Add fallback if /etc/hostname doesn't exist

manager/src/builder.rs

@@ -6,19 +6,16 @@ use futures::future::join_all;
 use std::ffi::OsStr;
 use std::io::ErrorKind;
 use std::path::PathBuf;
+use std::process::Command;
+use std::str::from_utf8;
 use tokio::fs::{copy, create_dir, read_dir, read_to_string, write};
 use tokio::join;
 
 pub const TEMPLATE_EXTENSION: &str = "tpl";
 
 pub async fn build_tree(cfg: &Config) -> Result<(), Errors> {
-    let hostname_path: PathBuf = "/etc/hostname".into();
-    let hostname = read_to_string(&hostname_path)
-        .await
-        .with_location(&hostname_path)?;
-
     let mut env = Env::new();
-    env.insert("hostname".into(), Value::Str(hostname));
+    env.insert("hostname".into(), Value::Str(get_hostname().await));
 
     for flag in &cfg.flags {
         env.insert(flag.to_string(), Value::Bool(true));
@@ -118,3 +115,24 @@ async fn file(cfg: &Config, env: &Env, relative: PathBuf) -> Result<(), Error> {
 
     Ok(())
 }
+
+async fn get_hostname() -> String {
+    async fn read_hostname_file() -> Option<String> {
+        read_to_string("/etc/hostname").await.ok()
+    }
+
+    // TODO: should be async
+    fn run_hostname_cmd() -> Option<String> {
+        Command::new("hostname")
+            .output()
+            .ok()
+            .and_then(|out| from_utf8(&out.stdout).ok().map(str::to_string))
+    }
+
+    read_hostname_file()
+        .await
+        .or_else(|| run_hostname_cmd())
+        .unwrap_or_else(|| String::new())
+        .trim()
+        .to_string()
+}