Wireshark · Wireshark-dev: Re: [Wireshark-dev] Using /var/tmp instead of /tmp

[John Thacker <johnthacker@xxxxxxxxx>]

On Thu, Jun 29, 2017 at 1:21 PM, Guy Harris <guy@xxxxxxxxxxxx> wrote:

On Jun 29, 2017, at 3:48 AM, John Thacker <johnthacker@xxxxxxxxx> wrote:

> I believe the main reason is that Fedora defaults /tmp to tmpfs (https://fedoraproject.org/wiki/Features/tmp-on-tmpfs) which thus limits it to the size of RAM (half that, at default).

Does Linux not have a *virtual* memory-based tmpfs, such as the one that Sun developed back in the late 1980's, allowing pages from temporary files either to be in memory or swap space?

Ah, to be correct, it is possible to set it to more than the amount of physical RAM, and it will use swap at that point (see https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt as well as someone actually testing it https://unix.stackexchange.com/questions/237030/how-safe-is-it-to-increase-tmpfs-to-more-than-physical-memory) but it's set to a defined maximum at mount time and has to be remounted to change. I've never actually set it to larger than my amount of RAM. I suspect that Fedora simply found it easier to leave the default and then change large files to use /var/tmp

The Sun version was the inspiration; the old Linux ramfs that tmpfs replaced was limited to the size of RAM, and thus not as flexible.

John