TEMP

doc/manual/src/command-ref/files/channels.md

@@ -1,13 +1,25 @@
 ## Channels
 
-A directory containing symlinks to Nix channels, managed by [`nix-channel`]:
+A directory containing symlinks to Nix channels, managed by [`nix-channel`].
 
-- `$XDG_STATE_HOME/nix/profiles/channels` for regular users
-- `$NIX_STATE_DIR/profiles/per-user/root/channels` for `root`
-
-[`nix-channel`] uses a [profile](@docroot@/command-ref/files/profiles.md) to store channels.
+The channels directory is a [profile](@docroot@/command-ref/files/profiles.md), so as to allow easy management of multiple versions and switching between them.
 This profile contains symlinks to the contents of those channels.
 
+### User-specific and global channels
+
+Channels are managed either for a specific user, or for all users globally on the system to share.
+This matches the [user-specific vs global conventions](@docroot@/command-ref/files/profiles.md#user-specific-and-global-profiles) of profiles themselves.
+
+- [User-specific channels]{#user-channels} are stored in:
+  ```
+  $XDG_STATE_HOME/nix/profiles/channels
+  ```
+
+- [Global channels]{#global-channels} are stored in
+  ```
+  $NIX_STATE_DIR/profiles/per-user/root/channels
+  ```
+
 ## Subscribed channels
 
 The list of subscribed channels is stored in

doc/manual/src/command-ref/files/default-nix-expression.md

@@ -42,8 +42,8 @@ A symlink that ensures that [`nix-env`] can find your channels:
 
 This symlink points to:
 
-- `$XDG_STATE_HOME/profiles/channels` for regular users
-- `$NIX_STATE_DIR/profiles/per-user/root/channels` for `root`
+- The [user-specific channels](@docroot@/command-ref/files/profiles.md#user-channels) (`$XDG_STATE_HOME/profiles/channels`) for regular users
+- The [global channels](@docroot@/command-ref/files/profiles.md#global-channels) (`$NIX_STATE_DIR/profiles/per-user/root/channels`) for `root`
 
 In a multi-user installation, you may also have `~/.nix-defexpr/channels_root`, which links to the channels of the root user.[`nix-env`]: ../nix-env.md
 

doc/manual/src/command-ref/files/profiles.md

@@ -1,11 +1,32 @@
 ## Profiles
 
-A directory that contains links to profiles managed by [`nix-env`] and [`nix profile`]:
+A directory that contains links to profiles managed by [`nix-env`] and [`nix profile`].
 
-- `$XDG_STATE_HOME/nix/profiles` for regular users
-- `$NIX_STATE_DIR/profiles/per-user/root` if the user is `root`
+### [User-specific and global profiles]{#user-specific-and-global-profiles}
 
-A profile is a directory of symlinks to files in the Nix store.
+Profiles can be placed in any directory, but by default, different locations are used depending on whether the profile is intended to be used by a single user, or shared globally by all users.
+
+- The default directory for user-specific profiles is:
+  ```
+  $XDG_STATE_HOME/nix/profiles
+  ```
+
+  Within it, the [default user profile]{#default-user-profile} is:
+  ```
+  $XDG_STATE_HOME/nix/profiles/profile
+  ```
+
+- The default directory for global profiles is
+  ```
+  $NIX_STATE_DIR/profiles
+  ```
+
+  Within it, the [default global profile]{#default-global-profile} is
+  ```
+  $NIX_STATE_DIR/profiles/default
+  ```
+
+Nix command will default to the default user profile for regular users, and the default global profiles for root, but often provide flags to override this behavior.
 
 ### Filesystem layout
 
@@ -63,8 +84,8 @@ A symbolic link to the user's current profile:
 
 By default, this symlink points to:
 
-- `$XDG_STATE_HOME/nix/profiles/profile` for regular users
-- `$NIX_STATE_DIR/profiles/per-user/root/profile` for `root`
+- The [default user profile](#default-user-profile) (`$XDG_STATE_HOME/nix/profiles/profile`) for regular users
+- The [default global profile](#default-global-profile) (`$NIX_STATE_DIR/profiles/per-user/root/profile`) for `root`
 
 The `PATH` environment variable should include `/bin` subdirectory of the profile link (e.g. `~/.nix-profile/bin`) for the user environment to be visible to the user.
 The [installer](@docroot@/installation/installing-binary.md) sets this up by default, unless you enable [`use-xdg-base-directories`].

doc/manual/src/command-ref/nix-channel.md

@@ -46,6 +46,14 @@ This command has the following operations:
 
 Note that `--add` does not automatically perform an update.
 
+It also has the following flags, which affect all operations:
+
+  - `--global`\
+    Operate on the [global channels](@docroot@/command-ref/files/channels.md#global-channels), i.e. the channels shared by all users.
+
+  - `--user`\
+    Operate on the [user channels](@docroot@/command-ref/files/channels.md#user-channels), i.e. the channels just for the current user.
+
 The list of subscribed channels is stored in `~/.nix-channels`.
 
 {{#include ./opt-common.md}}

doc/manual/src/command-ref/nix-env.md

@@ -9,7 +9,7 @@
   [`--arg` *name* *value*]
   [`--argstr` *name* *value*]
   [{`--file` | `-f`} *path*]
-  [{`--profile` | `-p`} *path*]
+  [{`--profile` | `-p`} *path* | `--global` | `--user`]
   [`--system-filter` *system*]
   [`--dry-run`]
 

doc/manual/src/command-ref/nix-env/opt-common.md

@@ -19,6 +19,16 @@ The following options are allowed for all `nix-env` operations, but may not alwa
     sequence of user environments called *generations*, one of which is
     the *current generation*.
 
+  - `--user`\
+    Specifies the profile as the [default user profile](@docroot@/command-ref/files/profiles.md#default-user-profile) private to this user.
+    This is a shorthand for passing `--profile` and the path to that default profile.
+    This is default if the current user is not root.
+
+  - `--global`\
+    Specifies the profile as the [default global profile](@docroot@/command-ref/files/profiles.md#default-global-profile) shared between all users.
+    A shorthand instead of passing `--profile` and the path to that default profile.
+    This is default if the current user is root.
+
   - `--dry-run`\
     For the `--install`, `--upgrade`, `--uninstall`,
     `--switch-generation`, `--delete-generations` and `--rollback`

src/libcmd/command.cc

@@ -271,7 +271,24 @@ void MixProfile::updateProfile(const BuiltPaths & buildables)
 
 MixDefaultProfile::MixDefaultProfile()
 {
-    profile = getDefaultProfile();
+
+    addFlag({
+        .longName = "user-profile",
+        .description = "Act on the profile for this current user",
+        .handler = {[this]() {
+            profile = getDefaultProfile(DefaultProfileKind::User);
+        }}
+    });
+
+    addFlag({
+        .longName = "global-profile",
+        .description = "Act on the global profile shared between all default users",
+        .handler = {[this]() {
+            profile = getDefaultProfile(DefaultProfileKind::Global);
+        }}
+    });
+
+    profile = getDefaultProfile(defaultDefaultProfileKind());
 }
 
 MixEnvironment::MixEnvironment() : ignoreEnvironment(false)

src/libexpr/def-expr.cc

@@ -0,0 +1,13 @@
+#include "def-expr.hh"
+#include "globals.hh"
+
+namespace nix {
+
+Path getNixDefExpr()
+{
+    return settings.useXDGBaseDirectories ?
+        getStateDir() + "/nix/defexpr"
+        : getHome() + "/.nix-defexpr";
+}
+
+}

src/libexpr/def-expr.hh

@@ -0,0 +1,13 @@
+#pragma once
+///@file
+
+#include "types.hh"
+
+namespace nix {
+
+/**
+ * Conventionally part of the default nix path in impure mode.
+ */
+Path getNixDefExpr();
+
+}

src/libexpr/eval.cc

@@ -10,6 +10,8 @@
 #include "function-trace.hh"
 #include "profiles.hh"
 #include "print.hh"
+#include "profiles/channels.hh"
+#include "def-expr.hh"
 
 #include <algorithm>
 #include <chrono>
@@ -2629,9 +2631,9 @@ Strings EvalSettings::getDefaultNixPath()
     };
 
     if (!evalSettings.restrictEval && !evalSettings.pureEval) {
-        add(settings.useXDGBaseDirectories ? getStateDir() + "/nix/defexpr/channels" : getHome() + "/.nix-defexpr/channels");
-        add(rootChannelsDir() + "/nixpkgs", "nixpkgs");
-        add(rootChannelsDir());
+        add(getNixDefExpr() + "/channels");
+        add(globalChannelsDir() + "/nixpkgs", "nixpkgs");
+        add(globalChannelsDir());
     }
 
     return res;

src/libstore/profiles.cc

@@ -280,50 +280,106 @@ std::string optimisticLockProfile(const Path & profile)
 }
 
 
-Path profilesDir()
+Path userProfilesDir()
 {
-    auto profileRoot =
-        (getuid() == 0)
-        ? rootProfilesDir()
-        : createNixStateDir() + "/profiles";
+    auto profileRoot = createNixStateDir() + "/profiles";
     createDirs(profileRoot);
     return profileRoot;
 }
 
-Path rootProfilesDir()
+/**
+ * Return the path to the global profile directory (but don't try creating it)
+ *
+ * Just used for the global profile and the global channels, but those
+ * go in different subdirs, so we do not expose this.
+ */
+static Path globalProfilesDir()
 {
-    return settings.nixStateDir + "/profiles/per-user/root";
+    return settings.nixStateDir + "/profiles";
 }
 
+/**
+ * The other directory used for global profiles
+ */
+static Path perUsersRootDir()
+{
+    return globalProfilesDir() + "/per-user/root/";
+}
+
+std::vector<Path> globalProfilesDirs()
+{
+    return {
+        globalProfilesDir(),
+        perUsersRootDir(),
+    };
+}
+
+Path getDefaultUserProfile()
+{
+    return userProfilesDir() + "/profile";
+}
+
+Path getDefaultGlobalProfile()
+{
+    return globalProfilesDir() + "/default";
+}
 
-Path getDefaultProfile()
+DefaultProfileKind defaultDefaultProfileKind()
 {
-    Path profileLink = settings.useXDGBaseDirectories ? createNixStateDir() + "/profile" : getHome() + "/.nix-profile";
+    return getuid() == 0
+        ? DefaultProfileKind::Global
+        : DefaultProfileKind::User;
+}
+
+Path defaultProfileLink()
+{
+    return settings.useXDGBaseDirectories ? createNixStateDir() + "/profile" : getHome() + "/.nix-profile";
+}
+
+std::optional<Path> tryGetDefaultProfile()
+{
+    Path profileLink = defaultProfileLink();
+    if (pathExists(profileLink))
+        return absPath(readLink(profileLink), dirOf(profileLink));
+    else
+        return std::nullopt;
+}
+
+Path getDefaultProfile(DefaultProfileKind profileKind)
+{
+    Path profileLink = defaultProfileLink();
     try {
-        auto profile = profilesDir() + "/profile";
         if (!pathExists(profileLink)) {
+            Path profile;
+            switch (profileKind) {
+                case DefaultProfileKind::Global:
+                    profile = getDefaultGlobalProfile();
+                    break;
+                case DefaultProfileKind::User:
+                    profile = getDefaultUserProfile();
+                    break;
+                default:
+                    assert(false);
+            }
             replaceSymlink(profile, profileLink);
         }
-        // Backwards compatibiliy measure: Make root's profile available as
-        // `.../default` as it's what NixOS and most of the init scripts expect
-        Path globalProfileLink = settings.nixStateDir + "/profiles/default";
-        if (getuid() == 0 && !pathExists(globalProfileLink)) {
-            replaceSymlink(profile, globalProfileLink);
-        }
         return absPath(readLink(profileLink), dirOf(profileLink));
     } catch (Error &) {
         return profileLink;
     }
 }
 
-Path defaultChannelsDir()
+Path userChannelsDir()
 {
-    return profilesDir() + "/channels";
+    return userProfilesDir() + "/channels";
 }
 
-Path rootChannelsDir()
+Path globalChannelsDir()
 {
-    return rootProfilesDir() + "/channels";
+    /* "per-user" might seem like a weird thing to include in the path
+       to the "global" channels dir; it is done this way for
+       back-compat. */
+    return perUsersRootDir() + "/channels";
 }
 
 }