When using mdev instead of udev, /dev/shm has a maximum size of 10 megabytes. Reproducible: Always Steps to Reproduce: 1. Attempt to copy an 11 megabyte file to /dev/shm Actual Results: Get error message about insufficient space Expected Results: The file should copy to /dev/shm with no errors. I am running mdev instead of udev. I believe the root of the problem is in /etc/init.d/mdev, specifically the "mount_it()" function... mount_it() { if fstabinfo --quiet /dev ; then mount -n /dev else # Some devices require exec, Bug #92921 mount -n -t tmpfs -o "exec,nosuid,mode=0755,size=10M" mdev /dev fi } Since /dev/shm sits on top of /dev, it cannot exceed the size of the underlying /dev. I changed the "size=10M" to "size=50%", and rebooted. The system is now working normally.
as i explained to you on the busybox lists, your understanding is incorrect