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OpenSuSE 11.1 Quick Start Guide
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11.4 Copying Files between Linux Computers

Linux offers a rich set of protocols you can use to copy files between computers. Which protocol you use depends on how much effort you want to invest and whether you need to be compatible with future Windows installations. The following sections feature various methods to transfer files from and to Linux computers. Make sure that you have a working network connection, because otherwise they will not work. All scenarios rely on working name resolution in the network. If your network does not include a name service, use IP addresses directly or add the IP addresses along with respective hostnames to /etc/hosts on all clients.

The following example IP addresses and hostnames are used across this section:

Target Hostname

jupiter.example.com

Target IP

192.168.2.100

Source Hostname

venus.example.com

Source IP

192.168.2.101

User

tux

11.4.1 Copying Files with SSH

The following requirements must be met on both computers that are accessed via SSH:

  1. If you use a hostname, make sure each hostname is listed in /etc/hosts on both computers (see /etc/hosts, (↑ Reference ).) If you use SSH with IP addresses, you do not need to change anything.

  2. If you use a firewall, open the SSH port. To do so, start YaST, and select Security and Users > Firewall. Go to Allowed Services and check whether SSH is displayed as part of the list. If this is not the case, select SSH from Service to Allow and click Add. Apply your changes and leave YaST with Next and Finish.

To copy files from one computer to another, you need to know where the files are located. For example, to copy a single file /srv/foo_file from computer jupiter.example.com to the current directory, use the following scp command (the dot represents the current directory as the copy target location):

scp [email protected]:/srv/foo_file .

To copy a whole directory structure, use the recursive mode of scp:

scp -r [email protected]:/srv/foo_directory .

If your network does not provide name resolution, use the server's IP address directly:

scp [email protected]:/srv/foo_file .

If you do not know exactly where your files are, use the sftp command. Copying files in KDE or GNOME with SFTP is very simple. Proceed as follows:

  1. Press Alt+F2.

  2. Enter the following at the address prompt:

    sftp://[email protected]
  3. Enter the password of tux on jupiter.example.com.

  4. Drag and drop the desired files or directories to your desktop or a local directory.

KDE provides another protocol called fish that can be used if sftp is not available. The use of this protocol is similar to sftp. Just replace the sftp protocol prefix of the URL with fish:

fish://[email protected]

11.4.2 Transferring Files with rsync

Before using rsync to synchronize files and directories between different computers, make sure that the following requirements are met:

  1. The package rsync is installed.

  2. Identical users are available on both systems.

  3. Enough disk space is available on the server.

  4. If you want to benefit from rsync's full potential, make sure that rsyncd is installed on the system to use as the server.

rsync is useful for archiving or copying data and can also be used as a daemon to provide directories to the network (see Advanced Setup for rsync Synchronization).

rsync Basic Mode

The basic mode of operation of rsync does not require any special configuration. rsync mirrors complete directories onto another system. Its usage is not much different from a regular copying tool, such as scp. The following command creates a backup of the home directory of tux on a backup server called jupiter:

rsync -Hbaz -e ssh /home/tux/ [email protected]:backup

Use the following command to restore your backup:

rsync -Haz -e ssh [email protected]:backup /home/tux/

rsync Daemon Mode

Start the rsyncd daemon on one of your systems to make use of the full functionality of rsync. In this mode, it is possible to create synchronization points (modules) that can be accessed without an account. To use the rsyncd daemon, proceed as follows:

Advanced Setup for rsync Synchronization

  1. Log in as root and install the rsync package.

  2. Configure your synchronization points in /etc/rsyncd.conf. Add a point with its name in brackets and add the path keyword like in the following example:

    						
    [FTP]
      path = /srv/ftp
     comment = An Example
  3. Start the rsyncd daemon as root with rcrsyncd start. To start the rsync service automatically during each system boot, run insserv rsyncd.

  4. List all files located in the /srv/ftp directory (note the double colon):

    rsync -avz jupiter::FTP
  5. Initiate the transfer by providing a target directory (in this example, the current directory is represented by a dot):

    rsync -avz jupiter::FTP .

By default, files are not deleted while synchronizing with rsync. To force file deletion, add the --delete option. To make sure that --delete does not accidentally remove newer files, use the --update option instead. Any conflicts that arise must be resolved manually.

11.4.3 Transferring Files with Unison

Before using Unison to synchronize files and directories between different computers, make sure that the following requirements are met:

  1. The package unison is installed.

  2. Enough disk space is available on your local and remote computer.

  3. If you want to benefit from Unison's full potential, make sure that Unison is also installed and running on the remote computer.

In case you need help, run Unison with the -doc topics option to get a full list of available sections.

For permanent settings, Unison allows to create profiles that specify Unison preferences such as the directories (roots) to synchronize, which types of files to ignore, and other options. The profiles are stored as text files in ~/.unison with the file extension *.prf.

Using the GUI

To synchronize different directories with Unison's GUI, proceed as follows:

  1. Start Unison by pressing Alt+F2 and entering unison.

  2. If you run Unison for the first time and without any further option, you are prompted for a source directory. Enter the source directory you want to synchronize and click OK.

  3. Enter the target directory. It can be either local or remote. If you want to synchronize to a remote directory, choose the method (SSH, RSH or Socket) and enter the hostname and an optional user.

  4. If you have not synchronized these two directories before, a warning dialog appears, informing you that Unison will now compare the contents of those directories. Close the warning with OK and wait until Unison has collected the information from both directories and displays the differences in the main window.

    The left column shows the source directory you have selected, the third column shows the target directory. If there are differences between the directories, the Action column shows a symbol, proposing an action. A green arrow indicates that a file has been modified, added or deleted in the source or the target directory. The direction of the arrow indicates the direction that the change would be propagated if you performed the synchronization now. A question mark indicates a conflict (both files have been changed and Unison cannot decide which one to overwrite).

    Figure 11-1 File Synchronization Proposal

  5. To modify the proposals Unison shows for each file (for example, if you want to change the direction), select the file and click Right to Left or Left to Right. With Skip, exclude a file from synchronization. The symbol in the Action column changes accordingly.

  6. To start the synchronization, click Go.

The next time you start Unison, a dialog box shows the existing profiles, each specifying a pair of directories to be synchronized. Select a profile or create a new profile (for another pair of directories) and perform the synchronization as described above.

Using the Command Line

Unison can also be operated through the command line. To synchronize a local directory to a remote computer, proceed as follows:

  1. Open a shell and enter the following command:

    unison -ui text DIR
             ssh://[email protected]//PATH

    Replace the placeholders with the respective values.

  2. Unison asks you what to do with your files and directories, for example:

    local                  jupiter
               <----  new file   dir [f]
  3. Press F if you want to follow Unison's recommendation. For other commands, press ?.

  4. Proceed with y, if you want to propagate your updates.

11.4.4 Copying Files with FTP

Before configuring your FTP server, make sure that the following requirements are met:

  1. The package vsftp is installed.

  2. You have root access to your FTP server.

  3. Enough disk space is available on your computer.

WARNING: For Home Networks Only

This setup is suited for use in home networks only. Do not deploy it to sites unprotected by firewalls and do not enable world wide access.

To configure an FTP server, proceed as follows:

  1. Prepare the FTP server:

    1. Open a shell, log in as root, and save a backup copy of /etc/vsftpd.conf:

      cp /etc/vsftpd.conf /etc/vsftpd.conf.bak
    2. Create an access point for anonymous FTP

      mkdir ~ftp/incoming
      chown -R ftp:ftp ~ftp/incoming
  2. Replace the configuration files according to the preferred scenario (refer to the manual page of vsftpd.conf for advanced configuration options):

    Allowing Anonymous Read and Write Access
    #
    listen=YES
    									
    # Enable anonymous access to FTP server
    anonymous_enable=YES
    									
    #
    local_enable=YES
    # Enable write access
    write_enable=YES
    anon_upload_enable=YES
    anon_mkdir_write_enable=YES
    dirmessage_enable=YES
    # Write log file 
    xferlog_enable=YES
    connect_from_port_20=YES
    chown_uploads=YES
    chown_username=ftp
    ftpd_banner=Welcome to FTP service.
    anon_root=/srv/ftp
    Grant Restricted Permissions to FTP Users (Home Only)
    chroot_local_users=YES
  3. Restart the FTP server:

    rcvsftp start

On the client, just enter the URL ftp://HOST in your browser or FTP client. Replace HOST with the hostname or IP address of your server. There are many graphical user interfaces available that are suited to browsing the contents of your FTP server. For a list of them, just enter FTP at the search prompt of the YaST package manager.

OpenSuSE 11.1 Quick Start Guide
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