master..a91f97d · nix-container

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README.md+26−35 c+13−43 flake.nix+77−49

README.md+26−35

@@ -5,10 +5,8 @@ A Nix flake that builds an **OCI image** (via

55Apple's [`container`](https://github.com/apple/container) CLI on macOS.

77It's a plain, single-process image — no NixOS, no systemd — defined in

8−[`flake.nix`](./flake.nix). `c start` drops you into a

9−[`herdr`](https://herdr.dev) session whose panes use your host login shell

10−(detected and bundled by `c init`). You choose what else it ships via a

11−per-project `container.nix`.

8+[`flake.nix`](./flake.nix). It runs `fish` by default (with a configured

9+prompt); you choose what else it ships via a per-project `container.nix`.

1210

1311## Prerequisites

1412

@@ -27,31 +25,24 @@ per-project `container.nix`.

2725

2826## Packages

2927

30−`init` builds the image from a **`container.nix`** in the current directory — an

31−attrset with a `packages` function (`{ pkgs, nur }` returning the package list;

32−`nur` is [NUR](https://github.com/nix-community/NUR), for packages outside

33−nixpkgs) and an optional `mounts` list. It is **required**; there is no default.

28+`init` builds the image from a **`container.nix`** in the current directory — a

29+`{ pkgs, nur }` function returning the package list (`nur` is

30+[NUR](https://github.com/nix-community/NUR), for packages outside nixpkgs). It

31+is **required**; there is no default set.

3432

3533```nix

3634# ./container.nix

37−{

38− packages = { pkgs, nur }: with pkgs; [

39− git

40− go

41− nur.repos.charmbracelet.crush

42− ];

43− # Extra "host:container" bind mounts, on top of $PWD → /workspace. A leading

44− # ~/ in the host path expands to $HOME. Optional.

45− mounts = [

46− "~/data:/data"

47− ];

48−}

35+{ pkgs, nur }: with pkgs; [

36+ coreutils

37+ git

38+ go

39+ nur.repos.charmbracelet.crush

40+]

4941```

5042

51−Your **host login shell** (detected by `c init`, bash fallback), **coreutils**,

52−[**herdr**](https://herdr.dev) (the session `c start` launches), **Nix** itself

53−(with CA certs and `nix-command`/`flakes` enabled, single-user), and the ncurses

54−**terminfo** database are always included — no need to list them.

43+**fish** (the default command, with a configured prompt) and **Nix** itself

44+(with CA certs and `nix-command`/`flakes` enabled, single-user) are always

45+included — no need to list them.

5546

5647Point at a different file with `-c`/`--config`:

5748

@@ -68,17 +59,18 @@ that holds a `container.nix`; the container is named after that directory.

6859# build the image, load it, and create the container (named after $PWD):

6960nix run github:ilyakooo0/nix-container -- init

7061

71−# start it and attach — drops you into a herdr session:

62+# start it and attach — drops you into fish:

7263nix run github:ilyakooo0/nix-container -- start

7364```

7465

7566- `init` builds the OCI archive in a temp dir, loads it into `container`,

7667 deletes the temp file, then (re)creates the container. It mounts the current

77− directory at `/workspace` (the container's working directory).

68+ directory at `/workspace` (the container's working directory) and your

69+ `~/.config` at `/root/.config` (fish runs with `--no-config`, so this won't

70+ override its bundled prompt; other tools still read it).

7871- `--ssh` forwards your host SSH agent socket into the container (so `git` over

7972 SSH works with your keys).

80−- Add more mounts persistently via `mounts` in `container.nix` (above), or

81− ad-hoc by passing them through to `create` (mounts can only be set at creation):

73+- Add more mounts by passing them through (mounts can only be set at creation):

8274

8375 ```sh

8476 nix run github:ilyakooo0/nix-container -- init -v $HOME/data:/data

@@ -99,19 +91,18 @@ nix run github:ilyakooo0/nix-container -- init

9991## Customize further

10092

10193Fork or clone to change what isn't per-project — `config.cmd`/`env` or the image

102−name — in [`flake.nix`](./flake.nix). The flake also exposes build helpers:

94+name — in [`flake.nix`](./flake.nix). The flake also exposes build helpers, both

95+taking a `{ pkgs, nur }: [ ... ]` function:

10396

104−- `lib.<system>.copyWith` → a skopeo copy app for a `{ pkgs, nur }: [ ... ]`

105− function, for building/pushing the image anywhere skopeo can write (e.g. a

106− registry):

97+- `lib.<system>.mkImage` → an OCI image.

98+- `lib.<system>.copyWith` → a skopeo copy app, for building/pushing the image

99+ anywhere skopeo can write (e.g. a registry):

107100

108101 ```sh

109102 drv=$(nix build --no-link --print-out-paths --impure --expr \

110− '(builtins.getFlake "github:ilyakooo0/nix-container").lib.${builtins.currentSystem}.copyWith (import ./container.nix).packages')

103+ '(builtins.getFlake "github:ilyakooo0/nix-container").lib.${builtins.currentSystem}.copyWith (import ./container.nix)')

111104 $drv/bin/copy-to docker://ghcr.io/me/img:latest

112105 ```

113−- `lib.<system>.mkImage <name> <shell>` → the underlying OCI image (`copyWith`

114− defaults these to `nix-container` / `bash`).

115106

116107The flake uses `flake-utils` over `{aarch64,x86_64}-{darwin,linux}`; the host

117108system maps to the matching Linux target automatically (an Intel Mac builds an

c+13−43

@@ -1,7 +1,7 @@

11#!/usr/bin/env fish

22# Manage a container named after the current directory.

33# c init [-c FILE] [extra create args] build + load the image, then (re)create it

4−# (config from FILE, default ./container.nix)

4+# (packages from FILE, default ./container.nix)

55# c start start it and attach

77set -l name (path basename $PWD)

@@ -22,23 +22,17 @@ switch $argv[1]

2222 end

2323

2424 if not test -e $config

25− echo "c: config file not found: $config" >&2

26− echo " create one ('{ packages = { pkgs, nur }: [ ... ]; mounts = [ ]; }') or pass -c FILE" >&2

25+ echo "c: package file not found: $config" >&2

26+ echo " create one ('{ pkgs, nur }: [ ... ]') or pass -c FILE" >&2

2727 exit 1

2828 end

2929

30− # Host login shell (by name): added to the image automatically and baked

31− # in as the cmd + default $SHELL (what herdr panes etc. spawn), so it

32− # needn't be listed in container.nix. Falls back to bash.

33− set -l shell bash

34− test -n "$SHELL"; and set shell (path basename $SHELL)

35−

36− # Build an image with the config's `packages` (plus the shell) into a

37− # temp dir, load it, then clean up.

30+ # Build an image with the packages from $config into a temp dir, load

31+ # it, then clean up.

3832 set -l tmp (mktemp -d)

3933 set -l archive $tmp/image.tar.gz

40− set -lx NIX_CONTAINER_CONFIG (path resolve $config)

41− set -l expr "(builtins.getFlake \"$flake\").lib.\${builtins.currentSystem}.copyWithShell \"nix-container-$name\" \"$shell\" (import (/. + builtins.getEnv \"NIX_CONTAINER_CONFIG\")).packages"

34+ set -lx NIX_CONTAINER_PKGS (path resolve $config)

35+ set -l expr "(builtins.getFlake \"$flake\").lib.\${builtins.currentSystem}.copyWith (import (/. + builtins.getEnv \"NIX_CONTAINER_PKGS\"))"

4236 set -l copyer (nix build --impure --no-link --print-out-paths --expr "$expr")

4337 set -l rc $status

4438 if test $rc -eq 0

@@ -53,40 +47,16 @@ switch $argv[1]

5347 rm -rf $tmp

5448 test $rc -eq 0; or exit $rc

5549

56− # Mount the project at /workspace (the default cwd), plus any extra

57− # mounts from the config (`mounts = [ "host:container" … ]`). A leading

58− # ~/ in the host path expands to $HOME (nix leaves it literal).

50+ # Mount the project at /workspace (the default cwd) and host ~/.config.

51+ # (fish runs with --no-config, so the mount can't shadow the prompt.)

5952 set -l mounts -v "$PWD:/workspace"

60− for m in (nix eval --impure --raw --expr "builtins.concatStringsSep \"\n\" ((import (/. + builtins.getEnv \"NIX_CONTAINER_CONFIG\")).mounts or [])")

61− set -a mounts -v (string replace -r '^~/' "$HOME/" -- $m)

62− end

63−

64− # TERM to bake into the container env (`-e TERM`): the runtime hands the

65− # `start -ai` session a bare "xterm", so set the host's real terminal,

66− # mapped to an entry the bundled ncurses ships — Ghostty reports

67− # "xterm-ghostty", which ncurses ships as "ghostty" — falling back to

68− # xterm-256color for an empty or bare-"xterm" value.

69− set -l term xterm-256color

70− if test "$TERM" = xterm-ghostty

71− set term ghostty

72− else if test -n "$TERM"; and test "$TERM" != xterm

73− set term $TERM

74− end

53+ test -d $HOME/.config; and set -a mounts -v "$HOME/.config:/root/.config"

7554

76− # Replace any existing container of the same name, then create it running

77− # herdr in a session named after the project (`<dir>-container`). This

78− # overrides the image's default plain-herdr cmd; `c start` attaches to it.

55+ # Replace any existing container of the same name. The image's cmd is

56+ # /bin/fish, so no command is passed.

7957 container rm --force $name 2>/dev/null

80− # The image only lays down /bin and /etc, so /tmp and /run don't exist;

81− # without them anything that writes temp files (herdr, build tools, …)

82− # fails with ENOENT. Mount writable tmpfs at both.

83− container create --name $name --ssh -it -e "TERM=$term" \

84− --tmpfs /tmp --tmpfs /run --memory 8g --cwd /workspace $mounts $argv \

85− $image /bin/herdr session attach "$name-container"

58+ container create --name $name --ssh -it --memory 8g --cwd /workspace $mounts $argv $image

8659 case start

87− # Start the container and attach to its cmd (herdr). TERM was baked into

88− # the container env at create time (`-e TERM`), which survives this path.

89− # Exiting herdr (PID1) stops the container; `c start` boots it again.

9060 container start -ai $name

9161 case '*'

9262 echo "usage: c init [-c FILE] [create args] | start" >&2

flake.nix+77−49

@@ -72,22 +72,62 @@

7272 # Host package set, for the wrapper app below.

7373 pkgsHost = nixpkgs.legacyPackages.${system};

7474

75− # Default image name (for `copyWith`); `c init` passes a per-directory

76− # name (`nix-container-<dir>`) to `copyWithShell` instead.

75+ # Name/tag baked into the image's OCI config.

7776 imageName = "nix-container";

7877 imageTag = "latest";

7978

80− # Build the OCI image (named `name`) from a `{ pkgs, nur }: [ ... ]`

81− # package function, for the named shell. The image's `cmd` is herdr

82− # (the session `c start` attaches to); the shell is the default `$SHELL`

83− # (what herdr panes spawn) and is added automatically, so `container.nix`

84− # lists only your extras. Nix (+ CA certs) and the ncurses terminfo

85− # database are always shipped too. Nothing here is fish-specific: the

86− # TERM fixup happens host-side in `c` (passed via `-e TERM` at create).

79+ # Fish prompt config. Installed at /etc/fish/prompt.fish and loaded via

80+ # `fish --no-config --init-command` (see `cmd` below), NOT from

81+ # $HOME/.config/fish — so the `~/.config` mount can't shadow it. Built

82+ # on the host arch (just a text file), so no Linux builder is needed.

83+ fishConfig = pkgsHost.writeText "prompt.fish" ''

84+ # No welcome banner.

85+ set -g fish_greeting

86+

87+ # The container runtime hands fish a bare TERM=xterm (8 colors) and

88+ # no COLORTERM, washing out colors. The bundled terminfo DB (via

89+ # ncurses) has the 256-color entry, so promote xterm→xterm-256color

90+ # and advertise truecolor for 24-bit-aware tools.

91+ if test "$TERM" = xterm; or test -z "$TERM"

92+ set -gx TERM xterm-256color

93+ end

94+ set -q COLORTERM; or set -gx COLORTERM truecolor

95+

96+ # Define the prompt as a function so fish renders it before every

97+ # command; at top level it would run once at startup and be ignored.

98+ function fish_prompt

99+ set -l nix_shell_info

100+ if set -q IN_NIX_SHELL; or set -q IN_NIX_RUN

101+ set nix_shell_info ' ❄️'

102+ end

103+

104+ set -l cwd (prompt_pwd)

105+

106+ set -l bookmark_info

107+ if jj root 2>/dev/null >/dev/null

108+ set -l jj_bookmark (jj log -r 'heads(::@ & bookmarks())' -T 'local_bookmarks ++ "\n"' --no-graph 2>/dev/null | tail -1)

109+ if test -n "$jj_bookmark"

110+ set bookmark_info ' ' (set_color brmagenta) $jj_bookmark (set_color normal)

111+ end

112+ end

113+

114+ echo -n -s (set_color $fish_color_cwd) $cwd (set_color normal) $bookmark_info ' 🏗️' $nix_shell_info '> '

115+ end

116+ '';

117+

118+ # Lay the prompt out at the path the cmd sources.

119+ fishRoot = pkgsHost.runCommand "fish-prompt" { } ''

120+ mkdir -p "$out/etc/fish"

121+ cp ${fishConfig} "$out/etc/fish/prompt.fish"

122+ '';

123+

124+ # Build the OCI image from a `{ pkgs, nur }: [ ... ]` package function.

125+ # The image always runs /bin/fish; fish, its prompt config, and Nix are

126+ # bundled automatically, so `container.nix` lists only your extras.

87127 mkImage =

88− name: shell: packages:

128+ packages:

89129 n2c.buildImage {

90− inherit name;

130+ name = imageName;

91131 tag = imageTag;

92132 inherit arch;

93133

@@ -95,6 +135,10 @@

95135 # buildEnv only *symlinks* paths (never runs them), so build it on

96136 # the host arch — the tree is arch-neutral and links the

97137 # (substituted) Linux store paths, sparing the Linux builder.

138+ #

139+ # Always shipped: fish (the cmd) + its prompt, and Nix (+ CA certs)

140+ # so every container can use Nix; `initializeNixDatabase` registers

141+ # the baked store.

98142 copyToRoot = pkgsHost.buildEnv {

99143 name = "root";

100144 paths =

@@ -102,27 +146,19 @@

102146 pkgs = pkgsLinux;

103147 nur = nurPkgs;

104148 }

105− # The shell (cmd + $SHELL), when it exists in nixpkgs.

106− ++ pkgsLinux.lib.optional (pkgsLinux ? ${shell}) pkgsLinux.${shell}

107149 ++ [

150+ pkgsLinux.fish

151+ fishRoot

108152 pkgsLinux.nix

109153 pkgsLinux.cacert

110− # Basic userland (ls, cat, cp, sleep, …) so the container is

111− # usable out of the box and tools that shell out don't fail.

112− pkgsLinux.coreutils-full

113154 # Networking glue glibc needs: /etc/nsswitch.conf (+passwd,

114155 # group) so DNS/host lookups resolve, and /etc/protocols,

115156 # /etc/services. Without these, hostname resolution fails.

116157 pkgsLinux.fakeNss

117158 pkgsLinux.iana-etc

118− # The terminfo database (+ tput/clear/reset) so TUIs find the

119− # entry for whatever TERM `c` passes in and render correctly.

120− pkgsLinux.ncurses

121− # The session `c start` always launches.

122− pkgsLinux.herdr

123159 ];

124160 # Link all of /etc so the above files (nsswitch.conf, protocols,

125− # services, passwd, group, ssl certs) are present.

161+ # services, passwd, group, ssl certs, fish prompt) are present.

126162 pathsToLink = [

127163 "/bin"

128164 "/etc"

@@ -133,25 +169,24 @@

133169

134170 config = {

135171 # `cmd` (not `entrypoint`): the default command, *replaced* by any

136− # command passed to `container run/create`. Plain herdr here;

137− # `c init` overrides it with `herdr session attach <dir>-container` so

138− # the session is named per project. `c start` attaches via

139− # `container start -ai`; exiting herdr (PID1) stops the container.

140− cmd = [ "/bin/herdr" ];

172+ # command passed to `container run/create`. `--no-config` skips

173+ # $HOME/.config/fish (so a mounted ~/.config can't override the

174+ # prompt); `--init-command` loads the bundled prompt instead.

175+ cmd = [

176+ "/bin/fish"

177+ "--no-config"

178+ "--init-command"

179+ "source /etc/fish/prompt.fish"

180+ ];

141181 env = [

142182 "PATH=/bin"

143183 "HOME=/root"

144− # Default shell for tools that spawn one (herdr panes, etc.).

145− "SHELL=/bin/${shell}"

146184 # Marker so shells/scripts can detect they're in here.

147185 "NIX_CONTAINER=1"

148− # Advertise truecolor for 24-bit-aware tools; `c` passes the

149− # resolved TERM via -e (the runtime would otherwise force xterm).

186+ # Advertise truecolor so `container exec` sessions (which don't

187+ # source the fish init) still get 24-bit color. TERM is fixed up

188+ # in the fish prompt init, since the runtime overrides it here.

150189 "COLORTERM=truecolor"

151− # A UTF-8 locale so tools handle multibyte/wide characters

152− # correctly. glibc ships C.UTF-8 built in, so this needs no

153− # locale-archive.

154− "LANG=C.UTF-8"

155190 # CA trust for every TLS client (curl/git/…) and Nix.

156191 "SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt"

157192 "NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-bundle.crt"

@@ -164,7 +199,7 @@

164199

165200 # `nix run . -- init|start` runs the bundled `c` manager script. Its

166201 # `init` builds the image from the project's `container.nix` (via

167− # `lib.copyWithShell`); the script finds the flake from its own (store)

202+ # `lib.copyWith`); the script finds the flake from its own (store)

168203 # location, so this works from a checkout or straight from

169204 # `nix run github:…/nix-container`.

170205 cApp = pkgsHost.writeShellScriptBin "c" ''

@@ -177,22 +212,15 @@

177212 default = flake-utils.lib.mkApp { drv = cApp; };

178213 };

179214

180− # Build helpers take a `{ pkgs, nur }: [ ... ]` packages function (the

181− # `packages` attr of a project's `container.nix`). `c init` uses

182− # `copyWithShell` (host shell baked in); `copyWith` is the generic form:

215+ # Build helpers. `c init` uses `copyWith` to honour a per-project

216+ # `container.nix`:

183217 # (builtins.getFlake "github:…/nix-container")

184− # .lib.<system>.copyWith (import ./container.nix).packages

218+ # .lib.<system>.copyWith (import ./container.nix)

185219 lib = {

186220 inherit mkImage;

187− # Build the image's `copyTo` script (a skopeo-copy wrapper) from a

188− # `{ pkgs, nur }: [ ... ]` function, named `imageName`. Defaults the

189− # shell (cmd + $SHELL) to bash; use `copyWithShell` to pick another.

190− copyWith = packages: (mkImage imageName "bash" packages).copyTo;

191− # Like `copyWith`, but for the given image `name` and shell — `c init`

192− # passes `nix-container-<dir>` and the host login shell, which is added

193− # to the image and used as cmd + $SHELL without being listed in

194− # `container.nix`.

195− copyWithShell = name: shell: packages: (mkImage name shell packages).copyTo;

221+ # skopeo copy app (`skopeo copy nix:<image> "$@"`) for an image built

222+ # from a `{ pkgs, nur }: [ ... ]` function.

223+ copyWith = packages: (mkImage packages).copyTo;

196224 };

197225 }

198226 );