# Trouble with addprocs

**URL:** <https://discourse.julialang.org/t/trouble-with-addprocs/7818>\
**Category:** Julia at Scale\
**Tags:** question, distributed, gettingstarted\
**Created:** [December 17, 2017, 5:48pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818 "2017-12-17T17:48:40Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 17, 2017, 5:48pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/1 "2017-12-17T17:48:40Z")

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I’m having trouble with `addprocs`. I have set up passwordless login via a key (though the key still asks for my password, in case that could be the issue, though I doubt it).

I also have looked at other posts here but they seem to be running in different problems, or are [unsolved](https://discourse.julialang.org/t/addprocs-remote-does-not-work-but-ssh-remote-julia-version-does-why/3400/8).

I am using the following call

```julia
julia> addprocs(["admin@some.server.com"],exename="julia",dir="/home/admin")
Enter passphrase for key '/c/Users/Jeremy/.ssh/id_rsa':
ERROR: connect: connection timed out (ETIMEDOUT)
try_yieldto(::Base.##296#297{Task}, ::Task) at .\event.jl:189
...

```

The connection is clearly working, since if I change the `exename`, I get an error from the server telling me the executable does not exist:

```julia
julia> addprocs(["admin@some.server.com"],exename="notjulia",dir="/home/admin")
Enter passphrase for key '/c/Users/Jeremy/.ssh/id_rsa':
bash: notjulia: command not found
ERROR: Unable to read host:port string from worker. Launch command exited with error?
read_worker_host_port(::Pipe) at .\distributed\cluster.jl:236
...

```

Finally, trying to use SSH tunnels:

```julia
julia> addprocs(["admin@some.server.com"],exename="julia",dir="/home/admin",tunnel=true)
Enter passphrase for key '/c/Users/Jeremy/.ssh/id_rsa':
ERROR: unable to create SSH tunnel after 100 tries. No free port?
ssh_tunnel(::SubString{String}, ::SubString{String}, ::SubString{String}, ::UInt16, ::Cmd) at .\distributed\managers.jl:278

```

I am guessing that these errors are due to the server’s firewall. I therefore have two questions: How do we know which ports to open for 1., the regular (non-SSH) workers, and 2., the SSH tunnel workers?

Thanks,  
Jeremy

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<div class="post-metadata">

**Author:** ![floswald](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/floswald/32/195_2.png) [@floswald](https://discourse.julialang.org/u/floswald)\
**Post date:** [December 17, 2017, 8:34pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/2 "2017-12-17T20:34:33Z")

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From what you write here the problem really seems to be the password on the ssh key. This won’t work - password less is a requirement. Just erase that key (both public and private part) - regenerate without passphrase and start from there.

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<div class="post-metadata">

**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 17, 2017, 10:17pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/3 "2017-12-17T22:17:02Z")

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Despite the ssh connection being clearly established properly?

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<div class="post-metadata">

**Author:** ![floswald](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/floswald/32/195_2.png) [@floswald](https://discourse.julialang.org/u/floswald)\
**Post date:** [December 17, 2017, 10:25pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/4 "2017-12-17T22:25:46Z")

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well the connection only works if you supply a password. julia won’t supply your password, so you won’t have a connection. that second error message just shows that the master couldn’t read back from the worker, it does not indicate that you established a connection.

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<div class="post-metadata">

**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 17, 2017, 10:29pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/5 "2017-12-17T22:29:35Z")

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I actually can supply the password when that prompt appears.

I also get an error message if I don’t give the right `dir`. I am therefore fairly certain the SSH connection works fine.

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<div class="post-metadata">

**Author:** ![floswald](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/floswald/32/195_2.png) [@floswald](https://discourse.julialang.org/u/floswald)\
**Post date:** [December 17, 2017, 10:31pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/6 "2017-12-17T22:31:36Z")

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Ok i see. Can you ssh from the worker back to the master? In general you need password less ssh that works both ways.

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<div class="post-metadata">

**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 17, 2017, 10:34pm UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/7 "2017-12-17T22:34:59Z")

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From what I understand, in non-tunnel mode, the master-worker connection does not use SSH, so that should not be the issue.

In tunnel mode, I am not sure how the SSH connection is established, but the docs don’t mention anything about needing a passwordless login from the worker. If that is needed then it obviously wouldn’t work in my current configuration.

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<div class="post-metadata">

**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 18, 2017, 2:46am UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/8 "2017-12-18T02:46:09Z")

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It turns out that the password was the issue for the tunnel workers. I used SSH agent and that fixed it.

It didn’t fix the non-tunnel workers, so that’s still probably a firewall issue, but it’s OK since I’d rather not have unsecured communication.

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<div class="post-metadata">

**Author:** ![vchuravy](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vchuravy/32/8_2.png) [@vchuravy](https://discourse.julialang.org/u/vchuravy)\
**Post date:** [December 18, 2017, 3:12am UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/9 "2017-12-18T03:12:03Z")

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The non-tunneled workers might be [https://github.com/JuliaLang/julia/pull/25126](https://github.com/JuliaLang/julia/pull/25126).

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<div class="post-metadata">

**Author:** ![jebej](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jebej/32/1784_2.png) [@jebej](https://discourse.julialang.org/u/jebej)\
**Post date:** [December 18, 2017, 3:26am UTC](https://discourse.julialang.org/t/trouble-with-addprocs/7818/10 "2017-12-18T03:26:57Z")

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The workers need to open a port, but if you have a firewall on the server, how do you know which ports to allow?

I guess that pull request gives a range, but I’m not sure how safe it is to leave ports open like this on a public server…