I am using a Linux server to perform my simulations. The login and the file-system of the server are protected using kerberos. The file-system is supported using NFS. Since my simulations take a lot of time to run, my ssh sessions used to hang regularly. So, I have started running my simulations in byobu (similar to screen). In order to make sure that my kerberos session remains active, I am using the krenew command. I have entered the following command in my .bash_profile file. (I am sure that it is called for every login) killall -9 krenew 2> /dev/null krenew -b -t -K 10 So everytime I ssh to the server, I kill the existing krenew command. Then, I spawn a new krenew command -b (which runs in background), -t (I forgot why I was using this option !), and -K 10 (It must run after every 10 minutes and refresh the kerberos cache). When I run the simulations, It runs for 14 hours and then suddenly, I am getting error for reading file Permission Denied Is the command that I am running incorrect ??