Binutils compilation: mkdir: cannot create directory `/tools': Permission denied

[jaredp]

Received a permission error while following the Binutils compilation from ch5:
http://www.linuxfromscratch.org/lfs/view/6.4/chapter05/binutils-pass1.html

The problem seems similar to the thread
http://www.linuxfromscratch.org/pipermail/lfs-support/2005-June/027472.html

What differed from the book was that the command time { ./configure
... && make && make install; }.
wouldn't work because there was no ./configure script.  So I just did
the following:
time { make && make install; }

I received the following error when compiling as lfs (i.e. after the su - lfs)
.......
make[4]: Leaving directory `/mnt/lfs/sources/binutils-build/ld'
make[3]: Leaving directory `/mnt/lfs/sources/binutils-build/ld'
make[2]: Leaving directory `/mnt/lfs/sources/binutils-build/ld'
make[1]: Nothing to be done for `all-target'.
make[1]: Leaving directory `/mnt/lfs/sources/binutils-build'
make[1]: Entering directory `/mnt/lfs/sources/binutils-build'
/bin/bash ../binutils-2.18/mkinstalldirs /tools /tools
mkdir -p -- /tools /tools
mkdir: cannot create directory `/tools': Permission denied
mkdir: cannot create directory `/tools': Permission denied
make[1]: *** [installdirs] Error 1
make[1]: Leaving directory `/mnt/lfs/sources/binutils-build'
make: *** [install] Error 2

real 3m33.981s
user 2m27.629s
sys 0m38.426s

=================

Permissions for /mnt/lfs/sources and /mnt/lfs/tools are:
drwxrwxrwt 4 lfs  root  4096 Feb 11 22:14 sources
drwxr-xr-x 2 lfs  root  4096 Feb 11 20:54 tools

Shouldn't root be my lfs group?
I followed instructions at
http://www.linuxfromscratch.org/lfs/view/6.4/chapter04/addinguser.html
and everything seemed to work

My host is Ubuntu 8.04.  Maybe it's something with sudo v.s. su when I
did su - lfs?

Thanks,
Jared