30.6.2. Configuring the Loopback Device Limit

The maximum number of loopback devices in Red Hat Enterprise Linux 6 is set by the max_loop kernel option. For example, to set the maximum number of loopback devices to 64, edit the /etc/grub.conf file, and add max_loop=64 at the end of the kernel line. The line in /etc/grub.conf would then look something like this:

kernel /vmlinuz-2.6.32-131.0.15.el6.x86_64 ro root=/dev/mapper/root rhgb quiet max_loop=64
initrd /initramfs-2.6.32-131.0.15.el6.x86_64.img

Reboot the system for the changes to take affect.

By default, eight /dev/loop* devices (/dev/loop0 to /dev/loop7) are automatically generated, but others can be created as desired. For example, to set up a ninth loop device named /dev/loop8, issue the following command as root:

~]# mknod /dev/loop8 b 7 8

Thus, an administrator on a system with a Red Hat Enterprise Linux 6 kernel can create the desired number of loopback devices manually, with an init script, or with a udev rule.

However, if max_loop has been set before the system booted, max_loop becomes a hard limit on the number of loopback devices, and the number of loopback devices cannot be dynamically grown beyond the limit.