GNU screen detached cannot write to file after ssh logout

Question

I am ssh-ing into a Linux cluster that uses an AFS home directory. I am trying to use GNU screen to run a long-running program in a detached screen. If I remain logged in the program executes perfectly, and this includes writing to a file.

I want to be able to logout from the ssh session and leave the program running in the detached screen. I try logging out and ssh-ing back in. However, when I check on the detached screen I see that my program has crashed because it did not have permissions to write to file.

[local]me: ssh info@inf.ed.us
[remote]user: screen    # this pops up a new screen
[remote]user: python get_data.py

I then hit Ctrl-a d (to detach screen)

[remote]user: logout
[local]me: ssh info@inf.ed.us
[local]me: screen

And this is what I see in the detached screen:

 Traceback (most recent call last):
      File "get_data.py", line 430, in <module>
      File "get_data.py", line 346, in produce_roof_patches
      File "get_data.py", line 225, in save_patch
    IOError: [Errno 13] Permission denied: '../data/training/labels.csv'

If I do not log out and simply detach (Ctrl-a d) and reattach via 'screen' then the program continues running without any trouble.

I have read that this is because when logging out my filesystem becomes unmounted and the program does not have permissions to write anywhere in my filesystem. Is there a workaround for this?

What kind of authentication do you have in place? Are your home directories encrypted, auto-mounted via nfs or something else? — Zoredache, Jul 01 '15 at 21:28
I have a feeling that you are using ecryptfs. Can you confirm that please? Do you see a /home/.ecryptfs directory on the system? — vagarwal, Jul 02 '15 at 12:50
Also, @Zoredache - how can I find that out? This [link](http://computing.help.inf.ed.ac.uk/external-login) has more info on the server, but I couldn't find the info you asked for. — unicorn_poet, Jul 03 '15 at 08:09
Using **absolute paths** instead of relative paths did the trick. — unicorn_poet, Jul 03 '15 at 12:08

score 0 · Answer 1 · answered Jul 01 '15 at 21:22

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Detached... as in... <control>-<z> then bg? or running with the & symbol? These are not detached. These are forked processes.

Detached processes can be started using the nohup command, or run in a tmux session or some such.

If you would like more information about any of these, feel free to ask.

answered Jul 01 '15 at 21:22

TheCompWiz

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`gnu-screen` is exactly what `tmux` resembles. Detaching means not the logout but disconnecting from the launched sessions. – Kondybas Jul 02 '15 at 07:04
I added more info to my question. Hope that clarifies things! – unicorn_poet Jul 03 '15 at 08:02

score 0 · Accepted Answer · answered Jul 06 '15 at 13:29

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Using absolute paths instead of relative paths to write to file fixed my problem.

answered Jul 06 '15 at 13:29

unicorn_poet

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GNU screen detached cannot write to file after ssh logout

2 Answers2