کد:
Quick HOWTO : Ch16 : Telnet, TFTP, and xinetd - Linux Home Networking
Many networking equipment manufacturers allow you to backup live configurations of their devices to centralized servers via the TFTP protocol. TFTP can be used with great versatility as a network management tool and not just for saving files. TFTP servers can be used to upload new configurations to replacement devices after serious hardware failures. They also can be used for uploading new versions of software to be run as network devices. Finally, they can be used to upload even partial configurations such as files containing updated access control lists (ACLs) that restrict access to networks and even the regular application of new passwords.
TFTP may not be an application used regularly in a home, but it will become increasingly important in an expanding small office/home office (SOHO) environment which is why the topic is covered here. The provided TFTP examples use equipment from Cisco Systems, a leading networking hardware manufacturer.
Installing The TFTP Server Software
Most Linux software products are available in a precompiled package format. Downloading and installing packages isn't hard. If you need a refresher, Chapter 6, "
Installing Linux Software", covers how to do this in detail.
When searching for the Fedora / Redhat file, remember that the TFTP server RPM's filename usually starts with the word "tftp-server" followed by a version number like this: tftp-server-0.33-3.i386.rpm.
With Debian / Ubuntu, the commonly use HPA TFTP server package would have a "tftp-hpa" prefix like this: tftpd-hpa_0.40-4.1ubuntu1_i386.deb.
Configuring The TFTP Server
The procedure to set up a TFTP Server is straightforward, but it is different between the Redhat and Debian distributions as we will soon see.
Redhat / Fedora
By default, the TFTP application expects files to be located in the /tftpboot directory. You can change this setting in the /etc/xinetd.d/tftp file via the server_args option. It is usually best to place the TFTP files in a partition other than the root partition. TFTP files of increasing size could eventually fill the partition affecting your ability to install new software or even the overall performance of your system. Creating a symbolic link for /tftpboot to another directory will not work with all versions of Fedora.
This example creates a new tftpboot directory in the /var partition, and then configures TFTP to be enabled while using the new directory.
کد:
[root@bigboy tmp]# mv /tftpboot /var[root@bigboy tmp]# vi /etc/xinetd.d/tftp## File /etc/xinetd.d/tftp#service tftp{...... server_args = -s /var/tftpboot disable = no}
You must then restart xinetd for the new configuration to take effect.
کد:
[root@bigboy tmp]# chkconfig tftp on
Debian / Ubuntu
With the Debian / Ubuntu distributions, the TFTP server configuration file is /etc/default/tftpd-hpa and by default it instructs the TFTP daemon to use the /var/lib/tftpboot directory to store its files. Also by default, the daemon is disabled.
Another thing to remember is that the tftpd-hpa server daemon runs independently of xinetd and has its own startup script in the /etc/init.d directory. By default, the daemon is started at boot time, but the configuration file's default configuration setting disables it by forcing the daemon to exit prematurely.
This example enables the daemon in the configuration file and then starts the TFTP server:
کد:
root@u-bigboy:/tmp# vi /etc/default/tftpd-hpa.........## File: /etc/default/tftpd-hpa ##Defaults for tftpd-hpaRUN_DAEMON="yes"OPTIONS="-l -s /var/lib/tftpboot".........root@u-bigboy:/tmp# /etc/init.d/tftpd-hpa startStarting HPA's tftpd: in.tftpd.root@u-bigboy:/tmp#
Note: With both Redhat and Debian distributions, you can test whether the TFTP process is running with the netstat command which is used to check the TCP/UDP ports on which your server is listening. If it isn't running then there will be no response.
کد:
[root@bigboy tmp]# netstat -a | grep tftpudp 0 0 *:tftp *:*[root@bigboy tmp]#
Preparing TFTP Server Files
The TFTP server will not create files in its transfer directory if they don't already exist. Each device must have a pre-existing configuration file in the tftpboot directory. The files also need to have their permissions adjusted to allow them to be updated by the TFTP daemon.
کد:
[root@bigboy tmp]# touch /tftpboot/pixfw-config[root@bigboy tmp]# chmod 666 /tftpboot/pixfw-config[root@bigboy tmp]# ll /tftpboot/total 1631-rw-rw-rw- 1 root root 3011 Oct 29 14:09 pixfw-config[root@bigboy tmp]#
Saving Cisco Configurations To The TFTP Server
You'll now have to configure your Cisco router/firewall to use the TFTP server. The following examples assume that the TFTP server's IP address is 192.168.1.100.
Cisco PIX firewall
Follow theses steps on a PIX firewall:
1) Log onto the device, get into enable mode and then enter the TFTP commands to initially configure TFTP.
کد:
pixfw> enablePassword: ********pixfw# configure terminalpixfw(config)# tftp-server inside 192.168.1.100 /pixfw-configpixfw(config)# exit
2) Save the configuration to non volatile memory
کد:
pixfw# write memoryBuilding configuration...Cryptochecksum: 3af43873 d35d6f06 51f8c999 180c2342[OK]pixfw#
3) Save the configuration to the TFTP server
کد:
pixfw# write networkBuilding configuration...TFTP write '/pixfw-config' at 192.168.1.100 on interface 1[OK]pixfw#
Your firewall configuration has now been successfully saved for later use in the event of unrecoverable human error or hardware failure.
Cisco Switch Running CATOS
To save the configuration of a Catalyst-series switch running CATOS, you need to log onto the device, get into Enable mode and then enter the write net TFTP command as show below.
کد:
ciscoswitch> (enable) wr netThis command shows non-default configurations only.Use 'write network all' to show both default and non-default configurations.IP address or name of remote host? [192.168.1.100]Name of configuration file?[ciscoswitch-config]Upload configuration to ciscoswitch-config on 192.168.1.100 (y/n) [n]? y.........Finished network upload. (30907 bytes)ciscoswitch> (enable)
Cisco Router
To save the configuration of a router, log onto the device, get into enable mode, then configure mode and then enter the TFTP commands as seen below:
کد:
ciscorouter> enableciscorouter# write netRemote host [192.168.1.100]? 192.168.1.100Name of configuration file to write [ciscorouter-config]? ciscorouter-configWrite file ciscorouter-config on host 192.168.1.100? [confirm] yciscorouter# exit
Cisco CSS 11000 "Arrowpoints"
To save the configuration of a Cisco CSS-series load balancer, log onto the device, and then enter the TFTP commands as seen below:
Log onto the device and then enter the TFTP commands as seen below:
کد:
ciscocss# copy running-config tftp 192.168.1.100 ciscocss-configWorking..(\) 100%Connecting (/)Completed successfully.ciscocss# exit
Cisco Local Director
To save the configuration of a Cisco Local Director load balancer, log onto the device, get into enable mode, then configure mode and then enter the TFTP commands
کد:
ciscold> enaPassword:ciscold# write net 192.168.1.100 ciscold-configBuilding configuration...writing configuration to //ciscold-config on 192.168.1.100:69 ...[OK]ciscold# exit
Uploading Cisco Configurations From The TFTP Server
From time to time you may have to upload configurations from your TFTP server to your network equipment. In this example, a small file containing a new encrypted password and access control list is uploaded from the TFTP server and inserted into a router configuration.
Sample Upload Configuration File
For this example, the configuration file is named config.file and looks like this.
کد:
!! Set the console password!line con 0 password 7 $1$qDwqJEjunK$tuff0HE/g31/b7G/IZ!! Delete and recreate access list #10!no access-list 10access-list 10 permit 192.168.1.0 0.0.0.255access-list 10 permit 192.168.10.0 0.0.0.255end
Procedure To Upload A Configuration File
Uploading the file can be done using either the copy tftp: running-config or the older configure network commands. In both cases you are prompted for the IP address of the TFTP server and the name of the file with the configuration commands. The filename provided is always relative to the tftpboot directory. So if the file was located in the tftpboot directory it would be referred to as config.file, but if it were in the tftpboot/configs<code> directory, it would be referred to as configs/config.file.
Consider this sample <code>configure network command
کد:
ciscorouter>enaPassword:ciscorouter#configure networkHost or network configuration file [host]?This command has been replaced by the command: 'copy <url> system:/running-config'Address or name of remote host []? 192.168.1.100Source filename []? config.fileConfigure using tftp://192.168.1.100/config.file? [confirm]Loading config.file from 192.168.1.100 (via FastEthernet0/0): !!!!!![OK - 26521/52224 bytes] ciscorouter#
Here's a sample copy tftp: running-config command.
کد:
ciscorouter#copy tftp: running-configAddress or name of remote host []? 192.168.1.100Source filename []? config.fileDestination filename [running-config]?Accessing tftp://192.168.1.100/config.file...Loading config.file from 192.168.1.100 (via FastEthernet0/0): !!!!!![OK - 26521/52224 bytes] 26521 bytes copied in 1.912 secs (26521 bytes/sec)ciscorouter#
Always remember to permanently save your configurations to nonvolatile RAM (NVRAM) afterwards with the write memory or copy running-config startup-config.
Using TFTP To Restore Your Router Configuration
In disastrous cases, where you have to replace a router completely, you can use TFTP to completely restore the configuration to the replacement device. If the replacement unit is identical, then you need to do very little editing of the saved configuration file, but expect to edit it if the interface names and software versions are different.
The procedure for restoring your configuration is simple:
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