Re: command "free" and meaning of "shared"

[Dan Ritter <dsr@randomstring.org>]

Vincent Lefevre wrote: 
> 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".

It can be used by any cooperating processes to send data back
and forth between them. The ipcs command shows the memory blocks
in use for interprocess communication.

-dsr-