Month: August 2022

error – sudo without being in the sudo group?

August 30, 2022 / abhijit

This was quite a head-scratcher. I wanted to remove a user sammy from the sudo group and did that by running this as root

root> deluser sammy sudo

However, when I logged in as sammy I was still able to run –

sammy> sudo su

Checking which groups the user belonged to was of no help either.

sammy> groups
sammy

When in doubt, choose the adventure.
Friedrich Nietzche

Postgres pg_dump without password

August 26, 2022 / abhijit

I have to do a dump of a Postgres database on a regular basis.

So pg_dump is the obvious choice to do this as is cron to do this periodically.

But the main problem with this is – pg_dump expects a password to be entered at the prompt. There’s no way to pass the password in the prompt to be able to do this.

Stackoverflow to the rescue.

What is required is a .pgpass file in the home directory.

‘asdf’ not finding program

August 26, 2022 / abhijit

I discovered asdf quite late! I was relying on a bunch of different programs to manage Ruby (rvm), Node (nvm).

asdf was an amazing headache saver. It already has core plugins for Elixir, Erlang, Node and Ruby. Plus, it has community plugins for what seems like practically anything under the sun.

I had installed asdf on a new system. And as usual, there were some crons to run on it. I kept getting a /bin/bash/ruby not found error.

After some time I realized I had faced this problem before as well!

Connect to server running on host from inside a Docker container

August 4, 2022 / abhijit

After installing the CloudBeaver as a Docker instance, I was trying to connect to the Postgres instance which I was running on my local machine.

In the HOST field, I tried with localhost which obviously wouldn’t work since that refers to the VM itself.

After some searching I found that to connect to the host, I need to set the connection as

host.docker.internal

Ruby Sequel migration – increment column in a group

August 2, 2022 / abhijit

The requirement was to add a column called position to the order_details table.

The order_details table is actually a table with a foreign key of order_id. The requirement is to increment the position starting from 1 in the position column grouped on order_id.

So, before the migration if the records are –

id  order_id
1   1
2   1
3   1
4   2
5   2
6   2

After the migration, the records should be –

id  order_id position
1   1       1
2   1       2
3   1       3
4   2       1
5   2       2
6   2       3

There are two solutions possible. One using window functions and one without.