Schrödinger's file - sh

Question

I am puzzled by the following sequence of commands.
sh-4.2$ pwd
/home/willard
sh-4.2$ ls -l f
-rwxr-xr-x 1 willard users 59116 Jan 23 14:54 f
sh-4.2$ file f
f: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, BuildID[sha1]=0xea0e08ff2b5a062698d45b78177acdd6bf140d1f, stripped
sh-4.2$ ./f
sh: ./f: No such file or directory
sh-4.2$ strace ./f
execve("./f", ["./f"], [/* 32 vars */]) = -1 ENOENT (No such file or directory)
write(2, "strace: exec: No such file or di"..., 40strace: exec: No such file or directory
) = 40
exit_group(1) = ?
+++ exited with 1 +++
sh-4.2$ ls -l f
-rwxr-xr-x 1 willard users 59116 Jan 23 14:54 f
sh-4.2$ uname -a
Linux xdat10 3.6.2-1-ARCH #1 SMP PREEMPT Fri Oct 12 23:58:58 CEST 2012 x86_64 GNU/Linux
How is this possible?

Answer 1

I found someone having the same problem (with relative explanation)
Running 32bit binary on a 64bit system
Quoting the most important sentences:
This situation often arises when you try to run a binary for the right
system (or family of systems) and superarchitecture but the wrong
subarchitecture. Here you have ELF binaries on a system that expects
ELF binaries, so the kernel loads them just fine. They are i386
binaries running on an x86_64 processor, so the instructions make
sense and get the program to the point where it can look for its
loader. But the program is a 32-bit program (as the file output
indicates), looking for the 32-bit loader /lib/ld-linux.so.2, and
you've presumably only installed the 64-bit loader
/lib64/ld-linux-x86-64.so.2 in the chroot.
You need to install the 32-bit runtime system in the chroot: the
loader, and all the libraries the programs need. On Debian amd64, the
32-bit loader is in the libc6-i386 package. You can install a bigger
set of 32-bit libraries by installing ia32-libs.
I bet there's a better way to verify this but i'd try to exec
ldd ./f
and search in the output which loader is needed to exec'it

Answer 2

man 2 execve:
ENOENT The file filename or a script or ELF interpreter does not
exist, or a shared library needed for file or interpreter can‐
not be found.
You could run ldd against this binary to look for libraries that could not be mapped and install them from multilib.