1 00:00:02,140 --> 00:00:04,890 So this was a never key module 2 00:00:04,890 --> 00:00:08,290 because you learned how you can persist data. 3 00:00:08,290 --> 00:00:09,840 And you learned that you can do this 4 00:00:09,840 --> 00:00:11,540 with volumes, of course. 5 00:00:11,540 --> 00:00:14,400 What you already learned before in this course. 6 00:00:14,400 --> 00:00:15,760 But with Kubernetes 7 00:00:15,760 --> 00:00:19,780 since our application runs in potentially multiple parts, 8 00:00:19,780 --> 00:00:24,320 potentially across multiple nodes, it's a bit more complex. 9 00:00:24,320 --> 00:00:26,430 Now you can add volumes directly 10 00:00:26,430 --> 00:00:28,500 in your pod specification, 11 00:00:28,500 --> 00:00:31,150 since volumes are attached to pods 12 00:00:31,150 --> 00:00:33,010 and configure everything there. 13 00:00:33,010 --> 00:00:34,490 Like we did it before, 14 00:00:34,490 --> 00:00:37,300 When we set this to hostPath 15 00:00:37,300 --> 00:00:39,200 or simply to emptyDir 16 00:00:39,200 --> 00:00:41,633 to have a very simple, basic volume. 17 00:00:42,500 --> 00:00:44,310 Then we mounted into our container 18 00:00:44,310 --> 00:00:46,680 with the volumeMounts configuration 19 00:00:46,680 --> 00:00:49,063 and everything works as we're used to. 20 00:00:49,970 --> 00:00:52,960 But especially if we have bigger applications, 21 00:00:52,960 --> 00:00:56,150 running on multiple nodes, with multiple pods, 22 00:00:56,150 --> 00:00:58,327 our data may still get lost 23 00:00:58,327 --> 00:01:01,750 because volumes are attached to pods 24 00:01:01,750 --> 00:01:04,830 and to nodes, by default. 25 00:01:04,830 --> 00:01:07,920 That's why we can work with persistent volumes. 26 00:01:07,920 --> 00:01:11,770 That allows us to create standalone detached volumes, 27 00:01:11,770 --> 00:01:15,130 using a broad variety of supported types 28 00:01:15,130 --> 00:01:18,170 which then will store the data somewhere else, 29 00:01:18,170 --> 00:01:21,410 not in our nodes, not in our pods. 30 00:01:21,410 --> 00:01:24,960 And that means that persistent volumes will survive 31 00:01:24,960 --> 00:01:27,770 even if we shut down our pod, 32 00:01:27,770 --> 00:01:31,080 and even if the pod then restarts on a different node. 33 00:01:31,080 --> 00:01:34,920 The data is always the same because it's detached. 34 00:01:34,920 --> 00:01:37,450 Now, you learned that a persistent volume alone 35 00:01:37,450 --> 00:01:38,810 isn't worth that much. 36 00:01:38,810 --> 00:01:42,030 We also need a persistent volume claim. 37 00:01:42,030 --> 00:01:44,160 That persistent volume claim 38 00:01:44,160 --> 00:01:47,220 is the counterpart to the persistent volume. 39 00:01:47,220 --> 00:01:50,410 It defines how the volume should be claimed, 40 00:01:50,410 --> 00:01:52,110 how much space we need, 41 00:01:52,110 --> 00:01:57,110 and then it's this claim which we set as a volume on a pod, 42 00:01:57,380 --> 00:01:58,720 like we're doing it here, 43 00:01:58,720 --> 00:02:02,070 by using the persistent volume claim type. 44 00:02:02,070 --> 00:02:04,520 This tells Kubernetes that this pod 45 00:02:04,520 --> 00:02:07,090 wants to use this specific claim 46 00:02:07,090 --> 00:02:12,090 to then target this specific volume defined in the claim. 47 00:02:13,850 --> 00:02:16,080 And that's how we then have access to pod 48 00:02:16,080 --> 00:02:19,000 and node independent storage and volumes, 49 00:02:19,000 --> 00:02:20,943 inside of our application. 50 00:02:21,830 --> 00:02:24,450 Now, besides that, over the last lectures, 51 00:02:24,450 --> 00:02:26,930 we also learned about environment variables 52 00:02:26,930 --> 00:02:29,460 which are easily added with the env key. 53 00:02:29,460 --> 00:02:30,470 And then you learned, 54 00:02:30,470 --> 00:02:33,160 we provide a name value field here, 55 00:02:33,160 --> 00:02:36,130 or we alternatively use a config map 56 00:02:36,130 --> 00:02:37,950 to store our data in there, 57 00:02:37,950 --> 00:02:40,020 and retrieve data as a value 58 00:02:40,020 --> 00:02:42,640 for an environment variable from there. 59 00:02:42,640 --> 00:02:44,610 And that's basically it. 60 00:02:44,610 --> 00:02:48,320 This is all you need to know as a foundation, at least, 61 00:02:48,320 --> 00:02:50,260 when it comes to working with data 62 00:02:50,260 --> 00:02:53,790 and volumes in Kubernetes-based applications. 63 00:02:53,790 --> 00:02:57,223 With that, again, let's dig deeper into Kubernetes.