How do I recreate /dev/shm after removing it by mistake?

Question

I'm running Ubuntu 13.04 and I removed by mistake few folders from /dev/. As a result i have some problems with some applications like Chrome, which is not able to work.

Answer 1

/dev/shm is a way processes use to share memory (see man shm_open for more information). Its content is determined by the processes you run, therefore you can't "download" it. You can however re-create it.

On Ubuntu, /dev/shm is a symlink to /run/shm; this is the command that you have to use to re-create it:

sudo ln -s /run/shm /dev/shm

This action is also performed by the /etc/init/mounted-dev.conf Upstart script. This means that (as it was already suggested) rebooting your system without doing anything special is an another way of fixing the problem.

Answer 2

/dev/shm is nothing but implementation of traditional shared memory concept. It is an efficient means of passing data between programs. One program will create a memory portion, which other processes (if permitted) can access. This will result into speeding up things on Linux.

you need to add or modify entry in /etc/fstab file so that system can read it after the reboot. Edit, /etc/fstab as a root user, enter:

sudo gedit /etc/fstab

add /dev/shm entry as follows to set size to XXGB

none      /dev/shm        tmpfs   defaults,size=XXG        0 0

replace XX by the size you wish to use as shared memory.

Save and close the file.

Now reboot.

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If you just want to restore your old /dev/shm file then use the current running memory which is a copy of /dev/shm

sudo cp /run/shm /dev/shm -r

then reboot