devtools | Blue Duck Valley Rd

Mini Xplus as a Server

Sun, 24 Aug 2014 00:00:00 +0000

Random, incomplete notes on using a Miniand Tech Mini Xplus H24 as a server machine.

v2

I’ve soldered up a serial port so doing things from scratch is much easier.

$ sudo cp -a hwpack/rootfs/* /media/removable/rootfs/
sun4i# set extraargs init=/bin/sh
sun4i# run bootcmd
# rm -rf /var/run
# ./debootstrap/debootstrap --second-stage
# passwd

v1

Start with the Lubuntu image: https://www.miniand.com/forums/forums/2/topics/1

I used http://dl.miniand.com/allwinnera10/ubuntu/lubuntu-desktop-12.04-4-720p-512MB-miniand.com.img.7z

Turns out my board has 1 GB and the board probed for it just fine.

Writing the image to an SD card gives a boot and rootfs partition similar to the OMAP series. The bootfs has a binary file and kernel image.

I don’t have a keyboard. Fix the wifi interface by editing /etc/network/interfaces:

auto wlan0
iface wlan0 inet dhcp
wpa-ssid "your network name"
wpa-psk your-network-key

The board doesn’t seem to register the hostname with the DHCP server. mDNS works though.

The Lubuntu image is armel based. The hard float armhf Precise image should be much faster for floating point workloads as the A8 takes some time to shift values back and forth between the core and VFP unit.

Grab the modules from /lib/modules. kpartx is your friend.

Grab the most recent Precise release. I used http://cdimage.ubuntu.com/releases/precise/release/ubuntu-12.04-preinstalled-server-armhf+omap4.img.gz

gunzip, mkfs.ext4 -L rootfs -m 0.5 /dev/sdc2, and tar across to the SD card.

Set a password for root by editing /etc/shadow.

Use QEMU to boot and apt-get install wireless-tools wpasupplicant openssh-server. adduser your-name. adduser your-name sudo.

You can now boot and login.

Set the default locale in /etc/default/locale

LANG=C
LANGUAGE=C

Add universe to /etc/apt/sources.list. Toast /var/lib/preinstalled-pool/.

Builder

Thu, 01 Aug 2013 00:00:00 +0000

I’d like to set up clean auto builds of my personal projects and some upstream projects like crosstool-ng, gcc, and binutils.

Clean install

I’d like the build to run in a clean setup so the base system can be used for general development without affecting the build results.

Some technologies are:

docker (LXC containers)
schroot (Debian specific chroot helper)

debootstrap or Ubuntu Core can be used for the base system. Use polipo as a cache for the packages.

Aside: what does the debootstrap buildd variant include?

/usr/share/debootstrap/scripts/ include the selectors
Adds build-essential (quite reasonable)
Or all tagged as Build-Essential

schroot

schroot is nice:

normal users can enter the chroot
you can spawn a session chroot off a seed
the startup scripts copy various files from the host across

C++11 abuse

Sat, 23 Jun 2012 00:00:00 +0000

I’d like to use the new features in C++11 and the GCC extensions in anger. What are they?

rvalue references:

Use?

Generalised constant expressions:

constexpr to mark a function/constructor as compile time constant
non-void return
can’t declare variables, declare types
single return
non-integrals are now OK: constexpr double foo = ...

POD:

Wider than before
trivial: can be statically initialised, can copy via memcpy()
standard layout: C compatible
No virtual functions, base classes
Same access control

Initialiser lists:

Class can have a std::initializer_list constructor
Foo foo = {1, 2, 3};
bar({4, 5, 6})
std::vector std::string v = { “x”, “y” }

Uniform initialisation:

Not sure?
struct Foo { int a; int b; } ... Foo get_bar() { return ( 5, 6 ); }

Type inference:

Awesome!
auto foo = wacky_template_type::yeah<int, bar>...
auto foo = 5;
decltype(some_variable) some_other;

Range based for:

for (int &x : some_int_array) {}
Also works with iterators, begin()/end()

Anonymous functions:

[](int arg1, int arg2) { return arg1 + arg2; }

Trailing return type:

Just like Go
auto foo(int x, int y) -> int;
auto foo(int x, int y) -> decltype(x+y);
Used as x, y are now defined

Constructors:

Delegation: Foo(int x) ...; Foo() : Foo(42) {}
Better than default values as the default gets spread across all callers
Base class constructor inheritance: Derived : Base { using Base::Base; }
Member initialisation: int value = 5; will be called by all constructors
explicit Constructor... to skip

Explicit override:

Mark that you intended to override a base function
virtual void do_it() override;

Final classes and functions:

struct Base final {}: can’t derrive from
virtual void the_last() final;

Null pointer constant:

No more zero, no more NULL: just nullptr
No ambiguity with int args

Fancy enums:

enum class Foo : char { X, Y };
Gives Foo::X
Explicit storage type

Extended templates:

Typedef for a partial template specialisation
using TypedefName = SomeType<OtherType, Second, 5>;
using OtherType = void (*)(double); is the same as typedef (*OtherType)(double)

Unrestricted unions:

union can hold a type with a non trivial constructor

String literals:

u8"I’m in UTF-8 and a const char and a random \u2012 character"
u"I’m in UTF-16 and a const char16_t"
U"I’m in UTF-32 and a const char32_t"
R"(I’m a raw string)"
R"xy(So am I)xy"

Explicitly deleted/defaulted members:

Explicit default constructor class Foo { Foo() = default; }
No default copy constructor class Foo { Foo(const Foo&) = delete; }
No implicit cast class Foo { void f(double); void f(int) = delete; }

Misc:

>> closes templates. Don’t need > >
explicit on conversion operators and constructors to prevent implicit conversion to other types
Variadic templates?
User defined literals: Type variable = 1234_suffix;
But when are they evaluated? compile, start, or runtime?
static_assert
sizeof on members: struct Foo { int bar; }; sizeof(Foo::bar);
alignof(), alignas()

Standard library:

std::thread
std::lock_guard, std::unique_lock
Futures, promises, and async
std::tuples

Running Ubuntu armel cloud instances manually

Sun, 22 Jan 2012 00:00:00 +0000

Documentation: https://help.ubuntu.com/community/UEC/Images

The image itself: http://uec-images.ubuntu.com/oneiric/current/oneiric-server-cloudimg-armel-disk1.img

This is the plain QCOW2 image. The normal one includes OMAP3/4(?) kernel but I’ll use the vexpress-a9 Linaro hwpack instead.

michaelh@crucis:~/linaro/tests/qemu/img$ qemu-img info oneiric-server-cloudimg-armel-disk1.img
image: oneiric-server-cloudimg-armel-disk1.img
file format: qcow2
virtual size: 808M (847203840 bytes)
disk size: 198M
cluster_size: 65536

Running with:

qemu-system-arm -M vexpress-a9 -m 1024 \
-drive file=../../img/ubuntu.img,if=sd,cache=writeback \
-serial stdio \
-append 'root=/dev/mmcblk0p1 rw mem=1024M console=ttyAMA0,38400n8 rootwait' \
-kernel ../../img/tip/uImage -initrd ../../img/tip/uInitrd

Sits there saying:

2012-01-09 03:12:12,509 - DataSourceEc2.py[WARNING]: ‘http://169.254.169.254’ failed: url error [[Errno 111] Connection refused]

Try different boot args:

root=/dev/mmcblk0p1 rw mem=1024M console=ttyAMA0,38400n8 rootwait \
init=/usr/lib/cloud-init/uncloud-init ubuntu-pass=ubuntu ds=unloud-init

Running:

qemu-system-arm -M vexpress-a9 -m 1024 \
-drive file=../../img/ubuntu.img,if=sd,cache=writeback \
-serial stdio \
-append 'root=/dev/mmcblk0p1 rw mem=1024M console=ttyAMA0,38400n8 rootwait init=/usr/lib/cloud-init/uncloud-init ubuntu-pass=ubuntu ds=nocloud' \
-kernel ../../img/tip/uImage -initrd ../../img/tip/uInitrd

Fails with:

Failed to execute /usr/lib/cloud-init/nocloud-init. Attempting defaults...

Should be uncloud-init.

uncloud-init assumes the console is on ttyS0. Patch to ttyAMA0.

Final fault is the ds=. Should be nocloud which causes cloud-init to use DataSourceNoCloud.py.

Forward SSH:

-redir tcp:5022::22

Giving:

qemu-system-arm -M vexpress-a9 -m 1024 \
-drive file=../../img/ubuntu.img,if=sd,cache=writeback -serial stdio \
-append 'root=/dev/mmcblk0p1 rw mem=1024M console=ttyAMA0,38400n8 rootwait init=/usr/lib/cloud-init/uncloud-init ubuntu-pass=ubuntu ds=nocloud' \
-kernel ../../img/tip/uImage -initrd ../../img/tip/uInitrd \
-redir tcp:5022::22