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Advanced Support for TeraGrid Applications

Common Errors and Pitfalls

• Upon executing a get command, I receive no error messages, and yet, the file does not appear in my directory. What happened?
• When I retrieve an executable file from UniTree and try to execute the file, I get the error message "Permission Denied". Why?
• What does the message "UniTree I/O Error" mean?
• How can I determine if a UniTree command failed?
• FTP Transfer appears to be hung, Firewall issue?

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Upon executing a get command, I receive no error messages, and yet, the file does not appear in my directory. What happened?

You have probably accessed UniTree through the command "ftp mss.ncsa.uiuc.edu". UniTree may take some time to retrieve a file that is stored on tape. If you use the `get' command, you will get a message that tells you the file is being retrieved from tape. Your local machine (the FTP client) will not wait until the file is cached from tape when you have the wait option (see below) turned off. Therefore, you must issue a second `get' command to obtain the file from disk. The alternative to issuing a second `get' command is to toggle wait by typing `quote wait' *prior* to issuing the first "get" command.

When I retrieve an executable file from UniTree and try to execute the file, I get the error message "Permission Denied". Why?

Files are returned from UniTree with only the permissions set by 'umask' (see man umask). To make a file executable, issue the command:

 % chmod u+x filename 

(see man chmod) after retrieving your file from UniTree before you run it. Alternatively, since 'tar' maintains the permissions of files, you can use 'tar' to save your files in UniTree and avoid using chmod after retrieving executable files (see man tar).

What does the message "UniTree I/O Error" mean?

The error message "UniTree I/O Error" means that UniTree is not currently available. It does NOT mean that your file is corrupted.

How can I determine if a UniTree command failed?

The mssftp command returns an error code. Each bit in the 8 bit integer that is returned via mssftp is associated with a particular meaning. For more details on mssftp error codes, consult the file Hot_Tips in the /DOCUMENTS directory of UniTree.

FTP Transfer appears to be hung, Firewall issue?

If you are behind a firewall, FTP file transfers may appear to hang as some firewalls block ports needed for active mode FTP. When a Firewall won't allow the server to connect to your client for the data transfer and it appears as though the transfer is 'hung', try enabling passive mode on your FTP client (some clients are set to active mode by default). The command "passive" toggles passive mode on or off.

 
Ex.
    ftp> passive
    Passive mode on.

    ftp> get file1.dat