diff --git a/README.md b/README.md
index 071687c..e043b39 100644
--- a/README.md
+++ b/README.md
@@ -1,16 +1,9 @@
-personal dotfiles.
+personal dotfiles
 
-## installation
+## repo URLs
 
-```sh
-curl -sSL https://dotfiles.krd.sh/get | sh -s
-```
-
-or
-
-```sh
-wget -q -O - https://dotfiles.krd.sh/get | sh -s
-```
+- https://git.krd.sh/krd/dotfiles (main)
+- https://github.com/rockdrilla/dotfiles (mirror)
 
 ## contents
 
@@ -22,6 +15,56 @@ wget -q -O - https://dotfiles.krd.sh/get | sh -s
 
 files are stored in separate branch (`main`)
 
+## installation
+
+- install dotfiles (select preferred variant):
+  - with `curl`:
+    - default URI:
+
+      ```sh
+      curl -sSL https://dotfiles.krd.sh/get | sh -s
+      ```
+
+    - explicit fallback to Github:
+
+      ```sh
+      curl -sSL https://github.com/rockdrilla/dotfiles/raw/main/.config/dotfiles/install.sh | sh -s
+      ```
+
+  - with `wget`:
+    - default URI:
+
+      ```sh
+      wget -q -O - https://dotfiles.krd.sh/get | sh -s
+      ```
+
+    - explicit fallback to Github:
+
+      ```sh
+      wget -q -O - https://github.com/rockdrilla/dotfiles/raw/main/.config/dotfiles/install.sh | sh -s
+      ```
+
+  - with `apt-helper` (very last-resort):
+    - default URI:
+
+      ```sh
+      /usr/lib/apt/apt-helper download-file https://dotfiles.krd.sh/get "${HOME}/dotfiles.install.sh"
+      sh "${HOME}/dotfiles.install.sh" ; rm -f "${HOME}/dotfiles.install.sh"
+      ```
+
+    - explicit fallback to Github:
+
+      ```sh
+      /usr/lib/apt/apt-helper download-file https://github.com/rockdrilla/dotfiles/raw/main/.config/dotfiles/install.sh "${HOME}/dotfiles.install.sh"
+      sh "${HOME}/dotfiles.install.sh" ; rm -f "${HOME}/dotfiles.install.sh"
+      ```
+
+- switch shell to `zsh`:
+
+  ```sh
+  chsh -s /bin/zsh
+  ```
+
 ## license
 
 BSD 3-Clause