command "free" and meaning of "shared"

[Vincent Lefevre <vincent@vinc17.net>]

The free(1) man page says for "shared":

  shared    Memory used (mostly) by tmpfs (Shmem in /proc/meminfo)

But I get:

qaa:~> free --human
               total        used        free      shared  buff/cache   available
Mem:            31Gi        17Gi       1.6Gi        10Gi        21Gi        13Gi
Swap:          975Mi        16Ki       975Mi

qaa:~> df --human-readable -t tmpfs
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           3.2G  3.3M  3.1G   1% /run
tmpfs            16G     0   16G   0% /dev/shm
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-cryptsetup@nvme0n1p3_crypt.service
tmpfs            16G   60K   16G   1% /tmp
tmpfs           1.0M     0  1.0M   0% /run/credentials/getty@tty1.service
tmpfs           3.2G   44K  3.2G   1% /run/user/1000

According to the free(1) man page, the 10Gi for "shared" is
"used (mostly) by tmpfs". But this contradicts the output of
"df --human-readable -t tmpfs".

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / Pascaline project (LIP, ENS-Lyon)