§ Nix weirdness on small machines
floobits@pixel-druid:~$ nix-env -iA nixpkgs.hello
+ nix-env -iA nixpkgs.hello
installing 'hello-2.10'
these paths will be fetched (0.04 MiB download, 0.20 MiB unpacked):
/nix/store/w9yy7v61ipb5rx6i35zq1mvc2iqfmps1-hello-2.10
copying path '/nix/store/w9yy7v61ipb5rx6i35zq1mvc2iqfmps1-hello-2.10' from 'https://cache.nixos.org'...
error: unable to fork: Cannot allocate memory
floobits@pixel-druid:~$ gdb --args nix-env -iA nixpkgs.hello
+ gdb --args nix-env -iA nixpkgs.hello
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
.
Find the GDB manual and other documentation resources online at:
.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from nix-env...(no debugging symbols found)...done.
(gdb) run
Starting program: /nix/store/d6axkgf0jq41jb537fnsg44080c4rd52-user-environment/bin/nix-env -iA nixpkgs.hello
warning: File "/nix/store/danv012gh0aakh8xnk2b35vahklz72mk-gcc-9.2.0-lib/lib/libstdc++.so.6.0.27-gdb.py" auto-loading has been declin
ed by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
add-auto-load-safe-path /nix/store/danv012gh0aakh8xnk2b35vahklz72mk-gcc-9.2.0-lib/lib/libstdc++.so.6.0.27-gdb.py
line to your configuration file "/home/floobits/.gdbinit".
To completely disable this security protection add
set auto-load safe-path /
line to your configuration file "/home/floobits/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
info "(gdb)Auto-loading safe path"
warning: File "/nix/store/xg6ilb9g9zhi2zg1dpi4zcp288rhnvns-glibc-2.30/lib/libthread_db-1.0.so" auto-loading has been declined by your
`auto-load safe-path' set to "$debugdir:$datadir/auto-load".
warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
^[[A[New LWP 21466]
GC Warning: Failed to expand heap by 128045056 bytes
installing 'hello-2.10'
building '/nix/store/k3kz3cwyqdwi5bmwcbl1fzv2b2wkqrl6-user-environment.drv'...
created 43 symlinks in user environment
[LWP 21466 exited]
[Inferior 1 (process 21462) exited normally]
(gdb) run
§ All nix subcommands are just symlinks
floobits@pixel-druid:~/idfk/nix-master$ ls -al /nix/store/4vz8sh9ngx34ivi0bw5hlycxdhvy5hvz-nix-2.3.7/bin/
total 1784
dr-xr-xr-x 2 floobits bollu 4096 Jan 1 1970 .
dr-xr-xr-x 9 floobits bollu 4096 Jan 1 1970 ..
-r-xr-xr-x 1 floobits bollu 1816768 Jan 1 1970 nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-build -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-channel -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-collect-garbage -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-copy-closure -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-daemon -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-env -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-hash -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-instantiate -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-prefetch-url -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-shell -> nix
lrwxrwxrwx 1 floobits bollu 3 Jan 1 1970 nix-store -> nix
It seems the way this works is that the nix tool figures out from what
symlink it's being invoked to decide what to do. God, that's ugly? brilliant?
I don't even know.
§ How does writeFile work?
-
cowsay in nixpkgs -
writeFile in nixpkgs -
runCommand' in nixpkgs -
mkDerivation in nixpkgs -
derivation in nixpkgs -
src/libexpr/primops/derivation.nix in nixos -
prim_derivationStrict in nixos c++ -
derivationArg in nixos c++ -
writeDerivation in nixos c++