How to setup local syslog-ng in docker container of CentOS 7? - docker

Question

I want to isolate a testing environment in docker, I did that on CentOS 6 How to let syslog workable in docker?
In CentOS 7, the syslog-ng's configuration is different, when I run
/usr/sbin/syslog-ng -F -p /var/run/syslogd.pid
It appears the following error message, but there is no proc/kmsg in config files.
syslog-ng: Error setting capabilities, capability management disabled; error='Operation not permitted'
Error opening file for reading; filename='/proc/kmsg', error='Operation not permitted (1)'
The Dockerfile
FROM centos
RUN yum update --exclude=systemd -y \
&& yum install -y yum-plugin-ovl \
&& yum install -y epel-release
RUN yum install -y syslog-ng syslog-ng-libdbi
The test process:
docker build -t t1 .
docker run --rm -i -t t1 /bin/bash
In container, run following commands
# check config, no keyword like proc/kmsg
cd /etc/syslog-ng
grep -r -E 'proc|kmsg'
/usr/sbin/syslog-ng -F -p /var/run/syslogd.pid

Answer 1

Change /etc/syslog-ng/syslog-ng.conf from
source s_sys {
system();
internal();
};
to
source s_sys {
unix-stream("/dev/log");
internal();
};
It still show error message, but running instead of exit
syslog-ng: Error setting capabilities, capability management disabled; error='Operation not permitted'
To solve this, just run with --no-caps option
/usr/sbin/syslog-ng --no-caps -F -p /var/run/syslogd.pid