You do not have enough disk space to run the command. Use the ls command to check the directory contents. You do not have read permission for the input file. The input file is locked because someone else is using it. Wait a few minutes and try again.
Some error messages result from problems with the network.
Your system lost its link to the network. The system you need to reach lost its link to the network. If the ping command returns an increasing number of packets sent, you are connected to the system you need. Press Ctrl-C to interrupt the ping. If the ping command returns 0 packets sent , you are not connected to the system you need.