OpenSuSE always had GIMP, which is a very powerful tool and is targeted as an alternative to Adobe Photoshop.  GraphicMagick is a simple to use tool that is small in size and is able to support most common image formats such as GIF, JPEG, PNG and TIFF.  Some of the functions include resize, rotate, sharpen, colour reduction and some image effects and even create a composite of image from combining several images.  HOWEVER, it has a very and I repeat, very primitive look and feel to it!  But it works.

There is also a version that runs on Windows.

Installation of GraphicsMagick

You can use YaSt –> Software Management and search for the GraphicsMagick.  It is a package under the OpenSuSE repository. Search for “GraphicsMagick” and it will show up in your YaST Software Management

Click on “Install” and then “Apply”.  After installation, it somehow does not show up in your list of applications. Run a terminal session and type in “gm display” for the graphical interface.

Didn’t I say it was primitive! It works well for simple editing such as sharpening, viewing at the image histogram, saturation and so on.  Give it a try, the interface may not be your cup of tea but maybe it is …

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Simple Image Editing in OpenSuSE: GraphicsMagick

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To compress a list of files

To compress (the c in the options) a list of files into a specific file (the f in the options) whilst having the tar program to provide progress of it (verbose mode, the v in the option), we use

# tar cvf <tarfile>.tar <list of files>

Leading / will be removed from the archived listing as this will prevent accidental replacement of system files if the file is uncompressed by root.

To uncompress a file

Similarly, we use the same command options where we replace the c with x (for eXtract).

# tar xvf tarfile.tar

This will extract all the files from the archive and recreate the directories and files in the location where the user is in.  Note that, it is good practice to create a new directory, change directory into it before you extract from a tar archive.  This is to prevent overwriting of existing files, unless that is the intention.

To view content of a file

Sometimes, we just want to check if we have a specific file in an archive.  For example, if we are accessing a tape drive (at /dev/st0), we can list (the t in the option) the content using

# tar tvf /dev/st0

More often than not, the listing will be too long for us.  We can pipe the output to grep.

# tar tvf /dev/st0 | grep <string-to-match>

Hope this is short enough.  Leave a comment if you want to ask questions pertaining to tar.

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Short and quick tutorial for the command “tar”

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compress for .Z files

The UNIX command compress is used to create and extract files with the .Z extension.  Unfortunately, this is not available on SuSE.  If you need to uncompress .Z files that you downloaded, you can use the command zcat.

gzip and gunzip for .gz files

This is the more common compression program and algorithm that’s used with Linux.

# gzip <filename>
# gunzip <filename>.gz

bzip2 and bunzip2 for .bz2 files

Known to have a more superior compression ratio than gzip but less frequently used.

# bzip2 <filename>
# bunzip2 <filename>.bz2

zip and unzip for .zip files

Being in a world where Windows seems to be the norm, we can’t avoid receiving file that’s compressed with WinZIP or other tools that create .zip file.  Luckily for us, we have zip and unzip for these files.

# zip <archive>.ZIP <filenames>
# unzip <archive>.ZIP

Please comment if you have any further questions.

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What are .Z, .gz and .bz2 files?

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• What is a tarball?

A tarball generally refers to a compressed archive file that contains the source codes for the software application. This is generally preferred method for source codes that are highly portable and have very little dependencies on the Linux distribution.  In addition to the source codes, the tarball will generally also contain the necessary compilation instructions (documentation) and the Makefile.

The tarball file is made using the UNIX tar command which basically appends all the files into a single file.  It is then compressed (using one of the various compression programs) resulting in either a .Z, .gz or a .bz2 extension.  The current common format of a tarball has a file extension .tar.gz or .tgz.

More on the .Z, .gz and .bz2 extensions later.

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What is a tarball?

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OpenSSH is a FREE version of the SSH connectivity tools. For many users of telnet, rlogin, and ftp, they may not realize that most of the time their password is transmitted across the Internet unencrypted. With OpenSSH, it encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other attacks. Besides that, OpenSSH provides secure tunneling capabilities and several authentication methods, and supports all SSH protocol versions.

To setup and enable OpenSSH for SUSE/OpenSUSE, here are some simple steps to take:

1. Navigate to Yast
2. Select install software
3. From within the search box type openssh and choose install
4. Now get back to yast and go to security and users
5. Select firewall and select allowed services
6. From the services to allow, choose the secured shell server (refer to the above picture)

Happy Trying!

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How to setup and enable OpenSSH

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In term of security, there are many basic security tools that you can add. Tripwire is one of the best file system monitoring tools around. In a nutshell, Tripwire helps to record information about important files (such as checksums) in a database. If anything changes in those files, Tripwire will catch the change when it runs (configure it as often as you like with cron) and will alert you.

Tripwire OpenSource project is based on codes that is originally contributed by Tripwire, Inc. in 2000. Tripwire can alert systems administrators whenever there is any possible intrusion attempts by periodically verifying the integrity of a server’s file systems. It is known that most systems intruders will often use trojan binaries for login, su, ps, and ls, etc. to cover their tracks and keep a low profile on the system. Thus, under normal circumstances even astute systems administrators may not observe the intrusion because the trojan binaries mimic the system binaries so well. By using a strong checksum method similar to MD5,

Tripwire can identify with absolute certainty whether or not a file has been modified, unlike similar programs that use weaker algorithms such as CRC to calculate checksums. While useful for detecting intrusions after the event, it can also serve many other purposes, such as integrity assurance, change management, and policy compliance.

Installation

To install Tripwire, you may issue the following commands as root:

  tar xvzf tripwire-2.3-47.i386.tar.gz

  rpm -ivh tripwire-2.3-47.i386.rpm

Once the software is installed with rpm, the installation shell script will need to be executed to finish the Tripwire installation. This is done by issuing the command:

  /etc/tripwire/twinstall.sh

as root. Note that all Tripwire associated files are kept in the /etc/tripwire directory.

Download Tripwire

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Tripwire : Open Source Security Utility

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