11---
22description : Learn how to optimize your use of AUFS driver.
3- keywords : ' container, storage, driver, AUFS '
3+ keywords : " container, storage, driver, AUFS "
44title : AUFS storage driver
55sitemap : false
66aliases :
@@ -14,7 +14,7 @@ aliases:
1414> before upgrading to Docker Engine v24.0. Read the [ Docker storage drivers] ( select-storage-driver.md )
1515> page for supported storage drivers.
1616
17- AUFS is a * union filesystem * . The ` aufs ` storage driver was previously the default
17+ AUFS is a _ union filesystem _ . The ` aufs ` storage driver was previously the default
1818storage driver used for managing images and layers on Docker for Ubuntu, and for
1919Debian versions prior to Stretch. If your Linux kernel is version 4.0 or higher,
2020and you use Docker Engine - Community, consider using the newer
@@ -26,7 +26,7 @@ potential performance advantages over the `aufs` storage driver.
2626- For Docker Engine - Community, AUFS is supported on Ubuntu, and on Debian versions prior to
2727 Stretch.
2828- If you use Ubuntu, you need to add the AUFS module to the kernel. If you do
29- not install these packages, you need to use ` overlay2 ` .
29+ not install these packages, you need to use ` overlay2 ` .
3030- AUFS cannot use the following backing filesystems: ` aufs ` , ` btrfs ` , or
3131 ` ecryptfs ` . This means that the filesystem which contains
3232 ` /var/lib/docker/aufs ` cannot be one of these filesystem types.
@@ -66,15 +66,15 @@ storage driver is configured, Docker uses it by default.
6666
6767## How the `aufs` storage driver works
6868
69- AUFS is a *union filesystem* , which means that it layers multiple directories on
69+ AUFS is a _union filesystem_ , which means that it layers multiple directories on
7070a single Linux host and presents them as a single directory. These directories
7171are called _branches_ in AUFS terminology, and _layers_ in Docker terminology.
7272
7373The unification process is referred to as a _union mount_.
7474
7575The diagram below shows a Docker container based on the `ubuntu:latest` image.
7676
77- 
77+ 
7878
7979Each image layer, and the container layer, are represented on the Docker host as
8080subdirectories within `/var/lib/docker/`. The union mount provides the unified
@@ -126,7 +126,7 @@ If a container is running, the contents of `/var/lib/docker/aufs/` change in the
126126following ways:
127127
128128- ` diff/ ` : Differences introduced in the writable container layer, such as new
129- or modified files.
129+ or modified files.
130130- ` layers/ ` : Metadata about the writable container layer's parent layers.
131131- ` mnt/ ` : A mount point for each running container's unified filesystem, exactly
132132 as it appears from within the container.
@@ -160,7 +160,7 @@ Consider some scenarios where files in a container are modified.
160160
161161- ** Writing to a file for the first time** : The first time a container writes
162162 to an existing file, that file does not exist in the container (` upperdir ` ).
163- The ` aufs ` driver performs a * copy_up * operation to copy the file from the
163+ The ` aufs ` driver performs a _ copy_up _ operation to copy the file from the
164164 image layer where it exists to the writable container layer. The container
165165 then writes the changes to the new copy of the file in the container layer.
166166
@@ -169,13 +169,12 @@ Consider some scenarios where files in a container are modified.
169169 very large and only a small part of it is being modified. This can have a
170170 noticeable impact on container write performance. AUFS can suffer
171171 noticeable latencies when searching for files in images with many layers.
172- However, it is worth noting that the copy_up operation only occurs the first
173- time a given file is written to. Subsequent writes to the same file operate
174- against the copy of the file already copied up to the container.
172+ However, the copy_up operation only occurs the first time a given file is
173+ written to. Subsequent writes to the same file operate against the copy of
174+ the file already copied up to the container.
175175
176176- ** Deleting files and directories** :
177-
178- - When a _ file_ is deleted within a container, a * whiteout* file is created
177+ - When a _ file_ is deleted within a container, a _ whiteout_ file is created
179178 in the container layer. The version of the file in the image layer is not
180179 deleted (because the image layers are read-only). However, the whiteout
181180 file prevents it from being available to the container.
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