Linux File-Sharing Services

You can share files from a Linux computer in many ways. Generally, you configure a server and then share files through a directory. The four major types of Linux sharing servers are FTP, NFS, Samba, and Apache. If you ve enabled NIS, it also shares configuration files. While there are graphical configuration tools available for each of these services, they all can be set up from the command-line interface as well, and they each include regular text commands for the client and server. For detailed information on these services, see Chapters 27 “ 30 .

FTP Servers

The basic FTP commands are covered in detail in Chapter 27 . This section summarizes associated commands and configuration files.. While the Red Hat Linux 9 Installation CD now includes only vsFTP, WU-FTP is a popular option also available in RPM format. The vsFTP server comes highly recommended; Red Hat uses it on its own FTP servers.

vsFTP Commands and Configuration Files

The vsFTP package includes its own set of configuration files. It is simpler than alternative servers such as WU-FTP; the only command you need is the vsftpd daemon. The vsFTP server is now a regular service in the /etc/rc.d/init.d directory; it is no longer an xinetd service. If both servers are installed, be sure to activate only one at a time. The vsFTP configuration files are shown in Table A.29.

Table A.29: vsFTP Configuration Files

File	Description
/etc/vsftpd.conf	The primary configuration file.
/etc/vsftpd.ftpusers	A list of users not allowed to log in; should include service-level users such as news, bin, and mail, as well as root.
/etc/vsftpd.user_list	A list of allowed or denied users, depending on the userlist_deny variable in /etc/vsftpd.conf .

WU-FTP Commands and Configuration Files

One major alternative to vsFTP is WU-FTP, which you can download through the home page of their development group at www.wu- ftpd .org or the resource center at www.landfield.com/wu-ftpd/ . The commands shown in Table A.30 are available to help you manage a WU-FTP server. Remember, WU-FTP is an xinetd service that you also need to activate through the wu-ftpd file in the /etc/ xinted.d directory. Alternatively, you can use chkconfig to activate this service.

Table A.30: WU-FTP Commands

Command	Description
ckconfig	Checks the integrity of the configuration files.
ftpcount	Lists the number of connections.
ftpwho	Lists connected users and origin IP addresses.
ftprestart	Stops and restarts an FTP server.
ftpshut	Allows you to shut down an FTP server now or at a specified time.
in.ftpd	Starts the FTP server daemon.
in.wuftpd	Starts the WU-FTP server.
privatepw	Adds and deletes FTP groups from /etc/ftpgroups; these groups need to correspond to a real group in /etc/group .

The WU-FTP server also has a group of configuration files, as shown in Table A.31. You might recall from Chapter 27 that the functionality of some of these files is now part of /etc/ftpaccess .

Table A.31: WU-FTP Configuration Files

File	Functionality
/etc/ftpaccess	Opens the basic WU-FTP configuration file.
/etc/ftpconversions	Lists commands that are run automatically during FTP uploads or downloads.
/etc/ftpgroups	Defines special groups with a specific password, defined through the privatepw command.
/etc/ftphosts	Allows or denies access to a specific user account.
/etc/ftpusers	Allows or denies access to specific users.

FTP Client

There are a number of FTP clients available; all that I ve seen are front-ends to the FTP text client. The list of available FTP client commands is quite varied. The more important commands were addressed in Chapter 27 . A fuller list follows in Table A.32. This is just a basic list, without options. You can get more information from the ftp > prompt by entering help command .

Table A.32: FTP Client Commands

Command	Description
!	Escapes to the shell; the !ls -l command gives you a full list of files in the current local directory.
$	Executes a macro.
append	Appends a file to another file; e.g., the append local remote command adds the contents of the local file to the remote file.
ascii	Sets file transfer to ASCII mode.
bell	Toggles a beep when a command, such as a file transfer, is complete.
binary	Sets file transfer to binary mode.
bye	Exits the current FTP session.
cd	Changes the directory.
cdup	Moves up one directory level.
close	Closes the connection without exiting FTP.
delete	Deletes the specified file on a remote directory.
dir	Equivalent to ls “l .
exit	Closes connection and exits FTP.
get	Copies a file from the FTP server.
hash	Toggles the use of hash marks, so you can monitor the progress of a file transfer.
lcd	Changes the working directory on the local computer.
ls	Equivalent to ls -l in the bash shell.
mdelete	Deletes multiple files.
mdir	Takes the contents of a remote directory and outputs them to a local file.
mget	Copies multiple files from the FTP server.
mkdir	Creates a new directory on the FTP server.
mput	Sends multiple files to the FTP server.
newer	Uses the get command if the remote file is newer.
open	From the FTP prompt, connects to a remote FTP server.
put	Copies a file to the FTP server.
pwd	Lists the working directory on the FTP server.
quit	Exits the FTP shell.
rename	Renames a file on the FTP server.
rmdir	Removes a remote directory.
status	Checks the status of the connection.
system	Shows the basic system type, usually Unix.
user	Logs in as a user.

NFS Commands

The Network File System (NFS) is used to share directories between Linux and Unix computers. The basic configuration process is described in detail in Chapter 28 ; Table A.33 summarizes some important commands.

Table A.33: NFS Commands

Command	Description
exportfs	Exports and maintains the list of available NFS directories, based on /etc/exports .
nfsstat	Returns information on shared NFS directories; the output from this command is a good place to look for connection problems.
nhfsstone	Tests the load on an NFS server.
rpc. mountd	Starts the NFS mount daemon, the service that actually checks mount requests against what s allowed in /etc/exports .
nhfsrun	Tests program; runs nhfsstone with a range of demands on the server.
showmount	Shows available directories from an NFS server.

NIS Commands

The Network Information System (NIS) allows you to set up a single database of key configuration files such as /etc/passwd in a LAN of Linux and Unix computers. The basic configuration process is described in detail in Chapter 28 ; the important commands are summarized in Table A.34. Many key NIS commands are in an unusual directory, /usr/lib/yp . If you use NIS, you might consider adding that directory to your PATH with the PATH=$PATH:/usr/lib/yp command.

Table A.34: NIS Commands

Command	Description
create_printcap	Processes an LPD file such as /etc/printcap to an NIS database map; does not process a CUPS printer configuration file.
makedbm	Creates an NIS database file.
match_printcap	Works with the printcap_path in /etc/lpd.conf; does not process a CUPS printer configuration file.
mknetid	Generates an NIS database map from key configuration files: /etc/passwd , /etc/group , and /etc/ hosts .
pwupdate	Updates the NIS database map for regular and shadow passwords.
revnetgroup	Generates reverse NIS netgroup data.
ypcat	Reads files from an NIS server database.
ypchfn	Changes a user s finger information in the NIS database.
ypchsh	Changes a user s default shell in the NIS database.
ypinit	Builds a database for a master or slave NIS server.
ypmatch	Searches for a user in the NIS database.
yppasswd	Changes a password in the NIS database.
yppush	Replicates an NIS master database to an NIS slave server.
ypxfr	Copies an NIS database; common for NIS slave servers.

Samba Commands

Samba lets you configure Linux to connect and share directories with Microsoft Windows computers. Linux and Unix computers can also use Samba to share directories with each other.

As discussed in Chapter 29 , you could use the SWAT utility to configure Samba. SWAT is certainly a rich and detailed tool. But remember, like other GUI tools, it is just a front end to a group of commands. There are a substantial number of Samba commands ”some related to the server, others used commonly by Samba clients.

Samba Server Commands

When you configure a Samba server, you re sharing directories and printers in a format compatible with Microsoft Windows. Important Samba server commands are shown in Table A.35.

Table A.35: Samba Server Commands

Command	Description
make_unicodemap	Specifies a translation ”from DOS or Unix text to 16-bit Unicode.
mksmbpasswd.sh	Starts a script that directly edits the SMB password file, /etc/samba/smbpasswd .
smbadduser	Sets up a database entry between a Linux user and a Microsoft Windows user; prompts for a password and enters the result in /etc/ smbusers and /etc/smbpasswd .
smbcontrol	Allows you to send messages to an SMB server, such as debug, elections , and ping messages.
smbpasswd	Changes a user s Samba password; can apply to local or remote Samba servers.
smbstatus	Displays the status of connections to the local SMB server.
testparm	Checks the syntax of smb.conf .
testprns	Checks a proposed Samba share name for a printer.
winbindd	Starts the name service daemon for Microsoft Windows “style server names .

Samba Client Commands

When you configure a Samba client, you re using commands on a Linux or Unix computer to connect to a shared Samba or Microsoft Windows directory. Important Samba client commands are shown in Table A.36.

Table A.36: Samba Client Commands

Command	Description
mount.smb	Allows you to use the mount command as a front end to connect to a shared Samba directory.
nmblookup	Searches for the IP address associated with a NetBIOS name.
rpcclient	Permits connections to remote procedure calls on a Microsoft Windows server.
smbcacls	Allows you to view and set the Access Control List on a Microsoft Windows server.
smbclient	Lets you connect directly to a Samba server, with an FTP-style interface.
smbmount	Mounts a Samba filesystem; you can use the mount command as a front end to this command.
smbprint	Sends a print job to a shared printer on a Samba server.
smbumount	Unmounts a shared Samba directory.

Apache Commands

Apache is the most popular web server on the Internet, as well as the default web server for Red Hat Linux. As discussed in Chapter 30 , the standard way to configure Apache is by editing the /etc/httpd/conf/httpd.conf configuration file. Commands are available to help you work with whatever Apache configuration you use. Some of the more important ones are listed in Table A.37.

Table A.37: Apache Commands

Command	Description
ab	A tool for testing the performance of your Apache server.
apachectl	A control script for your Apache server.
htdbm	A new Apache 2.0 tool for managing authorized user/password databases.
htdigest	A tool that creates an authentication database of users and passwords.
htpasswd	A tool that allows you to set up individual users and passwords for your web server.
httpd	The Apache daemon; httpd -t tests the syntax of your httpd.conf configuration file.
logresolve	A tool that performs a reverse name lookup for Apache log files, so you know the computers or domains that are connecting to your server.
rotatelogs	A tool that rotates Apache log files automatically; otherwise , to use the standard logrotate job, which is governed by cron , you d have to stop the Apache server.