Category Archives: Linux

LibreNMS bulk delete

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There is a php script in /opt/librenms/ that lets you delete a host from the command line.

sudo /opt/librenms/delhost.php 192.168.1.20

Replace 192.168.1.20 with the hostname/ip address of the host you want to delete.

Delete Multiple Hosts

First you’ll need to get a list of devices you want to remove.  You can do this by viewing the devices in the LibreNMS MySQL database;

Example:

$ mysql -u librenms -p librenms
MariaDB [librenms]> select hostname from devices;
+----------------------------------------+
| hostname |
+----------------------------------------+
| 192.168.88.1 |
| 192.168.1.20 |
| 192.168.1.12 |
| 192.168.88.5 |
4 rows in set (0.00 sec)
MariaDB [librenms]> exit

Put all the IP addresses you want to remove into a file and run the following for loop.  Replace “remove_ip.lst” with the name of your ip list file.

for i in `cat ~/remove_ip.lst`; do sudo /opt/librenms/delhost.php $i; done

Can’t restart auditd with systemctl

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The following command

systemctl restart auditd

Returns the following error on CentOS

Failed to restart auditd.service: Operation refused, unit auditd.service may be requested by dependency only (it is configured to refuse manual start/stop).
See system logs and 'systemctl status auditd.service' for details.

Work around is to use service for the restart

service auditd restart

 

Troubleshoot MySQL Performance

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Login to MySQL

mysql -u root -p

Show Active processes

SHOW PROCESSLIST;

or to list all the processes use “FULL”

SHOW FULL PROCESSLIST;

Run MySQL optimizer

wget https://raw.githubusercontent.com/major/MySQLTuner-perl/master/mysqltuner.pl
perl ./mysqltuner.pl

MySQL tuner should give some recommendations on settings to tweak.

Start Minecraft server on RAM disk Linux

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Create tmpfs ramdisk.  Note if your Linux user is something other than steve you’ll need to change where appropriate.

mkdir /home/steve/mcdisk

In etc/fstab add the following

tmpfs /home/steve/mcdisk tmpfs defaults,size=4096m 0 0

This creates a 4GB ram disk at /home/steve/mcdisk

To mount it you can either reboot, or run

mount -a

Copy your current Minecraft directory to the ram disk

cp -R /home/steve/Current_MC_Server/ /home/steve/mcdisk

Create a Bash script in “/home/steve” named “ramdisk_save.sh”

Paste the following in.  You may need to install rsync if you do not have it installed

!/bin/bash

RAMDISK="/home/steve/mcram/"
MCDIR="/home/steve/1.13"

rsync -r -t $RAMDISK/ $MCDIR/
rsync -r -t $MCSTORE/ $MCPATH/

Now add the script to crontab

crontab -e

and

 */5 * * * * /home/steve/ramdisk_save.sh

This will now run every 5 minutes and sync any changes on the ram disk to the original directory.

Start the Minecraft server

java -Xmx3072M -Xms3072M -jar server.jar nogui

Install VMware tools on Ubuntu VM

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In Ubuntu the simplest way to install the VMware tools is through apt.

sudo apt-get install open-vmware-tools

Shouldn’t have to do anything else.

You can also install the tools by hitting Install VMware tools from either the web UI, or vShpere.  This will mount a virtual CD on the OS, you can then copy the contents to a local directory in the vm.  You can then proceed to install them by extracting the tar file with

tar -xzf VMware*

cd into the new directory

cd vmware*

and run

sudo ./vmware-install.pl