I believe ubuntu comes with busybox. If ubuntu's version of busybox is compiled statically, it will provide a minimal shell and minimal toolset without any libraries. ...which is kind of the point of having it, so I hope so.
On my Gentoo system, /bin/bb is a minimal shell, and /bin/busybox can be used to call the builtin programs:
$ /bin/busybox
BusyBox v1.15.3 (2010-12-30 13:47:04 CST) multi-call binary
Copyright (C) 1998-2008 Erik Andersen, Rob Landley, Denys Vlasenko
and others. Licensed under GPLv2.
See source distribution for full notice.
Usage: busybox [function] [arguments]...
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, addgroup, adduser, adjtimex, ar, arp, arping, ash, awk,
basename, bb, bbconfig, bbsh, beep, blkid, brctl, bunzip2, bzcat,
bzip2, cal, cat, catv, chat, chattr, chgrp, chmod, chown, chpasswd,
chpst, chroot, chrt, chvt, cksum, clear, cmp, comm, cp, cpio, crond,
cryptpw, cttyhack, cut, date, dd, deallocvt, delgroup, deluser, depmod,
devmem, df, dhcprelay, diff, dirname, dmesg, dnsdomainname, dos2unix,
dpkg-deb, du, dumpkmap, dumpleases, echo, ed, egrep, eject, env,
envdir, envuidgid, ether-wake, expand, expr, false, fbset, fdflush,
fdformat, fdisk, fgrep, find, findfs, flash_eraseall, flash_lock,
flash_unlock, free, freeramdisk, fsck, fsck.minix, fsync, ftpd, fuser,
getopt, getty, grep, gunzip, gzip, halt, hd, hdparm, head, hexdump,
hostname, httpd, hwclock, id, ifconfig, ifdown, ifenslave, ifplugd,
ifup, init, insmod, install, ionice, ip, ipaddr, ipcrm, ipcs, iplink,
iproute, iprule, iptunnel, kbd_mode, kill, killall, killall5, klogd,
last, length, less, linux32, linux64, linuxrc, ln, loadfont, loadkmap,
logger, login, logread, losetup, lpq, lpr, ls, lsattr, lsmod, lzmacat,
lzop, lzopcat, makedevs, makemime, man, md5sum, mdev, mesg, microcom,
mkdir, mkdosfs, mkfifo, mkfs.minix, mkfs.vfat, mknod, mkpasswd, mkswap,
mktemp, modprobe, more, mount, mountpoint, mt, mv, nameif, nc, netstat,
nice, nmeter, nohup, nslookup, openvt, passwd, patch, pgrep, pidof,
ping, ping6, pipe_progress, pivot_root, pkill, popmaildir, poweroff,
printenv, printf, ps, pscan, pwd, raidautorun, rdate, rdev, readahead,
readlink, readprofile, realpath, reboot, reformime, renice, reset,
resize, rm, rmdir, rmmod, route, rtcwake, run-parts, runlevel, runsv,
runsvdir, rx, script, scriptreplay, sed, sendmail, seq, setarch,
setconsole, setfont, setkeycodes, setlogcons, setsid, setuidgid, sh,
sha1sum, sha256sum, sha512sum, showkey, sleep, softlimit, sort, split,
start-stop-daemon, stat, strings, stty, su, sum, sv, svlogd, swapoff,
swapon, switch_root, sync, sysctl, syslogd, tac, tail, tar, tee,
telnet, telnetd, test, tftp, tftpd, time, timeout, top, touch, tr,
traceroute, true, tty, ttysize, tunctl, udhcpc, udhcpd, umount, uname,
uncompress, unexpand, uniq, unix2dos, unlzma, unlzop, unzip, uptime,
usleep, vconfig, vi, vlock, volname, watch, watchdog, wc, wget, which,
who, whoami, xargs, yes, zcat, zcip
$ ls -l /bin/bb
lrwxrwxrwx 1 root root 7 Dec 30 13:48 /bin/bb -> busybox
$ ldd /bin/busybox
not a dynamic executable
$ /bin/bb
~ # /bin/busybox touch file
~ # /bin/busybox ls -l file
-rw-r--r-- 1 root root 0 Dec 30 13:52 file
~ # /bin/busybox mv file file2
~ # /bin/busybox ls -l file2
-rw-r--r-- 1 root root 0 Dec 30 13:52 file2
~ #
If you have a shell and nothing else, this might be able to save you. If not, you might be able to boot with "init=/bin/bb", maybe.
Otherwise, you're back at the livecd option.
