Single background for child elements

Question

How do I set the one background for all inner-blocks

<div class="outer-block">
   <div class="inner-block"></div>
   <div class="inner-block"></div>
   <div class="inner-block"></div>
</div>

To make it look like in the photo

In the example with the photo, I used the property: background-attachment: fixed;

.outer-block {
  position: relative;
  overflow: hidden;
}

.inner-block {
  background-image: url('./dsa.jpg');
  width: 100%;
  height: 200px;
  margin: 10px;
  background-size: contain;
  background-attachment: fixed;
  background-repeat: no-repeat;
}

But this implementation has a drawback. When scrolling the page, the image remains fixed relative to the page. Task: make sure that when scrolling, the internal blocks and the image move synchronously (expected behavior)

Answer 1

Use pseudo element positioned relatively to the container and clipped at child level

.outer-block {
  position: relative; /* relative on the container */
  width: 300px;
}
.inner-block {
  height: 150px;
  clip-path: inset(0); /* clip-path on the child */
  margin: 10px;
}
/* your background */
.inner-block:before {
  content:"";
  position: absolute;
  inset: 0;
  background: url(https://picsum.photos/id/1/200/600) center/cover;
}
/**/

body {
  background: lightblue;
}

<div class="outer-block">
  <div class="inner-block"></div>
  <div class="inner-block"></div>
  <div class="inner-block"></div>
</div>

Answer 2

Also...

body {
  background : #032b52;
  margin     : 20px;
  }
.img-block {
  background : url('https://picsum.photos/id/42/400/700');
  width      : 400px;
  height     : 700px;
  border     : solid white 10px;
  }
.img-block > div {
  border       : solid white 5px;
  border-right : none;
  border-left  : none;
  background   : transparent;
  height       : 225px;
  width        : 100%;
  }

<div class="img-block">
   <div></div>
   <div></div>
   <div></div>
</div>