libstore/ssh: Improve error message on failing execvp

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
```
This commit is contained in:
Profpatsch 2019-12-12 15:15:18 +01:00
parent f800d450b7
commit 38b29fb72c

View file

@ -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;