Why Alias Command With Itself

Aliasing the command to itself to suppress the original functionality of the command and provide it new added sets of functionality can come quite handy for linux users and administrators.

If you have been using linux shell for a while, I'm pretty sure you are now familiar with the `ls` command, if not I think you have just learnt to use man pages. Probably you've been using `ls -l` command to list files with the files size as well. Too bad, you won't just be able to instantly make the sense of the file size displayed using this command so why not alias `ls` command to always provide human readable file sizes. So here is my alias:

alias ls='ls -lh'

This is what I always want to see as the output with `ls` command. The same kind of alias can be used with `du` and `df` commands. There are number of other cases where aliasing a command with itself is good choice.

Another example is the less command. By default, you need to press q to exit less which can be quite annoying if the entire content can fit in a single screen. However, adding -F flag will gracefully quit after displaying the content if the content fits in a single screen. So I have my alias for less as below:

alias lesss='less -F'

If something shoots in your mind, feel free to share here as a comment :)


Read more...

Fix "trying to overwrite '*', which is also in package *"

Today I was updating few stuffs in edubuntu and dpkg was continually throwing me the problem while trying to install kdelibs-data. The error read as "trying to overwrite 'A', which is also in package X" and the fix was pretty straightforward but still I thought it would help someone out there.

Below is the exact error I was getting while trying to install kdelibs5-data from the deb file.

dpkg: error processing /var/cache/apt/archives/
kdelibs5-data_4%3a4.4.5-0ubuntu1.2_all.deb (--unpack):
trying to overwrite '/usr/share/polkit-1/actions
/org.kde.kcontrol.kcmremotewidgets.policy', which is also in package kdebase-runtime-data 4:4.6.5-0ubuntu1

The fix was pretty simple. Add the --force-overwrite switch in the dpkg command as below:

dpkg -i --force-overwrite kdelibs5-data_4.4.5-0ubuntu1.2_all.deb

I hope this comes useful sometimes.


Read more...

Recover Deleted Files From An NTFS Volume Using Ntfsundelete

Ntfsundelete is a part of ntfsprogs, a suite of NTFS utilities based around a shared library. It lets us recover the deleted files from any NTFS volumes without making any changes in the NTFS volume itself.

Generally when a file is deleted from disks, it is some kind of pointer to the physical file that gets deleted and the actual content still remains in the disk unless it is overwritten by new files so it is possible to recover those files.

ntfsundelete has three modes of operation: scan, undelete and copy. By default, it will run in the scan mode which simply reads an NTFS volume and looks for the files that have been deleted.



To use ntfsundelete, you'll have to install the ntfsprogs suite with following command in ubuntu and debian-based distros:

samar@Techgaun:~$ sudo apt-get install ntfsprogs

You'll have to first figure out which drive you want to recover. A handy command for this is:

samar@Techgaun:~$ sudo fdisk -l

Once you know the NTFS volume you want to recover, you can first run the scan mode to list the filenames that can be recovered.

samar@Techgaun:~$ sudo ntfsundelete /dev/sda4

The optional -f switch can be specified for the forceful scanning. There is a nice percentage field which gives the information on how much of the file can be recovered. You can apply the time and percentage filters to scan specific files. For example, you can use the following command to search for the files which can be recovered 100%

samar@Techgaun:~$ sudo ntfsundelete -p 100 /dev/sda4

And, you can apply the time filter to list the files altered/deleted after the specified time. For example, following command will scan and list the files deleted in the last 14 days.

samar@Techgaun:~$ sudo ntfsundelete -p 100 -t 2d /dev/sda4

Other suffices you can use are d, w, m, y for days, weeks, months or years ago respectively.

Once you get the files to be recovered, you can use the -u switch to undelete or recover the files. An example of recovering files by pattern matching is as below:

samar@Techgaun:~$ sudo ntfsundelete -u -m *.jpg /dev/sda4

Similarly you can recover by providing inode or inodes range using the -i switch. You can get the inode values from the first column in the scan mode.

samar@Techgaun:~$ sudo ntfsundelete -u -i 161922 /dev/sda4

Read more...

Accelerate Download Speed In Linux Using Axel

Axel is a lightweight command line download accelerator for linux. Axel is a program that downloads a file from a FTP or HTTP server through multiple connection, each connection downloads its own part of the file.

Unlike most other programs, Axel downloads all the data directly to the destination file, using one single thread. It just saves some time at the end because the program doesn't have to concatenate all the downloaded parts.

Axel tries to accelerate downloads by using multiple connections (possibly to multiple servers) for one download. Because of its size, it might be very useful on bootdisks or other small systems as a wget replacement.

One useful implementation of axel is in the apt-fast tool, a fusion of apt-get and axel to accelerate downloads of packages.

Installation under ubuntu and other debian distros: Open the terminal and type:

sudo apt-get install axel

Similarly, a graphical frontend axel-kapt is also available for download for GUI lovers. Also, flashgot plugin for firefox lets you make use of axel to download files. I should say, axel is a small yet good download accelerator for linux systems.


Read more...

How To Mount Folder or Filesystem Over SSh

Many times you need to interact a lot with some directory or a filesystem while working remotely on a server over SSh. Things will be way easier if you can mount the remote folder or filesystem over SSh and I am going to show how to do this thing in this very post.

SSHFS (Secure SHell FileSystem) is a file system for Linux (and other operating systems with a FUSE implementation, such as Mac OS X or FreeBSD) capable of operating on files on a remote computer using just a secure shell login on the remote computer. On the local computer where the SSHFS is mounted, the implementation makes use of the FUSE (Filesystem in Userspace) kernel module. The practical effect of this is that the end user can seamlessly interact with remote files being securely served over SSH just as if they were local files on his/her computer. On the remote computer the SFTP subsystem of SSH is used.

SSHFS can be downloaded and installed from HERE. Most linux distros have sshfs in their repositories. You can use the respective package managers to install the sshfs in the client system(i.e. your system).

Ubuntu and debian users can type the following in the terminal to install sshfs:

samar@Techgaun:~$ sudo apt-get install sshfs

Once you install sshfs, you are ready to mount the remote files and folders over SSh. The syntax for mounting the remote filesystem/folder is pretty straightforward.
The syntax is: sshfs -p SSHPort [user@]host:[dir] mountpoint

An example of mounting the remote system's /opt directory in my Desktop

samar@Techgaun:~$ sshfs -p 222 kubh@192.168.0.1:/opt/ ~/Desktop/remote/

Unmounting can be done by using the command as below:

samar@Techgaun:~$ fusermount -u ~/Desktop/remote/

I hope this counts as a useful tips for you. :)

Read more...

w3m - A Text Based Commandline Web Browser

w3m is a World Wide Web text based client. It will display hypertext markup language (HTML) documents containing links to files residing on the local system, as well as files residing on remote systems. It can display HTML tables and frames. In addition, it can be used as a "pager" in much the same manner as "more" or "less". Current versions of w3m run on Unix (Solaris, SunOS, HP-UX, Linux, FreeBSD, and EWS4800) and on Microsoft Windows 9x/NT.

Linux users can install the package from their respective repositories. Following is the example of installation in ubuntu and debian based linux.

samar@Techgaun:~$ sudo apt-get install w3m

Using the w3m browser is pretty straightforward. At start up, w3m will load any local file or remote URL specified at the command line. An example usage is as below:

samar@Techgaun:~$ w3m http://www.techgaun.com

You can see the whole list of available operation by pressing H(Shift + h) and you will know how comprehensive this seemingly simple command line browser actually is. w3m supports all kind of features we expect from a web browser such as hyperlink navigations, tabbed browsings, file I/O operations, bookmarking, and searching.

w3m can also be used as a pager and for translating HTML files. Taken directly from w3m manpage, following are the examples:

To use w3m as a pager:

samar@Techgaun:~$ ls | w3m

To use w3m to translate HTML files:

samar@Techgaun:~$ cat foo.html | w3m -T text/html

or

samar@Techgaun:~$ cat foo.html | w3m -dump -T text/html >foo.txt

Read more...

nmbscan - Network Shares Scanner Based On NMB/SMB/NetBIOS Protocol

NMB Scanner scans the shares of a NetBIOS/SMB network, using the NMB/SMB/NetBIOS protocols. It is useful for acquiring information on a local area network for such purposes as security auditing.

It can obtain such information as NMB/SMB/NetBIOS/Windows hostname, IP address, IP hostname, ethernet MAC address, Windows username, NMB/SMB/NetBIOS/Windows domain name, and master browser. It can discover all the NMB/SMB/NetBIOS/Windows hosts on a local area network by using the hosts lists maintained by master browsers.

You can download the version 1.2.6 of nmbscan tool from HERE.

After downloading, extract the files by typing:

mkdir nmbscan && tar -xvf nmbscan-1.2.6.tar.gz --directory nmbscan

Running nmbscan shows pretty much of information about the usage.

samar@Techgaun:~/Downloads/nmbscan$ ./nmbscan 
nmbscan version 1.2.6 - Techgaun - Sat Mar 31 00:04:15 NPT 2012

usage :
 ./nmbscan -L
  -L show licence agreement (GPL)

 ./nmbscan {-d|-m|-a}
  -d show all domains
  -m show all domains with master browsers
  -a show all domains, master browsers, and hosts

 ./nmbscan {-h|-n} host1 [host2 [...]]
  -h show information on hosts, known by ip name/address
  -n show information on hosts, known by nmb name

You can figure out the command line switches as per your necessity while using the tool. I hope this tool counts as useful for you. :)


Read more...

Determine Directory Size From Terminal In Linux [How To]

Sometimes you are working on command line and you want to find the total size of any directory. An instance is while working over SSh. Here is a technique on how you can determine the size of any directory from terminal.

du command lets us estimate the file space usage and can be recursively used for directories as well. This command can also be useful if you want to find the folder sizes of each subdirectories in any specified directory, something that would have been hard to achieve from the GUI.

To find the total size of a directory, use the -sch switch as below:

samar@Techgaun:~/Desktop/samar$ du -sch directory_name

The screenshot below will help you understand more clearly:

If you would like to see some more details like the size of each subdirectory, use the -hc switch as below:

samar@Techgaun:~/Desktop/samar$ du -hc directory_name

Check the screenshot below:

The du command provides more advanced stuffs such as exclusions of files and directories and depths for determining size. I hope this helps you. :)


Read more...