Handbook

Git

Remove files already added to git after you update .gitignore


git rm -r --cached .
git add .
git commit -m "remove useless files"

Push empty commit


git commit --allow-empty -m "empty commit"
git push

Set new remote origin


git remote set-url origin new.git.url/here

Revert commits from merged PRs


git revert HEAD -m 1

Linux

List crontab for specific user


# run crontab command for specific user
crontab -l -u <user>

# find crontab from spool 
cat /var/spool/cron/crontabs/<user>

Find out size of directories in the /home directory


 sudo du -sh /home/* | sort -h

s: Display only a total for each argument.

h: Print sizes in human-readable format (e.g., 1K, 234M, 2G).

Edit files in terminal without nano, vim, vi, etc.

I was helping a friend fix some issues but didn’t have access to the code repository so I had to figure out how to edit files directly inside a deployed docker container with no nano or vim. This worked like a charm. Also, in order to apply the changes, I had to exit out of the container and run docker restart container-id so it would apply the updated configurations without triggering a new build so the changes are not lost.


cat filename

Copy the entire text, change what you need to, then copy it again


cat >filename

Paste the edited text and hit CTRL + D to save and quite

Jupyter Notebook

Using kernelspec


jupyter kernelspec list
jupyter kernelspec install
jupyter kernelspec uninstall

In notebook commands


%pwd # print working directory
%cd # change directory

Python

Using secrets module

To generate a random password you should use the secrets module

PostgreSQL

Backup & Restore Dockerized Postgres

Backup your databases


docker exec -t your-db-container pg_dumpall -c -U postgres > dump_`date +%Y-%m-%d"_"%H_%M_%S`.sql

Restore your databases


cat your_dump.sql | docker exec -i your-db-container psql -U postgres

Show triggers


select event_object_schema as table_schema,
       event_object_table as table_name,
       trigger_schema,
       trigger_name,
       string_agg(event_manipulation, ',') as event,
       action_timing as activation,
       action_condition as condition,
       action_statement as definition
from information_schema.triggers
group by 1,2,3,4,6,7,8
order by table_schema,
         table_name;

Columns

table_schema - name of the table schema

table_name - name of the trigger table

trigger_schema - name of the trigger schema

trigger_name - name of the trigger

event - specific SQL operation: Insert, Update or Delete

activation - trigger activation time: After, Instead of or BEFORE

condition - trigger activation condition

definition - definition of trigger - in postgreSQL it is always EXECUTE PROCEDURE function_name()

Rows

One row represents one trigger

Scope of rows: all triggers in a database

Ordered by schema name, table name

Strapi

Running a project from your host machine

You can also use strapi/strapi to run a project you already have created (or cloned for a repo) on your computer.

First make sure to delete the node_modules folder if you have already installed your dependencies on your host machine. Then run:


cd my-project
docker run -it -p 1337:1337 -v `pwd`:/srv/app strapi/strapi