Add quickstart guide

Reviewed-by: Aleix Boné <abonerib@bsc.es>

web/content/doc/_index.md

@@ -0,0 +1,10 @@
+---
+title: "Docs"
+description: "Documentation for users of jungle machines"
+date: 2023-09-15
+---
+
+If this is the first time you use any of the jungle machines with NixOS, follow
+the [quick start guide](quickstart).
+
+

web/content/doc/quickstart.md

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+---
+title: "Quick start"
+date: 2023-09-15
+---
+
+This documentation will guide you on how to build custom packages of software
+and use them in the jungle machines. It has been designed to reduce the friction
+from users coming from module systems.
+
+You should be able to access the jungle machines, otherwise [request
+access](/access).
+
+## Changes from other HPC machines
+
+Users of other machines have been using the Lmod tool (module load ...) to add
+or remove programs from their environment, as well as manually building their
+own software for too many years.
+
+While we cannot prevent users from continuing to use this tedious mechanism, we
+have designed the jungle machines to be much easier to operate by using the nix
+package manager.
+
+### Freedom to install packages
+
+When a user wanted to install a package, it was forced to either do it on its
+own directory, or request a system administrator to install it in a shared
+directory, so other users can also use that package.
+
+This situation is gone, each user can install any package of software by
+themselves, without requiring any other authorization. When two users request
+the same package, the same copy will be provided.
+
+A new package will be downloaded if it is available (someone already built it)
+or will be built from source on demand.
+
+### No changes over time
+
+All users retain the same versions of the packages they request until they
+decide to update them.
+
+## Using nix to manage packages
+
+In this chapter we show how to install packages and enter a development shell to
+build new programs from source. The examples are done from the hut machine,
+read [this page](/access) to request access.
+
+### Installing binaries
+
+To temporarily install new packages, use:
+
+```text
+hut% nix shell jungle#gcc jungle#cowsay jungle#ovni
+```
+
+Notice that the packages are described as two parts divided by the `#` symbol.
+The first part defines where to take the package from and the second part is
+the name of the package. For now we will use `jungle#<package>`. You can find
+many more packages here:
+
+<https://search.nixos.org/packages>
+
+You will now enter a new shell, where those requested package **binaries are
+available in $PATH**:
+
+```text
+hut% cowsay hello world
+ _____________
+< hello world >
+ -------------
+        \   ^__^
+         \  (oo)\_______
+            (__)\       )\/\
+                ||----w |
+                ||     ||
+
+hut% ovniver
+LD_LIBRARY_PATH not set
+libovni: build v1.11.0 (a7103f8), dynamic v1.11.0 (a7103f8)
+
+hut% gcc --version
+gcc (GCC) 13.3.0
+Copyright (C) 2023 Free Software Foundation, Inc.
+This is free software; see the source for copying conditions.  There is NO
+warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+```
+
+### Building programs
+
+The above method only loads new binaries in the `$PATH`. If we try to build a
+program that includes headers or links with a library, it will fail to find
+them:
+
+```text
+hut$ cat test.c
+#include <ovni.h>
+
+int main()
+{
+        ovni_version_check();
+        return 0;
+}
+hut% gcc test.c -lovni -o test
+test.c:1:10: fatal error: ovni.h: No such file or directory
+    1 | #include <ovni.h>
+      |          ^~~~~~~~
+compilation terminated.
+```
+
+We could manually add the full path to the ovni include directory with `-I` and
+the libraries with `-L`, but there is a tool that already perform these steps
+automatically for us, `nix develop`.
+
+Let's go back to our original shell first, where those packages are not
+available anymore:
+
+```
+hut% ps
+    PID TTY          TIME CMD
+2356260 pts/1    00:00:01 zsh
+2457268 pts/1    00:00:00 zsh
+2457297 pts/1    00:00:00 ps
+hut% exit
+hut% ovniver
+ovniver: command not found
+```
+
+### Creating a flake.nix
+
+To define which packages we want, we will write a small file that list them, a
+flake.nix file.
+
+First, we will create a new directory where we are going to be working:
+
+```
+hut% mkdir example
+hut% cd exmple
+```
+
+Then place this flake.nix file:
+
+```nix
+{
+  inputs.jungle.url = "jungle";
+  outputs = { self, jungle }:  
+  let
+    pkgs = jungle.outputs.packages.x86_64-linux;
+  in {
+    devShells.x86_64-linux.default = pkgs.mkShell {
+      pname = "devshell";
+      buildInputs = with pkgs; [
+        ovni gcc cowsay # more packages here...
+      ];
+    };
+  };
+}
+```
+
+
+Now enter the shell with:
+
+```
+hut% nix develop
+warning: creating lock file '/home/Computational/rarias/example/flake.lock':
+• Added input 'jungle':
+    'path:/nix/store/27srv8haj6vv4ywrbmw0a8vds561m8rq-source?lastModified=1739479441&narHash=sha256-Kgjs8SO1w9NbPBu8ghwzCxYJ9kvWpoQOT%2BXwPvA9DcU%3D&rev=76396c0d67ef0cf32377d5c1894bb695293bca9d' (2025-02-13)
+• Added input 'jungle/agenix':
+    'github:ryantm/agenix/f6291c5935fdc4e0bef208cfc0dcab7e3f7a1c41?narHash=sha256-b%2Buqzj%2BWa6xgMS9aNbX4I%2BsXeb5biPDi39VgvSFqFvU%3D' (2024-08-10)
+• Added input 'jungle/agenix/darwin':
+    'github:lnl7/nix-darwin/4b9b83d5a92e8c1fbfd8eb27eda375908c11ec4d?narHash=sha256-gzGLZSiOhf155FW7262kdHo2YDeugp3VuIFb4/GGng0%3D' (2023-11-24)
+• Added input 'jungle/agenix/darwin/nixpkgs':
+    follows 'jungle/agenix/nixpkgs'
+• Added input 'jungle/agenix/home-manager':
+    'github:nix-community/home-manager/3bfaacf46133c037bb356193bd2f1765d9dc82c1?narHash=sha256-7ulcXOk63TIT2lVDSExj7XzFx09LpdSAPtvgtM7yQPE%3D' (2023-12-20)
+• Added input 'jungle/agenix/home-manager/nixpkgs':
+    follows 'jungle/agenix/nixpkgs'
+• Added input 'jungle/agenix/nixpkgs':
+    follows 'jungle/nixpkgs'
+• Added input 'jungle/agenix/systems':
+    'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e?narHash=sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768%3D' (2023-04-09)
+• Added input 'jungle/bscpkgs':
+    'git+https://git.sr.ht/~rodarima/bscpkgs?ref=refs/heads/master&rev=6782fc6c5b5a29e84a7f2c2d1064f4bcb1288c0f' (2024-11-29)
+• Added input 'jungle/bscpkgs/nixpkgs':
+    follows 'jungle/nixpkgs'
+• Added input 'jungle/nixpkgs':
+    'github:NixOS/nixpkgs/9c6b49aeac36e2ed73a8c472f1546f6d9cf1addc?narHash=sha256-i/UJ5I7HoqmFMwZEH6vAvBxOrjjOJNU739lnZnhUln8%3D' (2025-01-14)
+
+hut$ 
+```
+
+Notice that long list of messages is Nix creating a new flake.lock file with the
+current state of the packages. Next invocations will use the same packages as
+described by the lock file.
+
+### Building a program from nix develop
+
+Now let's try again building our test program:
+
+```text
+hut$ cat test.c
+#include <ovni.h>
+
+int main()
+{
+        ovni_version_check();
+        return 0;
+}
+hut$ gcc test.c -o test -lovni
+hut$ ldd test
+        linux-vdso.so.1 (0x00007ffff7fc4000)
+        libovni.so.1 => /nix/store/sqk972akjv0q8dchn8ccjln2llzyyfd0-ovni-1.11.0/lib/libovni.so.1 (0x00007ffff7fab000)
+        libc.so.6 => /nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/libc.so.6 (0x00007ffff7db2000)
+        /nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib/ld-linux-x86-64.so.2 => /nix/store/nqb2ns2d1lahnd5ncwmn6k84qfd7vx2k-glibc-2.40-36/lib64/ld-linux-x86-64.so.2 (0x00007ffff7fc6000)
+hut$ ./test
+```
+
+Now the ovni.h header and the libovni library are found and the program is
+successfully built, linked and executed.
+
+You can add more packages as needed in your flake.nix:
+
+```nix
+  buildInputs = with pkgs; [
+    ovni gcc cowsay # more packages here...
+  ];
+```
+
+Make sure you exit the develop shell first, and then enter again with `nix
+develop`.
+
+## Remember
+
+- `nix shell` places binaries in the `$PATH`.
+- `nix develop` enters a development shell where both binaries and the libraries
+  and includes are available so you can build new programs.

web/hugo.toml

@@ -3,32 +3,38 @@ languageCode = 'en-us'
 title = 'The jungle'
 theme = 'PaperMod'
 
+[[menu.main]]
+identifier = "doc"
+name = "Docs"
+url = "/doc/"
+weight = 10
+
 [[menu.main]]
 identifier = "grafana"
 name = "Grafana"
 url = "/grafana/"
-weight = 10
+weight = 20
 
 [[menu.main]]
 identifier = "Git"
 name = "Git"
 url = "/git/"
-weight = 20
+weight = 30
 
 [[menu.main]]
 identifier = "Lists"
 name = "Lists"
 url = "/lists/"
-weight = 30
+weight = 40
 
 [[menu.main]]
 identifier = "Paste"
 name = "Paste"
 url = "/paste/"
-weight = 40
+weight = 50
 
 [[menu.main]]
 identifier = "Posts"
 name = "Posts"
 url = "/posts/"
-weight = 50
+weight = 60