Discussion:
[Bug 219055] nice jail anomoly - values not passed into jailed processes when using jexec -U username
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b***@freebsd.org
2017-05-04 05:45:29 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219055

Mark Linimon <***@FreeBSD.org> changed:

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b***@freebsd.org
2017-05-04 13:28:32 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219055

Fabian Keil <***@fabiankeil.de> changed:

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--- Comment #1 from Fabian Keil <***@fabiankeil.de> ---
If one of its options is set, jexec(8) uses the login class information
which overrides the initial priority of jexec(8) itself.

While the man page could make this more obvious (I had to look at
the code), this is the "expected" behaviour and not a bug in the tool.

I frequently use commands like:
sudo jexec -U root poudriere env PS1='\u@\h \w \$' nice -n 20
/usr/local/bin/bash

They work as expected and don't rely on any "workarounds"
or undocumented jexec(8) behaviour.
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b***@freebsd.org
2017-05-05 06:54:53 UTC
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219055

--- Comment #2 from ***@heuristicsystems.com.au ---
(In reply to Fabian Keil from comment #1)
Thanks Fabian, you're quite right. And the example that you provided did have
the same successful outcome for me. Unfortunately I'm trying to elevate the
priority of a database over all other activies. So setting any priority less
than 0 doesn't work, whether I use

JAIL=b2 in my base or for you, (hint to cut/paste) ;)
JAIL=poudriere
nice -n -1 jexec -U root $JAIL ps -l
or
jexec -U root $JAIL nice -n -1 ps -l

The NI and PRI values remain 0 and 72 respectively, that is default (no nice)
value. I kinda get it that within the jail context the priority can't be
elevated, but with executing the process from within the context of the base
system should work.

This successful result also suggests that elevating via nice should work.
# rtprio 0 jexec -U root b2 ps -l
UID PID PPID CPU PRI NI VSZ RSS MWCHAN STAT TT TIME COMMAND
0 97468 90697 0 -52 0 21140 2276 - R+J 7 0:00.00 ps -l
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