server: check for expected files

When the configuration is loaded, check that expected files are present
early. This can prevent getting into a partial state later.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>

cmd/server/main.go

@@ -163,6 +163,10 @@ func main() {
 			return err
 		}
 
+		if err := config.Check(); err != nil {
+			return err
+		}
+
 		cf := &logrus.TextFormatter{
 			TimestampFormat: "2006-01-02 15:04:05.000000000Z07:00",
 			FullTimestamp:   true,

server/config.go

@@ -2,7 +2,9 @@ package server
 
 import (
 	"bytes"
+	"fmt"
 	"io/ioutil"
+	"os"
 
 	"github.com/BurntSushi/toml"
 )
@@ -152,3 +154,29 @@ func (c *Config) ToFile(path string) error {
 
 	return ioutil.WriteFile(path, w.Bytes(), 0644)
 }
+
+// Check resolves that all paths and files are available as expected
+func (c *Config) Check() error {
+	for _, file := range []string{
+		c.RootConfig.SandboxDir,
+		c.RootConfig.ContainerDir,
+		c.RuntimeConfig.Runtime,
+		c.RuntimeConfig.Conmon,
+		c.RuntimeConfig.SeccompProfile,
+		c.ImageConfig.Pause,
+	} {
+		if _, err := os.Stat(file); err != nil && os.IsNotExist(err) {
+			return checkError{Path: file}
+		}
+	}
+
+	return nil
+}
+
+type checkError struct {
+	Path string
+}
+
+func (ce checkError) Error() string {
+	return fmt.Sprintf("%q does not exist", ce.Path)
+}