AUTHORS busybox_unstripped.out docs include libpwdgrp Makefile.custom networking scripts TODO busybox Config.in e2fsprogs init LICENSE Makefile.flags printutils selinux TODO_config_nommu crifan@ubuntu:busybox-1.16.0$ cd _install/ crifan@ubuntu:_install$ find . . ./usr ./usr/bin ./usr/bin/traceroute ./usr/bin/setkeycodes ./usr/bin/ar ./usr/bin/sha512sum ./usr/bin/setsid ./usr/bin/pscan ./usr/bin/arping ./usr/bin/script ./usr/bin/length ./usr/bin/ifplugd ./usr/bin/nohup ./usr/bin/seq ./usr/bin/cryptpw ./usr/bin/nc ./usr/bin/find ./usr/bin/hostid ./usr/bin/mkfifo ./usr/bin/ipcs ./usr/bin/cmp ./usr/bin/bunzip2 ./usr/bin/logger ./usr/bin/ether-wake ./usr/bin/unexpand ./usr/bin/passwd ./usr/bin/sha256sum ./usr/bin/cut ./usr/bin/head ./usr/bin/tee ./usr/bin/tr ./usr/bin/runsv ./usr/bin/lzopcat ./usr/bin/tac ./usr/bin/deallocvt ./usr/bin/softlimit ./usr/bin/tail ./usr/bin/[ ./usr/bin/eject ./usr/bin/vlock ./usr/bin/wget ./usr/bin/yes ./usr/bin/fdformat ./usr/bin/tty ./usr/bin/envuidgid ./usr/bin/env ./usr/bin/last ./usr/bin/install ./usr/bin/sum ./usr/bin/uniq ./usr/bin/who ./usr/bin/runsvdir ./usr/bin/id ./usr/bin/whoami ./usr/bin/[[ ./usr/bin/killall5 ./usr/bin/tftpd ./usr/bin/dos2unix ./usr/bin/nslookup ./usr/bin/dirname ./usr/bin/ftpput ./usr/bin/du ./usr/bin/top ./usr/bin/sha1sum ./usr/bin/beep ./usr/bin/fuser ./usr/bin/kbd_mode ./usr/bin/realpath ./usr/bin/chat ./usr/bin/setuidgid ./usr/bin/nmeter ./usr/bin/lpq ./usr/bin/resize ./usr/bin/lzmacat ./usr/bin/envdir ./usr/bin/lpr ./usr/bin/readlink ./usr/bin/hd ./usr/bin/ftpget ./usr/bin/uptime ./usr/bin/timeout ./usr/bin/uuencode ./usr/bin/hexdump ./usr/bin/fold ./usr/bin/printf ./usr/bin/tcpsvd ./usr/bin/crontab ./usr/bin/patch ./usr/bin/readahead ./usr/bin/uudecode ./usr/bin/renice ./usr/bin/time ./usr/bin/cal ./usr/bin/pgrep ./usr/bin/wall ./usr/bin/tftp ./usr/bin/showkey ./usr/bin/udpsvd ./usr/bin/clear ./usr/bin/mkpasswd ./usr/bin/free ./usr/bin/basename ./usr/bin/chrt ./usr/bin/which ./usr/bin/strings ./usr/bin/awk ./usr/bin/unzip ./usr/bin/logname ./usr/bin/comm ./usr/bin/ttysize ./usr/bin/md5sum ./usr/bin/unlzop ./usr/bin/chvt ./usr/bin/mesg ./usr/bin/less ./usr/bin/bzcat ./usr/bin/expr ./usr/bin/xargs ./usr/bin/openvt ./usr/bin/split ./usr/bin/microcom ./usr/bin/bzip2 ./usr/bin/rx ./usr/bin/reset ./usr/bin/killall ./usr/bin/chpst ./usr/bin/sort ./usr/bin/sv ./usr/bin/ipcrm ./usr/bin/dc ./usr/bin/cksum ./usr/bin/unlzma ./usr/bin/telnet ./usr/bin/od ./usr/bin/volname ./usr/bin/wc ./usr/bin/unix2dos ./usr/bin/dumpleases ./usr/bin/diff ./usr/bin/test ./usr/bin/expand ./usr/bin/pkill ./usr/bin/rtcwake ./usr/sbin ./usr/sbin/telnetd ./usr/sbin/rdev ./usr/sbin/setfont ./usr/sbin/udhcpd ./usr/sbin/sendmail ./usr/sbin/svlogd ./usr/sbin/inetd ./usr/sbin/ftpd ./usr/sbin/lpd ./usr/sbin/chpasswd ./usr/sbin/crond ./usr/sbin/chroot ./usr/sbin/fbset ./usr/sbin/brctl ./usr/sbin/rdate ./usr/sbin/dnsd ./usr/sbin/fakeidentd ./usr/sbin/setlogcons ./usr/sbin/dhcprelay ./usr/sbin/popmaildir ./usr/sbin/httpd ./usr/sbin/loadfont ./usr/sbin/readprofile ./bin ./bin/hostname ./bin/date ./bin/ping6 ./bin/pipe_progress ./bin/stty ./bin/run-parts ./bin/vi ./bin/msh ./bin/egrep ./bin/gunzip ./bin/addgroup ./bin/more ./bin/usleep ./bin/linux64 ./bin/mt ./bin/uncompress ./bin/sleep ./bin/iptunnel ./bin/zcat ./bin/ps ./bin/iproute ./bin/linux32 ./bin/ash ./bin/df ./bin/cp ./bin/ed ./bin/ping ./bin/ipcalc ./bin/iplink ./bin/fgrep ./bin/cpio ./bin/stat ./bin/scriptreplay ./bin/dd ./bin/ls ./bin/netstat ./bin/tar ./bin/pwd ./bin/fsync ./bin/kill ./bin/iprule ./bin/touch ./bin/umount ./bin/hush ./bin/rmdir ./bin/sed ./bin/sh ./bin/chown ./bin/reformime ./bin/setarch ./bin/mkdir ./bin/cttyhack ./bin/getopt ./bin/false ./bin/deluser ./bin/printenv ./bin/adduser ./bin/gzip ./bin/lzop ./bin/login ./bin/ip ./bin/su ./bin/mv ./bin/rm ./bin/makemime ./bin/chattr ./bin/sync ./bin/dnsdomainname ./bin/watch ./bin/fdflush ./bin/ipaddr ./bin/ln ./bin/busybox ./bin/mknod ./bin/delgroup ./bin/nice ./bin/mountpoint ./bin/pidof ./bin/lsattr ./bin/dumpkmap ./bin/uname ./bin/echo ./bin/chmod ./bin/grep ./bin/cat ./bin/chgrp ./bin/ionice ./bin/mount ./bin/mktemp ./bin/catv ./bin/dmesg ./bin/true ./sbin ./sbin/ifenslave ./sbin/watchdog ./sbin/klogd ./sbin/fsck.minix ./sbin/getty ./sbin/losetup ./sbin/udhcpc ./sbin/reboot ./sbin/runlevel ./sbin/init ./sbin/mkfs.vfat ./sbin/devmem ./sbin/sulogin ./sbin/swapon ./sbin/hwclock ./sbin/depmod ./sbin/vconfig ./sbin/setconsole ./sbin/hdparm ./sbin/insmod ./sbin/lsmod ./sbin/route ./sbin/fdisk ./sbin/ifup ./sbin/adjtimex ./sbin/loadkmap ./sbin/ifdown ./sbin/tunctl ./sbin/switch_root ./sbin/raidautorun ./sbin/slattach ./sbin/mdev ./sbin/mkdosfs ./sbin/mkswap ./sbin/fbsplash ./sbin/freeramdisk ./sbin/nameif ./sbin/ifconfig ./sbin/logread ./sbin/syslogd ./sbin/mkfs.minix ./sbin/findfs ./sbin/man ./sbin/modprobe ./sbin/pivot_root ./sbin/sysctl ./sbin/blkid ./sbin/arp ./sbin/zcip ./sbin/makedevs ./sbin/swapoff ./sbin/fsck ./sbin/rmmod ./sbin/halt ./sbin/poweroff ./sbin/start-stop-daemon ./linuxrc crifan@ubuntu:_install$ find . | cpio -o --format=newc > ../rootfs.img 3520 blocks crifan@ubuntu:_install$ cd .. crifan@ubuntu:busybox-1.16.0$ ls applets busybox.links console-tools editors _install loginutils Makefile.help procps selinux TODO_config_nommu arch busybox_unstripped coreutils examples INSTALL mailutils miscutils README shell util-linux archival busybox_unstripped.map debianutils findutils libbb Makefile modutils rootfs.img sysklogd AUTHORS busybox_unstripped.out docs include libpwdgrp Makefile.custom networking runit testsuite busybox Config.in e2fsprogs init LICENSE Makefile.flags printutils scripts TODO crifan@ubuntu:busybox-1.16.0$ ls rootfs.img -lha -rw-rw-r-- 1 crifan crifan 1.8M Aug 19 00:17 rootfs.img crifan@ubuntu:busybox-1.16.0$ gzip -c rootfs.img > rootfs.img.gz crifan@ubuntu:busybox-1.16.0$ ls rootfs.img* -lha -rw-rw-r-- 1 crifan crifan 1.8M Aug 19 00:17 rootfs.img -rw-rw-r-- 1 crifan crifan 965K Aug 19 00:18 rootfs.img.gz crifan@ubuntu:busybox-1.16.0$
3.然后去测试一下：
crifan@ubuntu:busybox-1.16.0$ ls applets busybox_unstripped debianutils include LICENSE Makefile.help README shell zImage arch busybox_unstripped.map docs init loginutils miscutils rootfs.img sysklogd archival busybox_unstripped.out e2fsprogs _install mailutils modutils rootfs.img.gz testsuite AUTHORS Config.in editors INSTALL Makefile networking runit TODO busybox console-tools examples libbb Makefile.custom printutils scripts TODO_config_nommu busybox.links coreutils findutils libpwdgrp Makefile.flags procps selinux util-linux crifan@ubuntu:busybox-1.16.0$ qemu-system-arm -M versatilepb -m 128M -kernel zImage -initrd rootfs.img.gz -append "root=/dev/ram rdinit=/bin/sh"
然后是可以正常进入rootfs，进入linux命令行了：
而且的确是ps和mount都没有东西：
4.去操作：
# mkdir /proc # mount -t proc none /proc
效果如图：
5.的确，dev下面只有console：
所以去
# mkdir /sys # mount -t sysfs none /sys # mdev -s
效果是：
6.对应的，接着去Ubuntu下我们此处的busybox中，去创建对应的启动内容：
crifan@ubuntu:busybox-1.16.0$ cd _install/ crifan@ubuntu:_install$ pwd /home/crifan/develop/embedded/qemu/rootfs/busybox/busybox-1.16.0/_install crifan@ubuntu:_install$ ls bin linuxrc sbin usr crifan@ubuntu:_install$ mkdir proc sys dev etc etc/init.d crifan@ubuntu:_install$ ls -lha total 36K drwxrwxr-x 9 crifan crifan 4.0K Aug 19 00:33 . drwxr-xr-x 32 crifan crifan 4.0K Aug 19 00:22 .. drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:15 bin drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:33 dev drwxrwxr-x 3 crifan crifan 4.0K Aug 19 00:33 etc lrwxrwxrwx 1 crifan crifan 11 Aug 19 00:15 linuxrc -> bin/busybox drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:33 proc drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:15 sbin drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:33 sys drwxrwxr-x 4 crifan crifan 4.0K Aug 19 00:15 usr crifan@ubuntu:_install$ cd .. crifan@ubuntu:busybox-1.16.0$ gedit _install/etc/init.d/rcS
对应内容是：
#!/bin/sh mount -t proc none /proc mount -t sysfs none /sys /sbin/mdev -s
然后添加可执行的权限：
crifan@ubuntu:busybox-1.16.0$ chmod +x _install/etc/init.d/rcS crifan@ubuntu:busybox-1.16.0$ ls _install/etc/init.d/ -lha total 12K drwxrwxr-x 2 crifan crifan 4.0K Aug 19 00:34 . drwxrwxr-x 3 crifan crifan 4.0K Aug 19 00:33 .. -rwxrwxr-x 1 crifan crifan 74 Aug 19 00:34 rcS crifan@ubuntu:busybox-1.16.0$
重新创建rootfs：
crifan@ubuntu:busybox-1.16.0$ cd _install/ crifan@ubuntu:_install$ find . | cpio -o --format=newc > ../rootfs.img 3522 blocks crifan@ubuntu:_install$ cd .. crifan@ubuntu:busybox-1.16.0$ gzip -c rootfs.img > rootfs.img.gz crifan@ubuntu:busybox-1.16.0$ ls -lha total 11M drwxr-xr-x 32 crifan crifan 4.0K Aug 19 00:22 . drwxrwxr-x 3 crifan crifan 4.0K Aug 19 00:08 .. drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:14 applets drwxr-xr-x 3 crifan crifan 4.0K Jan 24 2010 arch drwxr-xr-x 4 crifan crifan 4.0K Aug 19 00:15 archival -rw-r--r-- 1 crifan crifan 5.1K Jan 24 2010 AUTHORS -rwxrwxr-x 1 crifan crifan 1.7M Aug 19 00:15 busybox -rw-rw-r-- 1 crifan crifan 4.3K Aug 19 00:15 busybox.links -rwxrwxr-x 1 crifan crifan 2.1M Aug 19 00:15 busybox_unstripped -rw-rw-r-- 1 crifan crifan 1.8K Aug 19 00:15 .busybox_unstripped.cmd -rw-rw-r-- 1 crifan crifan 1.7M Aug 19 00:15 busybox_unstripped.map -rw-rw-r-- 1 crifan crifan 109K Aug 19 00:15 busybox_unstripped.out -rw-rw-r-- 1 crifan crifan 22K Aug 19 00:14 .config -rw-r--r-- 1 crifan crifan 20K Jan 25 2010 Config.in -rw-rw-r-- 1 crifan crifan 22K Aug 19 00:13 .config.old drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 console-tools drwxr-xr-x 3 crifan crifan 12K Aug 19 00:15 coreutils drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 debianutils drwxr-xr-x 3 crifan crifan 4.0K Jan 24 2010 docs drwxr-xr-x 3 crifan crifan 4.0K Aug 19 00:15 e2fsprogs drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 editors drwxr-xr-x 5 crifan crifan 4.0K Jan 24 2010 examples drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 findutils -rw-r--r-- 1 crifan crifan 231 Jan 24 2010 .gitignore drwxr-xr-x 3 crifan crifan 4.0K Aug 19 00:14 include -rw-r--r-- 1 crifan crifan 871 Jan 24 2010 .indent.pro drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 init drwxrwxr-x 9 crifan crifan 4.0K Aug 19 00:33 _install -rw-r--r-- 1 crifan crifan 5.7K Jan 24 2010 INSTALL -rw-rw-r-- 1 crifan crifan 614 Aug 19 00:14 .kconfig.d -rw-rw-r-- 1 crifan crifan 7 Aug 19 00:14 .kernelrelease drwxr-xr-x 2 crifan crifan 20K Aug 19 00:15 libbb drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 libpwdgrp -rw-r--r-- 1 crifan crifan 18K Jan 24 2010 LICENSE drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 loginutils drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 mailutils -rw-r--r-- 1 crifan crifan 42K Jan 25 2010 Makefile -rw-r--r-- 1 crifan crifan 5.4K Jan 24 2010 Makefile.custom -rw-r--r-- 1 crifan crifan 4.3K Jan 24 2010 Makefile.flags -rw-r--r-- 1 crifan crifan 2.0K Jan 24 2010 Makefile.help drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 miscutils drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 modutils drwxr-xr-x 4 crifan crifan 4.0K Aug 19 00:15 networking drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 printutils drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 procps -rw-r--r-- 1 crifan crifan 8.6K Jan 24 2010 README -rw-rw-r-- 1 crifan crifan 1.8M Aug 19 00:37 rootfs.img -rw-rw-r-- 1 crifan crifan 965K Aug 19 00:38 rootfs.img.gz drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 runit drwxr-xr-x 4 crifan crifan 4.0K Jan 25 2010 scripts drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 selinux drwxr-xr-x 5 crifan crifan 4.0K Aug 19 00:15 shell drwxr-xr-x 2 crifan crifan 4.0K Aug 19 00:15 sysklogd drwxr-xr-x 45 crifan crifan 4.0K Jan 24 2010 testsuite -rw-r--r-- 1 crifan crifan 15K Jan 24 2010 TODO -rw-r--r-- 1 crifan crifan 21K Jan 24 2010 TODO_config_nommu drwxr-xr-x 3 crifan crifan 4.0K Aug 19 00:15 util-linux -rwxrwxr-x 1 crifan crifan 1.9M Aug 19 00:22 zImage crifan@ubuntu:busybox-1.16.0$
重新测试运行：
qemu-system-arm -M versatilepb -m 128M -kernel zImage -initrd rootfs.img.gz -append "root=/dev/ram rdinit=/sbin/init"
然后就可以看到熟悉的：
please press enter to active this console
了：
以及，可以看到对应的sys文件夹，mount的内容了：
至此，参考教程的折腾，算是结束了。
【总结】
至此，参考教程，完成了：
使用BusyBox作为最基本的，从ram启动的rootfs，可以正常的进入linux的命令行了。