git has a very simple solution to see all the commits in a graphical form. If you need to understand all the commits history all you need is
git graphviz|dot -Tpng -o /tmp/a.png
This will generate a file called /tmp/a.png which will diplay the complete commit history.
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.
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 🙂
Continue readingIf 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
Whenever a system/server is re-installed or the host key changed for any reason, you would have seen the “host key verification failed”. And as usual you would have to go to known_hosts file and delete the offending key. I will show you 2 simple ways to do this here.
The output that you get in such scenario is:
Offending ECDSA key in ~/.ssh/known_hosts:4
First, you can use sed to directly delete the offending key with a command like this :
Continue readingHere is link to a very nice and definitive guide to DNS. Very detailed and useful. There is a pdf version as well to download 🙂
https://webhostinggeeks.com/guides/dns/
Thanks to Andrijana Nikolic for providing a valuable resource to share with you all.
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.
Continue reading