[oracle@d4cdb dbs]$ df -h
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   46G   19G   27G  43% /
devtmpfs               3.8G     0  3.8G   0% /dev
tmpfs                  3.9G     0  3.9G   0% /dev/shm
tmpfs                  3.9G   13M  3.8G   1% /run
tmpfs                  3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sr0               4.4G  4.4G     0 100% /mnt/cdrom
/dev/sda1             1014M  170M  845M  17% /boot
.host:/                1.9T  1.4T  457G  76% /mnt/hgfs
tmpfs                  781M  4.0K  781M   1% /run/user/42
tmpfs                  781M   36K  781M   1% /run/user/1001

[root@d4cdb ~]# mount -o size=8G -o nr_inodes=1000000 -o noatime,nodiratime -o remount /dev/shm

[root@d4cdb ~]# df -h
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   46G   19G   27G  43% /
devtmpfs               3.8G     0  3.8G   0% /dev
tmpfs                  8.0G     0  8.0G   0% /dev/shm
tmpfs                  3.9G   13M  3.8G   1% /run
tmpfs                  3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/sr0               4.4G  4.4G     0 100% /mnt/cdrom
/dev/sda1             1014M  170M  845M  17% /boot
.host:/                1.9T  1.4T  457G  76% /mnt/hgfs
tmpfs                  781M  4.0K  781M   1% /run/user/42
tmpfs                  781M   36K  781M   1% /run/user/1001
[root@d4cdb ~]# vi /etc/fstab 
[root@d4cdb ~]# mount -a
[root@d4cdb ~]# cat /etc/fstab |grep -i shm
tmpfs                   /dev/shm                tmpfs   defaults,size=8G        0 0