Problem is not correlated with RAM. I have 4GB of RAM.
Hi neonix
... When I boot, I unmounted partition sdb3 where my extension are placed, ...
You unmounted your tce directory, so it's not currently writable.
Yes, but if I run system completely from RAM, so I don't need tce directory. What is more, I need to unmount sdb3, every time I run computer, to protect it from ext2 corruption (no journaling).
If I want to temporary install new extensions, I could manually change the path to /tmp. Appsbrowser don't have feature that allow me to change tce directory.