Recovering corrupted gzip files. gzip: compressed_file.gz: unexpected end of file

A tool to recover gzip corrupted compressed files is gzrecover. This comes with in the recovery toolkit package gzrt.

$gzip -d compressed_file.gz
gzip: compressed_file.gz: unexpected end of file

$file compressed_file.gz
compressed_file.gz: gzip compressed data, from Unix

$gzrecover compressed_file.gz
$ls compressed_file*
compressed_file.gz compressed_file.recovered

ssh tunnels set up and port forwarding

SSH tunnels allow you to forward a local TCP port to a remote machine and vice versa. The tunnel option is available in many ssh clients. I will give the example here on how to create SSH tunnels with putty and the openssh-client.
I will consider in the below that we want to access the SERVER on port 80 (http server).

Scenario 1. SSH tunnel setup with local port forwarding.

The SSH tunnel is shown with the red arrow. In order to access the SERVER through the ssh tunnel the connection will have to be made on the CLIENT's local forwarded port (2000 in the example). The traffic between the CLIENT and SSH-HELPER is encrypted by ssh, the traffic between the SSH-HELPER and the SERVER is not encrypted.

SSH tunnel  is set up on the CLIENT:

openssh-client:

ssh -L *:2000:server:80 ssh-helper

The '*' before the local port to be forwarded 2000 denotes that the port 2000 should be listening on all available interfaces on the client. This goes according to the openssh-client configuration.

putty:

The tunnel configuration is done under Connection - SSH - Tunnels. Source port is the local port, destination is where the connection will be forwarded after exiting the SSH tunnel.
After you specify source port and destination, you need to click "Add" for the configuration to take effect.
If you want to access the remote server from other hosts, make sure you check the box  "Local ports accept connections from other hosts", otherwise the port 2000 will be opened only for the loopback address (127.0.0.1)

Linux gnome add menu and desktop entry for applications

Users can create shortcuts for an application to appear in menus, desktop,  etc. by creating a .desktop file. This desktop file contains a listings of configuration for the application. In order for your desktop environment to "see" this file, this .desktop file will have to be placed either in /usr/share/applications - for system wide applications - or in ~/.local/share/applications - if the application should be available for a single user

Once the file is placed in this location the desktop uses this file to:

• put the application in the Main Menu. 
• list the application in the Run Application... dialog
• create appropriate launchers in the menu or on the desktop.
• associate the name and description of the application.
• use the appropriate icon.
• recognize the MIME types it supports for opening files.

Here's an example of a desktop file I have created for tinyCA application. I am running Debian Jessie and this application does not come with a any menu entries or desktop shortcut.

$ cat ~/.local/share/applications/tinyca2.desktop

[Desktop Entry]
Version=1.0
Type=Application
Name=TinyCA Certificate Authority
NoDisplay=false
Categories=Network;
Icon=security-low
Exec=/usr/bin/tinyca2
Terminal=false
Comment=TinyCA2 certificate authority

The entries one by one:

[Desktop Entry] - identifies the group name to which the desktop entry belongs. A group is name is enclosed in [ ] and there can be more than one group in a desktop file. [Desktop Entry] group is required by the basic desktop file entry

Version - version of the desktop entry specification. This field is not required

Connect Evolution email client to Exchange office365 server

Evolution is a personal information management application that provides integrated mail, calendaring and address book functionality.

To connect to office365 exchange you will need the evolution program and the evolution-ews plugin.

Installation:

% sudo apt-get install evolution evolution-ews

Account setup:

1. Obtain the information about your domain's office365 servers.

To find the exchange web services URL based on the verified answer on this office365 post:
-Logon to your e-mail account using Outlook Web App (OWA).

-Click Options > See All Options > Account > My Account > Settings for POP, IMAP, and SMTP access.

-In the list of entries, locate the server name. And the URL of exchange web service for your mailbox is the URL: "https://" + "Server name" + "/EWS/Exchange.amsx".

So, in my case the Exchange Web Services URL is https://outlook.office365.com/EWS/Exchange.asmx

2. In the evolution wizard enter the details.