busyboxをstatic linkでビルドする

ひとつ持っていると何かのときに役に立つと思って。

# busybox とは

"BusyBox: The Swiss Army Knife of Embedded Linux"
https://busybox.net/about.html

組み込みLinuxのルートファイルシステムではおなじみ。

# busyboxのソースの入手

```
wget https://busybox.net/downloads/busybox-1.28.3.tar.bz2
tar xf busybox-1.28.3.tar.bz2 
cd busybox-1.28.3/
```

# ビルド

ビルドはLinux kernelのビルドに似ている。

ソースツリーの中の `INSTALL` のファイルを参照。

```
make menuconfig
```

Settings -> の中の以下の項目をセットする。

```
 [*] Build static binary (no shared libs)     
```

CONFIG_STATIC=y になっている。

```
grep STATIC .config
CONFIG_STATIC=y
# CONFIG_FEATURE_LIBBUSYBOX_STATIC is not set
```

これでビルド。

```
make
```

```
$ file ./busybox
./busybox: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.32, BuildID[sha1]=e26510ca518837a7a082dc8ffe80d6d10ccb187e, stripped
koba@instance-3:~/busybox/busybox-1.28.3$ ls -lh ./busybox
-rwxrwxr-x 1 koba koba 2.6M Apr  9 03:05 ./busybox
```

ストリップされたサイズで2.6MB。

```
$ ./busybox
BusyBox v1.28.3 (2018-04-09 03:01:38 UTC) multi-call binary.
BusyBox is copyrighted by many authors between 1998-2015.
Licensed under GPLv2. See source distribution for detailed
copyright notices.

Usage: busybox [function [arguments]...]
   or: busybox --list[-full]
   or: busybox --install [-s] [DIR]
   or: function [arguments]...

	BusyBox is a multi-call binary that combines many common Unix
	utilities into a single executable.  Most people will create a
	link to busybox for each function they wish to use and BusyBox
	will act like whatever it was invoked as.

Currently defined functions:
	[, [[, acpid, add-shell, addgroup, adduser, adjtimex, arch, arp, arping, ash, awk, base64,
	basename, beep, blkdiscard, blkid, blockdev, bootchartd, brctl, bunzip2, bzcat, bzip2, cal,
	cat, chat, chattr, chgrp, chmod, chown, chpasswd, chpst, chroot, chrt, chvt, cksum, clear,
	cmp, comm, conspy, cp, cpio, crond, crontab, cryptpw, cttyhack, cut, date, dc, dd, deallocvt,
	delgroup, deluser, depmod, devmem, df, dhcprelay, diff, dirname, dmesg, dnsd, dnsdomainname,
	dos2unix, dpkg, dpkg-deb, du, dumpkmap, dumpleases, echo, ed, egrep, eject, env, envdir,
	envuidgid, ether-wake, expand, expr, factor, fakeidentd, fallocate, false, fatattr, fbset,
	fbsplash, fdflush, fdformat, fdisk, fgconsole, fgrep, find, findfs, flock, fold, free,
	freeramdisk, fsck, fsck.minix, fsfreeze, fstrim, fsync, ftpd, ftpget, ftpput, fuser, getopt,
	getty, grep, groups, gunzip, gzip, halt, hd, hdparm, head, hexdump, hexedit, hostid,
	hostname, httpd, hush, hwclock, i2cdetect, i2cdump, i2cget, i2cset, id, ifconfig, ifdown,
	ifenslave, ifplugd, ifup, inetd, init, insmod, install, ionice, iostat, ip, ipaddr, ipcalc,
	ipcrm, ipcs, iplink, ipneigh, iproute, iprule, iptunnel, kbd_mode, kill, killall, killall5,
	klogd, last, less, link, linux32, linux64, linuxrc, ln, loadfont, loadkmap, logger, login,
	logname, logread, losetup, lpd, lpq, lpr, ls, lsattr, lsmod, lsof, lspci, lsscsi, lsusb,
	lzcat, lzma, lzop, makedevs, makemime, man, md5sum, mdev, mesg, microcom, mkdir, mkdosfs,
	mke2fs, mkfifo, mkfs.ext2, mkfs.minix, mkfs.vfat, mknod, mkpasswd, mkswap, mktemp, modinfo,
	modprobe, more, mount, mountpoint, mpstat, mt, mv, nameif, nanddump, nandwrite, nbd-client,
	nc, netstat, nice, nl, nmeter, nohup, nproc, nsenter, nslookup, ntpd, nuke, od, openvt,
	partprobe, passwd, paste, patch, pgrep, pidof, ping, ping6, pipe_progress, pivot_root, pkill,
	pmap, popmaildir, poweroff, powertop, printenv, printf, ps, pscan, pstree, pwd, pwdx,
	raidautorun, rdate, rdev, readahead, readlink, readprofile, realpath, reboot, reformime,
	remove-shell, renice, reset, resize, resume, rev, rm, rmdir, rmmod, route, rpm, rpm2cpio,
	rtcwake, run-init, run-parts, runlevel, runsv, runsvdir, rx, script, scriptreplay, sed,
	sendmail, seq, setarch, setconsole, setfattr, setfont, setkeycodes, setlogcons, setpriv,
	setserial, setsid, setuidgid, sh, sha1sum, sha256sum, sha3sum, sha512sum, showkey, shred,
	shuf, slattach, sleep, smemcap, softlimit, sort, split, ssl_client, start-stop-daemon, stat,
	strings, stty, su, sulogin, sum, sv, svc, svlogd, swapoff, swapon, switch_root, sync, sysctl,
	syslogd, tac, tail, tar, taskset, tcpsvd, tee, telnet, telnetd, test, tftp, tftpd, time,
	timeout, top, touch, tr, traceroute, traceroute6, true, truncate, tty, ttysize, tunctl,
	ubiattach, ubidetach, ubimkvol, ubirename, ubirmvol, ubirsvol, ubiupdatevol, udhcpc, udhcpd,
	udpsvd, uevent, umount, uname, unexpand, uniq, unix2dos, unlink, unlzma, unshare, unxz,
	unzip, uptime, users, usleep, uudecode, uuencode, vconfig, vi, vlock, volname, w, wall,
	watch, watchdog, wc, wget, which, who, whoami, whois, xargs, xxd, xz, xzcat, yes, zcat, zcip
```

デフォルトでこれだけたくさんのコマンドが入っている。

# インストール

デフォルトではカレントディレクトリの下の `_install` ディレクトリにシンボリックリンクを作ってくれる。変更したい場合は `make menuconfig` で以下を変更する。

```
         (./_install) Destination path for 'make install'       
```

```
make install
```

```
$ ls -lR ./_install/
./_install/:
total 12
drwxrwxr-x 2 koba koba 4096 Apr  9 03:20 bin
lrwxrwxrwx 1 koba koba   11 Apr  9 03:20 linuxrc -> bin/busybox
drwxrwxr-x 2 koba koba 4096 Apr  9 03:20 sbin
drwxrwxr-x 4 koba koba 4096 Apr  9 03:20 usr

./_install/bin:
total 2572
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 arch -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ash -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 base64 -> busybox
-rwxr-xr-x 1 koba koba 2630040 Apr  9 03:20 busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 cat -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 chattr -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 chgrp -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 chmod -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 chown -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 conspy -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 cp -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 cpio -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 cttyhack -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 date -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 dd -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 df -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 dmesg -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 dnsdomainname -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 dumpkmap -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 echo -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ed -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 egrep -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 false -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 fatattr -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 fdflush -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 fgrep -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 fsync -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 getopt -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 grep -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 gunzip -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 gzip -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 hostname -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 hush -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ionice -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 iostat -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ipcalc -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 kbd_mode -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 kill -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 link -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 linux32 -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 linux64 -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ln -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 login -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ls -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 lsattr -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 lzop -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 makemime -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mkdir -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mknod -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mktemp -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 more -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mount -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mountpoint -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mpstat -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mt -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 mv -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 netstat -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 nice -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 nuke -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 pidof -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ping -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ping6 -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 pipe_progress -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 printenv -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 ps -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 pwd -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 reformime -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 resume -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 rev -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 rm -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 rmdir -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 rpm -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 run-parts -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 scriptreplay -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 sed -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 setarch -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 setpriv -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 setserial -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 sh -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 sleep -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 stat -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 stty -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 su -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 sync -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 tar -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 touch -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 true -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 umount -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 uname -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 usleep -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 vi -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 watch -> busybox
lrwxrwxrwx 1 koba koba       7 Apr  9 03:20 zcat -> busybox

./_install/sbin:
total 0
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 acpid -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 adjtimex -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 arp -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 blkid -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 blockdev -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 bootchartd -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 depmod -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 devmem -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 fbsplash -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 fdisk -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 findfs -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 freeramdisk -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 fsck -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 fsck.minix -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 fstrim -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 getty -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 halt -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 hdparm -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 hwclock -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ifconfig -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ifdown -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ifenslave -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ifup -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 init -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 insmod -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ip -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ipaddr -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 iplink -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 ipneigh -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 iproute -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 iprule -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 iptunnel -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 klogd -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 loadkmap -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 logread -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 losetup -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 lsmod -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 makedevs -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mdev -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mkdosfs -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mke2fs -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mkfs.ext2 -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mkfs.minix -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mkfs.vfat -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 mkswap -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 modinfo -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 modprobe -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 nameif -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 pivot_root -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 poweroff -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 raidautorun -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 reboot -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 rmmod -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 route -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 run-init -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 runlevel -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 setconsole -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 slattach -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 start-stop-daemon -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 sulogin -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 swapoff -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 swapon -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 switch_root -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 sysctl -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 syslogd -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 tunctl -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 udhcpc -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 uevent -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 vconfig -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 watchdog -> ../bin/busybox
lrwxrwxrwx 1 koba koba 14 Apr  9 03:20 zcip -> ../bin/busybox

./_install/usr:
total 8
drwxrwxr-x 2 koba koba 4096 Apr  9 03:20 bin
drwxrwxr-x 2 koba koba 4096 Apr  9 03:20 sbin

./_install/usr/bin:
total 0
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 [ -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 [[ -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 awk -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 basename -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 beep -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 blkdiscard -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 bunzip2 -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 bzcat -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 bzip2 -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 cal -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chpst -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chrt -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chvt -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 cksum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 clear -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 cmp -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 comm -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 crontab -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 cryptpw -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 cut -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dc -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 deallocvt -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 diff -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dirname -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dos2unix -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dpkg -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dpkg-deb -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 du -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dumpleases -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 eject -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 env -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 envdir -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 envuidgid -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 expand -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 expr -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 factor -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fallocate -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fgconsole -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 find -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 flock -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fold -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 free -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ftpget -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ftpput -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fuser -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 groups -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 hd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 head -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 hexdump -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 hexedit -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 hostid -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 id -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 install -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ipcrm -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ipcs -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 killall -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 last -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 less -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 logger -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 logname -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lpq -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lpr -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lsof -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lspci -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lsscsi -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lsusb -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lzcat -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lzma -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 man -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 md5sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 mesg -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 microcom -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 mkfifo -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 mkpasswd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nc -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nl -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nmeter -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nohup -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nproc -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nsenter -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nslookup -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 od -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 openvt -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 passwd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 paste -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 patch -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pgrep -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pkill -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pmap -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 printf -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pscan -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pstree -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 pwdx -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 readlink -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 realpath -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 renice -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 reset -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 resize -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 rpm2cpio -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 runsv -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 runsvdir -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 rx -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 script -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 seq -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setfattr -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setkeycodes -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setsid -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setuidgid -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sha1sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sha256sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sha3sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sha512sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 showkey -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 shred -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 shuf -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 smemcap -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 softlimit -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sort -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 split -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ssl_client -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 strings -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sum -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sv -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 svc -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tac -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tail -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 taskset -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tcpsvd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tee -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 telnet -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 test -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tftp -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 time -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 timeout -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 top -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tr -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 traceroute -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 traceroute6 -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 truncate -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tty -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ttysize -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 udpsvd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unexpand -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 uniq -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unix2dos -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unlink -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unlzma -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unshare -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unxz -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 unzip -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 uptime -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 users -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 uudecode -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 uuencode -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 vlock -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 volname -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 w -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 wall -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 wc -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 wget -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 which -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 who -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 whoami -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 whois -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 xargs -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 xxd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 xz -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 xzcat -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 yes -> ../../bin/busybox

./_install/usr/sbin:
total 0
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 addgroup -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 add-shell -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 adduser -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 arping -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 brctl -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chat -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chpasswd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 chroot -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 crond -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 delgroup -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 deluser -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dhcprelay -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 dnsd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ether-wake -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fakeidentd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fbset -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fdformat -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 fsfreeze -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ftpd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 httpd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 i2cdetect -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 i2cdump -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 i2cget -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 i2cset -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ifplugd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 inetd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 killall5 -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 loadfont -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 lpd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nanddump -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nandwrite -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 nbd-client -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ntpd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 partprobe -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 popmaildir -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 powertop -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 rdate -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 rdev -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 readahead -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 readprofile -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 remove-shell -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 rtcwake -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 sendmail -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setfont -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 setlogcons -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 svlogd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 telnetd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 tftpd -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubiattach -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubidetach -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubimkvol -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubirename -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubirmvol -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubirsvol -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 ubiupdatevol -> ../../bin/busybox
lrwxrwxrwx 1 koba koba 17 Apr  9 03:20 udhcpd -> ../../bin/busybox
```

# 追記

この記事の手順でx86_64のbusyboxをビルドすると、ビルドしている環境のlibcがリンクされます。大抵の場合glibc になると思います。
glibcはstatic link してもネットワークのホスト名の解決には外部ライブラリを使用します。なので、単体のbusyboxだけではホスト名を解決できません。
詳しくはこの記事で。
[dockerでbusybox一個だけのファイルを含むイメージを作って動かしたらどうなるか](https://qiita.com/tetsu_koba/items/d861d4bab3bb88612ef4)