Centos7 64bit在virtualbox编译制作busybox启动盘
1。 下载最新的 busybox-1.26.2， makemenuconfig 去掉不需要的功能（直接改.config文件也可以） make install 会在 busybox的源码_install目录下创建好所有的命令的软连接。
我编译出来的busybox有600多k。
[ming@centos7 initrd-busybox]$ ls -lh bin/busybox
-rwxr-xr-x. 1 ming ming 646K Apr 17 14:32 bin/busybox
- 基于这个 _install 目录和当前系统一个正在使用initramfs包来制作我们的最终镜像。 bin 和lib 和内核驱动都使用busybox和原始initramfs就可以了。 etc/passwd 和 etc/group etc/shadow 3个文件直接复制当前系统的过来修改。 编译出来的busybox 还依赖另外的c库，也复制过来到lib目录里面。 ```text [ming@centos7 initrd-busybox]$ ldd bin/busybox linux-vdso.so.1 => (0x00007ffe589f8000) libm.so.6 => /lib64/libm.so.6 (0x00007f6e9d797000) libc.so.6 => /lib64/libc.so.6 (0x00007f6e9d3d6000) /lib64/ld-linux-x86-64.so.2 (0x00007f6e9daa3000)
制作完成的initramfs包含如下文件
-----------------------------
```text
[ming@centos7 initrd-busybox]$ tree
.
├── bin
│ ├── ash -> busybox
│ ├── base64 -> busybox
│ ├── busybox
│ ├── cat -> busybox
│ ├── catv -> busybox
│ ├── chattr -> busybox
│ ├── chgrp -> busybox
│ ├── chmod -> busybox
│ ├── chown -> busybox
│ ├── cp -> busybox
│ ├── cpio -> busybox
│ ├── date -> busybox
│ ├── dd -> busybox
│ ├── df -> busybox
│ ├── dmesg -> busybox
│ ├── dumpkmap -> busybox
│ ├── echo -> busybox
│ ├── ed -> busybox
│ ├── egrep -> busybox
│ ├── false -> busybox
│ ├── fgrep -> busybox
│ ├── fsync -> busybox
│ ├── getopt -> busybox
│ ├── grep -> busybox
│ ├── gunzip -> busybox
│ ├── gzip -> busybox
│ ├── hostname -> busybox
│ ├── iostat -> busybox
│ ├── ipcalc -> busybox
│ ├── kbd_mode -> busybox
│ ├── kill -> busybox
│ ├── ln -> busybox
│ ├── login -> busybox
│ ├── ls -> busybox
│ ├── lsattr -> busybox
│ ├── mkdir -> busybox
│ ├── mknod -> busybox
│ ├── more -> busybox
│ ├── mount -> busybox
│ ├── mountpoint -> busybox
│ ├── mpstat -> busybox
│ ├── mt -> busybox
│ ├── mv -> busybox
│ ├── netstat -> busybox
│ ├── nice -> busybox
│ ├── pidof -> busybox
│ ├── ping -> busybox
│ ├── ping6 -> busybox
│ ├── printenv -> busybox
│ ├── ps -> busybox
│ ├── pwd -> busybox
│ ├── rm -> busybox
│ ├── rmdir -> busybox
│ ├── rpm -> busybox
│ ├── sed -> busybox
│ ├── sh -> busybox
│ ├── sleep -> busybox
│ ├── stat -> busybox
│ ├── stty -> busybox
│ ├── su -> busybox
│ ├── sync -> busybox
│ ├── tar -> busybox
│ ├── touch -> busybox
│ ├── true -> busybox
│ ├── umount -> busybox
│ ├── uname -> busybox
│ ├── usleep -> busybox
│ ├── vi -> busybox
│ ├── watch -> busybox
│ └── zcat -> busybox
├── cfg
├── data
├── dev
├── etc
│ ├── fstab
│ ├── group
│ ├── hostname
│ ├── init.d
│ │ └── rcS
│ ├── inittab
│ ├── mdev.conf
│ ├── passwd
│ └── shadow
├── init
├── lib
│ └── modules
│ └── 3.10.0-514.10.2.el7.x86_64
│ ├── kernel
│ │ ├── arch
│ │ │ └── x86
│ │ │ └── crypto
│ │ │ ├── crc32c-intel.ko
│ │ │ └── crct10dif-pclmul.ko
│ │ ├── crypto
│ │ │ ├── crct10dif_common.ko
│ │ │ └── crct10dif_generic.ko
│ │ ├── drivers
│ │ │ ├── ata
│ │ │ │ ├── ahci.ko
│ │ │ │ ├── ata_generic.ko
│ │ │ │ ├── ata_piix.ko
│ │ │ │ ├── libahci.ko
│ │ │ │ ├── libata.ko
│ │ │ │ └── pata_acpi.ko
│ │ │ ├── block
│ │ │ │ └── virtio_blk.ko
│ │ │ ├── cdrom
│ │ │ │ └── cdrom.ko
│ │ │ ├── char
│ │ │ │ └── virtio_console.ko
│ │ │ ├── firmware
│ │ │ │ └── iscsi_ibft.ko
│ │ │ ├── input
│ │ │ │ └── serio
│ │ │ │ └── serio_raw.ko
│ │ │ ├── md
│ │ │ │ ├── dm-log.ko
│ │ │ │ ├── dm-mirror.ko
│ │ │ │ ├── dm-mod.ko
│ │ │ │ └── dm-region-hash.ko
│ │ │ ├── net
│ │ │ │ ├── ethernet
│ │ │ │ │ └── intel
│ │ │ │ │ └── e1000
│ │ │ │ │ └── e1000.ko
│ │ │ │ └── fjes
│ │ │ │ └── fjes.ko
│ │ │ ├── scsi
│ │ │ │ ├── iscsi_boot_sysfs.ko
│ │ │ │ ├── sd_mod.ko
│ │ │ │ ├── sr_mod.ko
│ │ │ │ └── virtio_scsi.ko
│ │ │ └── virtio
│ │ │ ├── virtio.ko
│ │ │ ├── virtio_pci.ko
│ │ │ └── virtio_ring.ko
│ │ ├── fs
│ │ │ └── xfs
│ │ │ └── xfs.ko
│ │ ├── lib
│ │ │ ├── crc-t10dif.ko
│ │ │ └── libcrc32c.ko
│ │ └── net
│ │ ├── 802
│ │ │ └── stp.ko
│ │ ├── bridge
│ │ │ └── bridge.ko
│ │ └── llc
│ │ └── llc.ko
│ ├── modules.alias
│ ├── modules.alias.bin
│ ├── modules.builtin
│ ├── modules.builtin.bin
│ ├── modules.dep
│ ├── modules.dep.bin
│ ├── modules.devname
│ ├── modules.order
│ ├── modules.softdep
│ ├── modules.symbols
│ └── modules.symbols.bin
├── lib64
│ ├── ld-2.17.so
│ ├── ld-linux-x86-64.so.2 -> ld-2.17.so
│ ├── libc-2.17.so
│ ├── libc.so.6 -> libc-2.17.so
│ ├── libm-2.17.so
│ └── libm.so.6 -> libm-2.17.so
├── proc
├── root
├── run
├── sbin
│ ├── adjtimex -> ../bin/busybox
│ ├── arp -> ../bin/busybox
│ ├── bootchartd -> ../bin/busybox
│ ├── depmod -> ../bin/busybox
│ ├── fdisk -> ../bin/busybox
│ ├── freeramdisk -> ../bin/busybox
│ ├── fsck -> ../bin/busybox
│ ├── getty -> ../bin/busybox
│ ├── halt -> ../bin/busybox
│ ├── hwclock -> ../bin/busybox
│ ├── ifconfig -> ../bin/busybox
│ ├── ifdown -> ../bin/busybox
│ ├── ifenslave -> ../bin/busybox
│ ├── ifup -> ../bin/busybox
│ ├── init -> ../bin/busybox
│ ├── insmod -> ../bin/busybox
│ ├── ip -> ../bin/busybox
│ ├── ipaddr -> ../bin/busybox
│ ├── iplink -> ../bin/busybox
│ ├── ipneigh -> ../bin/busybox
│ ├── iproute -> ../bin/busybox
│ ├── iprule -> ../bin/busybox
│ ├── iptunnel -> ../bin/busybox
│ ├── klogd -> ../bin/busybox
│ ├── loadkmap -> ../bin/busybox
│ ├── logread -> ../bin/busybox
│ ├── lsmod -> ../bin/busybox
│ ├── makedevs -> ../bin/busybox
│ ├── mdev -> ../bin/busybox
│ ├── mkfs.ext2 -> ../bin/busybox
│ ├── modinfo -> ../bin/busybox
│ ├── modprobe -> ../bin/busybox
│ ├── pivot_root -> ../bin/busybox
│ ├── poweroff -> ../bin/busybox
│ ├── reboot -> ../bin/busybox
│ ├── rmmod -> ../bin/busybox
│ ├── route -> ../bin/busybox
│ ├── runlevel -> ../bin/busybox
│ ├── setconsole -> ../bin/busybox
│ ├── sulogin -> ../bin/busybox
│ ├── switch_root -> ../bin/busybox
│ ├── sysctl -> ../bin/busybox
│ ├── syslogd -> ../bin/busybox
│ ├── tunctl -> ../bin/busybox
│ ├── udhcpc -> ../bin/busybox
│ ├── vconfig -> ../bin/busybox
│ └── zcip -> ../bin/busybox
├── sys
├── sysroot
├── tmp
├── usr
│ ├── bin
│ │ ├── [ -> ../../bin/busybox
│ │ ├── [[ -> ../../bin/busybox
│ │ ├── awk -> ../../bin/busybox
│ │ ├── basename -> ../../bin/busybox
│ │ ├── bunzip2 -> ../../bin/busybox
│ │ ├── bzcat -> ../../bin/busybox
│ │ ├── bzip2 -> ../../bin/busybox
│ │ ├── cal -> ../../bin/busybox
│ │ ├── chrt -> ../../bin/busybox
│ │ ├── chvt -> ../../bin/busybox
│ │ ├── cksum -> ../../bin/busybox
│ │ ├── clear -> ../../bin/busybox
│ │ ├── cmp -> ../../bin/busybox
│ │ ├── comm -> ../../bin/busybox
│ │ ├── crontab -> ../../bin/busybox
│ │ ├── cryptpw -> ../../bin/busybox
│ │ ├── cut -> ../../bin/busybox
│ │ ├── dc -> ../../bin/busybox
│ │ ├── deallocvt -> ../../bin/busybox
│ │ ├── diff -> ../../bin/busybox
│ │ ├── dirname -> ../../bin/busybox
│ │ ├── dos2unix -> ../../bin/busybox
│ │ ├── du -> ../../bin/busybox
│ │ ├── env -> ../../bin/busybox
│ │ ├── envdir -> ../../bin/busybox
│ │ ├── envuidgid -> ../../bin/busybox
│ │ ├── expand -> ../../bin/busybox
│ │ ├── expr -> ../../bin/busybox
│ │ ├── find -> ../../bin/busybox
│ │ ├── fold -> ../../bin/busybox
│ │ ├── free -> ../../bin/busybox
│ │ ├── fuser -> ../../bin/busybox
│ │ ├── groups -> ../../bin/busybox
│ │ ├── head -> ../../bin/busybox
│ │ ├── hexdump -> ../../bin/busybox
│ │ ├── hostid -> ../../bin/busybox
│ │ ├── id -> ../../bin/busybox
│ │ ├── install -> ../../bin/busybox
│ │ ├── killall -> ../../bin/busybox
│ │ ├── last -> ../../bin/busybox
│ │ ├── less -> ../../bin/busybox
│ │ ├── logger -> ../../bin/busybox
│ │ ├── logname -> ../../bin/busybox
│ │ ├── lpq -> ../../bin/busybox
│ │ ├── lpr -> ../../bin/busybox
│ │ ├── lsof -> ../../bin/busybox
│ │ ├── lspci -> ../../bin/busybox
│ │ ├── md5sum -> ../../bin/busybox
│ │ ├── mesg -> ../../bin/busybox
│ │ ├── microcom -> ../../bin/busybox
│ │ ├── mkfifo -> ../../bin/busybox
│ │ ├── mkpasswd -> ../../bin/busybox
│ │ ├── nc -> ../../bin/busybox
│ │ ├── nmeter -> ../../bin/busybox
│ │ ├── nohup -> ../../bin/busybox
│ │ ├── nslookup -> ../../bin/busybox
│ │ ├── openvt -> ../../bin/busybox
│ │ ├── passwd -> ../../bin/busybox
│ │ ├── patch -> ../../bin/busybox
│ │ ├── pgrep -> ../../bin/busybox
│ │ ├── pkill -> ../../bin/busybox
│ │ ├── printf -> ../../bin/busybox
│ │ ├── pscan -> ../../bin/busybox
│ │ ├── readlink -> ../../bin/busybox
│ │ ├── realpath -> ../../bin/busybox
│ │ ├── renice -> ../../bin/busybox
│ │ ├── reset -> ../../bin/busybox
│ │ ├── resize -> ../../bin/busybox
│ │ ├── rpm2cpio -> ../../bin/busybox
│ │ ├── runsv -> ../../bin/busybox
│ │ ├── runsvdir -> ../../bin/busybox
│ │ ├── rx -> ../../bin/busybox
│ │ ├── script -> ../../bin/busybox
│ │ ├── seq -> ../../bin/busybox
│ │ ├── setkeycodes -> ../../bin/busybox
│ │ ├── setsid -> ../../bin/busybox
│ │ ├── setuidgid -> ../../bin/busybox
│ │ ├── sha1sum -> ../../bin/busybox
│ │ ├── sha256sum -> ../../bin/busybox
│ │ ├── sha3sum -> ../../bin/busybox
│ │ ├── sha512sum -> ../../bin/busybox
│ │ ├── softlimit -> ../../bin/busybox
│ │ ├── sort -> ../../bin/busybox
│ │ ├── split -> ../../bin/busybox
│ │ ├── strings -> ../../bin/busybox
│ │ ├── sum -> ../../bin/busybox
│ │ ├── tac -> ../../bin/busybox
│ │ ├── tail -> ../../bin/busybox
│ │ ├── tcpsvd -> ../../bin/busybox
│ │ ├── tee -> ../../bin/busybox
│ │ ├── telnet -> ../../bin/busybox
│ │ ├── test -> ../../bin/busybox
│ │ ├── tftp -> ../../bin/busybox
│ │ ├── time -> ../../bin/busybox
│ │ ├── top -> ../../bin/busybox
│ │ ├── tr -> ../../bin/busybox
│ │ ├── traceroute -> ../../bin/busybox
│ │ ├── traceroute6 -> ../../bin/busybox
│ │ ├── truncate -> ../../bin/busybox
│ │ ├── tty -> ../../bin/busybox
│ │ ├── ttysize -> ../../bin/busybox
│ │ ├── udpsvd -> ../../bin/busybox
│ │ ├── unexpand -> ../../bin/busybox
│ │ ├── uniq -> ../../bin/busybox
│ │ ├── unix2dos -> ../../bin/busybox
│ │ ├── unlink -> ../../bin/busybox
│ │ ├── unzip -> ../../bin/busybox
│ │ ├── uptime -> ../../bin/busybox
│ │ ├── users -> ../../bin/busybox
│ │ ├── uudecode -> ../../bin/busybox
│ │ ├── uuencode -> ../../bin/busybox
│ │ ├── vlock -> ../../bin/busybox
│ │ ├── wc -> ../../bin/busybox
│ │ ├── wget -> ../../bin/busybox
│ │ ├── who -> ../../bin/busybox
│ │ ├── whoami -> ../../bin/busybox
│ │ ├── whois -> ../../bin/busybox
│ │ ├── xargs -> ../../bin/busybox
│ │ └── yes -> ../../bin/busybox
│ ├── lib
│ ├── lib64
│ ├── sbin
│ │ ├── addgroup -> ../../bin/busybox
│ │ ├── add-shell -> ../../bin/busybox
│ │ ├── adduser -> ../../bin/busybox
│ │ ├── arping -> ../../bin/busybox
│ │ ├── brctl -> ../../bin/busybox
│ │ ├── chpasswd -> ../../bin/busybox
│ │ ├── chroot -> ../../bin/busybox
│ │ ├── crond -> ../../bin/busybox
│ │ ├── delgroup -> ../../bin/busybox
│ │ ├── deluser -> ../../bin/busybox
│ │ ├── dnsd -> ../../bin/busybox
│ │ ├── ether-wake -> ../../bin/busybox
│ │ ├── fakeidentd -> ../../bin/busybox
│ │ ├── httpd -> ../../bin/busybox
│ │ ├── inetd -> ../../bin/busybox
│ │ ├── killall5 -> ../../bin/busybox
│ │ ├── loadfont -> ../../bin/busybox
│ │ ├── lpd -> ../../bin/busybox
│ │ ├── ntpd -> ../../bin/busybox
│ │ ├── rdate -> ../../bin/busybox
│ │ ├── readahead -> ../../bin/busybox
│ │ ├── remove-shell -> ../../bin/busybox
│ │ ├── sendmail -> ../../bin/busybox
│ │ ├── setfont -> ../../bin/busybox
│ │ ├── setlogcons -> ../../bin/busybox
│ │ ├── svlogd -> ../../bin/busybox
│ │ ├── telnetd -> ../../bin/busybox
│ │ └── tftpd -> ../../bin/busybox
│ └── share
└── var
系统启动的init脚本，先做一些初始化工作再最后调用busybox的init
[ming@centos7 initrd-busybox]$ cat ./init
#!/bin/sh
echo "Heath customised init..."
echo "Mount the /proc and /sys filesystems"
mount -t proc proc /proc
mount -t sysfs sys /sys
echo "Creating /dev"
mount -o mode=0755 -t tmpfs /dev /dev
mkdir /dev/pts
mount -t devpts -o gid=5,mode=620 /dev/pts /dev/pts
mkdir /dev/shm
mkdir /dev/mapper
echo "Creating initial device nodes"
mknod /dev/null c 1 3
mknod /dev/zero c 1 5
mknod /dev/systty c 4 0
mknod /dev/tty c 5 0
mknod /dev/console c 5 1
mknod /dev/ptmx c 5 2
mknod /dev/rtc c 10 135
mknod /dev/tty0 c 4 0
mknod /dev/tty1 c 4 1
mknod /dev/tty2 c 4 2
mknod /dev/tty3 c 4 3
mknod /dev/tty4 c 4 4
mknod /dev/tty5 c 4 5
mknod /dev/tty6 c 4 6
mknod /dev/ttyS0 c 4 64
mknod /dev/ttyS1 c 4 65
mount -t usbfs /proc/bus/usb /proc/bus/usb
modprobe serio_raw
modprobe pata_acpi
modprobe libahci
modprobe ahci
modprobe sd_mod
modprobe libata
modprobe ata_piix
modprobe xfs
modprobe dm_mod
modprobe e1000
echo "Mounting root filesystem"
echo "switch_root and run /sbin/init"
#exec switch_root /mnt/root /sbin/init
exec /sbin/init
inittab文件
[ming@centos7 initrd-busybox]$ cat etc/inittab
::sysinit:/etc/init.d/rcS
::askfirst:-/bin/login
#::askfirst:/bin/sh
#::respawn:/sbin/getty 9600 tty1
#::respawn:/sbin/getty 9600 tty2
#::respawn:/sbin/getty 9600 tty3
::shutdown:/bin/umount -a -r
::ctrlaltdel:/sbin/reboot
[ming@centos7 initrd-busybox]$ cat etc/init.d/rcS
#!/bin/sh
echo "Run /etc/init.d/rcS"
if [ ! -e /proc/mounts ]; then
mount -n -t proc proc /proc
mount -n -t sysfs sysfs /sys
fi
echo /sbin/mdev > /proc/sys/kernel/hotplug
mdev -s
mount -a
mkdir -p /var/log
mkdir -p /var/run
mkdir -p /var/lock
mkdir -p /var/local
mkdir -p /var/cache
mkdir -p /var/local
mkdir -p /var/opt
mkdir -p /var/tmp
mkdir -p /var/spool
touch /var/log/lastlog
mkdir -p /tmp/root
/sbin/klogd -c 1
/sbin/syslogd
echo "Initializing ..."
mount -o remount,rw /
#ifconfig lo 127.0.0.1/24
echo "Done."
exit
mdev的配置文件
[ming@centos7 initrd-busybox]$ cat etc/mdev.conf
# https://git.busybox.net/busybox/tree/docs/mdev.txt?h=1_26_stable
# for debugging
# -.* root:root 0666 *{ date; set; echo; } >>/tmp/log
# null may already exist; therefore ownership has to be changed with command
null root:root 666 @/bin/chmod 666 "$MDEV"
zero root:root 666
full root:root 666
random root:root 666
urandom root:root 666
hwrandom root:root 666
kmsg root:root 600
mem root:kmem 640
# console may already exist; therefore ownership has to be changed with command
console root:tty 600 @/bin/chmod 600 "$MDEV"
ptmx root:tty 666
pty.* root:tty 666
tty[a-z][0-9a-f] root:tty 666
microcode root:root 600 =cpu/
# Typical devices
tty root:tty 666
tty[0-9] root:tty 620
vcsa?[0-9]* root:tty 620
ttyS[0-9]+ root:dialout 660
# block devices
ram[0-9]+ root:disk 660
loop[0-9]+ root:disk 660
sd[a-z].* root:disk 660
hd[a-z].* root:disk 660
# net and misc
tun[0-9]* root:root 660 =net/
tap[0-9]* root:root 660 =net/
fuse root:root 660
device-mapper root:root 600 >mapper/control
# alsa sound devices and audio stuff
pcm.* root:audio 660 =snd/
control.* root:audio 660 =snd/
midi.* root:audio 660 =snd/
seq root:audio 660 =snd/
timer root:audio 660 =snd/
# input stuff
event[0-9]+ root:root 660 =input/
mice root:root 660 =input/
mouse[0-9]+ root:root 660 =input/
- 制作完initramfs，配置grub2增加我们的内核和initramfs就可以了。 修改/etc/grub.d/40_custom 增加自定义的entry，然后 grub2-mkconfig -o /boot/grub2/grub.cfg 更新 ```text menuentry ‘CentOS Linux (busybox) 7 (Core)’ –class centos –class gnu-linux –class gnu –class os –unrestricted $menuentry_id_option ‘gnulinux-busybox-advanced-0940d618-e2e8-4621-9688-24e3cbe4c13c’ { load_video insmod gzio insmod part_msdos insmod xfs set root=’hd0,msdos1’ if [ x$feature_platform_search_hint = xy ]; then search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1 –hint=’hd0,msdos1’ 204d6bba-f874-4720-a784-24e99d6d28a6 else search –no-floppy –fs-uuid –set=root 204d6bba-f874-4720-a784-24e99d6d28a6 fi linux16 /vmlinuz-3.10.0-514.10.2.el7.x86_64 console=ttyS0 root=/dev/root ro crashkernel=auto rd.lvm.lv=cl_centos7/root rd.lvm.lv=cl_centos7/swap rhgb initrd16 /initramfs-busybox.img }
```
参考资料： https://wiki.gentoo.org/wiki/Custom_Initramfs#Busybox https://wiki.gentoo.org/wiki/Mdev http://www.tldp.org/HOWTO/Bootdisk-HOWTO/ https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sec-Customizing_the_GRUB_2_Configuration_File.html https://wiki.centos.org/zh/HowTos/Grub2 https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt https://github.com/mirror/busybox/blob/master/examples/inittab https://git.busybox.net/busybox/plain/docs/mdev.txt