From 38b29fb72ca4a07afbec1fd5067f59ca7d7f0fab Mon Sep 17 00:00:00 2001
From: Profpatsch <mail@profpatsch.de>
Date: Thu, 12 Dec 2019 15:15:18 +0100
Subject: [PATCH] libstore/ssh: Improve error message on failing `execvp`
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If the `throw` is reached, this means that execvp into `ssh` wasn’t
successful. We can hint at a usual problem, which is a missing `ssh`
executable.
Test with:
```
env PATH= ./result/bin/nix-copy-closure --builders '' unusedhost
```
and the bash version with
```
env PATH= ./result/bin/nix-copy-closure --builders '' localhost
```
---
src/libstore/ssh.cc | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/libstore/ssh.cc b/src/libstore/ssh.cc
index ac3ccd63d..ddc99a6cd 100644
--- a/src/libstore/ssh.cc
+++ b/src/libstore/ssh.cc
@@ -47,10 +47,13 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
throw SysError("duping over stderr");
Strings args;
+ const char * execInto;
if (fakeSSH) {
+ execInto = "bash";
args = { "bash", "-c" };
} else {
+ execInto = "ssh";
args = { "ssh", host.c_str(), "-x", "-a" };
addCommonSSHOpts(args);
if (socketPath != "")
@@ -62,7 +65,8 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
args.push_back(command);
execvp(args.begin()->c_str(), stringsToCharPtrs(args).data());
- throw SysError("executing '%s' on '%s'", command, host);
+ // could not exec ssh/bash
+ throw SysError("Failed to exec into %s. Is it in PATH?", execInto);
});
@@ -108,7 +112,7 @@ Path SSHMaster::startMaster()
addCommonSSHOpts(args);
execvp(args.begin()->c_str(), stringsToCharPtrs(args).data());
- throw SysError("starting SSH master");
+ throw SysError("Failed to exec into ssh. Is it in PATH?");
});
out.writeSide = -1;
--
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