Add an entry for CLONE_PIDFD. This flag is available starting
with kernel 5.2. If specified, a process file descriptor
("pidfd") referring to the child process will be returned in
the ptid argument.
Signed-off-by: Christian Brauner <christian@brauner.io>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
After my rewriting, almost nothing of the original page remains,
so update the copyright. As the author, I'm relicensing to the
"verbatim" license most commonly used in man pages.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The text stating that "pivot_root() may or may not change the
current root and the current working directory of any processes
or threads which use the old root directory" was written 19 years
ago, before the system call itself was even finalized in the
kernel. The implementation has never changed, and it won't
change in the future, since that would cause user-space breakage.
The existence of that text in DESCRIPTION, followed by qualifying
text stating what the implementation actually does (and has always
done) makes for confusing reading. Therefore, relegate this text
to a historical note in NOTES (so that readers with long memories
can see why the manual page was changed) and rework the text in
DESCRIPTION accordingly.
Reported-by: Philipp Wendler <ml@philippwendler.de>
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Reported-by: Reid Priedhorsky <reidpr@lanl.gov>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Quoting Eric:
If we are going to be pedantic "filesystem" is really the
wrong concept here. The section about bind mount clarifies
it, but I wonder if there is a better term.
I think I would say: "new_root and put_old must not be on
the same mount as the current root."
I think using "mount" instead of "filesystem" keeps the
concepts less confusing.
As I am reading through this email and seeing text that is
trying to be precise and clear then hitting the term
"filesystem" is a bit jarring. pivot_root doesn't care a
thing for file systems. pivot_root only cares about mounts.
And by a "mount" I mean the thing that you get when you
create a bind mount or you call mount normally.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Philipp Wendler noted that the text on the restrictions for
'new_root' was slightly contradictory, and things could be
clarified and simplified by describing the restrictions on
'new_root' in one place.
Reported-by: Philipp Wendler <ml@philippwendler.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Remove the text that suggests that pivot_root() changes the root
directory and CWD of process that have directory and CWD on the
old root *filesystem*. Change "filesystem" to "directory".
Reported-by: Philipp Wendler <ml@philippwendler.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Make the page more compact by removing the stub subsections that
list the manual pages for the namespace types. And while we're
here, add an explanation of the table columns.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Eric Biederman:
I hate to nitpick, but I am going to say that when I read
the text above the phrase "mount namespace of the process
that created the new mount namespace" feels wrong.
Either you use unshare(2) and the mount namespace of the
process that created the mount namespace changes.
Or you use clone(2) and you could argue it is the new child
that created the mount namespace.
Having a different mount namespace at the end of the
creation operation feels like it makes your phrase confusing
about what the starting mount namespace is. I hate to use
references that are ambiguous when things are changing.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Provide a more detailed explanation of the initialization of
the mount point list in a new mount namespace.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reid noted a confusion between 'old_root' (my attempt at a
shorthand for the old root point) and 'put_old. Eliminate the
confusion by replacing the shorthand with "old root mount point".
Reported-by: Reid Priedhorsky <reidpr@lanl.gov>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The current text talks about "parent mount namespaces", but there
is no such concept. As confirmed by Eric Biederman, what is mean
here is "the mount namespace this mount namespace started as a
copy of". So, this change writes up Eric's description in a more
detailed way.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Eric Biederman notes that the change in commit f646ac88ef was
not strictly necessary for this example, since one of the already
documented requirements is that various mount points must not have
shared propagation, or else pivot_root() will fail. So, simplify
the example.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
After creating a new mount namespace, it may be desirable to
disable mount propagation. Give the reader a more explicit
hint about this.
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
In a recent conversation with Mathieu Desnoyers I was reminded
that we haven't written up anything about how deferred
cancellation and asynchronous signal handlers interact. Mathieu
ran into some of this behaviour and I promised to improve the
documentation in this area to point out the potential pitfall.
Thoughts?
8< --- 8< --- 8<
In pthread_setcancelstate.3, pthreads.7, and signal-safety.7 we
describe that if you have an asynchronous signal nesting over a
deferred cancellation region that any cancellation point in the
signal handler may trigger a cancellation that will behave
as-if it was an asynchronous cancellation. This asynchronous
cancellation may have unexpected effects on the consistency of
the application. Therefore care should be taken with asynchronous
signals and deferred cancellation.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Update with all the missing errors the syscall can return, the
behaviour the syscall should have w.r.t. to copies within single
files, etc.
[Amir] updates for final released version.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk