diff --git a/source/agent-remote/common.sh b/source/agent-remote/common.sh
index a93815f..554d7db 100755
--- a/source/agent-remote/common.sh
+++ b/source/agent-remote/common.sh
@@ -153,7 +153,7 @@ _get_container_logs() {
 _check_required_env_vars() {
     local required_vars=("$@")
     for var in "${required_vars[@]}"; do
-        if [ -z "${!var}" ]; then
+        if [ -z "${!var:-}" ]; then
             _die "Required environment variable $var is not set"
         fi
     done
diff --git a/source/agent-remote/datacommands.sh b/source/agent-remote/datacommands.sh
index 12a1087..d006710 100755
--- a/source/agent-remote/datacommands.sh
+++ b/source/agent-remote/datacommands.sh
@@ -118,8 +118,8 @@ _autocommandrun_file() {
             echo "Restoring file ${filepath}"
             local file_name;
             file_name=$(basename "${filepath}")
-            rm -f "${filepath}" || die "Unable to remove existing file ${filepath}, restore failed."
-            cp "${backup_folder}/${file_name}" "${filepath}" || die "Unable to copy file ${backup_folder}/${file_name} to ${filepath}, restore failed."
+            rm -f "${filepath}" || return_die "Unable to remove existing file ${filepath}, restore failed."
+            cp "${backup_folder}/${file_name}" "${filepath}" || return_die "Unable to copy file ${backup_folder}/${file_name} to ${filepath}, restore failed."
             ;;
     esac
 }
diff --git a/source/install_build_prerequisites.sh b/source/install_build_prerequisites.sh
index 63d1bb1..8c051a3 100755
--- a/source/install_build_prerequisites.sh
+++ b/source/install_build_prerequisites.sh
@@ -64,7 +64,9 @@ esac
 # Function to check if a package is installed
 is_package_installed() {
     if [ "$OS" = "Alpine Linux" ]; then
-        apk info | grep -q "^$1$"
+        # Use apk info <pkg> and check exit status
+        apk info "$1" >/dev/null 2>&1
+        return $?
     else
         dpkg -l "$1" 2>/dev/null | grep -q "^ii"
     fi
diff --git a/source/src/commands/create-service.cpp b/source/src/commands/create-service.cpp
index 1ab81a7..6d51cc2 100644
--- a/source/src/commands/create-service.cpp
+++ b/source/src/commands/create-service.cpp
@@ -103,6 +103,11 @@ namespace dropshell
             if (server_name.empty() || template_name.empty() || service_name.empty())
                 return false;
 
+            if (!legal_service_name(service_name)) {
+                error << "Service name contains illegal characters: " << service_name << std::endl;
+                return false;
+            }
+
             ServerConfig server_info(server_name);
             if (!server_info.is_valid())
             {
diff --git a/source/src/commands/edit.cpp b/source/src/commands/edit.cpp
index 312bd9c..968bcc0 100644
--- a/source/src/commands/edit.cpp
+++ b/source/src/commands/edit.cpp
@@ -94,11 +94,11 @@ int edit_config()
 
     std::string config_file = localfile::dropshell_json();
     if (!edit_file(config_file, false) || !std::filesystem::exists(config_file))
-        return die("Failed to edit config file.");
+        return return_die("Failed to edit config file.");
 
     gConfig().load_config();
     if (!gConfig().is_config_set())
-        return die("Failed to load and parse edited config file!");
+        return return_die("Failed to load and parse edited config file!");
 
     gConfig().save_config(true);
 
diff --git a/source/src/commands/ssh.cpp b/source/src/commands/ssh.cpp
index f2361b6..b411f25 100644
--- a/source/src/commands/ssh.cpp
+++ b/source/src/commands/ssh.cpp
@@ -61,6 +61,12 @@ namespace dropshell
             return false;
         }
 
+        if (!legal_service_name(service))
+        {
+            error << "Service name contains illegal characters: " << service << std::endl;
+            return false;
+        }
+
         LocalServiceInfo sinfo = get_service_info(server, service);
         if (!SIvalid(sinfo))
         {
diff --git a/source/src/commands/start.cpp b/source/src/commands/start.cpp
index 8720422..1dd09f4 100644
--- a/source/src/commands/start.cpp
+++ b/source/src/commands/start.cpp
@@ -51,6 +51,12 @@ namespace dropshell
             return false;
         }
 
+        if (!legal_service_name(service))
+        {
+            error << "Service name contains illegal characters: " << service << std::endl;
+            return false;
+        }
+
         // run the start script.
         bool started = server_env.run_remote_template_command(service, "start", {}, false, {});
 
diff --git a/source/src/commands/stop.cpp b/source/src/commands/stop.cpp
index 039a932..13f4cfe 100644
--- a/source/src/commands/stop.cpp
+++ b/source/src/commands/stop.cpp
@@ -51,6 +51,12 @@ namespace dropshell
             return false;
         }
 
+        if (!legal_service_name(service))
+        {
+            error << "Service name contains illegal characters: " << service << std::endl;
+            return false;
+        }
+
         // run the stop script.
         bool stopped = server_env.run_remote_template_command(service, "stop", {}, false, {});
 
diff --git a/source/src/servers.cpp b/source/src/servers.cpp
index cd78781..39aaf38 100644
--- a/source/src/servers.cpp
+++ b/source/src/servers.cpp
@@ -149,12 +149,20 @@ namespace dropshell
 
     std::string get_user_for_service(const std::string &server, const std::string &service)
     {
+        if (!legal_service_name(service))
+        {
+            error << "Service name contains illegal characters: " + service << std::endl;
+            return "";
+        }
+
         auto services_info = get_server_services_info(server);
         auto it = std::find_if(services_info.begin(), services_info.end(),
                          [&service](const LocalServiceInfo &si)
                          { return si.service_name == service; });
         if (it != services_info.end() && SIvalid(*it))
             return it->user;
+
+        debug << "Couldn't find user for service \"" << service << "\" on server \"" << server << "\"" << std::endl;
         return "";
     }
 
diff --git a/source/src/services.cpp b/source/src/services.cpp
index 0e79267..114a865 100644
--- a/source/src/services.cpp
+++ b/source/src/services.cpp
@@ -80,6 +80,9 @@ namespace dropshell
         if (server_name.empty() || service_name.empty())
             return LocalServiceInfo();
 
+        if (!legal_service_name(service_name))
+            return LocalServiceInfo();
+
         service.service_name = service_name;
 
         service.local_service_path = localpath::service(server_name, service_name);
diff --git a/source/src/templates.cpp b/source/src/templates.cpp
index 5c803db..4073f70 100644
--- a/source/src/templates.cpp
+++ b/source/src/templates.cpp
@@ -171,6 +171,11 @@
 
     bool template_manager::create_template(const std::string &template_name) const
     {
+        if (!legal_service_name(template_name)) {
+            error << "Template name contains illegal characters: " << template_name << std::endl;
+            return false;
+        }
+
         // 1. Create a new directory in the user templates directory
         std::vector<std::string> local_server_definition_paths = gConfig().get_local_server_definition_paths();
         
diff --git a/source/src/utils/utils.cpp b/source/src/utils/utils.cpp
index bd5373c..77f9444 100644
--- a/source/src/utils/utils.cpp
+++ b/source/src/utils/utils.cpp
@@ -312,7 +312,7 @@ std::string requote(std::string str) {
 }
 
 
-int die(const std::string & msg) {
+int return_die(const std::string & msg) {
     error << "Fatal error:" << std::endl;
     error << msg << std::endl;
     return 1;
@@ -650,4 +650,11 @@ bool file_replace_or_add_segment(std::string filepath, std::string segment)
     return true;
 }
 
+bool legal_service_name(const std::string &service_name)
+{
+    // legal characters are alphanumeric, and - and _
+    std::regex legal_chars("^[a-zA-Z0-9_-]+$");
+    return std::regex_match(service_name, legal_chars);
+}
+
 } // namespace dropshell 
\ No newline at end of file
diff --git a/source/src/utils/utils.hpp b/source/src/utils/utils.hpp
index a97d5c7..a2c56e6 100644
--- a/source/src/utils/utils.hpp
+++ b/source/src/utils/utils.hpp
@@ -45,7 +45,7 @@ int count_substring(const std::string &substring, const std::string &text);
 
 std::string random_alphanumeric_string(int length);
 
-int die(const std::string & msg);
+int return_die(const std::string & msg);
 std::string safearg(int argc, char *argv[], int index);
 std::string safearg(const std::vector<std::string> & args, int index);
 
@@ -75,4 +75,7 @@ constexpr unsigned int switchhash(const char *s, int off = 0)
     return !s[off] ? 5381 : (switchhash(s, off + 1) * 33) ^ s[off];
 }
 
+bool legal_service_name(const std::string & service_name);
+
+
 } // namespace dropshell 
\ No newline at end of file