Multiple tmpfs partitions

Question

[mayur@mayur311-pc ~]$ df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   50G  3.6G   47G   8% /
devtmpfs                 3.9G     0  3.9G   0% /dev
tmpfs                    3.9G  148K  3.9G   1% /dev/shm
tmpfs                    3.9G  9.1M  3.9G   1% /run
tmpfs                    3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sda6                494M  159M  336M  33% /boot
/dev/mapper/centos-home   73G   62M   73G   1% /home
tmpfs                    782M   32K  782M   1% /run/user/1000

Why there are 4 tmpfs and /dev/mapper/ drives ?

Solution 1

There is nothing abnormal about having tmpfs filesystems in your Linux box. tmpfs is a memory only filesystem, much like the "RAM disks" of other operating systems. As the name implies, the content lives in RAM, so it goes away after a reboot. It is also extremely fast.

tmpfs is commonly used in situations where you don't care about the contents of a filesystem after reboot, and/or where performance is key.

In your example, you have /run (which is used for all sorts of temporary files from multiple subsystems), /dev/shm, which is an implementation of the shared memory concept, and /sys which is a pseudo filesystem that the kernel uses to report many different kinds of information about the system.

Solution 2

/dev/shm - shared memory, is used for programs to share things on the RAM.

/run - it contains small files, with information about programs in execution, is usefully for example, when a program cant be run twice, so the executing program can alert a second program preventing it to be executed, and other things.

/sys/fs/cgroups - https://wiki.archlinux.org/index.php/cgroups

Comments

[jasonwryan]

Why would you revert an edit that formatted text output to replace it with an image of the text? That is just asinine.

[Julie Pelletier]

@user172577: What problem are you trying to address?

[user172577]

I am new to Linux. I don't know whether it is a problem or not. I want to know why there are 4 tmpfs ? what is the use of those file systems ?

[jsbillings]

And /run/user/1000 is your $XDG_RUNTIME_DIR. It's automatically created and mounted for every logged in user.

[Artem Novikov]

The question was WHY there are 4 entries and how that works. Not about what those mean.

[Artem Novikov]

The question was WHY there are 4 entries and how that works. Not about what those mean.