Welcome!

Linux Containers Authors: Elizabeth White, Christopher Keene, Liz McMillan, Pat Romanski, Kareen Kircher

Related Topics: Linux Containers

Linux Containers: Article

Alternative Ways to Download Files with Linux

A sneak peek

Fedora Core (http://fedora.redhat.com) is one of the world's most popular Linux distributions in part from support by Red Hat and a strong community of users. It also has been a proving ground for Red Hat to develop technologies that will eventually make their way into Red Hat Enterprise Linux.

Recently Red Hat has spun off the Fedora Core Project into its own organization in much the same way that the Mozilla project was spun out of Netscape back in the late 1990s. Both Fedora and Red Hat Enterprise Linux have proven to be raging successes in their own right for both Red Hat and Linux users who choose to pursue a do-it-yourself approach to Linux. For those of you looking for additional resources to learn more about these distributions, you could consider the Red Hat Fedora and Enterprise Linux 4 Bible written by Christopher Negaus.

Christopher Negus has been working with UNIX systems, the Internet, and (most recently) Linux systems for more than two decades at AT&T Bell Laboratories, UNIX System Laboratories, and Novell, helping to develop the UNIX operating system. Features from many of the UNIX projects Chris worked on at AT&T have found their way into Red Hat Enterprise Linux, Fedora, and other Linux systems. Chris has written several books on UNIX and the Internet; his latest book is the Red Hat Fedora and Enterprise Linux 4 Bible (excerpted below) and released in July 2005. It discusses the features and capabilities of both operating systems. His book is written as a resource for users trying to adopt either of these technologies.

With your Fedora Core system connected to the Internet, you can take advantage of dozens of tools for browsing the Web, downloading files, getting e-mail, and communicating live with your friends. In most cases, you have several choices of GUI and command-line applications for using Internet services from your Linux desktop or shell. However, there are some utilities you may not be familiar with like wget, scp, and sftp.

Excerpt from Chapter 9...

Getting Files with wget
If you already know where a file is on the network, there are more efficient ways of downloading that file than opening an FTP session, moving around the FTP server, and running the get command. The wget command is a simple, efficient tool for doing non-interactive downloads of files over the Internet.

If there is a file you want to download from an FTP site or Web server (HTTP), and you know exactly where the file is, wget is a good way to download. The wget command is very useful if you want to copy a whole site, recursively, from one computer to another (for example, containing user home directories). When downloading from FTP sites, wget can let you just download as the anonymous user or add your own user name and password to the command line.

Downloading a File with User Name and Password
If you are doing an FTP file copy and need to log in as a user other than anonymous, you can add that information to the command line or to a .netrc file in your home directory (type man netrc to see the format of that file). Here is an example of adding the password to the command line:

$ wget ftp://joe:[email protected]/memol.doc .

CAUTION: Adding a password to a command line leaves the password exposed to onlookers. This practice is generally discouraged, except in cases where no one can see your monitor or your history files.

In the previous example, the user logs in as joe with the password my67chevy. The wget then copies the file memo1.doc from the current directory on the host computer named ftp.handsonhistory.com. That current directory is most likely /home/joe.

Downloading a Whole Web Site
Using wget, you can download a large number of files from Web servers as well. The wget command downloads files using the http protocol, if file addresses begin with http://. Downloading a single file, you would use the same form as you would for an FTP file (for example: wget http://host/file.). The best wget option for HTTP downloads is -r (recursive).

A recursive download lets you choose a point at a Web site and download all content below that point. Here is an example of a recursive download used to download the contents of the www.example.com Web site.

$ wget -r http://www.example.com

In this example, the HTML pages, images, and other content on the www.example.com Web site are copied below the current directory in the directory www.example.com. This is useful if you want to gather the contents of a Web site but don't have login access to that site. Because content is taken by following links, if there is content in a directory at the Web site that isn't in a link, it won't be downloaded.

Downloading an entire Web site can result in a massive amount of data being downloaded. If you want only part of a Web site, start from a point lower in the site's structure. Or, as an alternative, you can limit the number levels the wget will go down the site structure. Using the -l option (l as in level), the following example gets two levels of HTML content:

$ wget -r -l 2 http://www.example.com

To mirror a site, you can use the -m option instead of -r. With wget -m http://site, it is like asking to download an infinite number of levels recursively (-r -l inf), keep current time stamps (-N), and keep FTP directory listings (-nr).

Continuing a Download
In the old days, if you were downloading a particularly large file (such as an ISO image of a CD or DVD), if the download stopped for some reason (a disconnected network or errant reboot), you needed to start all over. With wget, you can choose to restart a download and have it continue right where it left off. This has been a lifesaver for me on many occasions.

Let's say that you were downloading a 4GB DVD ISO image named mydvd.iso from the site ftp://ftp.example.com and you killed the wget process by mistake after about 3GB of download. Make sure that your current directory is the one that contains the partially downloaded ISO. Then run the same wget command you did originally, adding the -c (continue) option as follows:

$ wget -c ftp://ftp.example.com/mydvd.iso

If you had not used the -c option, in this case, a new download would have started using the file name mydvd.iso.1 to download to.

NOTE: Another command that you might be interested in, similar to wget, is the curl command. Like wget, curl can download files using the ftp or http protocols. Curl can also do multiple file transfers on the same connection.

# ssh [email protected] "tail -f /var/log/messages"
[email protected]'s password:

After you typed the password in the preceding case, the last several lines of the /var/log/messages file on the remote computer would be displayed. As messages were received, they would continue to be displayed until you decided to exit (press Ctrl+C to exit the tail command).

NOTE: Find out more about the ssh command from the SSH Web site (www.openssh.org).

Using scp for Remote File Copy
The scp command is a simple yet secure way of copying files among Linux systems. It uses the underlying ssh facility, so if ssh is enabled, so is scp. Here is an example of using scp to copy a file from one computer to another:

# scp myfile toys.linuxtoys.net:/home/chris
[email protected]'s password: ******

In this example, the file myfile is copied to the computer named toys.linuxtoys.net in the /home/chris directory. If you don't provide a user name (as is the case here), scp assumes you are using the current user name. Unlike some tools that provide remote login, scp and ssh do allow you to login as root user over the network, by default. (Many people turn off this feature for security reasons.)

To use scp with a different user name, you can append the user name with an @ character. For example, [email protected]:/home/chris would attempt to log in as the user named chris to do the file copy.

The first time you connect to a remote computer using scp or ssh, those commands try to establish the authenticity of the remote host. If it cannot establish the host's authenticity, it will display the RSA key fingerprint and ask you if you want to continue. If you type yes, scp will not question the authenticity of that computer again for subsequent scp commands.

However, if the RSA key fingerprint should change in the future for the remote computer (which will happen if, for example, the operating system is reinstalled on that computer), scp will refuse to let you connect to that remote computer. To override that refusal, you need to edit your $HOME/.ssh/known_hosts file and delete the entry for the remote computer. You can then verify the authenticity of the remote computer and continue to use scp.

The sftp command, which also communicates using secure ssh protocols, is a command for copying files from an FTP server. It is considered a more secure way of getting files from an FTP server that has an sshd server running.

.  .  . 

You can receive more helpful tips on using Fedora and Red Hat Enterprise Linux 4 in Chris's book, Red Hat Fedora and Enterprise Linux 4 Bible available at your local retailer.

More Stories By Mark R. Hinkle

Mark Hinkle is the Senior Director, Open Soure Solutions at Citrix. He also is along-time open source expert and advocate. He is a co-founder of both the Open Source Management Consortium and the Desktop Linux Consortium. He has served as Editor-in-Chief for both LinuxWorld Magazine and Enterprise Open Source Magazine. Hinkle is also the author of the book, "Windows to Linux Business Desktop Migration" (Thomson, 2006). His blog on open source, technology, and new media can be found at http://www.socializedsoftware.com.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
With so much going on in this space you could be forgiven for thinking you were always working with yesterday’s technologies. So much change, so quickly. What do you do if you have to build a solution from the ground up that is expected to live in the field for at least 5-10 years? This is the challenge we faced when we looked to refresh our existing 10-year-old custom hardware stack to measure the fullness of trash cans and compactors.
The emerging Internet of Everything creates tremendous new opportunities for customer engagement and business model innovation. However, enterprises must overcome a number of critical challenges to bring these new solutions to market. In his session at @ThingsExpo, Michael Martin, CTO/CIO at nfrastructure, outlined these key challenges and recommended approaches for overcoming them to achieve speed and agility in the design, development and implementation of Internet of Everything solutions wi...
Cloud computing is being adopted in one form or another by 94% of enterprises today. Tens of billions of new devices are being connected to The Internet of Things. And Big Data is driving this bus. An exponential increase is expected in the amount of information being processed, managed, analyzed, and acted upon by enterprise IT. This amazing is not part of some distant future - it is happening today. One report shows a 650% increase in enterprise data by 2020. Other estimates are even higher....
Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more business becomes digital the more stakeholders are interested in this data including how it relates to business. Some of these people have never used a monitoring tool before. They have a question on their mind like “How is my application doing” but no id...
SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
SYS-CON Events announced today Telecom Reseller has been named “Media Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.
Smart Cities are here to stay, but for their promise to be delivered, the data they produce must not be put in new siloes. In his session at @ThingsExpo, Mathias Herberts, Co-founder and CTO of Cityzen Data, will deep dive into best practices that will ensure a successful smart city journey.
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
There is growing need for data-driven applications and the need for digital platforms to build these apps. In his session at 19th Cloud Expo, Muddu Sudhakar, VP and GM of Security & IoT at Splunk, will cover different PaaS solutions and Big Data platforms that are available to build applications. In addition, AI and machine learning are creating new requirements that developers need in the building of next-gen apps. The next-generation digital platforms have some of the past platform needs a...
Pulzze Systems was happy to participate in such a premier event and thankful to be receiving the winning investment and global network support from G-Startup Worldwide. It is an exciting time for Pulzze to showcase the effectiveness of innovative technologies and enable them to make the world smarter and better. The reputable contest is held to identify promising startups around the globe that are assured to change the world through their innovative products and disruptive technologies. There w...
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
19th Cloud Expo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Meanwhile, 94% of enterpri...
Personalization has long been the holy grail of marketing. Simply stated, communicate the most relevant offer to the right person and you will increase sales. To achieve this, you must understand the individual. Consequently, digital marketers developed many ways to gather and leverage customer information to deliver targeted experiences. In his session at @ThingsExpo, Lou Casal, Founder and Principal Consultant at Practicala, discussed how the Internet of Things (IoT) has accelerated our abil...
I wanted to gather all of my Internet of Things (IOT) blogs into a single blog (that I could later use with my University of San Francisco (USF) Big Data “MBA” course). However as I started to pull these blogs together, I realized that my IOT discussion lacked a vision; it lacked an end point towards which an organization could drive their IOT envisioning, proof of value, app dev, data engineering and data science efforts. And I think that the IOT end point is really quite simple…
Identity is in everything and customers are looking to their providers to ensure the security of their identities, transactions and data. With the increased reliance on cloud-based services, service providers must build security and trust into their offerings, adding value to customers and improving the user experience. Making identity, security and privacy easy for customers provides a unique advantage over the competition.
Is the ongoing quest for agility in the data center forcing you to evaluate how to be a part of infrastructure automation efforts? As organizations evolve toward bimodal IT operations, they are embracing new service delivery models and leveraging virtualization to increase infrastructure agility. Therefore, the network must evolve in parallel to become equally agile. Read this essential piece of Gartner research for recommendations on achieving greater agility.
SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
For basic one-to-one voice or video calling solutions, WebRTC has proven to be a very powerful technology. Although WebRTC’s core functionality is to provide secure, real-time p2p media streaming, leveraging native platform features and server-side components brings up new communication capabilities for web and native mobile applications, allowing for advanced multi-user use cases such as video broadcasting, conferencing, and media recording.