Mathias

RHCSA, RHCE, RHCI, RHCX, EX210, EX413

Jul 062017
 

…or is it maybe being broken by people who think it is broken?

I’m pretty sure a lot of people here in Germany have heard the common complaint about end user internet connections being slow in the afternoon and evening because “everybody is watching netflix now” and similar stuff.

I was voicing the same complaint, over and over. My 400MBit cable link at home would drop down to under 80MBit in the evenings, and in downspikes go as low as TEN megabit/second. So I started measuring regularly with speedtest-cli which measures against the closest speedtest..net server, and the graphs in munin were pretty awful. Every day at around noon the performance would start to drop, and go down to around 50mbit by 11pm, and then after midnight would normalize again.

NOT FUN.

but, here’s the thought: What if it is not actually my internet connection?

What if it’s because everybody thinks their internet connection is bad, and starts hitting the speedtest.net servers so hard that they start to slow down?

… So I switched to measuring against a speedtest.net mini server that I’m hosting myself, and no-one else uses… and guess what. My internet performance still drops in the afternoon and evening, but nowhere as dramatic as before.

Makes you think about self-fulfilling prophecies, or maybe internet speed is related to Schrödingers Cat.

 

Edit: Here are two bandwidth graphs from my connection. The first one’s from when I was measuring against the official speedtest.net servers:

Internet performance by day, measuring against speedtest.net servers

Internet performance by day, measuring against speedtest.net servers

The second one was created the same way, but instead of using a random speedtest.net server for every data point I have been measuring against my own speedtest mini server on my cloud host:

Internet performance by day, measuring against my own server

Internet performance by day, measuring against my own server

 

I just hope that that new test site run by the Bundesnetzagentur has enough power to handle the load without drooping.

Dec 092016
 

Oops I Did It Again…

Live Upgrade, with my tried and trusted method. By now that method is so polished that I had no issue whatsoever, so I did all three computers at the same time. I’m just glad to have a decent internet connection… I think the total downloads added up to somewhere near 15 gigabyte.

May 142016
 

I just finished a major heart surgery on my laptop. Many thanks to the guys who made some youtube tutorials about taking that laptop apart! The Acer E5-571G is definitely NOT built to be taken (apart) lightly (Here is the german tutorial that I was following, and here is an english one).

After swapping out the 2x 4G memory modules for 2x 8G ones, and the 1TB laptop hard disk drive for a 1TB SSD disk, and putting everything back together, the real fun began. First I just went to the store on my unu, the faster scooter ever, to get all the parts I needed. You can go to your local electronics store to get your parts.

  • install the old harddisk in an external USB3.0 harddisk enclosure (the drive was still good after all)
  • boot from a Windows 10 installer
  • partition the disk and install Windows 10 in about half of the available space
  • the usual windows installation hijinx: install a driver, reboot, repeat ad nauseam
  • when windows is about done with the initial installation stuff, plug in the old harddisk on USB3.0 and copy the data from your old user account to your new

Then the linux fun begins, but be aware that this method will only work if the existing linux installation on the old disk was based on a LVM setup!

  • boot from openSUSE 13.2 installer DVD, but boot into rescue mode!
  • partition the unused space on the new disk as follows:
    • 250MB /boot
    • one LVM physical volume from the remaining space, but do not create the actual PV yet
  • plug in the old disk again
  • mount the /boot partition from the old system somewhere
  • create ext4 filesystem on the new /boot partition, and mount it somewhere
  • rsync the content of the old /boot to the new one
  • unmount the old and new /boot partitions
  • check that you can see and access your old logical volumes via the usb3 connection to your old disk (lvs, lvdisplay, vgs, vgdisplay, pvs, pvdisplay)
  • now create a PV on the new partition that you created a few steps ago
  • add that PV to the volumegroup on your old disk
  • move all used extents away from the old disk with pvmove
  • once this is done you can remove the pv that is located on the old disk, unplug the disk and use it for something else.
  • make sure the /boot partition on the new disk is not mounted
  • mount your root volume to /mnt
  • prepare your mounted root for chroot
    mount -o bind /dev /mnt/dev
    mount -o bind /sys /mnt/sys
    mount -o bind /proc /mnt/proc
  • Change into your installed system with chroot
    chroot /mnt /bin/bash --login
  • Edit /etc/fstab, make sure all references to mounted filesystems are correct (partition label/identifer for the EFI partition, UUID for /boot, etc)
  • regenerate the initrd with mkinitrd
  • recreate the grub2 configuration with grub2-mkconfig
  • reboot, enter the BIOS setup, go to the UEFI boot settings and make sure the boot order is correct and secure boot is OFF.
  • the next reboot should get you into a working GRUB2 that lets you boot linux but not windows, so boot linux, start yast2 and reinstall the grub bootloader again from there.

That’s it folks!

Jan 092015
 

I finally updated my last machine from openSUSE 12.3 to 13.1 (in the usual way), and with that one I had a bit more fun than the other few times I’ve done this by now.

First mysql refused to start, then quite a few services that were enabled on 12.3 decided to be disabled on 13.1, but nothing during the update “told me so”… but now all seems to work fine.

Dec 022014
 

I have suggested firewalld from fedora/RHEL7 for inclusion in openSUSE, as an alternative for SuSEfirewall2 for setups with highly volatile networking.

test rpm packages for openSUSE 13.2 can be obtained here:

firewalld-0.3.12-1.noarch.rpm

firewall-config-0.3.12-1.noarch.rpm

firewall-applet-0.3.12-1.noarch.rpm

firewalld-0.3.12-1.src.rpm

You will also need to enable the repository from here to get the dependencies.

Nov 232014
 

I’ve done it again… a live upgrade from openSUSE 13.1 to 13.2.

I’ve been following the usual process that I’ve outlined in a few posts so far, and it went pretty smoothly on three different computers.

The actual process has evolved into this:

  1. run this script (after editing to fix the version numbers):
    #!/bin/bash
    old=13.1
    new=13.2
    repodir=/etc/zypp/repos.d
    newrepodir=/etc/zypp/repos.d_${new}
    
    mkdir -p ${newrepodir}
    cd ${repodir}
    for repofile in *repo; do
    {
        echo -n converting ${repofile} to ${newrepodir}/$(echo ${repofile}|sed -e "s/${old}/${new}/g") ... ;
        cat "${repofile}" | sed -e "s/${old}/${new}/g" > "${newrepodir}/$(echo ${repofile}|sed -e "s/${old}/${new}/g")" ;
        echo done.
    }
    done;
  2. move /etc/zypp/repos.d out of the way, for example rename it to /etc/zypp/repos.d_old
  3. move /etc/zypp/repos.d_13.2 to /etc/zypp/repos.d
  4. clean zyppers cache:
    zypper cc --all
  5. refresh zypper:
    zypper ref

    When you do this, you might get errors for some repositories because they don’t exist yet for 13.2. To disable them, do this:

    zypper mr -d -R 

    On the other hand you might want to investigate if there are 13.2 versions of those repositories, and edit the repo files accordingly.
    Then, repeat the zypper ref command.

  6. Once you can run through zypper ref without errors, get updated versions of zypper, libzypp and rpm, and install them:
    zypper up --download only zypper libzypp rpm
    zypper up zypper libzypp rpm
  7. Once that finished without errors, do the same two commands for the whole distribution (Pay attention to any warnings and/or conflicts here. You’ll have to make the right choices about what should be done to resolve them, and I can’t really give you a recipe):
    zypper dup -l --download only
    zypper dup -l
  8. After all is done you can reboot. The first reboot should lead into textmode in case you have to re-install/upgrade your nvidia or AMD binary drivers. To boot into text mode, append this kernel parameter:
    systemd.unit=multi-user.target

Have a lot of fun!

Jun 252014
 

Lately I’ve noticed a trend in mobile apps that started on iOS, and even is understandable there due to the sandbox nature of that os.

“Every mobile app will continue to evolve until it contains a web browser, antivirus, and anti theft features, no matter what is initial purpose was.”

In German we call that “eierlegende Wollmilchsau“.
An animal that produces wool, milk, eggs, and meat.
Sure would be nice to have for a farmer, but can’t be done.

So what is the connection to mobiles?

Well, look at this: right now I have on my tablet the different apps that can provide me with anti theft services, but only one of them had that when I installed it.
Same goes for anti virus, two of those, only one had such a feature when I choose to install it.
Or how about memory and storage cleaning… two again, one when I started with them.

Like I said, on iOS this can be understood, since the sand box nature of ios separates apps from each other to a much higher degree than on android…

But android should be different, its Unix after all, where the long standing tradition is to have small tools that do one job really well, and let them talk to each other.

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