semanage Allow and Delete ports in CentOS

The commands are for CentOS, but should work on Fedora and RedHat.

If semanage is not installed refer to here.

You would typically use this along with the systems firewall to allow a port through.  Guide for firewalld and iptables.  If you change it in the firewall and fail to add/edit it in semanage you can potentially get weird behavior like sshd not wanting to start after changing the port.

Add port

semanage port -a -t ssh_port_t tcp 2222

The above command allows the sshd service to start, using port 2222.

List allowed ports

semanage port -l

You can use grep to filter the results


[admin@localhost ~]# semanage port -l | grep ssh
ssh_port_t tcp 2222, 22
[admin@localhost ~]#

Delete port

semanage port -d -p tcp 2222

Other examples

Allow SNMP

semanage port -a -t snmp_port_t tcp 2222


How to install Broadcom WiFi drivers in Fedora 27

Install RPM Fusion

sudo dnf install$(rpm -E %fedora).noarch.rpm$(rpm -E %fedora).noarch.rpm

Install packages

sudo dnf install -y kernel-devel-$(uname -r)
sudo dnf install -y akmodssudo dnf install -y broadcom-wl

Give the computer a reboot and the Broadcom card should now work.

Allow KDE Connect through firewall


sudo firewall-cmd --zone=public --permanent --add-port=1714-1764/tcp
sudo firewall-cmd --zone=public --permanent --add-port=1714-1764/udp
sudo systemctl restart firewalld.service

UFW firewall

sudo ufw allow 1714:1764/udp
sudo ufw allow 1714:1764/tcp
sudo ufw reload

More information

Install Hashcat on Fedora

Install nVidia drivers.  Guide here.

Download binary files from the hashcat website

or use wget


Extract with p7zip

7z x hashcat-

cd into the hashcat directory

cd hashcat-4.1.0

Run hashcat

./hashcat64.bin -t 32 -a 7 example0.hash ?a?a?a?a example.dict

Example script:

sudo dnf install p7zip
7z x hashcat-
cd hashcat-4.1.0
./hashcat64.bin -t 32 -a 7 example0.hash ?a?a?a?a example.dict

If you get the following error, try re-extracting the 7z file with the “x” option, not “e”.  “x : eXtract files with full paths” and ” e : Extract files from archive (without using directory names)” No such file or directory

Install nVidia GeForce Drivers on Fedora 27

Install free and non-free rpmfusion

sudo dnf install$(rpm -E %fedora).noarch.rpm$(rpm -E %fedora).noarch.rpm

Install drivers

dnf install xorg-x11-drv-nvidia akmod-nvidia
dnf install xorg-x11-drv-nvidia-cuda 
dnf update -y



You may need to set the DPI settings.  See here for more details.

Add Self Signed SSL certificate to LibreNMS in CentOS

Install mod_ssl

yum install mod_ssl -y

Create Directory for SSL key.

mkdir /etc/ssl/key
chmod 700 /etc/ssl/key

Create certificate.

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/key/localhost.key -out /etc/ssl/certs/localhost.crt

Fill out the info or what is applicable.

Now edit the LibreNMS Apache config file /etc/httpd/conf.d/librenms.conf

All you have to do is add the following three lines under the VirtualHost and change *:80 to *:443.

SSLEngine on
SSLCertificateFile /etc/ssl/certs/localhost.crt
SSL CertificateKeyFile /etc/ssl/key/localhost.key

So when your finished the file should look like this.

<VirtualHost *:443>
 DocumentRoot /opt/librenms/html/
 ServerName server_hostname_or_IP
 SSLEngine on
 SSLCertificateFile /etc/ssl/certs/localhost.crt
 SSLCertificateKeyFile /etc/ssl/key/localhost.key
 CustomLog /opt/librenms/logs/access_log combined
 ErrorLog /opt/librenms/logs/error_log
 AllowEncodedSlashes NoDecode
 <Directory "/opt/librenms/html/">
 Require all granted
 AllowOverride All
 Options FollowSymLinks MultiViews

Don’t forget to allow https/port 443 traffic through the firewall.  Guide here

If you have any issues, you may need to chmod the key and crt file.

chmod 644 /etc/ssl/certs/localhost.crt
chmod 644 /etc/ssl/key/localhost.key

You should now be able to access LibreNMS using https.  Note, you’ll need to allow an exception in your browser for your self signed certificate.


Recovering LibreNMS from crashed XenServer VM

Had a LibreNMS instance crash, or the VM crashed, not bootable anymore.  Was able to boot it up on a CentOS iso with rescue mode, which gave me access to the files.  So the idea is to manually copy off the LibreNMS files and LibreNMS database and import them to a new LibreNMS instance


  • Need to access the the system files
  • MySQL doesn’t start in a chroot environment, so no way to do a mysqldump —  (Has to do with systemv or something)


  1. Create new LibreNMS VM with a new instance of LibreNMS installed
  2. Gain access to the crashed system
  3. Copy over LibreNMS MySQL databases to new LibreNMS instance
  4. Copy over LibreNMS files “/opt/librenms” to new LibreNMS instance
  5. Clean up.  Set users on directories, check SELinux etc.

1. Installing New LibreNMS VM

  • Guide for Ubuntu/Debian distro’s here
  • Guide for for Fedora/CentOS/RedHat here

2. Gaining access to crashed VM

There can be a couple of ways to gain access to a crashed XenServer VM.  One of the easiest ways is to boot up in recovery mode and go through the installers rescue mode.  Guide to boot up XenServer VM in recovery mode here.

The installer rescue mode should detect the OS and mount everything.  If not you should be able to mount the root partition manually.

Once booted up, you’ll need to enable network access if your going to use sftp or scp to copy files.  There are a few different ways to do this

  • Run “dhclient” to pull an address via DHCP
  • Set a static IP address
    • Guide for Ubuntu/Debian distro’s here
    • Guide for fedora/CentOS/RedHat here

3.Copy LibreNMS Mysql Database

Backup the LibreNMS MySQL database directory

tar czvf librenms_mysql.tgz /var/lib/mysql

Use scp or sftp to copy it to the new LibreNMS instance

scp librenms_mysql.tgz user@new_LibreNMS_ip

Now on the new LibreNMS instance we need to run the following few commands

systemctl stop mariadb
rm -rf /var/lib/mysql/*
tar xzvf librenms_mysql.tgz -C /
chown -R mysql:mysql /var/lib/mysql

4. Copy LibreNMS directory

Backup the LibreNMS directory

tar czvf librenms.tgz /opt/librenms

Use scp or sftp to copy it to the new LibreNMS instance

scp librenms.tgz user@new_LibreNMS_ip

Now on the new LibreNMS instance we need to run the following few commands

rm -rf /opt/librenms/*
tar xzvf librenms.tgz -C /
chown -R librenms:librenms /opt/librenms

5. Clean up

Disable SELinux if you have not already.  Guide here

Restart apache, and start mysql.  If your on Ubuntu, the services are named apache2 and mysql

systemctl restart httpd
systemctl restart mariadb

That should get it working, if not try a reboot.

Special notes

The whole MySQL directory needs to be copied, there are innodb files that will keep MySQL from starting if they are not copied.

There is some good info here

Install LibreNMS on CentOS

Install prerequisites

yum install -y epel-release 
rpm -Uvh
yum install -y policycoreutils-python cronie fping git httpd ImageMagick jwhois mariadb mariadb-server mtr MySQL-python net-snmp net-snmp-utils nmap php71w php71w-cli php71w-common php71w-curl php71w-gd php71w-mcrypt php71w-mysql php71w-process php71w-snmp php71w-xml php71w-zip python-memcached rrdtool

Setup LibreNMS user

useradd librenms -d /opt/librenms -M -r
usermod -a -G librenms apache

Install LibreNMS

cd /opt
git clone librenms

Configure MySQL

Start MySQL

systemctl start mariadb
mysql -u root

Create the Database and database user. Change password to a different password

CREATE DATABASE librenms CHARACTER SET utf8 COLLATE utf8_unicode_ci;
CREATE USER 'librenms'@'localhost' IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON librenms.* TO 'librenms'@'localhost';

Disable MySQL strict mode

vi /etc/my.cnf

Add the following in the [mysqld] section


Enable and restart mariadb i.e.(MySQL)

systemctl enable mariadb
systemctl restart mariadb

Configure PHP.  Set Timezone

You can go here to figure out which time zone you need.

vi  /etc/php.ini

Find the [Date] Section and change the timezone


date.timezone = America/New_York

Configure Apache

vi /etc/httpd/conf.d/librenms.conf

Add the following, change the server name.

<VirtualHost *:80>
  DocumentRoot /opt/librenms/html/

  AllowEncodedSlashes NoDecode
  <Directory "/opt/librenms/html/">
    Require all granted
    AllowOverride All
    Options FollowSymLinks MultiViews

Enable and restart apache

systemctl enable httpd
systemctl restart httpd

Allow fping

cd /opt/librenms

Add the following

module http_fping 1.0;

require {
type httpd_t;
class capability net_raw;
class rawip_socket { getopt create setopt write read };

#============= httpd_t ==============
allow httpd_t self:capability net_raw;
allow httpd_t self:rawip_socket { getopt create setopt write read };

Configure SELinux

You can disable SELinux completely in the /etc/selinux/config file or run these commands to make LibreNMS and SELinux play together.

semanage fcontext -a -t httpd_sys_content_t '/opt/librenms/logs(/.*)?'
semanage fcontext -a -t httpd_sys_rw_content_t '/opt/librenms/logs(/.*)?'
restorecon -RFvv /opt/librenms/logs/
semanage fcontext -a -t httpd_sys_content_t '/opt/librenms/rrd(/.*)?'
semanage fcontext -a -t httpd_sys_rw_content_t '/opt/librenms/rrd(/.*)?'
restorecon -RFvv /opt/librenms/rrd/
setsebool -P httpd_can_sendmail=1
checkmodule -M -m -o http_fping.mod
semodule_package -o http_fping.pp -m http_fping.mod
semodule -i http_fping.pp

Configure Firewall

firewall-cmd --zone public --add-service http
firewall-cmd --permanent --zone public --add-service http
firewall-cmd --zone public --add-service https
firewall-cmd --permanent --zone public --add-service https

Configure snmpd

cp /opt/librenms/snmpd.conf.example /etc/snmp/snmpd.conf

Edit the snmpd file and change RANDOMSTRINGGOESHERE to your community string

vi /etc/snmp/snmpd.conf

Enable and restart snmpd

curl -o /usr/bin/distro
chmod +x /usr/bin/distro
systemctl enable snmpd
systemctl restart snmpd

Setup Cron Job and Cycle logs

cp /opt/librenms/librenms.nonroot.cron /etc/cron.d/librenms
cp /opt/librenms/misc/librenms.logrotate /etc/logrotate.d/librenms

Set Permisions

chown -R librenms:librenms /opt/librenms
setfacl -d -m g::rwx /opt/librenms/rrd /opt/librenms/logs
setfacl -R -m g::rwx /opt/librenms/rrd /opt/librenms/logs

Finish Install

Finish the install by