* [PATCH] proc(5): clarify the root symlink and mount namespaces @ 2016-10-06 1:36 Mike Frysinger [not found] ` <20161006013609.17481-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Mike Frysinger @ 2016-10-06 1:36 UTC (permalink / raw) To: Michael Kerrisk; +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA If the target process is in a different mount namespace, the root symlink actually shows that view of the filesystem. As an example: /* Terminal 1 */ $ unshare -Urnm 17168 /* Terminal 2 */ Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> --- man5/proc.5 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/man5/proc.5 b/man5/proc.5 index 3a5f4407c657..0680902c54a5 100644 --- a/man5/proc.5 +++ b/man5/proc.5 @@ -1513,6 +1513,10 @@ root directory, and behaves in the same way as and .IR fd/* . +Note however that this file is not merely a symlink. +It provides the same view of the filesystem (including namespaces and the +set of per-process mounts) as the process itself. + .\" The following was still true as at kernel 2.6.13 In a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated -- 2.9.0 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply related [flat|nested] 7+ messages in thread
[parent not found: <20161006013609.17481-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>]
* Re: [PATCH] proc(5): clarify the root symlink and mount namespaces [not found] ` <20161006013609.17481-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> @ 2016-10-06 5:51 ` Michael Kerrisk (man-pages) [not found] ` <f464f3c8-7c76-7288-d3dd-a7d7ffc05a75-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2016-10-06 17:23 ` [PATCH v2] " Mike Frysinger 1 sibling, 1 reply; 7+ messages in thread From: Michael Kerrisk (man-pages) @ 2016-10-06 5:51 UTC (permalink / raw) To: Mike Frysinger Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w, linux-man-u79uwXL29TY76Z2rM5mHXA Hi Mike, On 10/06/2016 03:36 AM, Mike Frysinger wrote: > If the target process is in a different mount namespace, the root symlink > actually shows that view of the filesystem. As an example: > /* Terminal 1 */ > $ unshare -Urnm > 17168 > > /* Terminal 2 */ Your example appears to have been truncated. It'd be nice to have the complete example for the commit message. Could you send that? Thanks, Michael > Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> > --- > man5/proc.5 | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/man5/proc.5 b/man5/proc.5 > index 3a5f4407c657..0680902c54a5 100644 > --- a/man5/proc.5 > +++ b/man5/proc.5 > @@ -1513,6 +1513,10 @@ root directory, and behaves in the same way as > and > .IR fd/* . > > +Note however that this file is not merely a symlink. > +It provides the same view of the filesystem (including namespaces and the > +set of per-process mounts) as the process itself. > + > .\" The following was still true as at kernel 2.6.13 > In a multithreaded process, the contents of this symbolic link > are not available if the main thread has already terminated > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply [flat|nested] 7+ messages in thread
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* Re: [PATCH] proc(5): clarify the root symlink and mount namespaces [not found] ` <f464f3c8-7c76-7288-d3dd-a7d7ffc05a75-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> @ 2016-10-06 17:23 ` Mike Frysinger 0 siblings, 0 replies; 7+ messages in thread From: Mike Frysinger @ 2016-10-06 17:23 UTC (permalink / raw) To: Michael Kerrisk (man-pages); +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA [-- Attachment #1: Type: text/plain, Size: 613 bytes --] On 06 Oct 2016 07:51, Michael Kerrisk (man-pages) wrote: > On 10/06/2016 03:36 AM, Mike Frysinger wrote: > > If the target process is in a different mount namespace, the root symlink > > actually shows that view of the filesystem. As an example: > > /* Terminal 1 */ > > $ unshare -Urnm > > 17168 > > > > /* Terminal 2 */ > > Your example appears to have been truncated. It'd be nice to have the > complete example for the commit message. Could you send that? blah, i sometimes forget that git eats lines that start with a #, so trying to use that as your root prompt messes things up. -mike [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] proc(5): clarify the root symlink and mount namespaces [not found] ` <20161006013609.17481-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> 2016-10-06 5:51 ` Michael Kerrisk (man-pages) @ 2016-10-06 17:23 ` Mike Frysinger [not found] ` <20161006172322.3253-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> 1 sibling, 1 reply; 7+ messages in thread From: Mike Frysinger @ 2016-10-06 17:23 UTC (permalink / raw) To: Michael Kerrisk; +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA If the target process is in a different mount namespace, the root symlink actually shows that view of the filesystem. As an example: /* Terminal 1 */ $ unshare -Urnm # mount -t tmpfs tmpfs /etc # mount --bind /bin /dev # echo $$ 17168 /* Terminal 2 */ # ls /etc # Normal view of /etc files. # ls /proc/17168/root/etc # Empty view of the tmpfs. # ls /dev # Normal view of /dev files. # ls /proc/17168/root/dev # Contents of /bin files. Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> --- v2 - restore examples man5/proc.5 | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/man5/proc.5 b/man5/proc.5 index 3a5f4407c657..0680902c54a5 100644 --- a/man5/proc.5 +++ b/man5/proc.5 @@ -1513,6 +1513,10 @@ root directory, and behaves in the same way as and .IR fd/* . +Note however that this file is not merely a symlink. +It provides the same view of the filesystem (including namespaces and the +set of per-process mounts) as the process itself. + .\" The following was still true as at kernel 2.6.13 In a multithreaded process, the contents of this symbolic link are not available if the main thread has already terminated -- 2.9.0 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply related [flat|nested] 7+ messages in thread
[parent not found: <20161006172322.3253-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>]
* Re: [PATCH v2] proc(5): clarify the root symlink and mount namespaces [not found] ` <20161006172322.3253-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> @ 2016-10-07 12:33 ` Michael Kerrisk (man-pages) [not found] ` <03f48447-e197-fb88-c7fd-ec8c01c38cf7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Michael Kerrisk (man-pages) @ 2016-10-07 12:33 UTC (permalink / raw) To: Mike Frysinger Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w, linux-man-u79uwXL29TY76Z2rM5mHXA Hi Mike, On 10/06/2016 07:23 PM, Mike Frysinger wrote: > If the target process is in a different mount namespace, the root symlink > actually shows that view of the filesystem. As an example: > /* Terminal 1 */ > $ unshare -Urnm > # mount -t tmpfs tmpfs /etc > # mount --bind /bin /dev > # echo $$ > 17168 > > /* Terminal 2 */ > # ls /etc # Normal view of /etc files. > # ls /proc/17168/root/etc # Empty view of the tmpfs. > # ls /dev # Normal view of /dev files. > # ls /proc/17168/root/dev # Contents of /bin files. Thanks for the patch! And thanks for the commit message, which is I think actually useful text for the man page itself, so I added it (in somewhat modified form) to the page itself. Cheers, Michael > Signed-off-by: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> > --- > v2 > - restore examples > > man5/proc.5 | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/man5/proc.5 b/man5/proc.5 > index 3a5f4407c657..0680902c54a5 100644 > --- a/man5/proc.5 > +++ b/man5/proc.5 > @@ -1513,6 +1513,10 @@ root directory, and behaves in the same way as > and > .IR fd/* . > > +Note however that this file is not merely a symlink. > +It provides the same view of the filesystem (including namespaces and the > +set of per-process mounts) as the process itself. > + > .\" The following was still true as at kernel 2.6.13 > In a multithreaded process, the contents of this symbolic link > are not available if the main thread has already terminated > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply [flat|nested] 7+ messages in thread
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* Re: [PATCH v2] proc(5): clarify the root symlink and mount namespaces [not found] ` <03f48447-e197-fb88-c7fd-ec8c01c38cf7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> @ 2016-10-07 19:21 ` Mike Frysinger [not found] ` <20161007192100.GY21655-UgUKS2FnFs9+urZeOPWqwQ@public.gmane.org> 0 siblings, 1 reply; 7+ messages in thread From: Mike Frysinger @ 2016-10-07 19:21 UTC (permalink / raw) To: Michael Kerrisk (man-pages); +Cc: linux-man-u79uwXL29TY76Z2rM5mHXA [-- Attachment #1: Type: text/plain, Size: 1689 bytes --] On 07 Oct 2016 14:33, Michael Kerrisk (man-pages) wrote: > On 10/06/2016 07:23 PM, Mike Frysinger wrote: > > If the target process is in a different mount namespace, the root symlink > > actually shows that view of the filesystem. As an example: > > /* Terminal 1 */ > > $ unshare -Urnm > > # mount -t tmpfs tmpfs /etc > > # mount --bind /bin /dev > > # echo $$ > > 17168 > > > > /* Terminal 2 */ > > # ls /etc # Normal view of /etc files. > > # ls /proc/17168/root/etc # Empty view of the tmpfs. > > # ls /dev # Normal view of /dev files. > > # ls /proc/17168/root/dev # Contents of /bin files. > > Thanks for the patch! And thanks for the commit message, which is I think > actually useful text for the man page itself, so I added it (in somewhat > modified form) to the page itself. looks like some formatting is off ? -mike --- a/man5/proc.5 +++ b/man5/proc.5 @@ -1525,7 +1525,7 @@ and in that shell we create some new mount points: $ \fBPS1='sh1# ' unshare \-Urnm\fP sh1# \fBmount \-t tmpfs tmpfs /etc\fP # Mount empty tmpfs at /etc sh1# \fBmount \-\-bind /usr /dev\fP # Mount /usr at /dev -sh1# \fBecho $$ +sh1# \fBecho $$\fP 27123 .in .fi @@ -1533,10 +1533,10 @@ sh1# \fBecho $$ In a second terminal window, in the initial mount namespace, we look at the contents of the corresponding mounts in the initial and new namespaces: - + .nf .in +4n -$ \fBPS1='sh2# ' sudo sh +$ \fBPS1='sh2# ' sudo sh\fP sh2# \fBls /etc | wc \-l\fP # In initial NS 309 sh2# \fBls /proc/27123/root/etc | wc \-l\fP # /etc in other NS [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 819 bytes --] ^ permalink raw reply [flat|nested] 7+ messages in thread
[parent not found: <20161007192100.GY21655-UgUKS2FnFs9+urZeOPWqwQ@public.gmane.org>]
* Re: [PATCH v2] proc(5): clarify the root symlink and mount namespaces [not found] ` <20161007192100.GY21655-UgUKS2FnFs9+urZeOPWqwQ@public.gmane.org> @ 2016-10-07 20:50 ` Michael Kerrisk (man-pages) 0 siblings, 0 replies; 7+ messages in thread From: Michael Kerrisk (man-pages) @ 2016-10-07 20:50 UTC (permalink / raw) To: linux-man-u79uwXL29TY76Z2rM5mHXA; +Cc: mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w On 10/07/2016 09:21 PM, Mike Frysinger wrote: > On 07 Oct 2016 14:33, Michael Kerrisk (man-pages) wrote: >> On 10/06/2016 07:23 PM, Mike Frysinger wrote: >>> If the target process is in a different mount namespace, the root symlink >>> actually shows that view of the filesystem. As an example: >>> /* Terminal 1 */ >>> $ unshare -Urnm >>> # mount -t tmpfs tmpfs /etc >>> # mount --bind /bin /dev >>> # echo $$ >>> 17168 >>> >>> /* Terminal 2 */ >>> # ls /etc # Normal view of /etc files. >>> # ls /proc/17168/root/etc # Empty view of the tmpfs. >>> # ls /dev # Normal view of /dev files. >>> # ls /proc/17168/root/dev # Contents of /bin files. >> >> Thanks for the patch! And thanks for the commit message, which is I think >> actually useful text for the man page itself, so I added it (in somewhat >> modified form) to the page itself. > > looks like some formatting is off ? Thanks, Mike. Patch applied. Cheers, Michael > --- a/man5/proc.5 > +++ b/man5/proc.5 > @@ -1525,7 +1525,7 @@ and in that shell we create some new mount points: > $ \fBPS1='sh1# ' unshare \-Urnm\fP > sh1# \fBmount \-t tmpfs tmpfs /etc\fP # Mount empty tmpfs at /etc > sh1# \fBmount \-\-bind /usr /dev\fP # Mount /usr at /dev > -sh1# \fBecho $$ > +sh1# \fBecho $$\fP > 27123 > .in > .fi > @@ -1533,10 +1533,10 @@ sh1# \fBecho $$ > In a second terminal window, in the initial mount namespace, > we look at the contents of the corresponding mounts in > the initial and new namespaces: > - > + > .nf > .in +4n > -$ \fBPS1='sh2# ' sudo sh > +$ \fBPS1='sh2# ' sudo sh\fP > sh2# \fBls /etc | wc \-l\fP # In initial NS > 309 > sh2# \fBls /proc/27123/root/etc | wc \-l\fP # /etc in other NS > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2016-10-07 20:50 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-10-06 1:36 [PATCH] proc(5): clarify the root symlink and mount namespaces Mike Frysinger [not found] ` <20161006013609.17481-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> 2016-10-06 5:51 ` Michael Kerrisk (man-pages) [not found] ` <f464f3c8-7c76-7288-d3dd-a7d7ffc05a75-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2016-10-06 17:23 ` Mike Frysinger 2016-10-06 17:23 ` [PATCH v2] " Mike Frysinger [not found] ` <20161006172322.3253-1-vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org> 2016-10-07 12:33 ` Michael Kerrisk (man-pages) [not found] ` <03f48447-e197-fb88-c7fd-ec8c01c38cf7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 2016-10-07 19:21 ` Mike Frysinger [not found] ` <20161007192100.GY21655-UgUKS2FnFs9+urZeOPWqwQ@public.gmane.org> 2016-10-07 20:50 ` Michael Kerrisk (man-pages)
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