---
title: 容器镜像的垃圾收集
content_type: concept
weight: 70
---

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title: Garbage collection for container images
content_type: concept
weight: 70
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Garbage collection is a helpful function of kubelet that will clean up unused [images](/docs/concepts/containers/#container-images) and unused [containers](/docs/concepts/containers/). Kubelet will perform garbage collection for containers every minute and garbage collection for images every five minutes.

External garbage collection tools are not recommended as these tools can potentially break the behavior of kubelet by removing containers expected to exist.
-->

垃圾回收是 kubelet 的一个有用功能，它将清理未使用的[镜像](/zh/docs/concepts/containers/#container-images)和[容器](/zh/docs/concepts/containers/)。
Kubelet 将每分钟对容器执行一次垃圾回收，每五分钟对镜像执行一次垃圾回收。

不建议使用外部垃圾收集工具，因为这些工具可能会删除原本期望存在的容器进而破坏 kubelet 的行为。

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## Image Collection

Kubernetes manages lifecycle of all images through imageManager, with the cooperation
of cadvisor.

The policy for garbage collecting images takes two factors into consideration:
`HighThresholdPercent` and `LowThresholdPercent`.  Disk usage above the high threshold
will trigger garbage collection. The garbage collection will delete least recently used
images until the low threshold has been met.
-->
## 镜像回收   {#image-collection}

Kubernetes 借助于 cadvisor 通过 imageManager 来管理所有镜像的生命周期。

镜像垃圾回收策略只考虑两个因素：`HighThresholdPercent` 和 `LowThresholdPercent`。
磁盘使用率超过上限阈值（HighThresholdPercent）将触发垃圾回收。
垃圾回收将删除最近最少使用的镜像，直到磁盘使用率满足下限阈值（LowThresholdPercent）。

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## Container Collection

The policy for garbage collecting containers considers three user-defined variables. `MinAge` is the minimum age at which a container can be garbage collected. `MaxPerPodContainer` is the maximum number of dead containers every single
pod (UID, container name) pair is allowed to have. `MaxContainers` is the maximum number of total dead containers. These variables can be individually disabled by setting `MinAge` to zero and setting `MaxPerPodContainer` and `MaxContainers` respectively to less than zero.
-->
## 容器回收   {#container-collection}

容器垃圾回收策略考虑三个用户定义变量。
`MinAge` 是容器可以被执行垃圾回收的最小生命周期。
`MaxPerPodContainer` 是每个 pod 内允许存在的死亡容器的最大数量。
`MaxContainers` 是全部死亡容器的最大数量。
可以分别独立地通过将 `MinAge` 设置为 0，以及将 `MaxPerPodContainer` 和 `MaxContainers`
设置为小于 0 来禁用这些变量。

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Kubelet will act on containers that are unidentified, deleted, or outside of the boundaries set by the previously mentioned flags. The oldest containers will generally be removed first. `MaxPerPodContainer` and `MaxContainer` may potentially conflict with each other in situations where retaining the maximum number of containers per pod (`MaxPerPodContainer`) would go outside the allowable range of global dead containers (`MaxContainers`). `MaxPerPodContainer` would be adjusted in this situation: A worst case scenario would be to downgrade `MaxPerPodContainer` to 1 and evict the oldest containers. Additionally, containers owned by pods that have been deleted are removed once they are older than `MinAge`.
-->
`kubelet` 将处理无法辨识的、已删除的以及超出前面提到的参数所设置范围的容器。
最老的容器通常会先被移除。
`MaxPerPodContainer` 和 `MaxContainer` 在某些场景下可能会存在冲突，
例如在保证每个 pod 内死亡容器的最大数量（`MaxPerPodContainer`）的条件下可能会超过
允许存在的全部死亡容器的最大数量（`MaxContainer`）。
`MaxPerPodContainer` 在这种情况下会被进行调整：
最坏的情况是将 `MaxPerPodContainer` 降级为 1，并驱逐最老的容器。
此外，pod 内已经被删除的容器一旦年龄超过 `MinAge` 就会被清理。

<!--
Containers that are not managed by kubelet are not subject to container garbage collection.
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不被 kubelet 管理的容器不受容器垃圾回收的约束。

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## User Configuration

Users can adjust the following thresholds to tune image garbage collection with the following kubelet flags :
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## 用户配置   {#user-configuration}

用户可以使用以下 kubelet 参数调整相关阈值来优化镜像垃圾回收：

<!--
1. `image-gc-high-threshold`, the percent of disk usage which triggers image garbage collection.
Default is 85%.

2. `image-gc-low-threshold`, the percent of disk usage to which image garbage collection attempts
to free. Default is 80%.
-->

1. `image-gc-high-threshold`，触发镜像垃圾回收的磁盘使用率百分比。默认值为 85%。
2. `image-gc-low-threshold`，镜像垃圾回收试图释放资源后达到的磁盘使用率百分比。默认值为 80%。

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We also allow users to customize garbage collection policy through the following kubelet flags:
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我们还允许用户通过以下 kubelet 参数自定义垃圾收集策略：

<!--
1. `minimum-container-ttl-duration`, minimum age for a finished container before it is
garbage collected. Default is 0 minute, which means every finished container will be garbage collected.

2. `maximum-dead-containers-per-container`, maximum number of old instances to be retained
per container. Default is 1.

3. `maximum-dead-containers`, maximum number of old instances of containers to retain globally.
Default is -1, which means there is no global limit.
-->

1. `minimum-container-ttl-duration`，完成的容器在被垃圾回收之前的最小年龄，默认是 0 分钟。
   这意味着每个完成的容器都会被执行垃圾回收。

2. `maximum-dead-containers-per-container`，每个容器要保留的旧实例的最大数量。默认值为 1。

3. `maximum-dead-containers`，要全局保留的旧容器实例的最大数量。
   默认值是 -1，意味着没有全局限制。

<!--
Containers can potentially be garbage collected before their usefulness has expired. These containers
can contain logs and other data that can be useful for troubleshooting. A sufficiently large value for
`maximum-dead-containers-per-container` is highly recommended to allow at least 1 dead container to be
retained per expected container. A larger value for `maximum-dead-containers` is also recommended for a
similar reason.

See [this issue](https://github.com/kubernetes/kubernetes/issues/13287) for more details.
-->
容器可能会在其效用过期之前被垃圾回收。这些容器可能包含日志和其他对故障诊断有用的数据。
强烈建议为 `maximum-dead-containers-per-container` 设置一个足够大的值，以便每个预期容器至少保留一个死亡容器。
由于同样的原因，`maximum-dead-containers` 也建议使用一个足够大的值。

查阅[这个 Issue](https://github.com/kubernetes/kubernetes/issues/13287) 获取更多细节。

<!--
## Deprecation

Some kubelet Garbage Collection features in this doc will be replaced by kubelet eviction in the future.

Including:
-->
## 弃用  {#deprecation}

这篇文档中的一些 kubelet 垃圾收集（Garbage Collection）功能将在未来被 kubelet 驱逐回收（eviction）所替代。

包括:

<!--
| Existing Flag | New Flag | Rationale |
| ------------- | -------- | --------- |
| `--image-gc-high-threshold` | `--eviction-hard` or `--eviction-soft` | existing eviction signals can trigger image garbage collection |
| `--image-gc-low-threshold` | `--eviction-minimum-reclaim` | eviction reclaims achieve the same behavior |
| `--maximum-dead-containers` | | deprecated once old logs are stored outside of container's context |
| `--maximum-dead-containers-per-container` | | deprecated once old logs are stored outside of container's context |
| `--minimum-container-ttl-duration` | | deprecated once old logs are stored outside of container's context |
| `--low-diskspace-threshold-mb` | `--eviction-hard` or `eviction-soft` | eviction generalizes disk thresholds to other resources |
| `--outofdisk-transition-frequency` | `--eviction-pressure-transition-period` | eviction generalizes disk pressure transition to other resources |
-->
| 现存参数 | 新参数 | 解释 |
| ------------- | -------- | --------- |
| `--image-gc-high-threshold` | `--eviction-hard` 或 `--eviction-soft` | 现存的驱逐回收信号可以触发镜像垃圾回收 |
| `--image-gc-low-threshold` | `--eviction-minimum-reclaim` | 驱逐回收实现相同行为 |
| `--maximum-dead-containers` | | 一旦旧日志存储在容器上下文之外，就会被弃用 |
| `--maximum-dead-containers-per-container` | | 一旦旧日志存储在容器上下文之外，就会被弃用 |
| `--minimum-container-ttl-duration` | | 一旦旧日志存储在容器上下文之外，就会被弃用 |
| `--low-diskspace-threshold-mb` | `--eviction-hard` or `eviction-soft` | 驱逐回收将磁盘阈值泛化到其他资源 |
| `--outofdisk-transition-frequency` | `--eviction-pressure-transition-period` | 驱逐回收将磁盘压力转换到其他资源 | 

## {{% heading "whatsnext" %}}

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See [Configuring Out Of Resource Handling](/docs/tasks/administer-cluster/out-of-resource/) for more details.
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查阅[配置资源不足情况的处理](/zh/docs/tasks/administer-cluster/out-of-resource/)了解更多细节。