On Fri, Apr 19, 2019 at 8:51 PM Kaushal Shriyan kaushalshriyan@gmail.com wrote:
Does devtmpfs and tmpfs use underlying hard disk storage or does it uses Physical Memory (RAM). What is the purpose of devtmpfs which is mounted on /dev, tmpfs mounted on /dev/shm and so on and so forth. What is the difference between devtmpfs and tmpfs?
tmpfs *tries* not to use disk. /dev/shm is great to use as *fast* large scratch space.
Have used /dev/shm to greatly speed up a daily process to parse web server logs. Didn’t /seem/ like the process was IO or disk bound. . . Until I threw the logs in /dev/shm and a multi hour process completed in 1/4 the time.
Have used /dev/shm for other “things”.
There is /dev/ram# which should never be written to disk, but has the problem of being much much smaller (4MB iirc) and no filesystem access. So you’d have to `mkfs /dev/ram#` and then `mount /dev/ram# /somewhere`.
Once used /dev/ram# for USB camera “security system”. The camera gave large-ish files and couldn’t figure out how to get the camera app to output to stdOut to then shrink the file to a tiny jpeg with pipes. So had the camera write to /dev/ram and then read the file from /dev/ram through `convert` or something to jpeg-ify the image. Greatly sped up (like 2-3x) how often that could save images.
Happy learning how to Linux. (: