1. 2016-12-09 - Disable apt auto update and upgrade; Tags: Disable apt auto update and upgrade
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    Disable apt auto update and upgrade

    Running Ubuntu Server LTS in a virtual machine, is helpful to test out software installations. Therefore is helpful that apt maintains the update and upgrade periodically. On the other hand if you don’t want that behavior, this post demonstrates how to disable it.

    Login into the virtual machine, remember that you have to map the ssh port in the virtual machine to a different one in your host. In this example it is 1122 and the public key authentication is used.

    tan@omega:~$ ssh localhost -p 1122
    Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-51-generic x86_64)
     * Documentation:  https://help.ubuntu.com
     * Management:     https://landscape.canonical.com
     * Support:        https://ubuntu.com/advantage
    19 packages can be updated.
    8 updates are security updates.
    Last login: Fri Dec  9 16:28:50 2016
    

    You will notice if you try to install or remove anything, that apt is already used by the apt-daily.timer.

    tan@ubuntu:~$ sudo apt-get dist-upgrade
    E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
    E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?
    

    To disable it for the next time:

    tan@ubuntu:~$ sudo systemctl stop apt-daily.timer
    tan@ubuntu:~$ sudo systemctl disable apt-daily.timer
    tan@ubuntu:~$ sudo systemctl disable apt-daily.service
    tan@ubuntu:~$ sudo systemctl daemon-reload
    
  2. 2016-05-25 - Purge old packages from Linux; Tags: Purge old packages from Linux
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    Purge old packages from Linux

    For deb based distributions like Debian, Ubuntu, it is advisable to purge old packages (have status rc, r=removed, c=config).

    List all removed packages that have config files:

    dpkg -l | awk '/^rc/ { print $2 }'
    

    Remove all old and unnecessary packages using apt-get:

    apt-get purge $(dpkg -l | awk '/^rc/ { print $2 }')
    apt-get autoremove
    

    Can also be done with dpkg

  3. 2016-03-30 - Bodhi Linux - a damn good lightweight distribution; Tags: Bodhi Linux - a damn good lightweight distribution
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    Bodhi Linux - a damn good lightweight distribution

    My old Dell Latitude Notebook, 150 GB, 2 GB RAM, Intel Celeron, mainly used for writing stuff, needed a face lift. So I searched for a minimal Linux distribution based on apt. I found Bodhi, the Enlightened Linux Distribution. Bodhi is built on top of the latest Ubuntu LTS release featuring the Moksha Desktop.

    The 32-bit version performs very well, running with X he uses only 290 MB.

    vinh@latitude:~$ free -h
                 total       used       free     shared    buffers     cached
    Mem:          1.9G       290M       1.6G        28M        35M       157M
    -/+ buffers/cache:        98M       1.8G
    Swap:         2.0G         0B       2.0G
    

    Having asciidoctor, python, ruby, git and vim only uses 2.2 GB disk space. The user experience is great so far.

  4. 2016-03-29 - No protocol specified in Evince; Tags: No protocol specified in Evince
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    No protocol specified in Evince

    The evince pdf viewer under Ubuntu 14.04 LTS didn’t work anymore, after I have moved my home directory from /home to /data/home

    A symlink wasn’t sufficient.

    After looking up https://bugs.launchpad.net/ubuntu/+source/evince/+bug/1433165 the solution is simply to run bashsudo dpkg-reconfigure apparmor and configure the new home directory to /data/home/. The last / is important!

  5. 2016-02-22 - Disable online search results in Unity; Tags: Disable online search results in Unity
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    Disable online search results in Unity

    Using the new unity desktop is quite manageable. What annoys me is that every search term in the launcher is also invoking an online search. Therefore I found a quick way to disable it for my user.

    gsettings set com.canonical.Unity.Lenses remote-content-search 'none'
    
  6. 2015-08-07 - Configure Logitech Wireless Presenter R400 for Ubuntu 14.04; Tags: Configure Logitech Wireless Presenter R400 for Ubuntu 14.04
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    Configure Logitech Wireless Presenter R400 for Ubuntu 14.04

    The Logitech Wireless Presenter R400 is not working properly under Ubuntu 14.04. This post provides a solution, how to get the presenter working properly.

    create the udev file (rules)

    vim /etc/udev/hwdb.d/70-r400.hwdb
    

    contents of +70-r400.hwdb+

    # Logitech Presenter R400
    keyboard:usb:v046DpC52Dd*dc*dsc*dp*ic*isc*ip*in00*
     KEYBOARD_KEY_070029=esc
     KEYBOARD_KEY_07003e=f5
     KEYBOARD_KEY_070037=b
    

    update udev

    sudo udevadm hwdb --update
    sudo udevadm trigger /dev/input/event*
    

    Reboot and happy presenting.

    See also <a href=http://askubuntu.com/questions/565555/xubuntu-logitech-presenter-works-only-partialy”>http://askubuntu.com/questions/565555/xubuntu-logitech-presenter-works-only-partialy</a>

  7. 2015-08-05 - SSD caching with bcache for Linux; Tags: SSD caching with bcache for Linux
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    SSD caching with bcache for Linux

    This article describes SSD caching for the HDD drive on a new Ubuntu Linux installation. The contents might as well apply to Debian Jessie.

    Preconditions

    • Device: Thinkpad Edge S430, 500 GB hdd, 16 GB ssd, 16 GB ram
    • OS: Ubuntu 14.04.02 LTS (Desktop)
    • bcache as ssd cache

    Ubuntu base installation

    During the installation I partition my hdd drive like this

    hdd disk partitioning

    root@edge:~# fdisk -l
    Disk /dev/sda: 500.1 GB, 500107862016 bytes
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1   *        2048      499711      248832   83  Linux       (1)
    /dev/sda2          501758   976771071   488134657    5  Extended
    /dev/sda5       960774144   976771071     7998464   83  Linux       (2)
    /dev/sda6          501760   960774143   480136192   83  Linux       (3)
    Disk /dev/sdb: 16.0 GB, 16013942784 bytes
       Device Boot      Start         End      Blocks   Id  System
    /dev/sdb1            2048    31277231    15637592   83  Linux       (4)
    
    • /dev/sda1 ⇒ 256 MB boot partition, will not be cached, as precaution for dist-upgrades
    • /dev/sda5 ⇒ 8 GB for / (sufficient for basic installation and will be later used as swap partition)
    • /dev/sda6 ⇒ the remaining hdd disk space for migration to bcache, don’t assign a mount point
    • /dev/sdb1 ⇒ the 16 GB sdd cache

    Ubuntu will complain that there is no swap partition and /dev/sda6 has no mount point. These warnings can be ignored from the initial base installation. After you have finished the base installation, you are ready to install bcache.

    bcache installation

    If you have kernel version 3.10 or greater you should have bcache, eg. Ubuntu distributions since version 14.04. You can lookup the kernel version with

    tan@edge:~$ uname -a
    Linux edge 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
    

    bcache-tools

    The first thing you must do is install bcache-tools. This is the tool that will create and register the block devices to work with bcache. To install bcache-tools you must first add the repository. This is done with the following commands:

    sudo add-apt-repository ppa:g2p/storage
    sudo apt-get update
    sudo apt-get install bcache-tools
    
    sudo apt-get install git
    sudo apt-get install build-essential
    sudo apt-get install uuid-dev
    git clone http://evilpiepirate.org/git/bcache-tools.git
    cd bcache-tools
    make
    sudo make install
    

    If you are using higher ubuntu version like 14.10, bcache-tools are already in the repository.

    # install bcache-tools from repo
    apt-get install bcache-tools
    

    Concept

    bcache has two requirements: # a ‘backing’ device, the device that shall be cached, the empty hard disk or an empty partition on a hard disk # a ‘caching’ device, the device that is used as cache, the SSD, e.g. 16-32 GB contained in hybrid drives

    bcache

    It is designed around the unique characteristics of flash-based SSDs and uses a hybrid btree/log to track cached extents. It is designed to avoid random writes at all costs. bcache fills up an erase block sequentially and then issues a discard before reusing it. Both write-through and write-back caching are supported. Write-back defaults to off, but can be switched on and off arbitrarily at runtime. The virtual bcache device is created by attaching the backing device and caching device.

    Setup

    • the backing device is /dev/sda6, formatted as ext4
    • the caching device is /dev/sdb1, formatted as ext4

    Cleanup devices

    If the devices have already been used for bcache a cleanup is necessary. You may skip this section, if the devices are not used with bcache before.

    We put zeroes on the first 4kB of the disk:

    # wipe backing device
    sudo dd if=/dev/zero if=/dev/sda6 bs=512 count=8
    wipefs -a /dev/sda6
    # wipe caching device
    sudo dd if=/dev/zero if=/dev/sdb1 bs=512 count=8
    wipefs -a /dev/sdb1
    

    Create and register the devices

    The virtual bcache device is created by attaching the backing device and caching device.

    First set up the backing device (the empty partition on your hard drive).

    root@edge:/home/tan# make-bcache -B /dev/sda6
    UUID:			4bd28ddd-aae2-4b91-8ba9-a7347d365987
    Set UUID:		fc051fbd-37b1-4697-9ac9-fdd3e00ed92f
    version:		1
    block_size:		1
    data_offset:	16
    

    Then do the same thing for your caching partition.

    root@edge:/home/tan# make-bcache -C /dev/sdb1
    

    If you get an error that there are already non-bcache superblocks on the device(s), you have to remove those errors with the wipefs command (see above cleanup section).

    Once the backing device is registered, it will show up in /dev in the form of /dev/bcacheX (where X is a number – such as /dev/bcache0).

    You might need to format the devices

    mkfs.ext4 /dev/sda6
    mkfs.ext4 /dev/sdb1
    

    Show bcache superblock

    bcache-super-show prints the bcache superblock of a cache device or a backing device.

    root@edge:/home/tan# bcache-super-show /dev/sdb1
    sb.magic        ok
    sb.first_sector     8 [match]
    sb.csum         39497E70770FF75D [match]
    sb.version      3 [cache device]
    dev.label       (empty)
    dev.uuid        dc57ecd7-cc8d-468e-9853-9b0f6214faba
    dev.sectors_per_block   1
    dev.sectors_per_bucket  1024
    dev.cache.first_sector  1024
    dev.cache.cache_sectors 31273984
    dev.cache.total_sectors 31275008
    dev.cache.ordered   yes
    dev.cache.discard   no
    dev.cache.pos       0
    dev.cache.replacement   0 [lru]
    cset.uuid       9b1e7bf9-a97a-4785-bacb-0b17189adc08
    

    Attach devices

    The devices are now created and registered. You now have to attach the caching and backing devices to enable the caching feature. Here you will need the UUID (a long string of characters) found in /sys/fs/bcache/ (enter the command: ls /sys/fs/bcache and you’ll see the UUID). To attach the devices, you simply use the echo command to add the UUID to the attach file in /sys/block/bcache0/bcache/. The command is:

    echo UUID > /sys/block/bcache0/bcache/attach
    

    Where UUID is the actual UUID found in /sys/fs/bcache.

    root@edge:/mnt# ls /sys/fs/bcache/
    9b1e7bf9-a97a-4785-bacb-0b17189adc08  register  register_quiet
    root@edge:/mnt# echo 9b1e7bf9-a97a-4785-bacb-0b17189adc08 > /sys/block/bcache0/bcache/attach
    

    Check bcache status

    If bcache was properly setup, check with lsblk.

    root@edge:~# lsblk
    NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
    sda           8:0    0 465,8G  0 disk
    ├─sda1        8:1    0   243M  0 part /boot
    ├─sda2        8:2    0     1K  0 part
    ├─sda5        8:5    0   7,6G  0 part
    └─sda6        8:6    0 457,9G  0 part
      └─bcache0 251:0    0 457,9G  0 disk /  <b>(1)</b>
    sdb           8:16   0  14,9G  0 disk
    └─sdb1        8:17   0  14,9G  0 part
      └─bcache0 251:0    0 457,9G  0 disk /  <b>(2)</b>
    sr0          11:0    1  1024M  0 rom
    
    1. bcache0 for the backing device
    2. bcache0 for the caching device

    Migrate root partition

    create mount points

    cd /media
    mkdir OLD NEW
    mount /dev/sda5 OLD
    mount /dev/bcache0 NEW
    

    copy contents from old to new partition

    rsync -a OLD/ NEW/
    

    grub install

    mount /dev/sda1 NEW/boot
    mount -o bind /dev NEW/dev
    mount -t proc none NEW/proc
    mount -t sysfs none NEW/sys
    chroot NEW
    ls -l /dev/disk/by-uuid/ | grep bcache0     <b>(1)</b>
    vim NEW/etc/fstab                           <b>(2)</b>
    update-grub                                 <b>(3)</b>
    grub-install /dev/sda
    
    1. find out the UUID of /dev/bcache0
    2. replace the previous UUID of / with the new UUID/dev/bcache0
    3. creates a new grub.cfg with changed values from /etc/fstab

    Check caching

    After the grub installation, the next reboot should start from the backing device with bcache using the sdd as caching device.

    To check to see if the caching is working, open up a terminal window and issue the command:

    caching stats

    tan@edge:~$ tail /sys/block/bcache0/bcache/stats_total/*
    ==> /sys/block/bcache0/bcache/stats_total/bypassed <==
    294M
    ==> /sys/block/bcache0/bcache/stats_total/cache_bypass_hits <==
    3041
    ==> /sys/block/bcache0/bcache/stats_total/cache_bypass_misses <==
    0
    ==> /sys/block/bcache0/bcache/stats_total/cache_hit_ratio <==
    64
    ==> /sys/block/bcache0/bcache/stats_total/cache_hits <==
    7398
    ==> /sys/block/bcache0/bcache/stats_total/cache_miss_collisions <==
    0
    ==> /sys/block/bcache0/bcache/stats_total/cache_misses <==
    4069
    ==> /sys/block/bcache0/bcache/stats_total/cache_readaheads <==
    0
    

    Reuse old root as swap

    /dev/sda5 is no longer used and with 8 GB fits perfectly as swap for 16 GB main memory.

    You might change the partition type of /dev/sda5 to swap.

    root@edge:~# fdisk -l /dev/sda
    Disk /dev/sda: 500.1 GB, 500107862016 bytes
    255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
    Units = sectors of 1 * 512 = 512 bytes
    Sector size (logical/physical): 512 bytes / 4096 bytes
    I/O size (minimum/optimal): 4096 bytes / 4096 bytes
    Disk identifier: 0x00023929
       Device Boot      Start         End      Blocks   Id  System
    /dev/sda1   *        2048      499711      248832   83  Linux
    /dev/sda2          501758   976771071   488134657    5  Extended
    Partition 2 does not start on physical sector boundary.
    /dev/sda5       960774144   976771071     7998464   82  Linux swap / Solaris <b>(1)</b>
    /dev/sda6          501760   960774143   480136192   83  Linux
    Partition table entries are not in disk order
    
    1. Change this partition type to Linux swap

    make and enable swap

    mkswap /dev/sda5
    # output
    Setting up swapspace version 1, size = 15624188 KiB
    no label, UUID=3e021d3e-6faf-4f71-bef6-7acb1e49aa75
    # activate swap
    swapon /dev/sda5
    echo "UUID=3e021d3e-6faf-4f71-bef6-7acb1e49aa75 none swap defaults 0 0" >> /etc/fstab (1)
    
    1. add swap partition to /etc/fstab