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    SubjectRe: A Plumber’s Wish List for Linux
    Lennart Poettering <mzxreary@0pointer.de> writes:

    > On Fri, 07.10.11 00:49, Matt Helsley (matthltc@us.ibm.com) wrote:
    >
    >>
    >> On Fri, Oct 07, 2011 at 01:17:02AM +0200, Kay Sievers wrote:
    >>
    >> <snip>
    >>
    >> > * simple, reliable and future-proof way to detect whether a specific pid
    >> > is running in a CLONE_NEWPID container, i.e. not in the root PID
    >> > namespace. Currently, there are available a few ugly hacks to detect
    >>
    >> Is that precisely what's needed or would it be sufficient to know
    >> that the pid is running in a child pid namespace of the current pid
    >> namespace? If so, I think this could eventually be done by comparing
    >> the inode numbers assigned to /proc/<pid>/ns/pid to those of
    >> /proc/1/ns/pid.
    >
    > I think the most interesting test would be to figure out for a process
    > if itself is running in a PID namespace. And for that comparing inodes
    > wouldn't work since the namespace process would never get access to the
    > inode of the outside init.

    Strictly correct answer. All processes are running in a pid namespace.
    I think we can implement that in a libc header.

    static inline bool in_pid_namespace(void)
    {
    return true;
    }

    Why does it matter if you are running in something other than the
    initial pid namespace? I expect what you are really after is something
    else entirely, and you are asking the wrong question.

    Eric


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