No space left on device, what to do, the disk is empty?

Question

linux

For about 8 months the server worked without any changes. Today suddenly Apache hung, then everything hung.
As a result, I saw this picture with df -ih:

udev             370K   393  370K    1% /dev
tmpfs            375K   491  375K    1% /run
/dev/sda2        1,2M  1,2M   14K   99% /
tmpfs            375K     1  375K    1% /dev/shm
tmpfs            375K     7  375K    1% /run/lock
tmpfs            375K    16  375K    1% /sys/fs/cgroup
tmpfs            375K     4  375K    1% /run/user/0

what to do ?
ps: there is a lot of space on the disk, where a lot of files appeared and inodes ran out, you need to somehow find a partition where there are a lot of files. Perhaps something happened at night and ubunta started to make a lot of files.

Answer 1

This is how you can see the number of inodes by directory:
du -hsc --inodes /var/*

Answer 2

web server? most likely in /tmp or /var/lib/php/sessions