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The output of your command "$ df -h" is:

Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv  689G  224G  437G  34% /
tmpfs                               12G  252K   12G   1% /dev/shm
tmpfs                              2.4G  1.9M  2.4G   1% /run
tmpfs                              5.0M  8.0K  5.0M   1% /run/lock
tmpfs                              2.4G  152K  2.4G   1% /run/user/1000
/dev/sda2                          2.0G  415M  1.4G  23% /boot