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Reset /proc/sys/vm/drop_caches to default value 0 – Debian

Recently I tried to empty the buffers cache on a Debian webserver. The command I used was:

free && sync && echo 3 > /proc/sys/vm/drop_caches && free

So far so good, running cat /proc/sys/vm/drop_caches prints a value of 3.

When I try to reset the value to 0 with sync && echo 0 > /proc/sys/vm/drop_caches, this error shows:

bash: echo: write error: Invalid argument

Which is due to drop_caches being a command, not a variable to be set. I found this:

sudo sysctl -w vm.drop_caches=3

It immediately clears the pagecache, dentries and inodes and clears again only if you call sysctl -w again, there is no need to apparently set it back to 0 in an explicit manner. The command sysctl is not natively supported on Debian so I’m looking for an alternative command, more precisely:

How to reset drop_caches or immediately empty the cache to reset the value to 0?

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2

Answers


  1. 0

    The values 1-3 are just one time trigger for action. There is no value 0.

    sysctl is in package procps .

    apt install procps

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  2. 0

    To disable them, echo 4 (bit 2) into drop_caches.

    from https://www.kernel.org/doc/Documentation/sysctl/vm.txt

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