Error starting kernel

[luraess]

Upon fresh IJulia install on macOS arm64 with Julia installed via Juliaup, I am getting following error when trying to select the Julia 1.12 kernel in IJulia:

Error Starting Kernel

[Errno 2] No such file or directory: '/Users/ludovic/.julia/juliaup/bin/julia'

Effectively, on the system, /Users/ludovic/.julia/juliaup/bin/Julia is non existant. However, which julia points to /Users/ludovic/.juliaup/bin/Julia.

[JamesWrigley]

Ummm interesting, this'll be because IJulia uses juliaup now if it's detected. What does IJulia.julia_cmd() return? And what's your Sys.BINDIR?

[luraess]

julia> IJulia.julia_cmd()
`/Users/ludovic/.julia/juliaup/bin/julia +1.12`

julia> Sys.BINDIR
"/Users/ludovic/.julia/juliaup/julia-1.12.1+0.aarch64.apple.darwin14/bin"

[JamesWrigley]

It seems that I installed an older version of juliaup that uses different paths 🤦 Could you try the branch in #1214 to see if that fixes it?

[luraess]

Thanks. That fixes the error message above. However, now the selected Julia kernel silently dies upon executing a command.

[JamesWrigley]

You mean the kernel starts and then dies as soon as you execute a cell? Are there any errors in the Jupyter logs (if you're using jupyterlab()/notebook() you can pass verbose=true).

[luraess]

This is the output log:

julia> notebook(;verbose=true)
[ Info: running setenv(`/Users/ludovic/.julia/conda/3/aarch64/bin/jupyter notebook`,["XPC_FLAGS=0x0", "LSCOLORS=Gxfxcxdxbxegedabagacad", "COMMAND_MODE=unix2003", "PATH=/Users/ludovic/.julia/conda/3/aarch64/bin:/Users/ludovic/.juliaup/bin:/opt/homebrew/opt/python@3/libexec/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Library/TeX/texbin", "WARP_USE_SSH_WRAPPER=0", "PWD=/Users/ludovic", "WARP_IS_LOCAL_SHELL_SESSION=1", "XPC_SERVICE_NAME=0", "TERM_PROGRAM=WarpTerminal", "HOMEBREW_PREFIX=/opt/homebrew", "PYTHONIOENCODING=UTF-8", "OPENBLAS_MAIN_FREE=1", "SHELL=/bin/zsh", "SSH_SOCKET_DIR=~/.ssh", "__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0", "__CFBundleIdentifier=dev.warp.Warp-Stable", "TMPDIR=/var/folders/z0/kbjdk1sj1qxf5dc71sj7j28c0000gn/T/", "CONDARC=/Users/ludovic/.julia/conda/3/aarch64/condarc-julia.yml", "HOMEBREW_CELLAR=/opt/homebrew/Cellar", "WARP_HONOR_PS1=1", "LOGNAME=ludovic", "SHLVL=1", "LaunchInstanceID=3FF1DC7D-A4BF-4CAA-8338-FC4A67753B4B", "CONDA_PREFIX=/Users/ludovic/.julia/conda/3/aarch64", "SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.vWpOSs32LC/Listeners", "OLDPWD=/Users/ludovic/.julia", "INFOPATH=/opt/homebrew/share/info:", "_=/Users/ludovic/.juliaup/bin/julia", "PAGER=less", "HOMEBREW_REPOSITORY=/opt/homebrew", "OPENBLAS_DEFAULT_NUM_THREADS=1", "SECURITYSESSIONID=186b4", "USER=ludovic", "HOME=/Users/ludovic", "TERM=xterm-256color", "TERM_PROGRAM_VERSION=v0.2025.10.29.08.12.stable_04", "LS_COLORS=di=1;36:ln=35:so=32:pi=33:ex=31:bd=34;46:cd=34;43:su=30;41:sg=30;46:tw=30;42:ow=30;43", "COLORTERM=truecolor", "LESS=-R", "ZSH=/Users/ludovic/.oh-my-zsh"])           
[I 2025-11-05 00:30:05.487 ServerApp] jupyter_lsp | extension was successfully linked.                                                 
[I 2025-11-05 00:30:05.489 ServerApp] jupyter_server_terminals | extension was successfully linked.                                    
[I 2025-11-05 00:30:05.491 ServerApp] jupyterlab | extension was successfully linked.
[I 2025-11-05 00:30:05.493 ServerApp] notebook | extension was successfully linked.
[I 2025-11-05 00:30:05.700 ServerApp] notebook_shim | extension was successfully linked.
[I 2025-11-05 00:30:05.720 ServerApp] notebook_shim | extension was successfully loaded.
[I 2025-11-05 00:30:05.722 ServerApp] jupyter_lsp | extension was successfully loaded.
[I 2025-11-05 00:30:05.722 ServerApp] jupyter_server_terminals | extension was successfully loaded.
[I 2025-11-05 00:30:05.724 LabApp] JupyterLab extension loaded from /Users/ludovic/.julia/conda/3/aarch64/lib/python3.12/site-packages/jupyterlab
[I 2025-11-05 00:30:05.724 LabApp] JupyterLab application directory is /Users/ludovic/.julia/conda/3/aarch64/share/jupyter/lab
[I 2025-11-05 00:30:05.724 LabApp] Extension Manager is 'pypi'.
[I 2025-11-05 00:30:05.759 ServerApp] jupyterlab | extension was successfully loaded.
[I 2025-11-05 00:30:05.761 ServerApp] notebook | extension was successfully loaded.
[I 2025-11-05 00:30:05.762 ServerApp] Serving notebooks from local directory: /Users/ludovic
[I 2025-11-05 00:30:05.762 ServerApp] Jupyter Server 2.17.0 is running at:
[I 2025-11-05 00:30:05.762 ServerApp] http://localhost:8888/tree?token=6dd8d7ca24a5aeb9a161e11aec2f699fa0025ad3c418fd76
[I 2025-11-05 00:30:05.762 ServerApp]     http://127.0.0.1:8888/tree?token=6dd8d7ca24a5aeb9a161e11aec2f699fa0025ad3c418fd76
[I 2025-11-05 00:30:05.762 ServerApp] Use Control-C to stop this server and shut down all kernels (twice to skip confirmation).
[C 2025-11-05 00:30:05.768 ServerApp] 
    
    To access the server, open this file in a browser:
        file:///Users/ludovic/Library/Jupyter/runtime/jpserver-14718-open.html
    Or copy and paste one of these URLs:
        http://localhost:8888/tree?token=6dd8d7ca24a5aeb9a161e11aec2f699fa0025ad3c418fd76
        http://127.0.0.1:8888/tree?token=6dd8d7ca24a5aeb9a161e11aec2f699fa0025ad3c418fd76
[I 2025-11-05 00:30:06.706 ServerApp] Skipped non-installed server(s): basedpyright, bash-language-server, dockerfile-language-server-nodejs, javascript-typescript-langserver, jedi-language-server, julia-language-server, pyrefly, pyright, python-language-server, python-lsp-server, r-languageserver, sql-language-server, texlab, typescript-language-server, unified-language-server, vscode-css-languageserver-bin, vscode-html-languageserver-bin, vscode-json-languageserver-bin, yaml-language-server
[I 2025-11-05 00:30:42.069 ServerApp] Creating new notebook in /code/playground
[I 2025-11-05 00:30:42.258 ServerApp] Saving file at /code/playground/Untitled.ipynb
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[I 2025-11-05 00:30:42.289 ServerApp] Kernel started: ef9e8b10-4ca4-49da-b1b0-0cab6da3d030
[I 2025-11-05 00:30:45.278 ServerApp] AsyncIOLoopKernelRestarter: restarting kernel (1/5), new random ports
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[I 2025-11-05 00:30:48.301 ServerApp] AsyncIOLoopKernelRestarter: restarting kernel (2/5), new random ports
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[I 2025-11-05 00:30:51.320 ServerApp] AsyncIOLoopKernelRestarter: restarting kernel (3/5), new random ports
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[I 2025-11-05 00:30:54.340 ServerApp] AsyncIOLoopKernelRestarter: restarting kernel (4/5), new random ports
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[I 2025-11-05 00:30:57.360 ServerApp] AsyncIOLoopKernelRestarter: restarting kernel (5/5), new random ports
ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.
[W 2025-11-05 00:31:00.379 ServerApp] AsyncIOLoopKernelRestarter: restart failed
[W 2025-11-05 00:31:00.379 ServerApp] Kernel ef9e8b10-4ca4-49da-b1b0-0cab6da3d030 died, removing from map.

The error suggests that

ERROR: `1.12` is not installed. Please run `juliaup add 1.12` to install channel or version.

I indeed did not install 1.12 as juliaup add 1.12, but juliaup add release (which is 1.12).

[JamesWrigley]

Hum, that is... unfortunate. I don't think it'd be right to silently add the channel to juliaup so in this situation I guess we'd have to fall back to the absolute path and print a warning.

[JamesWrigley]

Output from the build script is not displayed but saved to a separate log file, alas 🙃 New version of #1214 will error out instead if the right channel isn't installed, though I wonder if that's too heavy-handed. Could you try it out?

[luraess]

Now getting

(@v1.12) pkg> add https://github.com/JuliaLang/IJulia.jl.git#juliaup
    Updating git-repo `https://github.com/JuliaLang/IJulia.jl.git`
   Resolving package versions...
    Updating `~/.julia/environments/v1.12/Project.toml`
  [7073ff75] ~ IJulia v1.32.1 `https://github.com/JuliaLang/IJulia.jl.git#juliaup` ⇒ v1.32.1 `https://github.com/JuliaLang/IJulia.jl.git#juliaup`
    Updating `~/.julia/environments/v1.12/Manifest.toml`
  [7073ff75] ~ IJulia v1.32.1 `https://github.com/JuliaLang/IJulia.jl.git#juliaup` ⇒ v1.32.1 `https://github.com/JuliaLang/IJulia.jl.git#juliaup`
    Building IJulia → `~/.julia/scratchspaces/44cfe95a-1eb2-52ea-b672-e2afdf69b78f/7a2b47dc296eedcfa07f045c012eb19d3299cfd0/build.log`
ERROR: Error building `IJulia`: 
ERROR: LoadError: Juliaup has been detected but the command `julia +1.12` is not
available. Ensure that the 1.12 channel is
installed with `juliaup add 1.12` and try building IJulia
again.

If you want to use an absolute path to the Julia binary in the
kernel defintion instead of using juliaup, set the
`IJULIA_NO_JULIAUP` environment variable with
`ENV["IJULIA_NO_JULIAUP"] = "1"` and try building IJulia
again.

Stacktrace:
  [1] error(s::String)
    @ Base ./error.jl:44
  [2] julia_cmd(bindir::String)
    @ Main ~/.julia/packages/IJulia/SreGa/deps/kspec.jl:100
  [3] julia_cmd
    @ ~/.julia/packages/IJulia/SreGa/deps/kspec.jl:88 [inlined]
  [4] installkernel(name::String, julia_options::String)
    @ Main ~/.julia/packages/IJulia/SreGa/deps/kspec.jl:162
  [5] top-level scope
    @ ~/.julia/packages/IJulia/SreGa/deps/build.jl:6
  [6] include(mapexpr::Function, mod::Module, _path::String)
    @ Base ./Base.jl:307
  [7] top-level scope
    @ none:5
  [8] eval(m::Module, e::Any)
    @ Core ./boot.jl:489
  [9] exec_options(opts::Base.JLOptions)
    @ Base ./client.jl:283
 [10] _start()
    @ Base ./client.jl:550
in expression starting at /Users/ludovic/.julia/packages/IJulia/SreGa/deps/build.jl:4

(@v1.12) pkg> 

which iiuc is the expected behaviour.

I am just wondering whether it would not be possible to have a mechanism that would allow to pick up the Julia versions even if it was installed on Julia channels not explicitly reflecting a specific version such as (release, lts, beta) and if this design would make sense?

[JamesWrigley]

Yep exactly. I'm not completely sold because it's a bit ugly that even installing the package would fail like this, but the alternative of falling back to an absolute path feels slightly worse to me because then people who have different channels installed will get different behaviour.

I am just wondering whether it would not be possible to have a mechanism that would allow to pick up the Julia versions even if it was installed on Julia channels not explicitly reflecting a specific version such as (release, lts, beta) and if this design would make sense?

That would be reaching a bit far into juliaup internals for my taste 😅 We could get partway there by parsing the juliaup.json file, but that would only give us the paths to the currently installed Julia versions and no way of automatically using newer versions.

[luraess]

I see. IDK what would best. An error is definitively verbose, so maybe a warning would be less bold. However, silently failing is definitively not a good option I would say.

[JamesWrigley]

The crux of the problem seems to be informing the user of what's going on, which feels much more suited to a regular REPL function than a build script. Coincidentally, @KristofferC proposed moving away from build scripts in #1211 😛

So another option would be to disable the juliaup integration and go back to the old behaviour until we replace the build script, and then we could display warnings and do anything we want. It would kinda suck to lose the juliaup integration but myeh 🤷

[luraess]

Thanks for sharing these insights. From my user perspective, I like to have the Juliaup integration given Juliaup is the encouraged way of handling Julia installs. Then, fine to have a verbose error and clear instructions on how to work-around the issue for now, hopefully having a smoother workflow once the WIP gets incorporated.