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The output of your command "$ df -F tmpfs" is:

Filesystem     1K-blocks  Used Available Use% Mounted on
tmpfs           12182456   252  12182204   1% /dev/shm
tmpfs            2436492  1872   2434620   1% /run
tmpfs               5120     8      5112   1% /run/lock
tmpfs            2436488   152   2436336   1% /run/user/1000