Tag Archives: sysctl

CLI

Modify network buffers in Linux using sysctl

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After installing Netdata I kept getting alerts that packets were being dropped. After some research I read you can alleviate this by increasing your system’s networking buffer. You can accomplish this with sysctl.

If you run sysctl manually it will not survive a reboot. If you want persistence you simply add the sysctl command line to /etc/sysctl.conf. Thanks to Brennen Smith on serverfault for the info on my particular problem with UDP drops:

#as root:
echo "net.core.rmem_default=8388608" >> /etc/sysctl.conf
echo "net.core.rmem_max=16777216" >> /etc/sysctl.conf
sysctl -p

The above solved my udp problem but you can modify it to change any sysctl things you want to quickly configure and persist.

CLI, OS, Web

FreeBSD: allow non-root processes to bind port 80

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In experimenting with FreeNAS jails I wanted to allow a web service to use port 80. Normally 80 is a high order port reserved for root-level processes for security reasons. Since this is a FreeBSD jail and not a full on system I’m not worried about this.

The command to do so is fairly simple (thanks to this page for information)

sysctl net.inet.ip.portrange.reservedhigh=0

The above command is not permanent; to make it so add it to /etc/sysctl.conf:

echo "net.inet.ip.portrange.reservedhigh=0" >> /etc/sysctl.conf