How to adjust available space in tmpfs without unmouting
A simple question with a simple answer (but not that easily googlable). I wouldn’t write this article if only I hadn’t spend about 15 minutes searching for the answer.
The problem: resize tmpfs without loosing data
When one use live image (with augfs, backed by both squashfs and tmpfs), there is a big desire to have a way to adjust how much memory server uses based on later stages of the server life. There is no way to unmount root (‘/’) on booted server, so I need to find a way to adjust amount of available space on tmpfs-based root partition without unmounting it.
The solution: remount
The answer is simple: remount.
mount -o remount,size=new_size /path/to/tmpfs
F.e.
mount -o remount,size=10G /lib/live/mount/overlay
This operation preserves data. If it’s not possible (f.e. you have more data on tmpfs than you are trying to set limit to), an error will raise:
mount point not mounted or bad option.