I nearly locked myself out updating a server (from -6 to -8). I booted the new kernel (single user), mounted /usr, /var and /tmp, extracted base.tgz (excluding /rescue, fortunately), but had forgotten to remount / rw. After that (I interrupted tar), tar didn't work any more. Well, I had /rescue/tar. Unfortunately, with z, it said Shared object "liblzma.so.2" not found Fortunately, I could /rescue/gzcat base.tgz >base.tar and tar x that.
So why does something in /rescue need a shared library?