Boost Linux Server Performance: Master /dev/shm and tmpfs to Eliminate Disk I/O

tmpfs is a memory‑based filesystem in Linux/Unix that can use RAM or swap to store files, offering dynamic sizing and lightning‑fast read/write because it resides entirely in memory.

Because data in tmpfs is volatile, it disappears after a reboot, so scripts are often needed to recreate mounts.

/dev/shm is a mount point that uses tmpfs (on CentOS/RedHat it links to /run/shm, on Ubuntu to /run/shm as well). By default its size is half of physical memory; you can view it with df -h.

To increase /dev/shm size, edit /etc/fstab entry for tmpfs and remount:

tmpfs   /dev/shm   tmpfs   defaults,size=512m   0 0
mount -o remount /dev/shm

After remount, df -h shows the new size.

Common use cases for tmpfs (/dev/shm) include placing cache directories, PHP session files, or service socket files in /tmp after binding it to /dev/shm, which can dramatically speed up web services.

Examples:

Set Squid cache directory to /tmp with cache_dir ufs /tmp 256 16 256.

Set PHP session path to /tmp via session.save_path = "/tmp".

Place nginx or MySQL socket files in /tmp.

Remember that data stored in tmpfs does not persist across reboots, so appropriate startup scripts should recreate any needed mounts or bindings.