Output compiler options from SSH

Question

How can I list the configuration options that ssh/sshd was compiled with?

I'm attempting to troubleshoot a SELinux configuration issue, and want to make sure that SSH was compiled with --with-selinux.

Answer 1

I don't think there's a way to list compilation options, but something like SELinux support should be apparent from the libraries that the executable is linked against:

$ ldd /usr/bin/ssh /usr/sbin/sshd | egrep '^/|selinux'
/usr/bin/ssh:
/usr/sbin/sshd:
        libselinux.so.1 => /lib/libselinux.so.1 (0x00007fbbfed5f000)

Looks like sshd has SELinux support but ssh doesn't (why would it?) on my system.

Another thing you could check (e.g. in case you had a static binary) is if there binary references some SELinux functions.

strings /usr/sbin/sshd |grep -i selinux

Answer 2

I think you may need to look at the packaging system for your distro and find the options it compiles with. Some programs can output their compile flags, but I don't know of such an option for sshd.

Answer 3

If you are installing the default distribution packages, and

• the distribution is Debian based, look at the debian/rules file (basically a Makefile) in the package source for the configuration options.

• the distribution is rpm based, look at the compilation options, probably in the source rpm's spec file.

For custom distributions like Gentoo, where there are no default compilations options, this is more difficult, and I'd talk to the person who built the package, and also look at ldd as people have suggested.

If you specify your distribution, as you should have done initially, people can presumably give you more specific pointers.