fix: Support creating file with open_file_nonblock

Updates the `OpenOptions` with `.create(true)` to support creating a
file when if it doesn't exist. This also brings the functionality
inline with the documentation which notes
`Create and opens a File for writing to it.`. This improves usability
simplifying setting up the logger.

Signed-off-by: Jonathan Woollett-Light <[email protected]>

docs/getting-started.md

@@ -134,9 +134,6 @@ sudo iptables -I FORWARD 1 -i tap0 -o eth0 -j ACCEPT
 API_SOCKET="/tmp/firecracker.socket"
 LOGFILE="./firecracker.log"
 
-# Create log file
-touch $LOGFILE
-
 # Set log file
 curl -X PUT --unix-socket "${API_SOCKET}" \
     --data "{

src/vmm/src/vmm_config/logger.rs

@@ -152,15 +152,6 @@ mod tests {
     fn test_init_logger() {
         let default_instance_info = InstanceInfo::default();
 
-        // Error case: initializing logger with invalid pipe returns error.
-        let desc = LoggerConfig {
-            log_path: PathBuf::from("not_found_file_log"),
-            level: LoggerLevel::Debug,
-            show_level: false,
-            show_log_origin: false,
-        };
-        assert!(init_logger(desc, &default_instance_info).is_err());
-
         // Initializing logger with valid pipe is ok.
         let log_file = TempFile::new().unwrap();
         let desc = LoggerConfig {

src/vmm/src/vmm_config/mod.rs

@@ -172,6 +172,7 @@ impl RateLimiterConfig {
 fn open_file_nonblock(path: &Path) -> Result<File, std::io::Error> {
     OpenOptions::new()
         .custom_flags(O_NONBLOCK)
+        .create(true)
         .read(true)
         .write(true)
         .open(path)