find large file and delete them in linux

for example in FreePBX Server we should delete file !

first df -h to sow free space of / Directory

and you could du -h -d 1 to show files by size in depth of 1 directory

and you can delete file by date in day by command find /var/log/asterisk -mtime +20 -exec rm -rf {} + this command delete the files in this directory older than 20 day !