diff --git a/doc/flk/update.md b/doc/flk/update.md
index e3a20e80..84f25208 100644
--- a/doc/flk/update.md
+++ b/doc/flk/update.md
@@ -4,3 +4,13 @@ The `update` subcommand is a simple alias for:
 nix flake update --recreate-lock-file --commit-lock-file
 ```
 As it sounds, this will update your lock file, and commit it.
+
+## Updating Package Sources
+If you pass an input name then it will only update that input.
+
+For example, you can update any
+[package sources](../../pkgs#automatic-source-updates) you may have declared
+in _pkgs/flake.nix_:
+```sh
+flk update srcs
+```
diff --git a/flake.lock b/flake.lock
index 3036624a..a330e95f 100644
--- a/flake.lock
+++ b/flake.lock
@@ -214,9 +214,21 @@
         "nixos-hardware": "nixos-hardware",
         "nur": "nur",
         "override": "override",
+        "srcs": "srcs",
         "utils": "utils"
       }
     },
+    "srcs": {
+      "locked": {
+        "narHash": "sha256-Ot96/oKT5+A5kdqkfYyT45cfEiqhI5UyPdEfEZjbXaA=",
+        "path": "./pkgs",
+        "type": "path"
+      },
+      "original": {
+        "path": "./pkgs",
+        "type": "path"
+      }
+    },
     "utils": {
       "locked": {
         "lastModified": 1608663846,
diff --git a/flake.nix b/flake.nix
index 0f4d60b9..03655363 100644
--- a/flake.nix
+++ b/flake.nix
@@ -23,6 +23,7 @@
       naersk.inputs.nixpkgs.follows = "override";
       flake-compat.url = "github:edolstra/flake-compat";
       flake-compat.flake = false;
+      srcs.url = "path:./pkgs";
     };
 
   outputs =
diff --git a/lib/default.nix b/lib/default.nix
index 5e3185a3..c60880c2 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -4,7 +4,7 @@ let
     pathExists filter;
 
   inherit (nixos.lib) fold filterAttrs hasSuffix mapAttrs' nameValuePair removeSuffix
-    recursiveUpdate genAttrs nixosSystem mkForce optionalAttrs;
+    recursiveUpdate genAttrs nixosSystem mkForce substring optionalAttrs;
 
   # mapFilterAttrs ::
   #   (name -> value -> bool )
@@ -93,6 +93,8 @@ in
 
   overlays = pathsToImportedAttrs overlayPaths;
 
+  mkVersion = src: "${substring 0 8 src.lastModifiedDate}_${src.shortRev}";
+
   genPkgs = { self }:
     let inherit (self) inputs;
     in
@@ -107,6 +109,7 @@ in
             (overridesOverlay overridePkgs)
             self.overlay
             (final: prev: {
+              srcs = self.inputs.srcs.inputs;
               lib = (prev.lib or { }) // {
                 inherit (nixos.lib) nixosSystem;
                 flk = self.lib;
diff --git a/pkgs/README.md b/pkgs/README.md
index dd9352fb..89e34fe8 100644
--- a/pkgs/README.md
+++ b/pkgs/README.md
@@ -14,22 +14,24 @@ the supported systems listed in the package's `meta.platforms` attribute.
 And, as usual, every package in the overlay is also available to any NixOS
 [host](../hosts).
 
+## Automatic Source Updates
+There is the added, but optional, convenience of declaring your sources in
+_pkgs/flake.nix_ as an input. This allows updates to be managed automatically
+by simply [updating](../doc/flk/update.md#updating-package-sources) the lock
+file. No more manually entering sha256 hashes!
+
+
 ## Example
 pkgs/development/libraries/libinih/default.nix:
 ```nix
-{ stdenv, meson, ninja, fetchFromGitHub, ... }:
-let version = "r50";
+{ stdenv, meson, ninja, lib, srcs, ... }:
+let version = "r53";
 in
 stdenv.mkDerivation {
   pname = "libinih";
   inherit version;
 
-  src = fetchFromGitHub {
-    owner = "benhoyt";
-    repo = "inih";
-    rev = "${version}";
-    hash = "sha256-GF+TVEysaXJxSBBjMsTr2IQvRKlzdEu3rlPQ88PE3nI=";
-  };
+  src = srcs.libinih;
 
   buildInputs = [ meson ninja ];
 
@@ -38,7 +40,7 @@ stdenv.mkDerivation {
     -Ddistro_install=true
   '';
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     description = "Simple .INI file parser in C";
     homepage = "https://github.com/benhoyt/inih";
     maintainers = [ maintainers.divnix ];
@@ -56,4 +58,16 @@ final: prev: {
 }
 ```
 
+pkgs/flake.nix:
+```nix
+{
+  description = "Package sources";
+
+  inputs = {
+    libinih.url = "github:benhoyt/inih/r53";
+    libinih.flake = false;
+  };
+}
+```
+
 [pkgs]: https://github.com/NixOS/nixpkgs/tree/master/pkgs
diff --git a/pkgs/flake.nix b/pkgs/flake.nix
new file mode 100644
index 00000000..257fbe3b
--- /dev/null
+++ b/pkgs/flake.nix
@@ -0,0 +1,7 @@
+{
+  description = "Package sources";
+
+  inputs = { };
+
+  outputs = { ... }: { };
+}
diff --git a/shell/flk.sh b/shell/flk.sh
index 99be02bb..32b0a210 100755
--- a/shell/flk.sh
+++ b/shell/flk.sh
@@ -17,12 +17,12 @@ usage () {
 
   printf "  %-30s %s\n\n" \
   "up" "Generate $DEVSHELL_ROOT/hosts/up-$HOSTNAME.nix" \
-  "update" "Update and commit the lock file" \
-  "get [core|community] DEST" "Copy the desired template to DEST" \
+  "update [INPUT]" "Update and commit the lock file" \
+  "get (core|community) [DEST]" "Copy the desired template to DEST" \
   "iso HOST" "Generate an ISO image of HOST" \
   "install HOST [ARGS]" "Shortcut for nixos-install" \
   "home HOST USER [switch]" "Home-manager config of USER from HOST" \
-  "HOST [switch|boot|test]" "Shortcut for nixos-rebuild"
+  "HOST (switch|boot|test)" "Shortcut for nixos-rebuild"
 }
 
 case "$1" in
@@ -49,14 +49,18 @@ case "$1" in
     ;;
 
   "update")
-    nix flake update --recreate-lock-file --commit-lock-file "$DEVSHELL_ROOT"
+    if [[ -n "$2" ]]; then
+      nix flake update --update-input "$2" --commit-lock-file "$DEVSHELL_ROOT"
+    else
+      nix flake update --recreate-lock-file --commit-lock-file "$DEVSHELL_ROOT"
+    fi
     ;;
 
   "get")
     if [[ "$2" == "core" || "$2" == "community" ]]; then
       nix flake new -t "github:divnix/devos/$2" "${3:-flk}"
     else
-      echo "flk get [core|community] {dest}"
+      echo "flk get (core|community) [DEST]"
       exit 1
     fi
     ;;