Strange root cronjob - I've never set it

Solution 1:

Yes, it's normal.

From man run-parts

NAME
       run-parts - run scripts or programs in a directory

In your case, run-parts run all scripts in the folder /etc/cron.hourly

My /etc/cron.hourly is empty therefore /etc/cron.daily

% ls -og /etc/cron.daily 
total 88
-rwxr-xr-x 1   311 Dez 29 00:15 0anacron
-rwxr-xr-x 1   625 Mär  9 12:55 apache2
-rwxr-xr-x 1   376 Mär  2 10:50 apport
-rwxr-xr-x 1 15481 Nov  3  2014 apt
-rwxr-xr-x 1   314 Feb 10 11:23 aptitude
-rwxr-xr-x 1   355 Dez 10  2014 bsdmainutils
-rwxr-xr-x 1   384 Okt 24  2014 cracklib-runtime
-rwxr-xr-x 1   532 Mär 23 16:31 debsums
-rwxr-xr-x 1  1597 Jan 17 02:10 dpkg
lrwxrwxrwx 1    47 Jun  8 22:59 google-chrome-beta -> /opt/google/chrome-beta/cron/google-chrome-beta
-rwxr-xr-x 1   372 Jan 22  2014 logrotate
-rwxr-xr-x 1  1293 Jan  1 00:16 man-db
-rwxr-xr-x 1   435 Nov 18  2014 mlocate
-rwxr-xr-x 1   249 Dez  2  2014 passwd
-rwxr-xr-x 1  2417 Mai 13  2013 popularity-contest
-rwxr-xr-x 1   982 Nov 30  2014 rkhunter
-rwxr-xr-x 1  2798 Feb  2 05:26 spamassassin
-rwxr-xr-x 1   441 Okt 25  2014 sysstat
-rwxr-xr-x 1   728 Mär 27 03:07 tomcat7
-rwxr-xr-x 1   214 Jan 20 10:39 update-notifier-common

The script starts with the default definitions in /etc/crontab

# /etc/crontab: system-wide crontab
# Unlike any other crontab you don't have to run the `crontab'
# command to install the new version when you edit this file
# and files in /etc/cron.d. These files also have username fields,
# that none of the other crontabs do.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

# m h dom mon dow user  command
17 *    * * *   root    cd / && run-parts --report /etc/cron.hourly
25 6    * * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6    * * 7   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6    1 * *   root    test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )
#

Solution 2:

Yes, this cronjob exists by default. It runs hourly and executes the scripts in /etc/cron.hourly/ (if there are any).