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Linux Mint Docker “Error loading docker apparmor profile”

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I’ve recently been experimenting with Docker containers, but found there’s an error with installing it on Linux Mint:

2015/07/30 14:00:53 WARNING: Your kernel does not support cgroup swap limit.
Error loading docker apparmor profile: exec: "/sbin/apparmor_parser": stat /sbin/apparmor_parser: no such file or directory ()

It’s quite easy to solve, you just have to install app-armour:

sudo apt-get install apparmor

Then start the docker demon from the terminal to make sure it’s loading okay:

sudo docker -d

You should see something similar to the following:

2015/07/30 14:07:14 docker daemon: 1.0.1 990021a; execdriver: native; graphdriver: 
[67068605] +job serveapi(unix:///var/run/docker.sock)
[67068605] +job initserver()
[67068605.initserver()] Creating server
2015/07/30 14:07:14 Listening for HTTP on unix (/var/run/docker.sock)
[67068605] +job init_networkdriver()
[67068605] -job init_networkdriver() = OK (0)
2015/07/30 14:07:14 WARNING: Your kernel does not support cgroup swap limit.
2015/07/30 14:07:14 Local (127.0.0.1) DNS resolver found in resolv.conf and containers can't use it. Using default external servers : [8.8.8.8 8.8.4.4]
Loading containers: : done.
[67068605.initserver()] Creating pidfile
[67068605.initserver()] Setting up signal traps
[67068605] -job initserver() = OK (0)
[67068605] +job acceptconnections()
[67068605] -job acceptconnections() = OK (0)

 

Once it loads this far, you can use ctrl + c to exit and start the service. If you have any further errors you’ll need to investigate further. Then start the service using:

sudo service docker.io start

Setting up a Buildroot Environment on Ubuntu or Mint

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I’ve got a project that requires really fast boot times, so I’ve been looking into buildroot, which is a tool for building embedded Linux systems. When I started playing with the tutotials I noticed that I was getting errors with the make menuconfig command:

make menuconfig

...

/development/rpi_buildroot/buildroot/output/build/buildroot-config/conf.o
 *** Unable to find the ncurses libraries or the
 *** required header files.
 *** 'make menuconfig' requires the ncurses libraries.
 *** 
 *** Install ncurses (ncurses-devel) and try again.
 ***

In order to use buildroot on Ubuntu or Linux Mint the following packages need to be installed:

sudo apt-get install build-essential ncurses-base ncurses-bin libncurses5-dev dialog

After which you should be able to run make menuconfig without errors.

 

Fixing Raspberry Pi Arch ‘pacman-db-upgrade’ Permissions Error

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I’ve installed Arch Linux on the Raspberry Pi for the first time, and after getting the package manager pacman to update all of the software to the latest versions I’ve been getting the following error:

error: try running pacman-db-upgrade

When running the upgrade command this permissions error was returned:

ERROR: You must have correct permissions to upgrade the database.

After looking at several forum posts I discovered that the upgrade made my filesystem read-only. To fix this edit /boot/cmdline.txt and add the rw flag

nano /boot/cmdline.txt

selinux=0 plymouth.enable=0 smsc95xx.turbo_mode=N dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p6 rootfstype=ext4 elevator=noop rw rootwait

Your installation my have a different cmdline.txt file, but the important bit is the rw flag, usually placed after the root filesystem is declared.

For more information see this forum post: https://www.raspberrypi.org/forums/viewtopic.php?f=53&t=97657

 

Solving Error: Piwik is already installed

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Recently, I’ve been migrating sites to a new server. This included my Piwik installation for website statistics. In order to move Piwik I used mysqldump to backup the database, copied the sites files and restored them to a new server. When accessing Piwik for the first time after the migration I was greeted by the error:

Error: Piwik is already installed

Now, I know this is the only instance on my brand new server, and I know I restored the database correctly. I did some googling to find this is a common problem for migrating Piwik to a new server, but solutions proved to be lacking. In the end I moved the config.ini.php that contains the database connection to a backup location:

mv config/config.ini.php config/config.ini.php.old

I then re-ran the Piwik installation with the same details as I had in the original config file. This wiped my data, but after setup was finished I restored my backup from the original server again:

mysql -u root -p piwik < piwik.sql

Once I logged in all of my old data was available and Piwik was working again!

 

You may be interested in the following forum posts on the Piwik site:

Solving Debian 8 Jessie resolv.conf update issues

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With Debian Jessie, resolv.conf, which stores the name servers for the computer to use when looking up DNS requests, seems to automatically reset every so often. This results in the DNS lookup time for each request sent through the proxy to take longer if the name servers listed are not accurate or fast. For example, my resolv.conf file contained the following by default:

nameserver 192.168.0.1

The IP address listed is that of the router, which for some reason was taking an age to actually respond to requests. Originally I tried to edit this file by hand but it kept clearing itself back to default. This seems to be a particular issue in Debian Jessie.

To resolve the problem, I installed resolvconf, which is a program which has been designed to update the systems information about name servers.

apt-get install resolvconf

Once installed it’s easy enough to add the new name servers to the configuration file. I chose Google’s as a test, since they’re likely to be fast.

nano /etc/resolvconf/resolv.conf.d/head

In the file I added the two IP v4 name servers for google so that it looked like this:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8
nameserver 8.8.4.4

Now that is in there, and of course you can change the name servers as you see fit, it’s just a case of running the update to resolvconf

resolvconf -u

Now your /etc/resolv.conf file should have your two lines prepended to it. Since the file works in top down priority your new requests will be sent to 8.8.8.8 by default. After implementing this Squid increased in speed significantly.

 

You may also be interested in reading alternative solutions on this particular thread at unix.stackexchagne.com.