A few recipes for remounting linux devices / disks. It mostly boils down to running mount -o remount as root.

Remount as read-write

If /dev/sdb1 is mounted on /mnt/data as read-only (ro), it could be remounted as rw:

% mount -o remount,rw /mnt/data

or

% mount -o remount,rw /dev/sdb1

Increase RAM disk size

/dev/shm (shared memory) is typically allocated half of the available amount of RAM in the system. For example, in my 8GB Arch Linux system:

$ df -h | grep /dev/shm
tmpfs                  3.9G  127M  3.8G   4% /dev/shm

To increase the amount of space allocated to it:

% mount -o remount,size=8G /dev/shm

The result:

$ df -h | grep /dev/shm
tmpfs                  8.0G   72M  8.0G   1% /dev/shm