root $ 
root $ pwd
/etc/apt/sources.list.d
root $ 
root $ ll
total 20
drwxr-xr-x 2 root root 4096 Sep 22 20:05 ./
drwxr-xr-x 7 root root 4096 Sep 22 20:05 ../
-rw-r--r-- 1 root root   40 Sep  8 04:45 jitsi-stable.list
-rw-r--r-- 1 root root   41 Sep  8 04:43 jitsi-unstable.list
-rw-r--r-- 1 root root  240 Sep 22 20:05 mariadb.list
root $ 
root $ cat mariadb.list 
# MariaDB Ubuntu Focal repository list
# http://mariadb.org/mariadb/repositories/
deb http://ams2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu focal main
deb-src http://ams2.mirrors.digitalocean.com/mariadb/repo/10.4/ubuntu focal main
root $