Notes and Stuff
I had to update a couple of NTP servers and after rebooting Nagios was returning an alert on the check_ntp_peer check, indicating a time drift.
To fix it, I forced a clock update with NTP servers:
systemctl stop ntpd
ntpdate -s ntp1.inrim.it
systemctl start ntpd
After configuring an Apache server on a CentOS 7.5 server, I tried to start the service but I got this error in return:
systemd[1]: Starting The Apache HTTP Server...
httpd[47662]: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:443
systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE
I was pretty sure that nothing was using port 443 but I did a quick check with netstat -tulpn
I double checked my config files, just to be sure that I wasn’t declaring Listen 443 twice:
# grep -ir listen
conf/httpd.conf:Listen 80
conf.d/ssl.conf:# When we also provide SSL we have to listen to the
conf.d/ssl.conf:Listen 443 https
conf.d/custom.conf:Listen 443
That’s it! I forgot to comment the directive in ssl.conf file (in this case). After this tiny fix I was able to start httpd without errors.
You will not need a secondary NIC but you’ll create virtual adapters as the secondary IP will be routing through the primary.
Network configurations are stored in /etc/sysconfig/network-scripts
network-scripts$ ls -l | grep ifcfg
-rw-r--r--. 1 root root 304 Nov 11 19:04 ifcfg-eth0
-rw-r--r--. 1 root root 254 May 25 2017 ifcfg-lo
You have to name the virtual adapter in a sequential order, e.g., ifcfg-eth0:1, ifcfg-eth0:2 etc.
Copy the physical adapter configuration file:
cp ifcfg-eth0 ifcfg-eth0:1
and configure it to include these parameters:
DEVICE=<device name>
IPADDR=<IP address>
NETMASK=<netmask>
There is no need to configure a MAC address or a default gateway.
To activate the interface you can restart the entire network server (if you can do it) or use:
ifup eth0:1
SSL stands for secure socket layer, a web protocol used to send traffic between the client and the server in a protected and encrypted wrapper. An SSL certificate also helps users verifying the identity of the sites they’re visiting.
httpdmod_sslHere’s a tiny plugin to check if a systemd service is running:
#!/bin/bash
#
# машины
#
# Check a if a systemd service is running
#
# Usage: $0
#
#Nagios exit codes
OK=0
WARNING=1
CRITICAL=2
UNKNOWN=3
SERVICE=$1
# Check service status
systemctl -q is-active $SERVICE
if [[ $? -ne 0 ]]; then
echo "ERROR: service $SERVICE is not running"
exit $CRITICAL
fi
echo "OK: service $SERVICE is running"
exit $OK
By default settings, Nagios will send email notifications as nagios@localhost, identified by $ADMINEMAIL$ macro.
If you want to change this behavior, you need to set the email address you want to use in the nagios.cfg file:
# ADMINISTRATOR EMAIL/PAGER ADDRESSES
# The email and pager address of a global administrator (likely you).
# Nagios never uses these values itself, but you can access them by
# using the $ADMINEMAIL$ and $ADMINPAGER$ macros in your notification
# commands.
admin_email=nagios@localhost
admin_pager=pagenagios@localhost
Welcome back to my (almost) daily appointment with “What’s wrong with Fedora today?”.
At work, our servers are VMs on a VMware vSphere; we access them using SSH of course, but sometimes we need to use the remote console from the vSphere Web Client (that is a vmrc link). I upgraded my kernel (and many libraries) last week but since I don’t use vSphere that often, I didn’t noticed anything until a couple of days ago, when a RAM stick failed and our machines crashed, rebooting in emergency mode.
Usually you login, select your VM, click on Launch Remote Console and you’re done. Unfortunately I got this:
reason appLoader killed by signal 11 cmdline /usr/lib/vmware/bin/vmrc executable /usr/lib/vmware/bin/appLoader [...] os_release Fedora release 26 (Twenty Six) kernel 4.12.11-300.fc26.x86_64
I upgraded to Fedora 26 weeks ago but I realize only today that I was having issues playing videos in Firefox, while I was trying to attend an online course.
At first I thought it was Flash Player’s fault: I always forget to have it and I always forget to update it. It was indeed out-of-date but the annoying “The media could not be played” error message was still there.
After a quick research and a little help from HTML5test, I noticed that few codecs were missing. I prefer not to install a bunch of codecs that I don’t even know what they’re for; if I am missing something I’m pretty sure it’ll come out! Continue reading