There are several ways to clean caches in Linux systems: 1. Use free -h to view the current cache usage; 2. Use sudo sync; sudo echo 1 > /proc/sys/vm/drop_caches to clean the page cache; 3. Use sudo sync; sudo echo 3 > /proc/sys/vm/drop_caches to clear the page cache, inode cache and directory item cache at the same time; 4. Write a script to automatically execute the cleaning command. Manually clearing the cache is suitable for freeing memory or troubleshooting problems, but the system itself automatically manages the cache without frequent intervention.
It is actually not difficult to clean caches in Linux systems, but many people may only know one or two methods, or are worried that the operation is risky. In fact, if you just want to free up memory or troubleshoot certain issues, manually clearing the cache is an easy and effective way. The following are several commonly used methods of clearing caches, which are suitable for most kernel-based Linux distributions.

Check the current cache usage
Before starting, it is best to take a look at the current memory and cache usage of the system, so that you can know more clearly whether you need to clean it up.
You can run:
free -h
This displays the current memory, cache, and swap partition usage. Focus on buffers/cache
part in Mem:
line. This part has high values, which means that the system uses a lot of caches to improve performance.

Clean Page Cache
Page cache is part of the memory used by Linux to temporarily store file contents, and it will be used extensively when frequently reading files. If you have just performed some large file operations, this part of the cache may take up a lot of memory.
To clear the page cache, you can use the following command:

sudo sync; sudo echo 1 > /proc/sys/vm/drop_caches
-
sync
writes the buffer data to disk to avoid data loss. -
echo 1
means that only the page cache is cleared.
This operation will not affect the running program, nor will it cause data loss, it will just free up the cache for other purposes.
Clear the inod and directory item caches at the same time
In addition to page caching, Linux also caches file system meta information, such as inode and directory structure. While these caches are helpful for performance, they may want to clear them when debugging or testing file system behavior.
To clear the page cache, inode cache and directory item cache at the same time, you can use:
sudo sync; sudo echo 3 > /proc/sys/vm/drop_caches
-
echo 3
means clearing all three caches.
Note: This method will affect system performance temporarily degradation because the system needs to reload data. If you are not doing performance testing or troubleshooting problems, it is recommended to use echo 1
.
Tips for automatic cache cleaning
If you often need to clean the cache, consider writing a simple script to automate it:
#!/bin/bash echo "Clearing cache..." sudo sync sudo sh -c 'echo 3 > /proc/sys/vm/drop_caches' echo "Cache cleared."
Save as clear_cache.sh
and then give execution permissions:
chmod x clear_cache.sh
Then run ./clear_cache.sh
directly.
Basically these are the methods. The Linux system itself automatically manages caches, so frequent manual intervention is generally not required. It is only necessary to actively clear the performance problems when debugging, testing or troubleshooting performance problems. Remember, clearing cache is not "optimizing", but "release" - don't treat it as a panacea to increase speed.
The above is the detailed content of how to clear cache in linux. For more information, please follow other related articles on the PHP Chinese website!

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