Why can't I dtrace processes running in a jail from the host?
Patrick M. Hausen
hausen at punkt.de
Thu Aug 16 07:25:41 UTC 2018
I did some further investigation and with help from Mark was
finally able to get it working.
Took quite some effort - documentation on the PHP side - NULL :-/
BTW: has anyone ever successfully subscribed to one of the PHP
mailing lists? Where is the community of the people developing that
OK, back to topic, in fact I had two issues, one FreeBSD, one PHP
1. DTrace'ing jailed userland probes requires /dev/dtrace/* to
be visible inside the jail.
add include $devfsrules_jail
add path dtrace/* unhide
iocage set devfs_ruleset=100 vpro0069
Voila - dtrace on the host, watch userland probes in the jail.
2. PHP > 5.6 needs the environment variable USE_ZEND_DTRACE
to be set to register it's probes.
Turned out that it was not sufficient to *configure* that into the PHP
FPM worker but you need to set (and export) the variable on the shell
before you start the FPM master daemon. Then everything works as expected.
What I regularly do in such a case is
sh -x /usr/local/etc/rc.d/php-fpm start
to find out what command is actually executed in the end. Then call that directly
after setting the environment. Result:
setenv USE_ZEND_DTRACE 1
limits -C daemon /usr/local/sbin/php-fpm
Bingo! Surprisingly enough it is *not* necessary to configure
clear_env = no
in PHP FPM ... DTrace is active as soon as the master daemon sees that
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