From a7a0821a3e23142265904806df5d0a6ecd2ed4b5 Mon Sep 17 00:00:00 2001
From: Christina Wang <christina@balena.io>
Date: Tue, 14 Jun 2022 15:45:03 -0700
Subject: [PATCH] Read hostname from config.json with container /etc/hostname
 as backup

We don't need to read the host's hostname through /mnt/root/etc/hostname,
because the hostname is written to config.json on a change. When the hostname
has never changed, it won't be found in config.json, so we can default to
the Supervisor container's /etc/hostname as it will match the host's
/etc/hostname, the network mode being `host`.

Closes: #1968
Change-type: patch
Signed-off-by: Christina Wang <christina@balena.io>
---
 src/compose/app.ts                               | 16 ++++++----------
 src/compose/service.ts                           |  2 +-
 src/compose/types/service.ts                     |  2 +-
 .../data/docker-states/entrypoint/imageInfo.json |  2 +-
 .../network-mode-service/imageInfo.json          |  2 +-
 test/data/docker-states/simple/imageInfo.json    |  2 +-
 6 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/src/compose/app.ts b/src/compose/app.ts
index 495afc7d..3cae07fe 100644
--- a/src/compose/app.ts
+++ b/src/compose/app.ts
@@ -1,6 +1,5 @@
 import * as _ from 'lodash';
 import { promises as fs } from 'fs';
-import * as path from 'path';
 
 import Network from './network';
 import Volume from './volume';
@@ -742,7 +741,7 @@ export class App {
 			opts,
 			supervisorApiHost,
 			hostPathExists,
-			hostnameOnHost,
+			hostname,
 		] = await Promise.all([
 			config.get('extendedEnvOptions'),
 			dockerUtils
@@ -752,20 +751,17 @@ export class App {
 				firmware: await pathExistsOnHost('/lib/firmware'),
 				modules: await pathExistsOnHost('/lib/modules'),
 			}))(),
-			(async () =>
-				_.trim(
-					await fs.readFile(
-						path.join(constants.rootMountPoint, '/etc/hostname'),
-						'utf8',
-					),
-				))(),
+			(
+				(await config.get('hostname')) ??
+				(await fs.readFile('/etc/hostname', 'utf-8'))
+			).trim(),
 		]);
 
 		const svcOpts = {
 			appName: app.name,
 			supervisorApiHost,
 			hostPathExists,
-			hostnameOnHost,
+			hostname,
 			...opts,
 		};
 
diff --git a/src/compose/service.ts b/src/compose/service.ts
index 23a3873c..ce30ff44 100644
--- a/src/compose/service.ts
+++ b/src/compose/service.ts
@@ -300,7 +300,7 @@ export class Service {
 
 		// Any other special case handling
 		if (config.networkMode === 'host' && !config.hostname) {
-			config.hostname = options.hostnameOnHost;
+			config.hostname = options.hostname;
 		}
 		config.restart = ComposeUtils.createRestartPolicy(config.restart);
 		config.command = ComposeUtils.getCommand(config.command, options.imageInfo);
diff --git a/src/compose/types/service.ts b/src/compose/types/service.ts
index 9cf05cad..28174975 100644
--- a/src/compose/types/service.ts
+++ b/src/compose/types/service.ts
@@ -327,7 +327,7 @@ export interface DeviceMetadata {
 	apiSecret: string;
 	supervisorApiHost: string;
 	osVersion: string;
-	hostnameOnHost: string;
+	hostname: string;
 	hostPathExists: {
 		modules: boolean;
 		firmware: boolean;
diff --git a/test/data/docker-states/entrypoint/imageInfo.json b/test/data/docker-states/entrypoint/imageInfo.json
index f34277f4..e84d60bd 100644
--- a/test/data/docker-states/entrypoint/imageInfo.json
+++ b/test/data/docker-states/entrypoint/imageInfo.json
@@ -90,7 +90,7 @@
 		"firmware": true,
 		"modules": true
 	},
-	"hostnameOnHost": "7dadabd",
+	"hostname": "7dadabd",
 	"uuid": "a7feb967fac7f559ccf2a006a36bcf5d",
 	"listenPort": "48484",
 	"name": "Office",
diff --git a/test/data/docker-states/network-mode-service/imageInfo.json b/test/data/docker-states/network-mode-service/imageInfo.json
index 0ba62dfc..45a98f2d 100644
--- a/test/data/docker-states/network-mode-service/imageInfo.json
+++ b/test/data/docker-states/network-mode-service/imageInfo.json
@@ -116,7 +116,7 @@
 		"firmware": true,
 		"modules": true
 	},
-	"hostnameOnHost": "7dadabd",
+	"hostname": "7dadabd",
 	"uuid": "7dadabd4edec3067948d5952c2f2f26f",
 	"listenPort": "48484",
 	"name": "Office",
diff --git a/test/data/docker-states/simple/imageInfo.json b/test/data/docker-states/simple/imageInfo.json
index 0ba62dfc..45a98f2d 100644
--- a/test/data/docker-states/simple/imageInfo.json
+++ b/test/data/docker-states/simple/imageInfo.json
@@ -116,7 +116,7 @@
 		"firmware": true,
 		"modules": true
 	},
-	"hostnameOnHost": "7dadabd",
+	"hostname": "7dadabd",
 	"uuid": "7dadabd4edec3067948d5952c2f2f26f",
 	"listenPort": "48484",
 	"name": "Office",