I have strange problem on my Linux machineWhen I do the following simple command  chmod +x  /tmp/filechmod is stuck and not returned the promptwhat could be the problem?the same issue when I run other commands as cp or ls ltr 
linux command stuck
files
This is probably an I/O error or corrupt filesystem (if /tmp is a separate filesystem).In case of a separate filesystem: Unmount it and run fsck. Otherwise check the kernel log (dmesg | tail -n 25) and SMART  (smartctl -a /dev/sda) for I/O errors.