ubuntu 14.04 - Why does crontab store my crontab under /var/spool/cron/crontabs/user instead of /etc/cron.daily

I wanted to create a crontab doing some job for me.
Because my server isn't running 24/7 i decided to use anacron instead.

Ok, so I took a short look into /etc/anacrontab:

1       5       cron.daily      run-parts --report /etc/cron.daily
7       10      cron.weekly     run-parts --report /etc/cron.weekly
@monthly        15      cron.monthly    run-parts --report /etc/cron.monthly

I saw that anacron is already executing the daily/weekly and monthly crontabs.

In my case I want to execute the command on a daily basis, so I focused on the first line where I can clearly see that anacron is executing all scripts in cron.daily every day with a delay of 5 minutes.

So I discarded the idea of creating an anacrontab or more likely an entry in /etc/anacrontab and intended to create a crontab which is placed in cron.daily because anacron will execute every script inside this folder anyway.

Now when I create a "daily"-crontab with:

crontab -e

regarding to man crontab the crontab is placed under var/spool/cron/crontabs/user instead of /etc/cron.daily where I was hoping the get my crontab into cron.daily getting executed by anacron.

The questions

1. Why is my intention wrong that my crontab is not automatically executed by anacron because it is not placed inside cron.daily.


2. Is the purpose of cron.daily just to include system and custom scripts and not crontabs itself.


3. Is the right way to get my job done to place a anacrontab inside etc/anacrontab instead of creating a crontab.

Answer

You should really read the documentation, from man crontab(1)

crontab - maintain crontab files for individual users

The crontab -e command edits the current user's crontab(5) file which is found in (or created in) /var/spool/cron/crontabs/user.

If you want to run a file daily, all you have to do is put it in the /etc/cron.daily directory and ensure that the permissions are correct.

I wouldn't mess around with anacrontab if I were you.