[patch] unshare.2: Add note about potential capabilities confusion

[Patrick Reader <_@pxeger.com>]

See https://bugzilla.kernel.org/show_bug.cgi?id=216215 for context.

I know nothing about groff formatting, so what I wrote here is based on 
my inference from reading the existing source. If it's wrong, I apologise.


Signed-off-by: Patrick Reader <_@pxeger.com>
---
  man/man2/unshare.2 | 10 ++++++++++
  1 file changed, 10 insertions(+)

diff --git a/man/man2/unshare.2 b/man/man2/unshare.2
index e72464950..851129022 100644
--- a/man/man2/unshare.2
+++ b/man/man2/unshare.2
@@ -461,6 +461,16 @@ Such functionality may be added in the future, if 
required.
  .\"be incrementally added to unshare without affecting legacy
  .\"applications using unshare.
  .\"
+.PP
+Creating all kinds of namespace, except user namespaces, requires the
+.B CAP_SYS_ADMIN
+capability. However, since creating a user namespace automatically 
confers a
+full set of capabilities, creating both a user namespace and any other type
+of namespace in the same
+.BR unshare ()
+call does not require the
+.B CAP_SYS_ADMIN
+capability in the original namespace.
  .SH EXAMPLES
  The program below provides a simple implementation of the
  .BR unshare (1)
-- 
2.37.3