Merge pull request #24428 from dvdksn/fix/issue-18191-overlayfs-duplicate-sections

docs: fix duplicate headings in overlayfs driver page

Author: dvdksn

content/manuals/engine/storage/drivers/overlayfs-driver.md

@@ -224,7 +224,7 @@ the image's top layer plus a new directory for the container. The image's
 layers are the `lowerdirs` in the overlay and are read-only. The new directory for
 the container is the `upperdir` and is writable.
 
-### Image and container layers on-disk
+### Image and container layers on-disk (legacy overlay driver)
 
 The following `docker pull` command shows a Docker host downloading a Docker
 image comprising five layers.
@@ -442,25 +442,25 @@ filesystems:
 
 [`open(2)`](https://linux.die.net/man/2/open)
 : OverlayFS only implements a subset of the POSIX standards.
-  This can result in certain OverlayFS operations breaking POSIX standards. One
-  such operation is the copy-up operation. Suppose that your application calls
-  `fd1=open("foo", O_RDONLY)` and then `fd2=open("foo", O_RDWR)`. In this case,
-  your application expects `fd1` and `fd2` to refer to the same file. However, due
-  to a copy-up operation that occurs after the second calling to `open(2)`, the
-  descriptors refer to different files. The `fd1` continues to reference the file
-  in the image (`lowerdir`) and the `fd2` references the file in the container
-  (`upperdir`). A workaround for this is to `touch` the files which causes the
-  copy-up operation to happen. All subsequent `open(2)` operations regardless of
-  read-only or read-write access mode reference the file in the
-  container (`upperdir`).
-
-  `yum` is known to be affected unless the `yum-plugin-ovl` package is installed.
-  If the `yum-plugin-ovl` package is not available in your distribution such as
-  RHEL/CentOS prior to 6.8 or 7.2, you may need to run `touch /var/lib/rpm/*`
-  before running `yum install`. This package implements the `touch` workaround
-  referenced above for `yum`.
+This can result in certain OverlayFS operations breaking POSIX standards. One
+such operation is the copy-up operation. Suppose that your application calls
+`fd1=open("foo", O_RDONLY)` and then `fd2=open("foo", O_RDWR)`. In this case,
+your application expects `fd1` and `fd2` to refer to the same file. However, due
+to a copy-up operation that occurs after the second calling to `open(2)`, the
+descriptors refer to different files. The `fd1` continues to reference the file
+in the image (`lowerdir`) and the `fd2` references the file in the container
+(`upperdir`). A workaround for this is to `touch` the files which causes the
+copy-up operation to happen. All subsequent `open(2)` operations regardless of
+read-only or read-write access mode reference the file in the
+container (`upperdir`).
+
+`yum` is known to be affected unless the `yum-plugin-ovl` package is installed.
+If the `yum-plugin-ovl` package is not available in your distribution such as
+RHEL/CentOS prior to 6.8 or 7.2, you may need to run `touch /var/lib/rpm/*`
+before running `yum install`. This package implements the `touch` workaround
+referenced above for `yum`.
 
 [`rename(2)`](https://linux.die.net/man/2/rename)
 : OverlayFS does not fully support the `rename(2)` system call. Your
-  application needs to detect its failure and fall back to a "copy and unlink"
-  strategy.
+application needs to detect its failure and fall back to a "copy and unlink"
+strategy.