1 files changed, 23 insertions, 1 deletions
diff --git a/setup.sh b/setup.sh
index 959a48f..8159db6 100755
--- a/setup.sh
+++ b/setup.sh
@@ -1,9 +1,31 @@
 #!/bin/sh
 
+# https://stackoverflow.com/questions/2990414/echo-that-outputs-to-stderr
+errcho(){ >&2 echo "$@"; }
+
 # run this script as root, once, at installation
+if id -u 0tdns > /dev/null 2>&1; then
+    errcho "User 0tdns already exists."
+    errcho "Do you have Zero Trust DNS already set up?"
+    errcho "If so, you need to uninstall it properly"
+    errcho "(e.g. via provided uninstall.sh script)"
+    errcho "before setting it up again"
+    exit 1
+fi
 
-# more will go here (e.g. initialization of postgres database)
+if [ `id -u` != 0 ]; then
+    errcho "This script needs to be run as root"
+    exit 1
+fi
 
 # part of the program running inside network namespace
 # will run under this user
 useradd --system 0tdns
+
+# crontab automatically adds a 'DO NOT EDIT' header to
+# crontab file; if we don't remove it every time - headers
+# will accumulate :/ (not on Debian, though)
+# line we want to add to crontab is in 0tdns_crontab file
+crontab -l 2> /dev/null |
+    grep -vE '^# DO NOT EDIT THIS FILE|^# \(- installed on .*\)|^# \(Cron version .*\)' |
+    cat - 0tdns_crontab | crontab