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Update garbage-collection.md (#3110)

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Wang Jie 2017-04-29 04:44:41 +08:00 committed by John Mulhausen
parent 03c6a6c335
commit 2df7c199ef
1 changed files with 12 additions and 12 deletions
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datacenter/dtr/2.2/guides/admin/configure/garbage-collection.md
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@ -10,26 +10,26 @@ title: Docker Trusted Registry 2.2 Garbage Collection
unused layers unused layers
2. GC can be configured to run automatically with a cron schedule, and can also 2. GC can be configured to run automatically with a cron schedule, and can also
be run manually. Only admins can configure these be run manually. Only admins can configure these
3. When GC runs DTR will be placed in read-only mode. Pulls will work but 3. When GC runs DTR will be placed in read-only mode. Pulls will work but
pushes will fail pushes will fail
4. The UI will show when GC is running, and an admin can stop GC within the UI 4. The UI will show when GC is running, and an admin can stop GC within the UI
**Important notes** **Important notes**
The GC cron schedule is set to run in **UTC time**. Containers typically run in The GC cron schedule is set to run in **UTC time**. Containers typically run in
UTC time (unless the system time is mounted), therefore remember that the cron UTC time (unless the system time is mounted), therefore remember that the cron
schedule will run based off of UTC time when configuring. schedule will run based off of UTC time when configuring.
GC puts DTR into read only mode; pulls succeed while pushes fail. Pushing an GC puts DTR into read-only mode; pulls succeed while pushes fail. Pushing an
image while GC runs may lead to undefined behavior and data loss, therefore image while GC runs may lead to undefined behavior and data loss, therefore
this is disabled for safety. For this reason it's generally best practice to this is disabled for safety. For this reason, it's generally best practice to
ensure GC runs in the early morning on a Saturday or Sunday night. ensure GC runs in the early morning on a Saturday or Sunday night.
## Setting up garbage collection ## Setting up garbage collection
You can set up GC if you're an admin by hitting "Settings" in the UI then You can set up GC if you're an admin by hitting "Settings" in the UI then
choosing "Garbage Collection". By default, GC will be disabled, showing this choosing "Garbage Collection". By default, GC will be disabled, showing this
screen: screen:
![](../../images/garbage-collection-1.png){: .with-border} ![](../../images/garbage-collection-1.png){: .with-border}
@ -52,14 +52,14 @@ the schedule ("Save") or save the schedule *and* start GC immediately ("Save
## Stopping GC while it's running ## Stopping GC while it's running
When GC runs the garbage collection settings page looks as follows: When GC runs the garbage collection, the settings page looks as follows:
![](../../images/garbage-collection-3.png){: .with-border} ![](../../images/garbage-collection-3.png){: .with-border}
Note the global banner visible to all users, ensuring everyone knows that GC is Note the global banner visible to all users, ensuring everyone knows that GC is
running. running.
An admin can stop the current GC process by hitting "Stop". This safely shuts An admin can stop the current GC process by hitting "Stop". This safely shuts
down the running GC job and moves the registry into read-write mode, ensuring down the running GC job and moves the registry into read-write mode, ensuring
pushes work as expected. pushes work as expected.
@ -70,13 +70,13 @@ pushes work as expected.
Each image stored in DTR is made up of multiple files: Each image stored in DTR is made up of multiple files:
- A list of "layers", which represent the image's filesystem - A list of "layers", which represent the image's filesystem
- The "config" file, which dictates the OS, architecture and other image - The "config" file, which dictates the OS, architecture, and other image
metadata metadata
- The "manifest", which is pulled first and lists all layers and the config file - The "manifest", which is pulled first and lists all layers and the config file
for the image. for the image.
All of these files are stored in a content-addressable manner. We take the All of these files are stored in a content-addressable manner. We take the
sha256 hash of the file's content and use the hash as the filename. This means sha256 hash of the file's content and use the hash as the filename. This means
that if tag `example.com/user/blog:1.11.0` and `example.com/user/blog:latest` that if tag `example.com/user/blog:1.11.0` and `example.com/user/blog:latest`
use the same layers we only store them once. use the same layers we only store them once.
@ -90,7 +90,7 @@ can still be pulled.
This means that we can't delete layers when tags or manifests are deleted. This means that we can't delete layers when tags or manifests are deleted.
Instead, we need to pause writing and take reference counts to see how many Instead, we need to pause writing and take reference counts to see how many
times a file is used. If the file is never used only then is it safe to delete. times a file is used. If the file is never used only then is it safe to delete.
This is the basis of our "mark and sweep" collection: This is the basis of our "mark and sweep" collection: