Bug: /def/shm does not use /etc/fstab attributes after reboot

SOLVED: this issue is solved in Linux 6.4 (kernel: 2.6.39-400.17.1.el6uek and 2.6.32-358.el6).
A single entry in /etc/fstab like [tmpfs /dev/shm tmpfs size=3g 0 0] now works as it should!

There is a bug in Red Hat Linux 6 and Oracle Enterprise Linux 6 (UEK and RHEL-kernel) and probably all other Red Hat 6 related Linux Distro’s.

When you need more memory for SGA/PGA when using MEMORY_MAX_TARGET, you need to resize /dev/shm. By default this is 50% of total memory and Oracle tells you to add the following to /etc/fstab, ‘mounting’ the /dev/shm twice (?):

shmfs /dev/shm tmpfs size=3g 0 0

Which works…But, there is another line in /etc/fstab which in my opinion should be used and should work:

#tmpfs /dev/shm tmpfs defaults 0 0
tmpfs /dev/shm tmpfs size=3g 0 0

This works after a remount: ‘mount -o remount /dev/shm’, but it doesn’t work after a reboot…

It seems to be a bug in a module called ‘dracut’. Setting attributes for /dev/shm should work at tmpfs entry, but the attributes are not taken from /etc/fstab :

https://bugzilla.redhat.com/show_bug.cgi?id=669700

https://bugzilla.redhat.com/show_bug.cgi?id=783884

“Cause: /dev/shm is mounted in dracut without attributes from fstab. Consequence: /dev/shm does not have attributes from fstab. Fix: Remount /dev/shm in rc.sysinit. Result: /dev/shm has attributes from fstab.”

But, adding it again (shmfs see above) to /etc/fstab also works…

This is the case when using the Oracle Enterprise Linux 6 (UEK and RHEL) and Red Hat Linux 6, so I think also Red Hat 6 related distributions like CentOS will suffer from this bug.

Happy rebooting!

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