DOCKER_OPTS in /etc/default/docker ignored on Ubuntu

For some reason, in debian 8 and ubuntu 15.01 systemd is skipping the execution of /etc/default/docker.

How to fix?

Copy the original systemd service file to /etc/systemd/system/

sudo cp  /lib/systemd/system/docker.service /etc/systemd/system/

Edit file /etc/systemd/system/docker.service

...
[Service]
ExecStart=/usr/bin/docker -d -H fd:// $DOCKER_OPTS
...
EnvironmentFile=-/etc/default/docker
...

Then execute:

sudo systemctl daemon-reload
sudo systemctl restart docker

Verify that /etc/default/docker is loaded

ps auxwww | grep docker
root      4989  0.8  0.1 265540 16608 ?        Ssl  10:37   0:00 /usr/bin/docker -d -H fd:// --insecure-registry 

That's it.

Enable Layer3 on a Cisco Switch

This is what worked for me on a Cisco WS-C2960-24PS-L switch:

First you need to change the sdm prefer from dafult to lanbase-routing.
The lanbase-routing template supports IPv4 unicast routes for configuring static routing SVIs.
Static routing is supported only on switched virtual interfaces (SVIs) and not on physical interfaces. The switch does not support routing protocols.

conf t
sdm prefer lanbase-routing
end
wr
reload 

Then you have to enable ip routing:

conf t
ip routing

Then you can add the static routes you like.

Configure CISCO Catalyst 2960 ports to monitoring/mirroring mode

This will send all traffic that comes on the 0/1-0/9 ports to the Ga0/1 interface:

switch>enable
switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.

switch(config)#monitor session 1 source interface fastEthernet 0/1
switch(config)#monitor session 1 source interface fastEthernet 0/2
switch(config)#monitor session 1 source interface fastEthernet 0/3
switch(config)#monitor session 1 source interface fastEthernet 0/4
switch(config)#monitor session 1 source interface fastEthernet 0/5
switch(config)#monitor session 1 source interface fastEthernet 0/6
switch(config)#monitor session 1 source interface fastEthernet 0/7
switch(config)#monitor session 1 source interface fastEthernet 0/8

switch(config)#monitor session 1 destination interface gigabitEthernet 0/1

Show info:

switch#show monitor session 1
Session 1
---------
Type    : Local Session
Source Ports :
 Both: Fa0/1-8
Destination Ports : Gi0/1
 Encapsulation : Native
  Ingress : Disabled

And now we can capture this traffic:

# tcpdump -i eth0 -n

One line web server

The following one line script will create a web server running on port 80 using nc (netcat):

while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; cat index.html; } | nc -l 8080; done

Purge Removed packages

Packages marked as rc by dpkg mean that the configuration files are not yet removed. The following command will purge them:

dpkg --list |grep "^rc" | cut -d " " -f 3 | xargs -r sudo dpkg --purge

How to permanently delete ALL older kernels

This script will remove ALL versions but two, the currently active and the most recent of the remaining installed versions:

#/bin/bash
keep=2
ls /boot/ | grep vmlinuz | sed 's@vmlinuz-@linux-image-@g' | grep -v $(uname -r) | sort -Vr | tail -n +$keep | while read I
do
    aptitude purge -y $I
done
update-grub

you can specify how many kernels to keep by adjusting the keep variable, if you set it to 1, only the active kernel will be left installed.

Or you can do it in one line:

ls /boot/ | grep vmlinuz | sed 's@vmlinuz-@linux-image-@g' | grep -v $(uname -r) | sort -Vr | tail -n +2 | xargs -r sudo aptitude purge -y

that you can use in crontab.

GitLab update script

I've recently installed GitLab and they provide easy to install deb and rpm packages but not a repository to help us keep our installation up to date. So I developed the following script that will check https://about.gitlab.com/downloads/archives/ for newer versions and install them when available:

#!/bin/bash
OS="ubuntu"
OS_Version="14.04"
OS_ARCHITECTURE="amd64"
# Ubuntu/Debian:
INSTALLED_VERSION=$(dpkg -s gitlab | grep -i version | cut -d" " -f2)
# CentOS:
#INSTALLED_VERSION=$(rpm -qa | grep omnibus)
# Uses sort -V to compare versions
LATEST=$(wget -q -O- https://about.gitlab.com/downloads/archives/ | grep -i "$OS" | grep -i "$OS_VERSION" | grep -i $OS_ARCHITECTURE | grep -Eo 'href=".*"' | cut -d'"' -f2 | sort -V | tail -n 1)
PACKAGE=${LATEST##*/}
LATEST_VERSION=$(echo $PACKAGE | cut -d_ -f2)
echo ""
echo " Current version: $INSTALLED_VERSION"
echo " Latest version: $LATEST_VERSION"
if [[ "$INSTALLED_VERSION" != "$LATEST_VERSION" && "$LATEST_VERSION" != "" ]]; then
    echo "    Update to $LATEST_VERSION available!"
    echo -n "     Do you wich to upgrade? [y/N]? "
    read answer
    case $answer in
        y*)
            # Backup branding:
            cp /opt/gitlab/embedded/service/gitlab-rails/public/assets/*logo*.png /tmp/
            wget $LATEST
            # Stop unicorn and sidekiq so we can do database migrations
            sudo gitlab-ctl stop unicorn
            sudo gitlab-ctl stop sidekiq
            # Create a database backup in case the upgrade fails
            sudo gitlab-rake gitlab:backup:create
            # Install the latest package
            # Ubuntu/Debian:
            sudo dpkg -i $PACKAGE
            # CentOS:
            #sudo rpm -Uvh $PACKAGE
            # Restore branding:
            sudo cp /tmp/*logo*.png /opt/gitlab/embedded/service/gitlab-rails/public/assets/
            # Reconfigure GitLab (includes database migrations)
            sudo gitlab-ctl reconfigure
            # Restart all gitlab services
            sudo gitlab-ctl restart
            rm $PACKAGE
        ;;
        *)
            echo "No change"
        ;;
    esac
else
    echo "    Nothing to do!"
fi
echo ""

I haven't tested this script on a CentOS machine so it might need some adjustments to work there.