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Having a SSD - it is recommended to mount /tmp as tmpfs.

Examples:

• https://askubuntu.com/questions/550589/best-way-to-mount-tmp-in-fstab


• https://yktoo.com/en/blog/post/233


• https://askubuntu.com/questions/173094/how-can-i-use-ram-storage-for-the-tmp-directory-and-how-to-set-a-maximum-amount

The mounting options are different in each example - why???

The default Ubuntu 16 installation sets the mounting options for root (/) as (from /etc/mtab):

/dev/sda1 / ext4 rw,relatime,errors=remount-ro,data=ordered 0 0

Ergo all other options - as suggested in the examples/links - shouldn't be applied.

Some of the mounting options in the various examples on the web are:

defaults,noatime,mode=1777

or:

defaults,noatime,nosuid,nodev,noexec,mode=1777,size=512M

But:

• Having noatime feels useless because that the data is stored in RAM which is fast anyway.


• Why nosuid,nodev,noexec ?
  
  How do they know whether softwares are dependent on certain options or not?

I think it is best to stick with the default permissions that the installation applied, meaning:

rw,relatime,mode=1777,uid=0,gid=0

In order to ensure proper operation of various softwares:

• The permissions are 1777 because that the default permissions for /tmp are also drwxrwxrwt (see stat -c "%a %n" /tmp).


• The uid and gid are root because that /tmp has the same.

Is there something which I'm missing here?

Before systemd, the standard way to activate tmpfs on /tmp was to activate it in /etc/default/tmpfs and set RAMTMP=yes (even if almost everyone was editing /etc/fstab). This way you can see what are the default options. On my Devuan Ascii the mounting options are:

$ mount -l | grep "/tmp"
tmpfs on /tmp type tmpfs (rw,nosuid,nodev,relatime,size=3293980k)

size defaults to 20% physical memory + swap.

So I guess you could not go wrong using the same options in /etc/fstab.