I need some help to understand why a PHP-FPM chrooted PHP script fails to resolve an FQDN few instants after the PHP-FPM service started.
When I (re)start the PHP-FPM service, it works (resolution succeeds) a few seconds and then resolution fails.
I chrooted a PHP application (a WordPress actually) via PHP-FPM (settings `` chroot` in the PHP-FPM pool configuration file) and gave PHP what it needed:
/etc/hosts
filemount --bind
of /etc/ssl/certs /dev/urandom
(via mknod
) mount --bind
of /usr/share/zoneinfo mount --bind
of /var/run/mysqld for the socket to MySQL.mount --bind
of /var/run/nscd for the socket to nscd resolver.I noticed the issue when WordPress complained it could not download updates with:
stream_socket_client(): php_network_getaddresses: getaddrinfo failed: Name or service not known stream_socket_client(): unable to connect to tcp://www.wordpress.org:80 (php_network_getaddresses: getaddrinfo failed: Name or service not known)
Sample script:
<?php
$domain = 'www.example.com';
echo 'gethostbynamel(): '; var_dump(gethostbynamel($domain));
echo 'checkdnsrr(): '; var_dump(checkdnsrr($domain, 'A'));
echo 'dns_get_record(): '; var_dump(dns_get_record($domain));
?>
When it works:
gethostbynamel(): array(1) {
[0]=>
string(13) "93.184.216.34"
}
checkdnsrr(): bool(true)
dns_get_record(): array(1) {
[0]=>
array(5) {
["host"]=>
string(15) "www.example.com"
["class"]=>
string(2) "IN"
["ttl"]=>
int(86348)
["type"]=>
string(1) "A"
["ip"]=>
string(13) "93.184.216.34"
}
}
After a few instants:
gethostbynamel(): bool(false)
checkdnsrr(): bool(true)
dns_get_record(): array(1) {
[0]=>
array(5) {
["host"]=>
string(15) "www.example.com"
["class"]=>
string(2) "IN"
["ttl"]=>
int(86400)
["type"]=>
string(1) "A"
["ip"]=>
string(13) "93.184.216.34"
}
}
Note that, in any case, both dns_get_record()
and checkdnsrr()
always works fine.
Three questions:
dns_get_record()
and checkdnsrr()
achieve to resolve FQDN when gethostbynamel()
fails?gethostbynamel()
need in a chrooted setup? Software versions:
Thanks
Per the comment on the question, Chrooted PHP-FPM script cannot resolve DNS after a moment , the OP was able to resolve the issue by adding the following files to the jail:
/lib/x86_64-linux-gnu/libnss_dns.so.2
(or depending on OS variant, /lib/libnss_dns.so
) /etc/nsswitch.conf
/etc/resolv.conf
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