Как узнать версию библиотеки libc?

Достаточно просто запустить файл библиотеки:

/lib/libc.so.6

GNU C Library stable release version 2.14.1, by Roland McGrath et al.
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.5.3.
Compiled on a Linux 3.2.0 system on 2012-01-18.
Available extensions:
        C stubs add-on version 2.1.2
        crypt add-on version 2.1 by Michael Glad and others
        Gentoo patchset 3
        GNU Libidn by Simon Josefsson
        Native POSIX Threads Library by Ulrich Drepper et al
        Support for some architectures added on, not maintained in glibc core.
        BIND-8.2.3-T5B
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
.