This is the easy way to do it;
https://guides.wp-bullet.com/how-to-find-large-folders-taking-up-space-on-linux/
Or this command line solution shows files and directories 1GB and over.
(1) Check root for directories over 1GB;
sudo du -h --threshold=1G --max-depth=1 /
(2) Do the same inside directories you want to check;
sudo du -h --threshold=1G --max-depth=1 .
(3) Once you've found the directory, search for files over 1GB;
sudo find . -size +1G -exec ls -sh {} \;
Btw. on Macs the command is:
du -hd1
If you’ve deleted any log files that were in use so they didn’t free up space.
With this command you can see them in human-readable format;
lsof +L1 | numfmt --field=7 --to=iec --invalid=ignore
If rsyslogd is using the files you can just run this;
sudo service rsyslog restart
To truncate log files for example;
> /var/log/mail.log
I’ve used these with Ubuntu 16.04, mainly to find oversized log files.