firewalld – enable logging

firewalld by default does not allow packets that are dropped. In some cases, you need to find out if some packet is being dropped or not. For doing so you may want to enable logging of dropped packets with the following command:

sudo firewall-cmd  --set-log-denied=all

This will enable logging all the packets and help you figure out if firewalld is dropping the packet.

speed up journalctl

Sometime back I noticed that whenever I run my favourite command, viz.

journalctl -xn -f -l

it was taking more time than usual. So, I thought to dig more into it and finally found that the following command:

sudo journalctl --disk-usage

showed that journalctl was using some huge space in tune of about 4GB. So, the solution was simple, vaccum the journal entries and the command to do so is :

sudo journalctl --vacuum-size 90M

Checking journalctl size after that confirms the size is reduced and after that indeed the above journal command takes no time 🙂

Most simple and fast lightweight container with Fedora systemd

If you need to have a quick bash shell in sandbox with not network as well, then the most simple command I could find so far is:

sudo virt-sandbox -c lxc:/// /bin/bash

For this you will need to have libvirt-sandbox installed which you can do with the following command:

sudo yum install libvirt-sandbox

virsh – show ip address of all running VMs

If you are using the libvirt and associated tools, then you must be aware about virt-manager. However this being a GUI tools, it is not possible to always use this. “virsh” is a good option for this.

To start with, if you need to know all the VMs all the running VMs, then you can use (to only view the names):

virsh list --name

Extending this to make it more useful is the case if you need to know the IP address for the running VMs. Here is a simple code that you can put in alias or function that can be used to get the IP address of the running VM’s.

Disk usage by file type

Trying to find the total usage for each of the file types by extension, then here is a quick bash function for you :

disk_usage_type () 
{ 
    find . -name '*'$1 -ls | awk '
    BEGIN{
        a[0]="Bytes";
        a[1]="KB";
        a[2]="MB";
        a[3]="GB";
    }
    {sum+=$7; files++;}
    END{
    print "Total sum is ::\t" sum;
    print "Total files  ::\t" files;
        while (sum > 1024) {
            sum=sum/1024;
            count++;
            };
        print sum" "a[count];
    }'
}

Just define the function in one of your bash startup files. After that to use the function pass in the extension for which you would like to find the total size. Output should be something like below:

Text file based presentation tool – pinpoint

Pinpoint description:

Name        : pinpoint

Summary     : A tool for making hackers do excellent presentations

URL         : https://live.gnome.org/Pinpoint

License     : LGPLv2+

Description : Pinpoint a simple presentation tool that hopes to avoid audience death

by bullet point and instead encourage presentations containing

beautiful images and small amounts of concise text in slides.

Pinpoint is a presentation tool. The source file for the presentation is text file and thus very easy to manage. You can see an example with :

Executing commands on multiple hosts

If you have to execute the same command in multiple hosts, then you can use mussh:

Description : Mussh is a shell script that allows you to execute a command or script

over ssh on multiple hosts with one command. When possible mussh will use

ssh-agent and RSA/DSA keys to minimize the need to enter your password

more than once.

First install mussh with the following command

dnf install mussh

Now to run this for multiple hosts, you can run like this