If you are going for a complete reinstall of OS and you need to get a list of packages you have at present, so that you can reinstall them after you have installed Linux from scratch, run the following:
#!/bin/bash
sudo dpkg --get-selections | awk '{ ORS=" "; print $1; }' > packagelist.txt
This saves the everything to packagelist.txt. Mind blown!
Sluggishness on your system running Linux can be caused by numerous factors – among them is a process called gvfsd-metadata.
From what I’ve heard other people say, its caused by fragmentation – possibly due to a partition that’s nearly full.
All you can do is just terminate the process or delete the script from your ~/ folder.
rm -rf ~/.local/share/gvfs-metadata
Every now and then its a good idea to make sure that your home folder is not filled up past 90% or so.
To monitor the instantaneous network usage, execute the ifstat command in bash. You may need to acquire it from a repository if you don’t have it already.
sudo apt-get install ifstat
To display usage on eth0, with a 5 second delay, just once:
ifstat -i eth0 5 1
You can change the number of seconds, and the number of times you want the output displayed. If you don’t specify the count, it will go on forever until you ctrl-c out of it.
So here is a script that displays the download rates in MB/s and upload rates in KB/s every 5 seconds until you hit ctrl-c.
while : do # Press ctrl-c to exit x=`ifstat -i eth0 5 1 | tail -1 | tr '\t' ' '`; #tail -1 takes the DL and UL speeds in KB/S x1=`echo $x | cut -d ' ' -f1`; x2=`echo $x | cut -d ' ' -f2`; x1=$(echo "scale=3; $x1/1024" | bc); # Convert DL rate to MB/S printf "D: %0.3f MB/s\t U: %0.3f KB/s\n" "$x1" "$x2" done
The newer releases of Ubuntu and Linux Mint have started getting stuck during LiveCD installation or after distribution/kernel upgrade. Usually the point where it gets stagnant is when it reaches this line:
kernel_thread_helper+0x7/0x10Nothing happens past that point. A solution or a workaround to this is to insert the nolapic acpi=off switch in the grub boot line. There are 3 ways to do this:
1: If you are starting a fresh install from a CD and the installation pauses at the kernel_thread_helper line, you need to restart your computer.
When you boot from your installation CD, choose F6 before you continue trying out the LiveCD. This give you boot option at the bottom of your screen.
At the very end of the line add nolapic acpi=off and hit enter to continue booting from LiveCD. In most cases this should work.
2. The same problem may arise when you do a distribution upgrade or even a kernel upgrade. In that case you need to change your grub.cfg file. Follow these steps:
sudo nano /boot/grub/grub.cfg
Enter your sudo password and it will bring you to your grub menu configuration.
Look for the section that read similar to this:
menuentry 'Ubuntu, with Linux 2.6.38-11-generic' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
set gfxpayload=$linux_gfx_mode
insmod part_msdos
insmod ext2
set root='(hd0,msdos6)'
search --no-floppy --fs-uuid --set=root 337e2841-fc82-61b3-84be-5a9c71ae43b8
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=337e2841-fc82-61b3-84be-5a9c71ae43b8 ro quiet splash vt.handoff=7
initrd /boot/initrd.img-2.6.38-11-generic
}
You want to change the line that I have identified above to read:
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=337e2841-fc82-61b3-84be-5a9c71ae43b8 ro quiet splash vt.handoff=7 nolapic acpi=off
After adding these switches to the boot menu option, press ctrl-X, then save and exit.
This is for a permanent change if you can boot using an older kernel.
3: If you cannot login to an older kernel or recovery mode because of the kernel_thread_helper error, you have to press “e” (without the quotation marks) to edit the boot options when you get the grub menu.
For the kernel you want to use, edit the end of the line that reads
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=337e2841-fc82-61b3-84be-5a9c71ae43b8 ro quiet splash vt.handoff=7
to
linux /boot/vmlinuz-2.6.38-11-generic root=UUID=337e2841-fc82-61b3-84be-5a9c71ae43b8 ro quiet splash vt.handoff=7 nolapic acpi=off
Press Enter and you should be able to boot.
Some .avi files tend to have an out of sync audio track, some can’t be scrolled through (forward/reverse), while others might show an message that says the index file needs to be recreated.
Solution is to create a copy of that file that has an index recreated and remove the original and save the copy and all the usual replacement methods.
mencoder -idx files1.avi -ovc copy -oac copy -o file2.avi
Here file1.avi is the input file, and file2 is the output file with corrected index.
For the first time I was able to get VNC to work with Ubuntu with Gnome session instead of a xterm on gray background. The steps involved were exactly the same as I was following earlier, with one exception: the setup of xstartup in the ~/.vnc folder.
For your xstartup file in ~/.vnc (the “.vnc” folder in
your home directory), you need the following:
#—————————–
#!/bin/sh
# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc
[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80×24+10+10 -ls -title “$VNCDESKTOP Desktop” &
gnome-session &
# twm &
#————————
instead of uncommenting the lines as the script suggests, you change the window manager to gnome-session
make sure restart vnc4server
The line which got Gnome working was “gnome-session &”
========================================
Now for all the steps involved (works in Karmic Koala Alpha 2, Ubuntu 9.10, kernel 2.6.30-10)
1. Install ssh server, ssh client, VNC viewer, VNC server, and xinetd
sudo apt-get install openssh-server openssh-client vnc4server xinetd vncviewer
2. Setup the ssh password for your login
ssh-keygen
3. Test out the ssh server by typing in
ssh localhost or ssh your_login@your_ip_address
4. Then create a vnc password
sudo vncpasswd ~/.vncpasswd
5. Edit the xstartup file in ~/.vnc directory
For your xstartup file in ~/.vnc (the “.vnc” folder in
your home directory), you need the following:
—————————–
#!/bin/sh
# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc
[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80×24+10+10 -ls -title “$VNCDESKTOP Desktop” &
gnome-session &
# twm &
————————
instead of uncommenting the lines as the script suggests, you change the window manager to gnome-session
6. Create a VNC desktop
vnc4server :1 -geometry 1024×768
7. Then to tunnel into your VNC desktop, first create a SSH tunnel by logging into SSH with the comand:
ssh -L 5901:your_ip_address:5901 your_username@your_ipaddress
8. Finally, load up your VNC desktop
vncviewer localhost:1
And now you are ready to use connect to your machine remotely and use administer the computer remotely.
P.S: If you are using a firewall (hardware or software, you need to get enable port forwarding and unblock ports 22 and 5900-5999 on the Ubuntu machine to allow SSH and VNC to be accessed.
Running scripts in serial order on a multi-core machine will take quite a bit of time. If the tasks are repetitive, the command can be run under GNU Parallel.
You can install it on RPM or Debian based distribution from the GNU Parallel repository. Install the binary that fits your flavour of Linux. Please note that even though the latest release of GNU Parallel has a flavour of Linux associated with it, it runs on most of the older AND newer distributions. For instance I was able to install the April 21st 2011 release of amd_64 RPM on a RHEL5 machine, and it ran just fine for that 8 core machine.
After installation you can try it out on a sample directory by running:
ls -d */ | sed ‘s/\///g’ | parallel zip -r -q {}.zip {}
This will recursively zip all the directories within a given folder, in parallel. By default, it will use up the maximum number of cores, but you can check the man pages of parallel to check how to employ N number of processors to run the task in parallel.
ls *.jpg | parallel convert {} -resize 75% -quality 80% {}
If you have imagemagick installed, you could save a whole bunch of space by converting some of the high-res images to a slightly lower resolution. The above example will resize the images to 75% of their original size with 80% quality. The original images will be overwritten by the resize and downsampled ones. While this is running, you can fire up htop in another terminal window to watch all the processors working in parallel.
I followed the procedure outlined by UbuntuGeek, but some of the things are little different – at least when I installed it today.
First, you’ll need to add the repository which contains the deb for Chrome.
sudo gedit /etc/apt/sources.list
Assuming you are running Karmic Koala (Ubuntu 9.10), you’ll need to add the following two lines towards the end of that file.
deb http://ppa.launchpad.net/chromium-daily/ppa/ubuntu karmic main
deb-src http://ppa.launchpad.net/chromium-daily/ppa/ubuntu karmic main
Next, you’ll have to retrieve the PGP keys for this repository.
sudo add-apt-repository ppa:chromium-daily/ppa
Update the sources,
sudo apt-get update
And then instal Chrome
sudo apt-get install chromium-browser
After the installation is successful, you can launch the browser, and import settings from Mozilla Firefox. However, Firefox needs to be closed when the importing of options and favourites is taking place. When Chrome restarts, it will have options configured like you had them in Firefox. The are no add-ons that I could find for Chrome, though – Adblock Plus and Video Download Helper are the two plugins that would make me stick with Firefox for a while.
Sometimes when you change some of the IP settings, or are using a different wireless card on a machine that has been registered with a server, and for many other reasons, you might have encountered a warning which would’ve looked like this:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
f2:92:1d:da:81:2a:d7:16:0a:48:f0:43:20:1c:f4:b5
………………..
The simplest way to deal with this is to remove the ~/.ssh folder, however this clears out all the exchanged keys with all the ssh machines you have ever communicated with. Removing the ~/.ssh folder would mean that each time you reconnect to a SSH server that you have previously connected to, you will have to confirm that the connection is secure and all that.
There is however another simple way to change just the entry for a specific server in question. At the terminal type in -
ssh-keygen -R name_of_the_server.com
name_of_the_server.com in the above example would need to be replaced by the actual server name that you are trying to connect.
The snapshot before the LTS version of Ubuntu is out now! Karmic Koala would be supported for about another year after which one will have to upgrade to Lucid Lynx, which would be coming out in April 2010, this the name Ubuntu 10.04 LTS.
Karmic has been functional on my machines since Alpha 3 – so no surprises await me as of today. But I would be posting some observations and neat tricks that one can use with Karmic Koala and Ubuntu Linux in general.
The first trick is to use a torrent for downloading the .iso image instead of downloading it directly from some mirror. The advantage of doing that is that you get much faster download rates when using P2P networks for downloading the .iso image, this is especially true for a week since the release, since the mirrors literally crawl to a halt from all the traffic following the release.
Karmic Koala (Ubuntu 9.10): Header used during release
The listing of all the torrents for Ubuntu 9.10 codenamed Karmic Koala can be found at:
Karmic Koala (Ubuntu 9.10) : List of releases on bit torrent
If you come across some performance issues, you can always take your questions to Ubuntu Forums, where you can search if someone has already resolved that issue, and if not, post a query.
For the first time I was able to get VNC to work with Ubuntu with Gnome session instead of a xterm on gray background. The steps involved were exactly the same as I was following earlier, with one exception: the setup of xstartup in the ~/.vnc folder.
For your xstartup file in ~/.vnc (the “.vnc” folder in
your home directory), you need the following:
—————————–
#!/bin/sh# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80×24+10+10 -ls -title “$VNCDESKTOP Desktop” &
gnome-session &
# twm &
————————instead of uncommenting the lines as the script suggests, you change the window manager to gnome-session
make sure restart vnc4server
The line which got Gnome working was “gnome-session &”
========================================
Now for all the steps involved (works in Karmic Koala Alpha 2, Ubuntu 9.10, kernel 2.6.30-10)
1. Install ssh server, ssh client, VNC viewer, VNC server, and xinetd
sudo apt-get install openssh-server openssh-client vnc4server xinetd vncviewer
2. Setup the ssh password for your login
ssh-keygen
3. Test out the ssh server by typing in
ssh localhost or ssh your_login@your_ip_address
4. Then create a vnc password
sudo vncpasswd ~/.vncpasswd
5. Edit the xstartup file in ~/.vnc directory
For your xstartup file in ~/.vnc (the “.vnc” folder in
your home directory), you need the following:
—————————–
#!/bin/sh# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
xsetroot -solid grey
vncconfig -iconic &
xterm -geometry 80×24+10+10 -ls -title “$VNCDESKTOP Desktop” &
gnome-session &
# twm &
————————instead of uncommenting the lines as teh script suggests, you change the window manager to gnome-session
6. Create a VNC desktop
vnc4server :1 -geometry 1024×768
7. Then to tunnel into your VNC desktop, first create a SSH tunnel by logging into SSH with the comand:
ssh -L 5901:your_ip_address:5901 your_username@your_ipaddress
8. Finally, load up your VNC desktop
vncviewer localhost:1
And now you are ready to use connect to your machine remotely and use t
In order to find the exact address maps and to see a list of devices attached to different ports one can use:
sudo lshw
This outputs the hardware specs to the terminal. However in order to check the detailed specs in a graphical format, we need to use the lshw-gtk command. Before you do that, you first need to install it using:
sudo apt-get install lshw-gtk
Then running the lshw-gtk as sudo brings up the list of hardware that you can browse through. It is similar to checking the hardware information from Windows’ control panel.
List detailed hardware specs under linux: lshw-gtk
That’s it. It provides you with relevant information about your processor, memory, display cards, and also some information about the devices connected to USB ports. A quite handy tool for Linux.
I had to create a movie/animation out of a series of images that I had in my folder. There were several methods described on several forums which suggested using GIMP for creating GIF files from JPG or PNG files when one is using Linux. Now the problem was that I had 70 files in total and it would have taken me a long to time to add all those images to GIMP in order to create my animation file.
Then I read somewhere that we can actually create GIF images in command line mode using Imagemagick. But to do so you need to have Imagemagick installed on your system. To install it in Ubuntu, run:
sudo apt-get install imagemagick
This program has several features that would let you do all sorts of things with images. I was interested in converting a bunch of PNG files into an animated GIF file. To do so, we need to rename the files in a way that they would lie in a sequence when arranged alphabetically (if you plan on doing it the easy way). Suppose you have files named slide_01.png, slide_02.png, slide_02.png….slide_xx.png, and you want to convert them to movie.gif, we run:
convert -delay 10 -loop 0 slide*.png movie.gif
The parameter delay inserts a desired delay between two consecutive slides. The number x used for delay inserts 10x milliseconds of delay between two frames. Loop parameter 0 makes it repeat infinitely.
If you had files with non-uniform names, then you need to input each of them in a sequence after the delay and loop parameters. Suppose you have file summer.jpg, fall, winter.jpg, fall.jpg and spring.jpg and you want to order them as fall, winter, spring and summer in the gif image seasons.gif with a 1 second delay between each of them, use:
convert -delay 100 -loop 0 fall.jpg winter.jpg spring.jpg summer.jpg seasons.gif
Here are some animations of numbers from 0 to 9 with varying delays.
The delay values specified the above cases were: 1, 5, 15, 25, 50 and 100.
GIF animation with 10 millisecond frame delay
GIF animation with 50 millisecond frame delay
GIF animation with 150 millisecond frame delay
GIF animation with 250 millisecond frame delay
GIF animation with 500 millisecond frame delay
GIF animation 1 second frame delay
=================
A few days ago an article appeared on geekzone that described how the KDE and Gnome based linux desktop systems are vulnerable to virus and trojans. The point that jumped out was a statement by the blog author: “False sense of security is worse than no security”, and I’ve been guilty of having this false sense of security all along. By all along I mean whenever I was logged in to some Linux distro.
The article is titled: How to write a Linux virus in 5 easy steps
Linux is vulnerable to Viruses and Trojans
Its an interesting read, and one can only hope that everyone in the Linux community takes this as a serious flaw in their beloved OSs and helps out in addressing this issue whichever way they can.
The system beep is one of the most distracting and annoying occurrences when you are doing some constructive work. Be it working in a text editor, or a terminal, or a program window – wherever a sound notification is programmed into any module, it emits a fairly audible beep. To disable the beep, we have to disable the PC speaker by adding it to the blacklist.
sudo gedit /etc/modprobe.d/blacklist
Add the following line to the end of that file:
blacklist pcspkr
Save and exit. Then in terminal,
sudo modprobe -r pcspkr
This completely turns off the speaker. You won’t hear your system beep, even if there is something truly wrong. If you are doing something critical and need to rely on the beeps, comment out the line from the blacklist and run the modprobe command. Beeping will restart.