lost and found ( for me ? ): August 2015

CentOS 6.7 : ethtool “rx_discards” errors

Here is a memo about “rx_discards” error.

Reference

http://wiki.centos.org/Events/Dojo/Bangalore2014

(Topic: Network Debugging -> Slides: Network-jkalliyat.pdf )

# cat /etc/centos-release

CentOS release 6.7 (Final)

# uname -ri

2.6.32-573.3.1.el6.x86_64 x86_64

I found a number of “rx_discards” is counting up on one of interfaces, which processes approximately 300,000 UDP packet / sec.

In my case, I was able to solve that by increasing buffers on that interface.

rx_discards errors on interface ‘eth0’

# while :; do ethtool -S eth0 | grep discard ; sleep 1; done

tx_discards: 0

rx_discards: 49070

tx_discards: 0

rx_discards: 49071

Red line: current setting

# ethtool -g eth0

Ring parameters for eth0:

Pre-set maximums:

RX: 2047

RX Mini: 0

RX Jumbo: 0

TX: 511

Current hardware settings:

RX: 200

RX Mini: 0

RX Jumbo: 0

TX: 511

Increase RX buffers to 2047 from 200

# ethtool -G eth0 rx 2047

After increasing buffers.

# ethtool -g eth0

Ring parameters for eth0:

Pre-set maximums:

RX: 2047

RX Mini: 0

RX Jumbo: 0

TX: 511

Current hardware settings:

RX: 2047

RX Mini: 0

RX Jumbo: 0

TX: 511

Here are my kernel parameters.

sysctl -w net.ipv4.tcp_rmem="4096 873800 4194304"

sysctl -w net.ipv4.tcp_wmem="4096 873800 4194304"

sysctl -w net.ipv4.tcp_mem="5194304 5194304 5194304"

sysctl -w net.core.rmem_default=4194304

sysctl -w net.core.wmem_default=4194304

sysctl -w net.core.rmem_max=4194304

sysctl -w net.core.wmem_max=4194304

sysctl -w net.core.optmem_max=20480

/sbin/ethtool -G eth0 rx 2047

create a temporary text file under directory or in memory

small tips.

Here is how to create a temporary text file with python ‘tempfile’ module.

the first one is creating a temporary text file under /tmp directory and the second one is in memory

mint-note untitled # cat virtual_file01.py

__author__ = 'root'

import tempfile

import os

# create a temporary text file under /tmp directory

temp_file = tempfile.NamedTemporaryFile(mode='w+t',suffix='_suffix',prefix='prefix_',dir='/tmp')

try:

temp_file.writelines(['first\n','second\n'])

temp_file.seek(0)

print temp_file

print temp_file.name

for line in temp_file:

print line.rstrip()

finally:

temp_file.close()

# create a virtual text file in memory

temp_memory_file = tempfile.SpooledTemporaryFile(mode='w+t',max_size=10000,prefix='prefix_',suffix='_suffix')

try:

temp_memory_file.writelines(['first\n','second\n'])

temp_memory_file.seek(0)

print temp_memory_file

print temp_memory_file.name

for line in temp_memory_file:

print line.rstrip()

finally:

temp_memory_file.close()

mint-note untitled # python virtual_file01.py

/tmp/prefix_qONxA9_suffix

first

second

<tempfile.SpooledTemporaryFile instance at 0x7f2179bde878>

None

first

second

install docker on Ubuntu 14.04 running within virtualbox

Here are trial and error logs when installing docker on Ubuntu 14.04 which is running within virtualbox as a virtual machine.

I used vagrant to prepare VMs for docker testing environment.

I already downloaded some boxes in my machine and used trusty64(virtualbox).

$ vagrant box list

centos60 (virtualbox, 0)

coreos-alpha (virtualbox, 752.1.0)

coreos-stable (virtualbox, 717.3.0)

trusty64 (libvirt, 0)

trusty64 (virtualbox, 0)

initialize a new vagrant environment for docker testing environment.

$ vagrant init trusty64

Here is a Vagrantfile.

I prepared two VMs for a clustering test( I will evaluate that later) and each VM has three vNICs.

$ cat Vagrantfile

Vagrant.configure(2) do |config|

config.vm.box = "trusty64"

config.vm.provider "virtualbox" do |v|

v.memory = 2048

v.cpus = 1

end

config.vm.define :ubuntu01 do |ubuntu01|

ubuntu01.vm.hostname = "ubuntu01"

ubuntu01.vm.network :private_network, ip: "192.168.33.10"

ubuntu01.vm.network :private_network, ip: "192.168.34.10"

ubuntu01.vm.network :private_network, ip: "192.168.35.10"

end

config.vm.define :ubuntu02 do |ubuntu02|

ubuntu02.vm.hostname = "ubuntu02"

ubuntu02.vm.network :private_network, ip: "192.168.33.20"

ubuntu02.vm.network :private_network, ip: "192.168.34.20"

ubuntu02.vm.network :private_network, ip: "192.168.35.20"

end

start the VMs

$ vagrant up

$ vagrant status

Current machine states:

ubuntu01 running (virtualbox)

ubuntu02 running (virtualbox)

access to the “ubuntu01” VM

$ vagrant ssh ubuntu01

vagrant@ubuntu01:~$ ifconfig -a | grep 192

inet addr:192.168.33.10 Bcast:192.168.33.255 Mask:255.255.255.0

inet addr:192.168.34.10 Bcast:192.168.34.255 Mask:255.255.255.0

inet addr:192.168.35.10 Bcast:192.168.35.255 Mask:255.255.255.0

install docker within this virtual machine(ubuntu01).

vagrant@ubuntu01:~$ sudo apt-get update

vagrant@ubuntu01:~$ sudo apt-get install docker.io

vagrant@ubuntu01:~$ docker --version

Docker version 1.0.1, build 990021a

docker.io is a symbolic link file of docker.

Googling docker installation tutorials, it seems that we need to create a symbolic link manually, however, in my case, I do not need to do that.

The symbolic link was created automatically.

vagrant@ubuntu01:~$ ls -l /usr/bin/docker*

-rwxr-xr-x 1 root root 15240483 Aug 21 2014 /usr/bin/docker

lrwxrwxrwx 1 root root 6 Aug 21 2014 /usr/bin/docker.io -> docker

confirm docker is running as a background process.

vagrant@ubuntu01:~$ sudo service docker.io status

docker.io start/running, process 26735

start docker.io when a server boots up.

vagrant@ubuntu01:~$ sudo update-rc.d docker.io defaults

download a docker container

vagrant@ubuntu01:~$ sudo docker pull ubuntu

run a docker container.

vagrant@ubuntu01:~$ sudo docker run -i -t ubuntu /bin/bash

root@84bf7f3be749:/#

open another terminal

list containers running.

vagrant@ubuntu01:~$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

84bf7f3be749 ubuntu:14.04 /bin/bash About a minute ago Up About a minute furious_curie

vagrant@ubuntu01:~$

stop the container

vagrant@ubuntu01:~$ sudo docker stop 84bf7f3be749

84bf7f3be749

vagrant@ubuntu01:~$ sudo docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

vagrant@ubuntu01:~$

Reference

http://www.liquidweb.com/kb/how-to-install-docker-on-ubuntu-14-04-lts/