Learning Linux Step by Step

Fixing Grub after a Windows upgrade in Linux Mint

2010-12-19T16:14:00.000-08:00

This is a useful answer I found in the Linux Mint forums:

1. Ok 1st thing you want to do is boot into your LiveCD of Mint. (best to use the same version as the one you are using)

2. Once everything is loaded and your at the mint desktop. Open the Mint Menu and type "Gparted" into the filter text box.

3. When it loads you should see all the partitons that are on the hard drive. Linux Mint partitions will probaly be EXT4 and the windows partitions will probaly be NTFS.

4. Look at the list of partitons and see what one is the Linux Mint partiton.You can tell this by looking at the Mount Points of the partitons. You should see one with a "/" under Mount Point and its File system will likely be EXT4. When you have located this partition look to the left and see what it is called. For example mine is called dev/sda6 (yours may be something different like dev/sda1 etc)

5. Now that you know what partition is the Linux Mint partition, just leave gparted open so you can look back at it again incase you forget. Now open up a Terminal by clicking the Mint menu then clicking "Terminal" under System.

6. Now we need to mount the Linux Mint partition so that we are able to use it (access it) . To do this copy and paste this code into the terminal -

Code: Select all: sudo mount /dev/sdXY /mnt

**You will need to change the XY part of the code to match the name of your Linux Mint partition. For example my mint partition is dev/sda6 so i would change the code to - sudo mount /dev/sda6 /mnt

7. Now that you edited the line of code to match your mint partiton, go ahead and press Enter on your keyboard then type in your password if your asked for it then press Enter again.(When your entering in your password you will not see any characters, letters numbers etc)

8. It may look as if nothing has happened, but your Linux Mint partition will now be mounted. The terminal will display nothing after the $ sign like it did when you 1st open it.

9. Now we need to tell the computer to reinstall grub2 to the Linux Mint partition we just mounted. To do this copy and paste this line of code into the terminal

Code: Select all: sudo grub-install --root-directory=/mnt/ /dev/sdX

**Again you will need to change this line of code to match your Linux Mint partition. Change the "X" at the end to match your mint partiton. My partition is dev/sda6 so i will change the the line of code to - sudo grub-install --root-directory=/mnt/ /dev/sda
It is IMPORTANT that you do not enter any number just the letters of the partitions.

10. When you have edited the line of code press Enter on your keyboard. You should then see a message saying Grub installer finished or something like that. Now close the terminal and gparted and reboot your pc/laptop without the livecd in the disc drive. To restart click the mint menu then click "Quit" then "Reboot".
***Note after you reboot you should see the grub2 menu you had before you installed/repaired windows. You may need to refresh (update) this menu so that it detects the new windows partition.
This can easily be done by logging into your Linux Mint, opening a Terminal then copying and pasting

Code: Select all: sudo update-grub

then press Enter then enter your password then hit Enter again. You will then see it detecting all the bootable partitons on the Hard drive. Now just reboot again and you should be able to boot into windows again.

Configuring my machine to use a proxy server to connect via ssh

2009-12-22T15:28:00.000-08:00

Problem:

I need to ssh to server.com, but the corporate firewall does not allow me to access it from my machine home.com.
I can use proxyserver.com:1080 via the SOCKS5 protocol.

First I need to install tsocks on home.com (via sudo apt-get install)

Then I need to configure etc/tsocks.conf
Under local networks I need to include the network of my proxy (I found the IP address of my proxyserver by pinging it).
e.g.
local = 192.240.0.0/255.255.255.0

Then I need to define the server:
server = IP address of proxyserver.com
# Server type defaults to 4 so we need to specify it as 5 for this one
server_type = 5
# The port defaults to 1080 but I've stated it here for clarity
server_port = 1080

Finally, I need to use tsocks to access server.com

tsocks ssh server.com

Security and Encryption links

2009-01-27T17:35:00.000-08:00

A comprehensive list of security tools for Linux

Guide to GnuPG

GnuPG Tutorial

Encrypting a USB Drive with TrueCrypt

Another guide to encrypting a USB Drive with TrueCrypt

Yet another USB and TrueCrypt tutorial

LUKS as an alternative to TrueCrypt

archiving

2009-01-27T12:27:00.000-08:00

Source

ZIP

Zip is probably the most commonly used archiving format out there today. Its biggest advantage is the fact that it is available on all operating system platforms such as Linux, Windows, and Mac OS, and generally supported out of the box. The downside of the zip format is that it does not offer the best level of compression. Tar.gz and tar.bz2 are far superior in that respect. Let’s move on to usage now.

To compress a directory with zip do the following:

# zip -r archive_name.zip directory_to_compress

Here’s how you extract a zip archive:

# unzip archive_name.zip
TAR

Tar is a very commonly used archiving format on Linux systems. The advantage with tar is that it consumes very little time and CPU to compress files, but the compression isn’t very much either. Tar is probably the Linux/UNIX version of zip - quick and dirty. Here’s how you compress a directory:

# tar -cvf archive_name.tar directory_to_compress

And to extract the archive:

# tar -xvf archive_name.tar.gz

This will extract the files in the archive_name.tar archive in the current directory. Like with the tar format you can optionally extract the files to a different directory:

# tar -xvf archive_name.tar -C /tmp/extract_here/
TAR.GZ

This format is my weapon of choice for most compression. It gives very good compression while not utilizing too much of the CPU while it is compressing the data. To compress a directory use the following syntax:

# tar -zcvf archive_name.tar.gz directory_to_compress

To decompress an archive use the following syntax:

# tar -zxvf archive_name.tar.gz

This will extract the files in the archive_name.tar.gz archive in the current directory. Like with the tar format you can optionally extract the files to a different directory:

# tar -zxvf archive_name.tar.gz -C /tmp/extract_here/
TAR.BZ2

This format has the best level of compression among all of the formats I’ve mentioned here. But this comes at a cost - in time and in CPU. Here’s how you compress a directory using tar.bz2:

# tar -jcvf archive_name.tar.bz2 directory_to_compress

This will extract the files in the archive_name.tar.bz2 archive in the current directory. To extract the files to a different directory use:

# tar -jxvf archive_name.tar.bz2 -C /tmp/extract_here/

Recovering files on emacs

2009-01-15T11:57:00.000-08:00

You can use the contents of an auto-save file to recover from a loss
of data with the command `M-x recover-file FILE '.
This visits FILE and then (after your confirmation) restores the contents
from its auto-save file `#FILE#'. You can then save with `C-x C-s' to
put the recovered text into FILE itself. For example, to recover file
`foo.c' from its auto-save file `#foo.c#', do:

M-x recover-file foo.c
yes
C-x C-s

Recall that the M key is the alt key and simply means the "Return" key.

Keeping Jobs Alive When You Log Off

2009-01-14T17:53:00.000-08:00

The nohup command allows you to run programs in the background even after you log out.

E.g. to tun the command abcd,

$ nohup abcd &

Running Win2k on the PS3

2008-10-10T23:24:00.000-07:00

I am very happy with my Ubuntu installation on the PS3, but one thing that disappointed me is the lack of a Flash player for the PowerPC architecture of Linux.

Since I had an old Win2k installation disk, I decided to try Windows on the PS3. In order to run Windows I need to install QEMU

$sudo apt-get install qemu

Then I need to create a hard drive disk (of size 2 G)

$qemu-img create disk.img 2G

and then I have to boot with my Windows CD. Unfortunately I wasn't able to boot from my CD (I don't know why) so I created an ISO image of the installation disk. (The iso image is the CD/DVD Master option of the DiskUtility in the Mac OS X, I just needed to rename the .cdr extension to .iso.)

Once I had transferred the iso image of the install CD to my home directory I just typed

$qemu -hda disk.img -cdrom W2POEM_ES.iso -m 64 -boot d

This command starts the i386 virtual machine with 64MB of RAM. It seems this is the amount recommended for using Qemu on the PS3 by a psubuntu user.

After the installation, every time I want to run again Windows I should type

$qemu -hda disk.img -m 64 (or 128 or 256 etc)

So far I haven't been able to enable sound and neither full screen resolution. When I type ctrl+alt+f (the full screen mode) it goes into full screen mode but in a tiny window in the center of the screen. Perhaps this is a PS3 problem as the resolution configuration is not done in the standard Linux way. :-(

Some references that I may read later:

Guide 1

Audio under the Windows version of Qemu

Guide 2

Guide 3

Maintaining Ubuntu

2008-10-08T10:15:00.000-07:00

A good article on how to find and remove unnecessary files and other general maintenance operations.

Installing Ubuntu on the PS3

2008-10-04T19:33:00.000-07:00

After browsing several sites that provide instructions on how to install UBUNTU on the PS3 I decided to make a list of the ones I found most useful:

http://www.popularmechanics.com/technology/how_to/4263321.html

http://news.softpedia.com/news/Ubuntu-7-10-on-PS3-73272.shtml

http://psubuntu.com/wiki/InstallUbuntu

http://www.ps3linuxworld.com/

You might also want to upgrade your hard drive before installing Ubuntu:

http://ps3.ign.com/dor/articles/915441/ps3-hard-drive-upgrade/videos/PS3HDFeature093008.html

The installation was not smooth: I got a an error telling me that the linux-cell kernel couldn't be installed. This seems to be a very popular problem (I found it in several forums); however, there is a simple a solution.

http://ikerspot.blogspot.com/2007/10/howto-install-kubuntu-710-gusty-on-ps3.html

To correct the resolution I followed this link
http://psubuntu.com/wiki/SetupMonitor

However I didn't restart gdm (because every time I restarted I went to low resolution). Instead, I edited the startup file with nano directly from the console that appeared using ctr-alt-F1.

*Update* I just realized that you cannot watch Flash videos on linux PPC computers. I tried the alternatives gnatch and swf but with very limited success.

Manipulating (merging, etc.) PDF Files

2008-09-26T14:49:00.000-07:00

I am not sure if Adobe supports pdf merging for OS X and Linux (or maybe they only support it in the full adobe reader version?); but if you want to merge different pdf files into a single one by using the command line, this is the solution:

gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=merged.pdf source1.pdf source2.pdf source3.pdf etc.pdf

Update

I just found a Site that describes pdfjam

It is a very useful tool for manipulating pdf files. For example,To put 2x4 pages on one page, use the following command:

pdfnup --nup 2x4 slides.pdf

2nd Update

pdftk seems even easier (and avialable from the universe repositories in ubuntu) to use for extracting and merging documents.

Creating a mirror of a website

2008-09-25T17:50:00.000-07:00

From wget's manual:

If you wish Wget to keep a mirror of a page (or ftp subdirectories), use ‘--mirror’ (‘-m’), which is the shorthand for ‘-r -l inf -N’. You can put Wget in the crontab file asking it to recheck a site each Sunday:
```
          crontab
         0 0 * * 0 wget --mirror http://www.gnu.org/ -o /home/me/weeklog
```
In addition to the above, you want the links to be converted for local viewing. But, after having read this manual, you know that link conversion doesn't play well with timestamping, so you also want Wget to back up the original html files before the conversion. Wget invocation would look like this:
```
          wget --mirror --convert-links --backup-converted  \
              http://www.gnu.org/ -o /home/me/weeklog
```
But you've also noticed that local viewing doesn't work all that well when html files are saved under extensions other than ‘.html’, perhaps because they were served as index.cgi. So you'd like Wget to rename all the files served with content-type ‘text/html’ or ‘application/xhtml+xml’ to name.html.
```
          wget --mirror --convert-links --backup-converted \
              --html-extension -o /home/me/weeklog        \
              http://www.gnu.org/
```
Or, with less typing:
```
          wget -m -k -K -E http://www.gnu.org/ -o /home/me/weeklog
```

I would probably add crontab -e so I can edit crontab with my standard editor. I would also add the -P /path option so that I can save the website in a specified folder.


crontab -e
0 0 * * 0 wget -m -k -K -E  -P ~/Work/Mules/bobmirror http://www.gnu.org/

Printing Source Code in Linux

2008-09-19T19:44:00.000-07:00

Lately I have been spending a lot of time Googling commands for different tasks in Linux, so I decided to start summarizing some of my findings before I forget about them and have to start Googling them again.

So today I wanted to print C source code to a printer; however, I knew that the standard way of printing would have wasted a lot of paper and space. I Googled a bit and found out that there are essentially three main programs to format ASCII to Postcript --a2ps, mpage, and enscript. I decided use enscript with the following command line:

enscript --pretty-print --color --landscape --columns=2 --fancy-header code.c

After executing the command I didn't see any of my local printers processing the job. To learn which printer was processing this request I had to use the command lpoptions which showed under "printer-info" that the default printer was in my previous office!

Therefore I had to learn how to select a printer. For example, a command to print in 2-column format to printer zp2:
enscript -2r -Pzp2 file

Finally, there may be some problems with the margins. I fixed mine by using the option -MLetter.

enscript --pretty-print --color -2r -MLetter -Plwc391c2 te_4_pi.m