Stop mounting ISO files in Linux with “-t iso9660”

Google “How do I mount an ISO image in Linux” and most of the links still say to use “-t iso9660”. For example:

mount -t iso9660 -o loop,ro diskimage.iso /mnt/iso

That worked fine 10 years ago, but these days not all ISOs use ISO9660 file systems. Many use the UDF (Universal Disk Format) file system, and if you specify ISO9660 when mounting a UDF ISO file, subtle problems can occur. For instance, file names that contain upper case letters on a UDF file system will appear in lower case when that ISO is mounted using ISO9660.

On any modern Linux distro mount is smart enough to figure out what type of file system to use when mounting an ISO file, so it’s perfectly fine to let mount infer the type, e.g.:

mount -o loop,ro diskimage.iso /mnt/iso

Here’s an example of what happens when you try to mount a type UDF ISO as type ISO9660. Note that the case of the file names changes to all lower case when mounting as iso9660, which in this case causes subtle errors to occur within the software.

[~]$ blkid /srv/isos/specsfs/SPECsfs2014-1.0.iso
/srv/isos/specsfs/SPECsfs2014-1.0.iso: UUID="2014-10-22-15-52-41-00" LABEL="SPEC_SFS2014" TYPE="udf"

[~]$ mount -t iso9660 -o loop,ro /srv/isos/specsfs/SPECsfs2014-1.0.iso /mnt/iso
[~]$ cd /mnt/iso
[/mnt/iso]$ ls
benchmarks.xml    netmist_modify     redistributable_sources
binaries          netmist_modify.c   sfs2014result.css
copyright.txt     netmist_monitor    sfs_ext_mon
docs              netmist_monitor.c  sfsmanager
import.c          netmist_pro.in     sfs_rc
license.txt       netmist_proj       spec_license.txt
makefile          netmist.sln        specreport
map_share_script  notice             submission_template.xml
mempool.c         pdsm               token_config_file
mix_table.c       pdsmlib.c          win32lib
netmist.c         rcschangelog.txt   workload.c
netmist.h         readme.txt

[/mnt/iso]$ cd
[~]$ umount /mnt/iso
[~]$ mount -o loop,ro /srv/isos/specsfs/SPECsfs2014-1.0.iso /mnt/iso
[~]$ cd /mnt/iso
[/mnt/iso]$ ls
benchmarks.xml    netmist_modify     redistributable_sources
binaries          netmist_modify.c   sfs2014result.css
copyright.txt     netmist_monitor    sfs_ext_mon
docs              netmist_monitor.c  SfsManager
import.c          netmist_pro.in     sfs_rc
license.txt       netmist_proj       SPEC_LICENSE.txt
makefile          netmist.sln        SpecReport
Map_share_script  NOTICE             submission_template.xml
mempool.c         pdsm               token_config_file
mix_table.c       pdsmlib.c          win32lib
netmist.c         rcschangelog.txt   workload.c
netmist.h         README.txt
Share Button

Click to stream .m3u files in Ubuntu

I just recently heard about CCMixter.org on FLOSS Weekly. CCMixter.org is a resource and collaborative space for musicians and remixers. They have thousands of music tracks which can be downloaded, remixed, sampled, or streamed.

I recently did a fresh install of Ubuntu on the computer I was using, and clicking on any of CCMixter’s streaming links caused a window to pop up asking me if I wanted to play the stream using Rhythmbox or “Other”. Selecting Rhythmbox popped up Rhythmbox, but it wouldn’t play the stream. Googling around a bit led me to discussions of Rhythmbox brokenness going back to 2008, so I took a different tack.

I fired up Synaptic Package Manager and installed the VLC Media Player.

Then I clicked the gear icon on Unity’s upper right menu bar, selected “About this Computer”, clicked Default Applications, and changed the default application for Music to “VLC Media Player.”

Now when I click on a link to an .m3u stream, Ubuntu sends the link to VLC, and the music starts to play.

Hope you find this useful.

Share Button

Increase a VM’s available memory with virsh

If you try to increase the amount of available memory using the obvious command it fails with an error message:

# virsh setmem <vm name> 16G --live
error: invalid argument: cannot set memory higher than max memory

The physical host in this case has 128G RAM and 32 CPUs. Plenty of capacity. To increase the maximum amount of memory that can be allocated to the VM:

# virsh setmaxmem <vm name> 16G --config

There are also –live and –current options which claim to affect the running/current domain. These options do not actually work. You have to use the –config option (changes take effect after next boot) and then power off the machine by logging in and running “poweroff”.

Once the machine is off set the actual memory with:

# virsh setmem <vm name> 16G --config

Then start the vm:

# virsh start <vm name>

Once the VM starts up it will have more memory.

Hope you find this useful.

Share Button

Increase a VM’s vcpu count with virsh

You have a virtual machine you created with virsh. You want to increase the number of vcpus in the virtual machine, so you use the obvious command:

virsh setvcpus --count 8 <vm name>

… and get the irritating error message:

error: invalid argument: requested vcpus is greater than max allowable vcpus for the domain: 8 > 2

This is virsh telling you that you can’t increase the number of vcpus to a number larger than what you started with.

Although virsh doesn’t support increasing the number of vcpus while the VM is running, you can change the number of vcpus if you’re willing to reboot the VM. All you need to to is to edit the virsh XML file with:

virsh edit <vm name>

Look for the line “vcpu placement” and increase the value to the number of vcpus that you want. I changed the vcpus from 2 to 8 here:

<vcpu placement='static'>8</vcpu>

Save the file.

Shutdown the VM:

virsh shutdown <vm name>

Wait until the VM’s status is “shut down”.

virsh list --all

Destroy the VM:

virsh destroy <vm name>

Start up the VM:

virsh start <vm name>

Once the VM starts you’ll have more vcpus running.

Hope you find this useful.

Share Button

Getting rid of the “redirecting to systemctl” message in OpenSUSE

On OpenSUSE systems running systemd all rcX scripts now redirect start, stop, reload, restart, etc. service commands to systemctl. The messages that  used to appear on STDOUT telling you that a command is successful (or not) are now logged, but are no longer displayed on STDOUT.

That I can deal with, but every call to an rcX script now generates the message “redirecting to systemctl” to STDERR. I have a lot of scripts that call rcX scripts, and they interpret STDERR messages as “something just broke”.

The culprit is the new /etc/rc.status script that ships with OpenSUSE. It spews out the “redirecting to systemctl” message to STDERR for every operation that you do. The following command will modify the script and remove this stupid message:

if ( grep -q 'redirecting to systemctl' /etc/rc.status ) ; then
    # Save a copy of the original file
    cp -p /etc/rc.status /etc/rc.status.orig;

    # OpenSUSE 12.1:
    perl -i.bak -pe 's,echo "redirecting to systemctl" >/dev/stderr,,;' /etc/rc.status;

    # OpenSUSE 12.3:
    perl -i.bak -pe 's,echo "redirecting to systemctl \${SYSTEMCTL_OPTIONS} \$1 \${_rc_base}" 1>&2,,;' /etc/rc.status;
fi

This works for OpenSUSE 12.1 and 12.3. I did not have a 12.2 system available to test with.

Hope you find this useful.

Share Button

Bring Pidgin’s window into front focus when there’s an inbound IM

I was talking to a co-worker about Pidgin not coming into focus when there’s a new, inbound IM. The Pidgin window used to come into focus, front and center, when I was running Ubuntu/Gnome and when running OpenSUSE/KDE, but when I upgraded my office desktop to Ubuntu/Unity it stopped behaving this way. My co-worker noticed the same behavior with Fedora17/Gnome. A new IM would come in, but the Pidgin IM window would remain in the background, hidden, unseen and unread.

I thought “There has to be a setting that controls this,” and there is…

  • Bring up Pidgin’s Buddy List
  • Click Tools > Plugins
  • Locate the Message Notification plugin and highlight it
  • At the bottom of the Plugins window is a Configure Plugin button. Click it
  • Under Notification Methods check both Raise conversation window and Present conversation window
  • Click Close

That’s it. The next time someone IM’s you, your Pidgin Conversation will pop up in the center of your screen, in front of all of your other windows.

Hope you find this useful.

Share Button

Creating differential backups with hard links and rsync

You can use a hard link in Linux to create two file names that both point to the same physical location on a hard disk. For instance, if I type:

> echo xxxx > a
> cp -l a b
> cat a
xxxx
> cat b
xxxx

I create a file named “a” that contains the string “xxxx”. Then I create a hard link “b” that also points to the same spot on the disk. Now if I write to the file “a” whatever I write also appears in file “b” and vice versa:

> echo yyyy > b
> cat b
yyyy
> cat a
yyyy
> echo zzzz > a
> cat a
zzzz
> cat b
zzzz

Copying to a hard link updates the data on the disk that each hard link points to:

> rm a b c
> echo xxxx > a
> echo yyyy > c
> cp -l a b
> cat a b c
xxxx
xxxx
yyyy

“a” and “b” point to the same file on disk, “c” is a separate file. If I copy a file “c” to “b” that also updates “a”:

> cp c b 
> cat a b c
yyyy
yyyy
yyyy
> echo zzzz > c
> cat a b c
yyyy
yyyy
zzzz 

What most people don’t know is that rsync is an exception to this rule. If you use rsync to sync two files, and it sees that the target file is a hard link, it will create a new target file but only if the contents of the two files are not the same:

> rm a
> rm b
> echo xxxx > a
> cp -l a b
> cat a
xxxx
> cat b
xxxx
> echo yyyy > c
> cat c
yyyy
> rsync -av c b
sending incremental file list
c
sent 87 bytes  received 31 bytes  236.00 bytes/sec
total size is 5  speedup is 0.04
> cat b
yyyy
> cat c
yyyy
> cat a
xxxx

File “b” is no longer a hard link of “a”, it’s a new file. If I update “a” it no longer updates “b”:

> echo zzzz > a
> cat a b c
zzzz
yyyy
yyyy

However, if the file that I’m rsync-ing is the same as “b”, then rsync does NOT break the hard link, it leaves the file alone:

> rm a
> rm b
> rm c
> echo xxxx > a
> cp -al a b
> cp -p a c
> cat a b c
xxxx
xxxx
xxxx

At this point “a” and “b” both point to the same file on the disk, which contains the string “xxxx”. “c” is a separate file that also contains the string “xxxx” and has the same permissions and timestamp as “a”.

> rsync -av c b
sending incremental file list
sent 39 bytes  received 12 bytes  102.00 bytes/sec
total size is 5  speedup is 0.10
> cat a b c
xxxx
xxxx
xxxx

At this point I’ve rsynced file “c” to “b”, but since c has the same contents and timestamp as “a” and “b” rsync does nothing at all. It doesn’t break the hard link. If I change “b” it still updates “a”:

> echo yyyy > b
> cat a b c
yyyy
yyyy
xxxx

This is how many modern file system backup programs work. On day 1 you make an rsync copy of your entire file system:

backup@backup_server> DAY1=`date +%Y%m%d%H%M%S`
backup@backup_server> rsync -av -e ssh earl@192.168.1.20:/home/earl/ /var/backups/$DAY1/

On day 2 you make a hard link copy of the backup, then a fresh rsync:

backup@backup_server> DAY2=`date +%Y%m%d%H%M%S`
backup@backup_server> cp -al /var/backups/$DAY1 /var/backups/$DAY2
backup@backup_server> rsync -av -e ssh --delete earl@192.168.1.20:/home/earl/ /var/backups/$DAY2/

“cp -al” makes a hard link copy of the entire /home/earl/ directory structure from the previous day, then rsync runs against the copy of the tree. If a file remains unchanged then rsync does nothing — the file remains a hard link. However, if the file’s contents changed, then rsync will create a new copy of the file in the target directory. If a file was deleted from /home/earl then rsync deletes the hard link from that day’s copy.

In this way, the $DAY1 directory has a snapshot of the /home/earl tree as it existed on day 1, and the $DAY2 directory has a snapshot of the /home/earl tree as it existed on day 2, but only the files that changed take up additional disk space. If you need to find a file as it existed at some point in time you can look at that day’s tree. If you need to restore yesterday’s backup you can rsync the tree from yesterday, but you don’t have to store a copy of all of the data from each day, you only use additional disk space for files that changed or were added.

I use this technique to keep 90 daily backups of a 500GB file system on a 1TB drive.

One caveat: The hard links do use up inodes. If you’re using a file system such as ext3, which has a set number of inodes, you should allocate extra inodes on the backup volume when you create it. If you’re using a file system that can dynamically add inodes, such as ext4, zfs or btrfs, then you don’t need to worry about this.

Share Button

Workaround to fix the problem of KDE “forgetting” your multi-monitor setup

I originally reported this KDE4 bug as https://bugs.kde.org/show_bug.cgi?id=312190. It’s also reported as bugs #311641, #309356, and #307589.

In my case I have 3 monitors on one video card. The card and all three monitors are detected correctly, but after I reboot the “Position” settings have all reverted to what they were when I first installed KDE.

I can change the position settings back to the correct settings, click “Save as Default”, log  out, log in, and the position settings have once again reverted to what they were when I first installed KDE.

After trying several things I still haven’t fixed the problem (I suspect a timing issue in the KDE startup) but I did figure out a work-around that anyone can use to “fix” their system so their monitors come up correctly. I posted the work-around on bugs.kde.org and I’m also posting it here.

Here’s how you do it:

Get your monitors set up the way you want them using Configure Desktop > Display and Monitor and click “Save as Default.” This updates the file ~/.kde4/share/config/krandrrc.

Open ~/.kde4/share/config/krandrrc, copy everything on the line after “StartupCommands=”. In my case the line looks like this:

xrandr --output DVI-I-1 --pos 1680x0 --mode 1680x1050 --refresh 60\nxrandr --output DP-0 
  --pos 3360x0 --mode 1680x1050 --refresh 60\nxrandr --output DVI-D-0 --pos 0x0 --mode 1680x1050
  --refresh 60\nxrandr --output DVI-I-1 --primary

Create a new script called ~/bin/workaround-for-kde-bug-312190.sh:

mkdir -p ~/bin
vim ~/bin/workaround-for-kde-bug-312190.sh

(If you don’t like vim, use whatever editor you like.)

Paste the line into the script file.

Change the “\n” characters into actual newlines so you end up with each “xrandr” command on a separate line. In my case I ended up with:

xrandr --output DVI-I-1 --pos 1680x0 --mode 1680x1050 --refresh 60
xrandr --output DP-0 --pos 3360x0 --mode 1680x1050 --refresh 60
xrandr --output DVI-D-0 --pos 0x0 --mode 1680x1050 --refresh 60
xrandr --output DVI-I-1 --primary

These are the settings for MY desktop. Yours will look different!

Make it executable:

chmod +x ~/bin/workaround-for-kde-bug-312190.sh

Run the script ~/bin/workaround-for-kde-bug-312190.sh. Your monitors should still be set up correctly. If they’re messed up, you probably didn’t cut and paste the line correctly. Repeat the above steps again.

Pick Autostart from the KDE menu. (Use the Search function if you can’t figure out where it’s buried.)

Click “Add Script” and paste the line “~/bin/workaround-for-kde-bug-312190.sh” into the “Shell script path” text box.

Click OK, click OK.

The next time you restart KDE it will still start up with the wrong configuration, then Autostart will execute ~/bin/workaround-for-kde-bug-312190.sh and fix the problem.

Share Button

Getting rid of self-resizing windows in Ubuntu Linux 12.04

I’ve been using a pre-release “daily build” installation of Ubuntu 12.04 “Precise Pangolin” and noticed that current default for Gnome is for windows to resize themselves when you get close to the edge of the screen. I have two 22″ widescreen monitors and if I moved a window near the top edge it would maximize and fill the screen. If I moved a window to any edge Gnome would decide for me that what I “really” wanted was to enlarge the window to fill half the screen or do something else equally annoying. This might work well on a 10″ netbook screen, but on dual 22″ monitors it’s annoying as hell.

I tracked the problem down to a setting in Compiz, the screen compositing tool used by many Linux desktop environments, so if you’re using KDE or Unity with Compiz and you’re finding self-resizing windows irritating this fix should work for you as well.

To fix the problem you need to install the CompizConfig Settings Manager, so fire up Synaptic Package Manager and search for “compizconfig-settings-manager” and install it.

Once installed, if you’re using Gnome go to Applications > System Tools > Preferences and click “CompizConfig Settings Manager” to start the tool.

Scroll down to “Window Management.”

Uncheck “Place Windows”.

Leave “Grid” checked, but click the word “Grid” to get the Grid settings, then go to the Edges tab and change all Resize Actions to “None”.

Click Back.

Now your desktop will do what you tell it to do, rather than second-guessing you and doing something that you do not want.

One thing that you can now do (that you probably really don’t want) is to have the title bar (and it’s controls) move off-screen, which means you can’t move or resize the window unless you Alt-right-click on it. To fix that issue:

Check the “Put” plugin.

Click the word “Put” to bring up more options, go to the “Misc Options” tab, check “Avoid Offscreen”, click Back, then Close Window.

Hope you find this useful.

Share Button

Fixing the “broken horizontal scrollbar” problem in LibreOffice Calc

This problem affects people using the KDE4 desktop with the “Oxygen” style and a recent version of the LibreOffice suite. (I’m running LibreOffice 3.4.2 on OpenSUSE 11.4) The horizontal scrollbar in Calc just doesn’t work, so if your spreadsheet is wider than your screen you can’t use the scollbar to view the right hand side.

The problem is with the Oxygen widget style. On a host running OpenSUSE 11.4 you can change this by going to:

Applications > Configure Desktop > Application Appearance > Style

Then set “Widget Style” to any style except “Oxygen”. Click Apply.

Problem solved.

Share Button