How to list imported symbols in ELF executable?

Try objdump -T 'ELF-file'

The output from objdump is a little excessive for this purpose, and requires a good bit of parsing to find the actual imports.

I prefer readelf for this purpose:

readelf -d dynamic-buffer-test

Dynamic section at offset 0x630a8 contains 23 entries:
 Tag                Type                 Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libstdc++.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libm.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]
 0x0000000000000001 (NEEDED)             Shared library: [libgcc_s.so.1]

As you can see, the required libraries are marked with "NEEDED".

I prefer readelf.

readelf -s <file>