diff --git a/README.md b/README.md
index e19e70c..387f9e6 100644
--- a/README.md
+++ b/README.md
@@ -3,14 +3,14 @@
 Add to `Dockerfile`:
 
 ```
-RUN apt-get update && apt-get install -y curl
+RUN apt-get update && apt-get install -y curl jq bash
 RUN curl -fsSL https://git.eeqj.de/sneak/ubuntulocal/raw/branch/main/updatemirror.sh | bash
 ```
 
 Alternately, paste in:
 
 ```
-apt-get update && apt-get install -y curl jq
+apt-get update && apt-get install -y curl jq bash
 curl -fsSL https://git.eeqj.de/sneak/ubuntulocal/raw/branch/main/updatemirror.sh | bash
 ```
 
diff --git a/updatemirror.sh b/updatemirror.sh
index 025c0bf..7f700b4 100644
--- a/updatemirror.sh
+++ b/updatemirror.sh
@@ -29,7 +29,13 @@ function main () {
     fi
 
     apt_update_if_stale
-    apt install -y jq curl
+    if ! which jq > /dev/null; then
+        apt-get install -y jq
+    fi
+
+    if ! which curl > /dev/null; then
+        apt-get install -y curl
+    fi
 
     echo "Changing mirror country to US as a first approximation..." > /dev/stderr
     find /etc/apt/sources.list.d/ -type f -exec \
@@ -65,6 +71,7 @@ function main () {
     find /etc/apt/sources.list.d/ -type f -exec \
       sed -i "s|us\.archive\.ubuntu\.com|$MIRRORHOST|g" {} +
 
+    # update is actually mandatory after changing the mirror:
     apt-get update
 
     echo "Finished." > /dev/stderr