FTP

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FTP (or File Transfer Protocol) is a protocol that allows you to transfer files from a server to a client and vice versa (as FTP uses a client-server architecture). FTP is among the oldest protocols as its origins can be traced as far back as 1971 (more on Wikipedia).

There are also varients of FTP. Such include SFTP (SSH FTP, not to be confused with Simple FTP), FTPS (FTP SSL), and others. SFTP, as the name implies, is done over SSH. FTPS is plain FTP with TLS/SSL encryption.

Alpine Linux has various FTP clients and servers that you can install and use:

  • vsftpd (server)
  • ncftp (client)
  • lftpd (client, but see below for more details).
  • You can also use pcmanfm with the gvfs plugin as a graphical FTP client.

There are also plenty of other clients available too. However, we will only be covering the clients and servers mentioned above.

FTP Server: vsftpd

In Alpine Linux the default FTP server is vsftpd. However, it is not very used due common hosting panels does not handle it's configurations management. In constrast vsftpd are secured respect rest of others without so much updates.

FTP server: About vsftpd package

It was the most secured FTP server. It is the default FTP server in NimbleX, Slackware, and many others.

Note: As for minimal FTP's and fast server purposes are very recommended due it easy configuration process and perfect performance without much configuration.
Feature Value/Name Observations
Package name vsftpd apk add vsftpd
Manpages and DOCs packages vsftpd-doc apk add vsftpd-doc
Configuration file /etc/vsftpd/vsftpd.conf It's not close to alpine, just vanilla provived!
Default path for files /var/lib/ftp cos anonnimous are default, is home for daemon user
Log files (error, access, etc) /var/log/vsftpd.log Defined in vsftp.conf also
User running the service vsftpd Others Linux used "ftp" alpine has as a group
Group to common to vsftpd Used to share things among others daemons or services, like Redis or Apache files
Written in C Main engine code in C

Important Limitations

vsftp does not support SFTP, but it does have support for FTPS.

Install vsftpd

The installation does not work out of the box, cos enable by default anonymous access is enabled and it only works with IPv4 only.

Per user ftp files can be supported by special directive in the vsftp.conf file using user_sub_token to something like /home/$USER/public_ftp directory by example if we enable it (process are described below in further section "vsftpd configuration".

vsftpd is available in the Alpine Linux repositories. To install and run vsftpd, simply run the commands below:


apk add vsftpd

rc-update add vsftpd default

rc-service vsftpd restart

vsftpd Configuration

By default, Alpine's vsftpd package does not provide any special configuration, just vanilla provided so we must specify what we want!

Configurations depends of the purpose of the FTP nature to serve, the most common cases are anonymously ftp service, user system ftp service and virtual users ftp service..

For production purposes the Production FTP virtual users: vsftpd + MySQL wiki page will explain in details all the needs for a virtual users case, there's the Production FTP user service: vsftpd wiki page with futher information to use with system users and lets encrypt certificates.

Due to the minimalism of alpine linux, unfortunately the vsftpd packaging only provided vanilla configurations not close to alpine or easy admin maintenance, see the Production VSFTP system: vsftpd + MySQL + SFTP wiki page to goin in deep about configuring lighttpd web server.

Controlling vsftpd

Start vsftpd: After the installation vsftpd is not running. As we said in first section, was started already but if you want to start vsftpd manually use:

rc-service vsftpd start

You will get a feedback about the status.

 * Caching service dependencies ...                           [ ok ]
 * Starting vsftpd...                                         [ ok ]

Stop vsftpd: If you want to stop the web server use stop in the same way of previous command:

rc-service vsftpd stop

Restart lighttpd: After changing the configuration file lighttpd needs to be restarted.

rc-service vsftpd restart

Proper Runlevel: By default no services are added to start process, sysadmin must know what we want and what will services do, also other main reason are due in dockers there's no runlevels per se and Alpine linux are mostly used in dockers containers. You must added the servide only to the default runlevel, not to boot, because need networking activated

rc-update add vsftpd default


Testing vsftpd

This section is assuming that vsftpd is running. Well, at the moment there is no user ftp allowed available but the server is up and running.

nc -zv 127.0.0.1 21

Note that we used "127.0.0.1" if you are using alpine as the only machine for all as your main desktop/pc/machine.

If you are using alpine remotely as web server and just install it the package, change 127.0.0.1 with IP of the alpine machine. The "webserveripaddres" are the IP address of your setup/server machine.

The common response will be OPEN if server are running.

See also about vsftpd

FTP clients

As FTP uses a client-server architecture, you will need an FTP client if you want to interact with an FTP server. Alpine Linux provides two packages for command line and batch processing of FTP protocol, apart of the firefox package: the lftp and the ncftp packages.

So then, commonly a web browser (firefox) supports FTP protocol so our FTP server just configured can be browsed using the address ftp://<webserveripaddres> The "webserveripaddres" are the ip address of your setup/server machine.

lftp

LFTP is a sophisticated file transfer program that supports a number of network protocols. Such include FTP, HTTP, SFTP, FISH, and BitTorrent (and potentially more).

lftp has the following features:

  • Has job control and..
  • uses the readline library for input.
  • It has bookmarks,
  • Has built-in mirror command
  • Can transfer several files in parallel.
Feature Value/Name Notes
Main package name lftp Install: apk add lftp
Manpages and DOCs packages vsftpd-doc Install: apk add lftp-doc
Configuration file (system) /etc/lftp.conf This is just a default configuration file (no Alpine customizations).
Configuration file (user) ~/.lftprc The first user configuration file to read from.
Configuration file (user) ~/.lftp/rc Second user configuration file to read from (if there's a problem with the first one).
Written in C Main engine code in C

Installing lftp

To install lftp, run the following command:


apk add lftp

lftp has been provided in the main repository since Alpine 3.6, so it's a supported package that's ready for production use.

Configuring lftp

The main configuration file, /etc/lftp.conf comes with various examples and comments. On startup, lftp reads /etc/lftp.conf, ~/.lftprc, and ~/.lftp/rc (in the specified order). You can use those files to set system-wide and user-specific settings.

In your configuration file, simply use the command set followed by the name of the setting, followed by its value. Use on/off for boolean values. Check this example:


set ftp:ssl-force on
set ssl:verify-certificate on
set ftp:use-feat off
set ftp:ssl-protect-data on

You can set specific settings for specific servers only. Simply append a slash (/) and the server name to the setting.


set ftp:use-feat off /example.com
set ftp:ssl-force on /example.com

Note: The closure for `dns:', `net:', `ftp:', `http:', `hftp:' domain variables is currently just the host name as you specify it in the `open' command (with some exceptions where closure is meaningless, e.g. dns:cache-size). For some `cmd:' domain variables the closure is current URL without path. For other variables it is not currently used. See examples in the sample lftp.conf.

General lftp usage examples

By default, lftp is silent about the operations it performs in the background. If you need some more output, e.g. for debugging purposes, you can use the 'debug' command (without the 'set' command):

  • debug 5 will display the full debug output.
  • debug 3 will only display greeting messages and error messages.

Note that if you use the -d switch from the command line, the debug setting will be overruled and the full debug output will be displayed.

If you prefer some commands to be called by another name, you can set aliases:


alias dir ls
alias less more
alias zless zmore
alias bzless bzmore
alias reconnect "close; cache flush; cd ."
alias edit "eval -f "get $0 -o ~/.lftp/edit.tmp.$$ && shell \\"cp -p ~/.lftp/edit.tmp.$$ ~/.lftp/edit.tmp.$$.orig && vim ~/.lftp/edit.tmp.$$ && test ~/.lftp/edit.tmp.$$ -nt ~/.lftp/edit.tmp.$$.orig\\" && put ~/.lftp/edit.tmp.$$ -o $0; shell rm -f ~/.lftp/edit.tmp.$$*"

The last alias (edit) should be all in one line. It allows you to get a remote file, edit it with vim (change as needed), and place the edited file back on the server. This is very convenient!

  • Example usage

Below is an example of a mult-part download over the SFTP protocol:

$ lftp -e 'pget -c -n 5 /path/to/file' sftp://username@server

short explanation:

  • -e: lftp option to execute command
  • pget: is the command for partial download
  • -c: pget option to resume
  • -n: pget option for number of parts

PCManFM with GVfs

While PCManFM is a filemanager, by using the gvfs plugin, we can use PCManFM as a graphical FTP client. To use PCManFM as an FTP client, you can do the following:

  1. From the menubar open the "go" menu
  2. Choose "Connect to a server"
  3. Choose the FTP protocol and input username (path is optional)
  4. After a while you will input the password

Check the picture for further reference:

Ftp-gui-pcmanfm at 2020-09-11 14-13-03.png

See Also

link