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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 ??

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You really need automatic ticket renewal. Contact your system administrator. –  Michael Hampton Aug 26 '13 at 15:10
    
What is the max renewal time of a ticket? Would k5start be a better option? It usually comes in the same package. –  84104 Aug 26 '13 at 20:03
    
@MichaelHampton I am the system administrator. What should the system administrator do in this case ?? I am not overly bothered about security. My main aim is to get my script running. –  prathmesh.kallurkar Aug 30 '13 at 7:23
    
@84104 What is the primary difference between k5start and krenew ?? I guess both the programs are renewing tickets only right ?? –  prathmesh.kallurkar Aug 30 '13 at 7:24
    
@prathmesh.kallurkar man k5start –  84104 Aug 30 '13 at 15:57

1 Answer 1

You might not be getting renewable tickets by default. Check the flags on the ticket using

klist -f ( MIT )

or

klist -v ( Hiemdal )

if you don't have renewable or R in the flags, use the -r option to kinit to get a renewable ticket. If you are getting a renewable ticket, it's more than likely that you aren't renewing the same ticket every time.

On linux kerberos tickets are files in /tmp and every login session gets a different file. I'd suggest you use kstart instead to start your job with it's own ticket and a daemon to manage that ticket.

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It is showing a R flag. The flags are : FPRT. I have actually found a hack for this solution. I use script in my client machine logs into the server machine every 20 minutes using sshpass tool. However, I would still prefer a cleaner solution for kerberos. –  prathmesh.kallurkar Nov 18 '13 at 12:08

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