Like the title says, the disk space in my "/" partition is at 97% and that's after deleting GBs worth of files. I'm running Ubuntu 18.04.2 LTS.

After running df -Th , I get the following output:

Filesystem Type Size Used Avail Use% Mounted on udev devtmpfs 3.9G 0 3.9G 0% /dev tmpfs tmpfs 787M 3.2M 784M 1% /run /dev/sda2 ext4 102G 94G 3.1G 97% / tmpfs tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs tmpfs 5.0M 4.0K 5.0M 1% /run/lock tmpfs tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup /dev/loop0 squashfs 3.8M 3.8M 0 100% /snap/gnome-system-monitor/100 /dev/loop3 squashfs 55M 55M 0 100% /snap/core18/1055 /dev/loop1 squashfs 15M 15M 0 100% /snap/gnome-characters/292 /dev/loop2 squashfs 141M 141M 0 100% /snap/gnome-3-26-1604/88 /dev/loop4 squashfs 2.3M 2.3M 0 100% /snap/gnome-calculator/260 /dev/loop5 squashfs 43M 43M 0 100% /snap/gtk-common-themes/1313 /dev/loop8 squashfs 15M 15M 0 100% /snap/gnome-characters/296 /dev/loop6 squashfs 4.2M 4.2M 0 100% /snap/gnome-calculator/352 /dev/loop7 squashfs 15M 15M 0 100% /snap/gnome-logs/45 /dev/loop11 squashfs 1.0M 1.0M 0 100% /snap/gnome-logs/61 /dev/loop9 squashfs 1.0M 1.0M 0 100% /snap/gnome-logs/57 /dev/loop10 squashfs 150M 150M 0 100% /snap/gnome-3-28-1804/63 /dev/loop12 squashfs 89M 89M 0 100% /snap/core/7169 /dev/loop13 squashfs 4.2M 4.2M 0 100% /snap/gnome-calculator/406 /dev/loop14 squashfs 150M 150M 0 100% /snap/gnome-3-28-1804/67 /dev/loop16 squashfs 8.5M 8.5M 0 100% /snap/canonical-livepatch/81 /dev/loop15 squashfs 8.5M 8.5M 0 100% /snap/canonical-livepatch/77 /dev/loop18 squashfs 89M 89M 0 100% /snap/core/7270 /dev/loop17 squashfs 36M 36M 0 100% /snap/gtk-common-themes/1198 /dev/loop19 squashfs 3.8M 3.8M 0 100% /snap/gnome-system-monitor/95 /dev/loop20 squashfs 141M 141M 0 100% /snap/gnome-3-26-1604/90 /dev/loop21 squashfs 55M 55M 0 100% /snap/core18/1066 /dev/sdb ext4 1.8T 1.3T 430G 76% /mnt/Plex /dev/sdc ext4 3.6T 89M 3.4T 1% /mnt/Plex2 /dev/sda1 vfat 511M 6.1M 505M 2% /boot/efi tmpfs tmpfs 787M 16K 787M 1% /run/user/128 tmpfs tmpfs 787M 0 787M 0% /run/user/1000

After that, I run sudo du --max-depth=1 -axh | sort -n where I get this:

0 ./initrd.img 0 ./initrd.img.old 0 ./vmlinuz 0 ./vmlinuz.old 3.8G ./usr 4.0K ./cdrom 4.0K ./lib64 4.0K ./srv 4.8G ./var 8.0K ./media 8.0K ./mnt 11G . 12M ./sbin 13M ./bin 16K ./lost+found 16M ./etc 52K ./snap 100K ./tmp 107M ./boot 203M ./opt 296K ./root 560M ./home 846M ./lib

I've read on a couple of other forums that there may be some files in lsof that haven't been freed up. So I run sudo lsof | grep deleted which gets me:

mysqld 1128 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1163 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1163 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1163 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1163 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1163 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1164 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1164 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1164 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1164 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1164 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1165 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1165 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1165 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1165 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1165 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1166 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1166 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1166 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1166 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1166 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1167 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1167 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1167 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1167 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1167 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1168 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1168 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1168 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1168 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1168 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1169 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1169 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1169 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1169 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1169 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1170 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1170 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1170 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1170 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1170 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1171 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1171 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1171 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1171 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1171 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1172 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1172 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1172 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1172 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1172 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1173 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1173 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1173 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1173 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1173 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1174 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1174 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1174 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1174 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1174 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1206 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1206 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1206 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1206 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1206 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1207 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1207 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1207 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1207 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1207 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1208 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1208 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1208 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1208 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1208 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1209 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1209 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1209 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1209 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1209 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1210 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1210 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1210 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1210 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1210 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1211 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1211 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1211 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1211 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1211 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1212 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1212 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1212 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1212 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1212 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1214 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1214 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1214 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1214 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1214 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1215 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1215 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1215 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1215 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1215 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1216 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1216 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1216 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1216 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1216 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1217 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1217 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1217 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1217 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1217 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1218 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1218 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1218 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1218 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1218 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1225 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1225 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1225 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1225 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1225 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) mysqld 1128 1226 mysql 5u REG 8,2 0 3014658 /tmp/ibbG3efy (deleted) mysqld 1128 1226 mysql 6u REG 8,2 0 3014659 /tmp/ib58jSsO (deleted) mysqld 1128 1226 mysql 7u REG 8,2 0 3014660 /tmp/ib9uQvG4 (deleted) mysqld 1128 1226 mysql 8u REG 8,2 0 3014661 /tmp/ibPox2aB (deleted) mysqld 1128 1226 mysql 12u REG 8,2 0 3014662 /tmp/ibl6rfCR (deleted) apache2 1176 root 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) apache2 1220 www-data 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) apache2 1221 www-data 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) apache2 1222 www-data 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) apache2 1223 www-data 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) apache2 1224 www-data 9u REG 8,2 0 3014663 /tmp/.ZendSem.zhgjQN (deleted) pulseaudi 1593 gdm 6u REG 0,5 67108864 33974 /memfd:pulseaudio (deleted) null-sink 1593 1598 gdm 6u REG 0,5 67108864 33974 /memfd:pulseaudio (deleted)

I can't seem to find where the missing ~83GB is, unless I'm totally missing something, which is entirely possible.

GUI version. The top-left shows the main partition with 8.8 GB / 111 GB free. the bottom shows 3.3 GB / 109.1 GB free. Finally, the top-right shows the root directory with 10.5 GB worth of space taken.