From c9a35b01a1983ff9277202f0c8e2975b2e57ac02 Mon Sep 17 00:00:00 2001 From: Michael Kerrisk Date: Sun, 14 Oct 2018 13:56:27 +0200 Subject: [PATCH] cgroup_namespaces.7: Clarify Clarify the example by making an implied detail more explicit. Quoting the Troy Engel on the problem with the original text: The problem is "and a process in a sibling cgroup (sub2)" (shown as PID 20124 here) - how did this get here? How do I recreate this? Following this example, there's no mention of how, it's out of place when following the instructions. There is nothing in any of the cgroup files which contain this (# grep freezer /proc/*/cgroup) while at this stage. The intent is understood, however the man page seems to skip a step to create this in the teaching example. We should add whatever simple steps are needed to create the "process in a sibling cgroup" as outlined so it makes sense - as written, I have no clue where "sibling cgroup (sub2)" came from, it just appeared out of the blue in that step. Thanks! See https://bugzilla.kernel.org/show_bug.cgi?id=201047 Reported-by: Troy Engel Signed-off-by: Michael Kerrisk --- man7/cgroup_namespaces.7 | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/man7/cgroup_namespaces.7 b/man7/cgroup_namespaces.7 index 135e5d7bd..72a473cf6 100644 --- a/man7/cgroup_namespaces.7 +++ b/man7/cgroup_namespaces.7 @@ -67,9 +67,24 @@ entries for each ancestor level in the cgroup hierarchy. .PP The following shell session demonstrates the effect of creating a new cgroup namespace. +.PP First, (as superuser) we create a child cgroup in the .I freezer -hierarchy, and put the shell into that cgroup: +hierarchy, and place a process in that cgroup that we will +use as part of the demonstration below: +.PP +.in +4n +.EX +# \fBmkdir \-p /sys/fs/cgroup/freezer/sub2\fP +# \fBsleep 10000 &\fP # Create a process that lives for a while +[1] 20124 +# \fBecho 20124 > /sys/fs/cgroup/freezer/sub2/cgroup.procs\fP +.EE +.in +.PP +We then create another child cgroup in the +.I freezer +hierarchy and put the shell into that cgroup: .PP .in +4n .EX @@ -98,7 +113,7 @@ files of, respectively, the new shell process started by the .BR unshare (1) command, a process that is in the original cgroup namespace .RI ( init , -with PID 1), and a process in a sibling cgroup +with PID 1), and the process in the sibling cgroup .RI ( sub2 ): .PP .EX