x/build: can't ssh to x_tools-gotip-netbsd-arm64 gomote

[ianlancetaylor]

Go version

HEAD

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/iant/.cache/go-build'
GOENV='/home/iant/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/iant/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/iant/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org'
GOROOT='/home/iant/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/iant/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='devel go1.24-bae2e968e2 Mon Sep 30 22:04:40 2024 +0000'
GODEBUG=''
GOTELEMETRY='on'
GOTELEMETRYDIR='/home/iant/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/iant/gopath/src/golang.org/x/tools/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build4106496375=/tmp/go-build -gno-record-gcc-switches'

What did you do?

> gomote create x_tools-gotip-netbsd-arm64
> gomote ssh iant-x_tools-gotip-netbsd-arm64-0

What did you see happen?

unable to start shell "": exec: no command

What did you expect to see?

I expected to be connected to the gomote

CC @golang/release

[gabyhelp]

Related Issues and Documentation

• x/build: `gomote ssh` to plan9-arm fails with `Failed to get IP out of "pi4g": <nil>` #53571
• x/build/cmd/gomote: `unexpected /connect-ssh response: 502 Bad Gateway` when connecting multiple SSH sessions #53394 (closed)
• x/build/cmd/gomote: default SSH environment is still not usable on Windows #56015 (closed)
• cmd/go: locating GOROOT fails when the `go` command is run from the cross-compiled `bin` subdirectory #62119 (closed)
• x/build/cmd/gomote: long wait times trying to create aix-ppc64 gomote #39029
• cmd/dist: I/O error: read src/xxx.go: is a directory #35776 (closed)
• x/build: `502 Bad Gateway` ssh'ing to an `android-amd64-emu` gomote #59809
• cmd/go: can't invoke go in src directory #67853 (closed)
• affected/package: golang.org/x/tools #55912 (closed)
• x/build/cmd/gomote: push failed for gotip-linux-ppc64-power10 #66619 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[ianlancetaylor]

CC @golang/release

[ianlancetaylor]

The same happens for a plain gotip-netbsd-arm64 gomote.

[dmitshur]

Thanks for reporting. Also CC @golang/netbsd.

ssh.go#L52 calls shell() to determine the command name, and on GOOS=netbsd, its implementation returns whatever the SHELL environment variable is set to:

https://cs.opensource.google/go/x/build/+/master:cmd/buildlet/buildlet.go;l=2041-2042;drc=0d31c9b6e4b5ca7b9505a983bd19ae246447f8ad

Unsurprisingly given the error, that environment variable isn't currently set on this builder:

$ gomote run $USER-gotip-netbsd-arm64-0 env | grep SHELL | wc -l
       0

I see that bash is available on the builder, and in PATH, so setting SHELL to bash in the environment of the swarming client might be all that's needed to let gomote ssh work on this builder. CC @bsiegert as the builder owner who would need to make that change.

An (inconvenient) workaround is to use gomote run, e.g.:

$ gomote run -system $USER-gotip-netbsd-arm64-0 bash -c 'echo test'
test

[bsiegert]

I can set the SHELL environment variable. There is at least bash and ksh available.

[ianlancetaylor]

Can we change the shell function to return a reasonable default if SHELL is not set in the environment? Using /bin/sh would be far better than completely failing.

[gopherbot]

Change https://go.dev/cl/624796 mentions this issue: cmd/buildlet: set a safe default for shell