Category: system admin

cron jobs failing with no log

January 10, 2021 / abhijit

So, we set up a project on a new Digital Ocean droplet and the cron jobs started failing.

Not just that, the log file that we had set up to track the cron was showing up empty!

After a lot of head scratching, I had a look at /var/log/syslog

Use Wake-On-LAN to wake up another computer when your PC resumes

August 15, 2020 / abhijit

Starting up another computer on a network itself is such a fascinating idea! For me, it literally feels like magic!

There are so many things involved. The computer which needs to be started (or woken up) has to have the capability, both at the hardware and the software level.

Also the computer doing the waking needs to send a magic packet!

When I initially heard this, I honestly thought this was a joke of some kind. A magic packet? Really?

pipe localhost to the internet using inlets over Nginx

February 21, 2020 / abhijit

Many times during developing some application it becomes important to show the progress to someone over the internet.

Most of the time we end up using some screen sharing software. That, however, can only show my screen to the other person. They cannot really interact with the application.

We can use some software for remote desktop sharing but then I cannot work while the other person is using my screen.

One very nice solution is ngrok, which essentially creates a tunnel from the local system to ngrok’s servers and gives a nice URL.

However, I was a bit concerned since all my traffic was getting redirected via ngrok’s servers.

I was looking around for something which would do the same thing but via my servers and finally came across inlets. This is an open source project, written in Go, which can be easily self hosted.

nginx auto-index styling

December 16, 2019 / abhijit

I’ve always been envious of the directory listing that Caddy has for serving files. Nginx also has the capability to list directories and files.

This is extremely useful to serve a directory out quickly over LAN or even where it is required to serve a directory listing instead of a web page.

However, the default Nginx styling leaves a lot to be desired!

different ways to run program as root

August 28, 2019 / abhijit

I discovered that there are many different ways to run a program as root.

The most well known way is to use the sudo command

$> sudo run_as_root_program.sh

This, of course, prompts for the password which you need to then enter.

But what if we need to run the program itself from another program so that the password prompt doesn’t appear?

I came across this requirement recently and it took quite a few iterations before I got it right.

change default sudo editor in visudo

March 15, 2018 / abhijit

For whatever reason, the default editor to change sudo permissions, which pops up when visudo is entered, is set to nano. I don’t have a clue why an option can’t be given on first use to change the editor.

The way to change it is to run the update-alternatives command

$> sudo update-alternatives --config editor

Which gives us these options.

Select 3 for vim.basic and we’re back to sanity.

linux – user, group configuration

February 1, 2018 / abhijit

When I’m setting up a linux system, since it’s not very often, I have to keep looking up the basic commands for user setup.

I had started putting them in a text file and now it’s reached here!

set default cron editor

January 28, 2018 / abhijit

By default when crontab-e is run for the first time, we get the choice to set the editor.

The selected editor is stored in a file ~/.selected_editor

However, if the selected editor needs to be changed later, the command is –

select-editor

To reset or unset the selected-editor completely, we can remove the ~/.selected_editor file completely.

Ref: https://www.howtogeek.com/410995/how-to-change-the-default-crontab-editor/