Lower GPU clock of ODROID-XU4 for headless servers to save energy

Per default the Mali-T628 GPU inside the ODROID-XU4 will run at maximum speed (600MHz) the whole time.
This doesn’t consume that much energy if there is no load on the GPU but nevertheless you can tune this a little bit if you don’t need the GPU at all.

Your kernel needs the following commit: mali: restore sysfs entries
Newer 3.10 ODROID-XU4 kernels should have this activated. I tested this with my own custom build kernel. You can grab it here. Source.

To lock the GPU frequency to the lowest frequency possible (177MHz) do the following. This will automatically lower the voltage as well (see cat /sys/devices/11800000.mali/vol  before and after the change).

I did some measurements with a power meter and this change reduced the power consumption by 0.7 – 0.8W. At first glance, this doesn’t sound that much, but it’s a reduction of about 20% compared to the idle power consumption of an ODROID-XU4 with ondemand governor, which is just 3-4W!
The SOC will be 1-3°C cooler as well 🙂 Perfect for headless servers.

ODROID-XU4 with OpenMediaVault


Nearly 3 years ago I have bought myself a PogoplugV2 (see Post). It is still an awesome device for this price and worked without any issue the whole time.

However it is time for an upgrade.  USB 2.0 was a little bit too slow for me (~30MB/s). In addition I have a lot of external USB 3.0 HDDs and it is time to use their full potential. So there are 4 key points a device needs to become my next NAS (Network-attached storage) and home server system:

  1. reasonable fast ARM processor with at least 2 cores (I prefer ARM over x86 for this use case because of its low energy consumption)
  2. Gigabit ethernet
  3. at least 2 USB 3.0 ports because I want to attach 2 active 4-port USB hubs. Almost all USB hubs >4 ports are cascaded 4 port hubs. This is quite bad because it can cause a lot of compatibility and of course performance issues.
  4. all together <150€. I do not want to pay 300-400€ for a simple NAS with USB disks…


After a bit of research I have bought an ODROID-XU4.
Let’s look at the specs:

  • ODROID-XU4Samsung Exynos5422 Cortex™-A15 2Ghz and Cortex™-A7 Octa core CPUs
  • Mali-T628 MP6(OpenGL ES 3.0/2.0/1.1 and OpenCL 1.1 Full profile)
  • 2Gbyte LPDDR3 RAM PoP stacked
  • eMMC5.0 HS400 Flash Storage
  • 2 x USB 3.0 Host, 1 x USB 2.0 Host
  • Gigabit Ethernet port
  • HDMI 1.4a for display
  • Size : 82 x 58 x 22 mm
  • Price: ~80 € + PSU ~8 € + Case ~8€ = ~96 €

I do not need the GPU and display output but whatever… the price is quite good for this performance. It is less expensive in US than it is in germany. But that is always the case 😉

Additional equipment

I am using a microSD Card for OS because eMMC is quite expensive. Boot times and program loading times are not that important my use case.
With two additional 4 port active USB 3.0 hubs I have 8 USB 3.0 ports and 1 USB 2.0 port. At the moment 5 disks are connected with a total of 7.5 TB storage.
Connecting a 2 TB disk to each USB 3.0 port would be 16 TB storage which should be good enough for some time.

  • SanDisk Extreme 32GB microSDHC UHS-I  ~20 €microSD card
  • 2x EasyAcc® Superspeed USB 3.0 4 Port Bus-Powered and Self-Powered 2-in-1 Hub  2x ~11 €easyacc-superspeed-usb-3-0-4-port-bus-powered-and-self-powered-2-in-1-hub
  • Anker 20W Dual-Port USB Wall Charger to power USB Hubs  ~10 €Anker wall charger


OS Choices

The ODROID-XU4 SOC is the same as its predecessor ODROID-XU3. That is why they share a common kernel and os images are compatible.
Nevertheless Exynos5422 SOC is not fully integrated in mainline kernel yet. That is why you have to use a custom kernel from hardkernel. But that is not a big issue because there a quite a few OS choices with the custom kernel like Android (ofc pretty useless for NAS), Ubuntu 15.04, Arch Linux, Fedora, Kali Linux, …

Also I really like Arch Linux I have chosen a different path this time. There is OpenMediaVault (OMV) for some Odroids. I thought hey let’s give it a try the web interface looks quite nice.
After a few days I can say I really like it. The web interface is really good and looks modern.
OMV is running on Debian Wheezy 7.9.


Download OpenMediaVault Image from: http://sourceforge.net/projects/openmediavault/files/Odroid-XU3_XU4/

Extract the downloaded image

Search for the path of your microSD Card with lsblk  or sudo fdisk -l

Write the image to your microSD card with the following command:

Insert your microSD card and power your Odroid.
Then you can login via SSH or web interface:

username: root
password: odroid

Web interface
username: admin
password: openmediavault

I will not go into detail on how to configure stuff in the web interface because that is really easy and straightforward. I will focus on optimizing performance and adding a few neat features.

Basic configuration

Connect to your Odroid via SSH with default login credentials (see above).

Afterwards change your root password with passwd

You should change your web interface password, too.

Colorful Shell

Because we will use the shell for quite some time let’s add some color to it:

vi ~/.bashrc and comment out the following lines:

vi /etc/vim/vimrc and comment out the following line:

and some more set’s from the bottom of the file as you like.

Note: If you are not familiar with vi/vim  you can use  nano  to edit all files.

Performance tuning

Performance with default settings was really bad. Disk read and write was around 30MB/s to ext4 and SSH was laggy. After a few minutes I have found the issue. Per default OMV sets the conservative governor. This may work well with x86 CPUs or other ARM CPUs but with Odroid it is a pain.

In the web interface under “Power Management” is an option called “Monitoring – Specifies whether to monitor the system status and select the most appropriate CPU level.” This sounds quite good, problem is this option sets the cpu governor to conservative. Conservative governor with default settings works really bad on Odroid in combination with I/O.
Disabling this option sets governor to performance. All 8 cores at max clock speed the whole time produce quite a bit of heat (fan spinning a lot) and it is not really energy efficient.

CPU governor

But no problem we can change the governor to ondemand and with a little bit tuning your Odroid will fly. The following settings will replace conservative with ondemand governor if you enable the Power Management option.

vi /etc/default/openmediavault and append the following lines to this file:

Then regenerate the config with

Note: There seems to be a bug in OpenMediaVault. After disabling Power Management and enabling it again it does not change cpu governor anymore. To fix this do the following:

Ondemand governor tuning

I did a few benchmarks and this showed I/O performance (my main focus) depends a lot on the cpu frequency. Therefore we further have to tune ondemand governor to get full I/O throughput. To do so do the following:

Copy the following to this file

Afterwards change to ondemand governor and activate these values with

I did benchmarks with all these settings and for me this is the sweet spot. Nearly same performance as performance governor but lower frequency and less power consumption when idle.

Some explanation of all 3 settings:

sampling_down_factor: this parameter controls the rate at which the kernel makes a decision on when to decrease the frequency while running at top speed. When set to 1 (the default) decisions to reevaluate load are made at the same interval regardless of current clock speed. But when set to greater than 1 (e.g. 100) it acts as a multiplier for the scheduling interval for reevaluating load when the CPU is at its top speed due to high load. This improves performance by reducing the overhead of load evaluation and helping the CPU stay at its top speed when truly busy, rather than shifting back and forth in speed. This tunable has no effect on behavior at lower speeds/lower CPU loads.

up_threshold: defines what the average CPU usage between the samplings of ‘sampling_rate’ needs to be for the kernel to make a decision on whether it should increase the frequency. For example when it is set to its default value of ’95’ it means that between the checking intervals the CPU needs to be on average more than 95% in use to then decide that the CPU frequency needs to be increased.

io_is_busy:  if 1 waiting for I/O will increase the calculated cpu usage. The governor will calculate iowait as busy and not idle time. Thus cpu will reach higher frequencies faster with I/O load.

NTFS mount options

Besides the ondemand governor we will add the big_writes mount option to all NTFS mounts. In addition we will add noatime.

big_writes: this option prevents fuse from splitting write buffers into 4K chunks, enabling big write buffers to be transferred from the application in a single step (up to some system limit, generally 128K bytes).

noatime this option disables inode access time updates which can speed up file operations and prevent sleeping (notebook) disks spinning up too often thus saving energy and disk lifetime.

vi /etc/default/openmediavault and append the following

Then you have to unmount, apply, mount, apply all your NTFS volumes in the web interface.

With default mount options you get around 16 MB/s write. With big_writes you get up to 62 MB/s write. See this comparison below:

NTFS diagram

This looks fairly fast but keep in mind NTFS is very cpu intensive on such a system. Therefore real network throughput via samba (which is cpu heavy as well) is way less compared to a native linux filesystem. I tested this disk with samba and measured only ~30MB/s read and write speeds. This is considerably less than a native linux filesystem (see Samba benchmarks).

If you want to get full performance you have to use a native linux filesystem like ext4 or xfs. You really should!

More Monitoring

I really like the monitoring setup of OMV with rrdtool. Nevertheless I miss 2 graphs which I am interested in. It would be nice to have CPU frequency and CPU temperature graphs, therefore I extended the existing monitoring plugin.

Monitoring cpu frequency is no big deal because there is a native collectd plugin for CPU frequency. For CPU temperature we have to write our own collectd plugin which looks like this:

In addition to the script above you have to create new collectd configs and additional tabs in the web interface. I have done all that and uploaded the full sourcecode (including the script above) to GitHub: https://github.com/Obihoernchen/openmediavault-monitoring-odroid-xu4

Install these CPU frequency and temperature monitoring plugins with the following commands:

The default diagrams are a little small for my taste, that is why I have increased the size a bit:

vi /etc/default/openmediavault and add the following to this file

Afterwards update OMV’s config files with

Afterwards you will have 2 new tabs which show graphs like these:



Finally reboot to see if everything is working as expected.


All benchmarks were done with performance governor to get consistent results.


I have several USB disks connected to my Odroid. Expect one disk all are 2.5″ USB 3.0 disks. All USB 3.0 disks are connected to two active USB 3.0 hubs. The USB 2.0 disk is connected to the USB 2.0 port.
In the following you can find hdparm read and dd read/write benchmarks for all connected disks. As you can see the performance is quite good and should be near the maximum the disks can handle.

dd benchmark


All network settings are default OMV/debian settings.

Receive: 832 Mbit/s = 104 MByte/s
Send: 896 Mbit/s = 112 MByte/s

I am satisfied with these results as it is close to the theoretical maximum of 1Gbit/s.


Disk and network speed looks fine. Because there are windows machines in my network I have to use samba to share files. As you can see samba speed is quite good and very stable.

Writing 2.7 GB test file to Odroid (USB 3.0 ext4 disk)


Reading 2.7 GB test file from Odroid (USB 3.0 ext4 disk)



If you have any additional questions feel free to ask 🙂
I will try to update this post regularly with new optimizations etc.

Convert your Nexus 4 to F2FS without loosing data


My Nexus 4 was really slow because the sequential write speed of the filesystem was around 3MB/s. Random write speed was nearly zero…
Fstrim (or LagFix) didn’t help at all 🙁 I think a lot of you already know about F2FS the flash friendly file system from Samsung. Benchmarks show that it really boosts I/O Performance. So time for me to try it and see whether it will fix my performance issues.

F2FS (Flash-Friendly File System) is a flash file system created by Kim Jaegeuk at Samsung for the Linux operating system kernel. The motive for F2FS was to build a file system that from the start takes into account the characteristics of NAND flash memory-based storage devices (such as solid-state disks, eMMC, and SD cards), which are widely used in computer systems ranging from mobile devices to servers.

You can format your /data and /cache partition to F2FS. Normally you’ll loose all data in this process and have to reinstall everything. But this small howto will show you how to recover your data so you can continue where you left off. Just like a “dirty” ROM flash.

Note: In my mind it doesn’t make much sense to format/system to F2FS because you would need a modified ROM to use it. Everytime you update your ROM you would have to modify it to use /system as F2FS. On top of that there shouldn’t be a real performance gain with a F2FS /system partition because it’s read-only. And reading operations are fast with ext4, too. The difference is non-existent or very low. In my humble opinion the so called All-F2FS is pretty useless.


This following method should work with all devices which have FSFS compatible TWRP recovery, rom and kernel available.



  • Flash the F2FS compatible TWRP Recovery with Flashify for example
  • Boot into Recovery
  • Backup > Data
  • Save your internal SD card with one of the following options
  • Either reboot to system and copy files to your PC via USB (MTP)
    • Or pull files via adb (adb pull /data/media sd_backup)
    • Copy the kernel and the sdcard fix script to your created backup folder
  • Wipe > Advanced Wipe > Data > Repair or Change File System > Change File System > F2FS
  • Wipe > Advanced Wipe > Cache > Repair or Change File System > Change File System > F2FS
  • Copy the saved SD card content back to your device with: adb push sd_backup /data/media/0/
    Afterwards the folder structure should look like this: /data/media/0/…Folders like DCIM, Music, Downloads, …
    You can check with: adb shell ls -R /data/media
  • Restore > Choose backup > Data (the warning about ext4 backup doesn’t matter)
  • Advanced > Fix Permissions
  • Flash the sdcard Fix Permissions script with: Install > Choose sdcard fix zip
  • Wipe > Advanced Wipe > Cache & Dalvik Cache
  • Flash a F2FS compatible kernel with: Install > Choose kernel zip
  • Reboot to system

Now your Android device should fly again 🙂

Cyanogenmod 10.2 for Nexus 4

Here are fresh builds of Cyanogenmod 10.2 for Google Nexus 4 (mako)


ROM: http://obihoernchen.net/downloads/?dir=Nexus+4+CM+10.2
Gapps: http://obihoernchen.net/downloads/Gapps/pa_gapps-full-4.3-20130808-signed.zip

You can find Modems and Bootloaders there as well.

Update #01: New Build: 11.08.2013 ~ 13:30 – Changelog

Update #02: New Build: 12.08.2013 ~ 02:15 – Changelog

Update #03: New Build: 12.08.2013 V2 ~ 14:00 – Changelog

Update #04: New Build: 13.08.2013 ~ 09:30 – Changelog

Update #05: New Build: 14.08.2013 ~ 08:30 – Changelog

Daily Newspaper on E-Book Reader via Arch Linux

My friend x23b5 has an Amazon Kindle and wants to read daily newspapers each morning.

Time for a cron job on my Pogoplug to send some newspapers to this Kindle 🙂

There is a pretty cool package called calibre.
It can convert online newspapers to ebook specific files and send it via email to your eBook Reader.

Install calibre

Calibre uses recipes to fetch news and convert those to ebook files like .mobi or .epub.
You can list all available recipes with the following command:

Note: It’s a good idea to create a new email for this task because your password will be saved in plain text. Use a freemailer or create a new user on your own mailserver.
Create the following file in /usr/local/bin/calibre-cron and replace all variables and recipes with yours.
I used another usb stick (cacheStick) to save the temp files because I want to protect my arch linux stick.
To change the output format just change the file extension.

Make it executable:

Execute it and check whether it works.

Now we have to create a cron job to execute this script each morning.
Execute this command before you edit your crontab file.

Edit your crontab file:

> /dev/null 2>&1” because I don’t need any email or log output.

Now enable cron service:

Calibre is pretty memory and cpu intensive and takes pretty long! You should run it overnight otherwise your plug pc will be very slow.

How it looks like:

Kindle newspaper

Setup Samba 4 on Arch Linux

Updated: [03.05.2015] Sync some performance settings with my own personal settings, added a link to some more performance tips (see bottom).
Updated: [28.09.2015] Sync again

Note: Check this article if you want to install arch on your pogoplug.

Samba 4 is out now 🙂
So I’ll make this tutorial for Samba 4 because it seems to be slightly faster.
This article will tell you how to install it on your PogoplugV2 or another PlugPC.
Should be pretty much the same for all arch installations.

Samba 3 is going to be removed once Samba 4 is installed.
Your old config will be saved to /etc/samba/smb.conf.pacorig

Installation of Samba 4 is pretty easy.

Now enable the services.

Create Users

If you want to create shares for multiple users you have to create new Unix user and add this one to samba as well.
To make it clean we will create a group called “samba”.

Now we can add a new user to this group. This user “fabian” is not able to login (-s /sbin/nologin) for security purposes.

To use this user in samba shares you have to add it to samba

Create Shares

We are ready to configure our samba shares.
At the beginning configure
To do so edit /etc/samba/smb.conf

Here is an example configuration.
You have to edit the Share definitions below so it fits your setup.

Optimize performance

The stock performance of samba isn’t that great. Especially with NTFS.
But there are some parameters which will increase Samba performance significantly.

Add all these settings to the global section in your smb.conf file.

The main problem for slow file transfer speeds is NTFS, because NTFS needs much CPU on linux.
Nevertheless there are 2 options which will boost the speed:

write cache size

If this integer parameter is set to non-zero value, Samba will create an in-memory cache for each oplocked file (it does not do this for non-oplocked files). All writes that the client does not request to be flushed directly to disk will be stored in this cache if possible. The cache is flushed onto disk when a write comes in whose offset would not fit into the cache or when the file is closed by the client. Reads for the file are also served from this cache if the data is stored within it.

This cache allows Samba to batch client writes into a more efficient write size for RAID disks (i.e. writes may be tuned to be the RAID stripe size) and can improve performance on systems where the disk subsystem is a bottleneck but there is free memory for userspace programs.

The integer parameter specifies the size of this cache (per oplocked file) in bytes.

Default: write cache size = 0

Example: write cache size = 262144 # for a 256k cache size per file

Some example values are:

(262144 = 256KB – you should test some values it’s pretty memory intensive)

Don’t forget to start the samba services or reboot:

For some additonal performance tips check this blogpost: https://linuxengineering.wordpress.com/2014/08/03/performance-tuning-with-pogoplug-v4/

Installing Arch Linux and setting up everything on Plug Computers like PogoplugV2

Some weeks ago I’ve ordered a so called “Plug Computer”.PogoplugV2
These Computers are very small devices with an ARM SoC.
They are pretty cheap! I’ve got my PogoplugV2 for 10€ 🙂

I was lucky and got the gray version 😀
Some device info:

  • ARMv5te CPU (Marvell Kirkwood 1.2GHz)
  • 256MB RAM
  • 128MB NAND
  • 4 USB 2.0 Ports

Pretty great to use this device as a small homeserver/fileserver. Remember 10€!
I want to use my Pogoplug as a fileserver (for Windows PCs) and DLNA server to stream to my TV.
On top of that maybe some additional stuff in the feature 😉

But the default software sucks. No Samba support, no DLNA, no FTP, …
But this doesn’t matter because there is an Arch Linux for ARM Port.
This is an instruction how to install Arch Linux on a PogoplugV2.
Everything after the Arch Linux installation (Install Webmin, Samba, DLNA, …) can be used for all devices which run Arch Linux for ARM.

Prepare device and install Arch Linux

Arch Linux

Everything we have to do to install Arch Linux are 4 steps.

    1. Enabe SSH Access
    2. Format an USB Stick (min. 2GB size)
    3. Flash a custom Bootloader to boot from your USB Stick
    4. Install Arch Linux

An instruction how to do that is available here: http://archlinuxarm.org/platforms/armv5/pogoplug-v2-pinkgray
There are instuctions for other devices as well.
If you use Windows use PuTTY as a SSH client.

Setup everything

1. Login via SSH

Use PuTTY or another SSH client to access your Pogoplug.

username: root
password: root

 2. Change your root password

First you should change your root password.
Use the following command to do so:

 3. Update Arch Linux

Arch Linux has an own package manager called pacman.
With pacman you can install/remove packages and update Arch Linux.

To update Arch Linux use the following command:

 4. Change hostname and timezone

Note: For GUI lovers: skip this step and set hostname and timezone in the webmin interface (next step)

The default hostname is “alarm”. Let’s change it!

To get all available timezones use:

And to set your timezone:

For example:

Now reboot:

Wait a few seconds and reconnect to SSH.

 5. Install Webmin

Webmin is a pretty cool web-based interface for system administration.
It’s easy to use  and will help you to configure stuff faster.
To install it use:

Now we have to allow access from more IP addresses.
You have to edit the configuration file.

Find the following line: allow=
Now add a new allow line with your local network broadcast ip or a specific ip and save the file.
For example:

Now we’ll enable & start the webmin service so it autostarts.

To access the Webmin interface open a browser and go to:

To lower memory usage go to:
Webmin>Webmin Configuration>Advanced Configuration and disable Pre-load Webmin functions library?”

 6. USB Auto Mount

If you want to remove your USB HDD and use it anywhere else it would be cool to have automounting like Windows.
There are a lot of auto mounting mechanisms for Arch Linux but a lot of them are outdated.
This one is using udevil to auto mount all USB HDDs on attach as /media/PARTITION_LABEL. So make sure all partitions have a label!

I want to access my HDDs via Samba to use them in Windows so I have to use either FAT32 or NTFS.
This sucks because FAT32 isn’t able to handle files >4GB so it’s useless.
And NTFS is fucking slow on Linux.

But with some special mount options we are able to increase the speed dramatically!
I’ve did some benchmarks with hdparm and dd before and after the optimization.
The read speed was pretty good already (about 29MB/s –> USB 2.0 limit).
But the write speed was really bad!

Before: ~6,5 MB/s write speed
After: ~28,5 MB/s write speed

As you can see the write speed on NTFS was really slow before. But there is a way to fix it 🙂
We have to edit the mount options and add a special ntfs-3g option to our udevil automount settings.
Open the udevil config file and edit it:

Search for default_options_ntfs= and allowed_options=

Now we add the option “big_writes” to both lines so it looks like:

Save the file.

Create the /media directory

Add the udevil service to autostart.

Let’s reboot to see whether it works

Wait a few seconds and reconnect to SSH.
Now you’ll have a new folder: /media/yourHDDname where your HDD is mounted.
And you should see something like /dev/sdX1 on /media/… if you type:

Note: All USB HDDs should go to standby automatically.
You can check with:

7. Blink LED to HDD activity

The PogoplugV2 has a green and orange LED.
So I thought it would be a cool idea change the color to HDD activity.
I’ve created an systemd service.


Only If you have a PogoplugV2!

You have to correct your arcNumber and matchid because there is a bug in the current uboot and your Pogoplug isn’t detected as a PogoplugV2.


We need the iostat binary to create our own deamon.
Iostat will check hdd activity.

Create a new file called /usr/lib/systemd/system/blinkled.service with the following content:

Create another file called /usr/local/bin/blinkled
This command is pretty long 😉 It will execute iostat every 3 seconds. If there is HDD activity the Pogoplug will start to blink orange.
You can change heartbeat to default-on or timer as well.

And make it executable

To start our service use:

To autostart use:

 8. Update Kernel to >3.2

Warning: This specific instruction works for PogoplugV2 only!
You can brick your device!

The current kernel for PogoplugV2 is 3.1.x but 3.8.x or newer is available.
You have to update manually because newer kernels need a new uboot.

You need the newest uboot to boot Kernels >3.2 so you have to install it before:
If this is a fresh installation you probably have the newest uboot already and you don’t have to do that!

Then you have to correct your arcNumber and matchid if you didn’t follow “Blink LED to HDD activity”.

Now you can install the new Kernel files with:

 9. Install Samba

See this post

10. Install MiniDLNA

Install MiniDLNA and enable the service.

Now edit the config file

It’s pretty easy to understand the config file and the documentation is well.
You have to set at least one media_dir
All USB devices are mounted at /media/DEVICE_LABEL
For example:

Here are some additional options you could set:

MiniDLNA will update the DB automatically.
If you have a lot of files (>8192) you should increase your max inotify value for a single user so MiniDLNA can watch all files.
Create /etc/sysctl.d/90-inotify.conf and insert the following:

MiniDLNA is able to use thumbnails or cover images.
I’ve created a small bash script which will generate thumbnails for videos recursively.
You need ffmpegthumbnailer to create these thumbnails.

Let’s create the script:

This script will generate a thumbnails for every video file recursively.
You can add even more extensions to the TYPES array.

See: https://github.com/Obihoernchen/generateThumbs

Make it executable:

Execute it with something like:

Now start MiniDLNA

12. Configure static IP

Be careful you can mess up your whole network connection!

I don’t like dynamic IP addresses in my LAN. Especially for servers.
They should have a static IP like every server. Of course there are hostnames but not all devices are able to resolve them.

Arch uses netcfg to configure your network adapters. You can create multiple profile.
To create a new static ip profile create a new profile in /etc/network.d/ named wired-static-eth0

And add the following content, replace everything with your values and save the file.
Note: I use custom DNS settings because my router doesn’t allow me to edit DNS settings.

Now you need to change the default network profile to the new one.

Find NETWORKS= and edit it:

You have to be sure that everything is correct otherwise you are going to loose network connection and have to edit all files from your USB stick with another PC.
Just restart the netcfg service or restart to apply the new settings

 13. Enable color in Bash prompt

The current terminal doesn’t look that nice. Everything is white and boring…
But we can change this so your terminal will look like this:

Terminal with color

Just replace /etc/bash.bashrc with the following content:

More information and other examples: https://wiki.archlinux.org/index.php/Color_Bash_Prompt

To search for available packages in repos if your command doesn’t exist on your current system configuration install pkgfile

14. Disable some logging to extend USB stick lifetime

Flash drives have limited number of write cycles and default linux logging will write pretty much so your USB will be destroyed pretty fast.
That’s why a swap file on your USB stick is a really bad idea!
But you can disable some logging to extend the liefetime of your USB stick.

Just edit syslog-ng.conf and disable some of the “log { source(src); filter…” lines at the end of the file.
You can comment out (add a “#” in front of the line) all lines if you want to disable everything.

I’ve disabled some of them. That’s my example:

On top of that you could disable logging of some servers like samba, minidlna and so on.
I don’t do that because I want to have these logs but to do so set the log path in the config files to /dev/null

Das Mysterium – ZRAM

Da ich immer wieder so viele falsche Informationen über ZRAM sehe habe ich beschlossen mal etwas Klarheit in die ganze Materie zu bringen 
Oft wird über einen Performance Vorteil gesprochen, da ZRAM schneller als Swap ist. Das ganze mag für normale PCs stimmen aber wir sind hier mit Android unterwegs und da sieht das ganze etwas anders aus!

Erst einmal eine kurze Feststellung für alle, die noch nicht so lange in der Android Szene unterwegs sind:
ZRAM = ramzswap = Compcache

Um ZRAM genauer zu erklären müssen erstmal andere Begriffe genauer geklärt werden:
Swap kann man mit der Auslagerungsdatei unter Windows vergleichen werden. Wird der Arbeitsspeicher (RAM) zu voll kann der PC die Daten, die gerade nicht aktiv gebraucht werden (z.B. Hintergrundanwendungen) auslagern um so wieder RAM frei zu räumen. Dazu werden diese Daten auf eine Festplatte geschrieben. Bei Bedarf können diese Daten dann einfach wieder von dort aus gelesen werden. Selbst die schnellste SSD ist aber langsamer als der Arbeitsspeicher. Unter Android gibt es Swap nicht!

Bei ZRAM werden nicht benötigte Speicherressourcen komprimiert und dann in einen fest reservierten Bereich im RAM verschoben (ZRAM). Also eine Art Swap Partition im Arbeitsspeicher.
Dadurch ist mehr Ram frei, da die Daten dann nur noch ca. 1/4 des ehemaligen Speicherbedarfs haben. Allerdings muss die CPU dadurch mehr arbeiten, da sie die Daten komprimieren muss (oder auch wieder entpacken wenn sie wieder gebraucht werden). Der Vorteil hierbei liegt ganz klar in der Geschwindigkeit. Da die Swap Partition sich im RAM befindet ist diese viel schneller als eine Swap Partition auf einer Festplatte.

An und für sich eine ganz tolle Sache. Aber Android besitzt keine Swap Partition und daher bringt ZRAM unter Android keinen Performance Gewinn wie es bei einem normalen PC der Fall wäre.

Beim normalen PC würde das folgendermaßen aussehen:
Swap = Auslagerungsdatei (auf Festplatte) –> Langsam
ZRAM (Swap im RAM) –> Schneller als Swap
RAM –> Schnell

Bei Android gibt es keine Swap Partition und daher bringt ZRAM auch keinen Performance Boost.
Das einzige was ZRAM bringt ist “mehr” RAM. Durch das komprimieren “vergrößert” sich sozusagen der verfügbare Arbeitsspeicher. Das ist auf Geräten mit sehr wenig RAM (<256MB) auch ziemlich nützlich. Das S2 hat aber 1GB und die reichen mehr als aus. Da muss nicht künstlich auf 1,5GB hochgepusht werden.

Denn aktiviert man ZRAM hat das auch 2 Nachteile. Das komprimieren und dekomprimieren verbraucht CPU Time, welche wiederum höheren Stromverbrauch zur Folge hat.

Grob kann man also sagen (Für Geräte mit mehr als 512MB RAM):
Ohne ZRAM: +CPU Performance | +Battery | -RAM
Mit ZRAM: -CPU Performance | -Battery | +RAM

Für Geräte mit zu wenig RAM also durchaus sinnvoll. Aber wer ballert beim S2 schon sein kompletten RAM voll und braucht dann immer noch mehr?

Überprüfen ob ZRAM läuft kann man im Terminal mit
free oder cat /proc/meminfo

ZRAM aus:

ZRAM an:

Weiterführende Infos:
Swap and Compcache – CyanogenMod Wiki