Re: /etc/sysctl.d/01_ec2.conf sets vm.swappiness = 0
On Mon, Dec 06, 2021 at 02:28:35PM +0000, Phil Endecott wrote:
> On one of my Lightsail instances, which was created a few years
> ago from a Debian image and has subsequently been upgraded a few
> times, I have a /etc/sysctl.d/01_ec2.conf file which sets
> vm.swappiness = 0. On another newer EC2 instance I don't have this
> file.
Right; we haven't shipped that file since (IIRC) jessie.
> dpkg -S doesn't tell me where this file came from. I don't
> think I created it myself!!
It was installed as part of the image creation process. Similar to
files like /etc/hosts, it is not actually owned by a package.
> Does anyone recognise this? Of course the issue is that I
> discovered the hard way that the system was not using its
> swapfile. The file has a pile of other configuration settings
> and I wonder if any of those are also undesirable, see below.
Most of the settings from that file were lifted from Amazon Linux, IIRC,
and are pretty reasonable for a default "server" class VM. Even
vm.swappiness is a reasonable default, given that there's no swap file
created by default. But nothing will break if you choose to remove the
file.
noah
> vm.swappiness = 0
> vm.dirty_ratio = 80
> vm.dirty_background_ratio = 5
> vm.dirty_expire_centisecs = 12000
> net.core.somaxconn = 1000
> net.core.netdev_max_backlog = 5000
> net.core.rmem_max = 16777216
> net.core.wmem_max = 16777216
> net.ipv4.tcp_wmem = 4096 12582912 16777216
> net.ipv4.tcp_rmem = 4096 12582912 16777216
> net.ipv4.tcp_max_syn_backlog = 8096
> net.ipv4.tcp_slow_start_after_idle = 0
> net.ipv4.tcp_tw_reuse = 1
> net.ipv4.ip_local_port_range = 10240 65535
> kernel.sysrq = 0
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