Linux Command Directory


Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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tftpd

in.tftpd [options] [directories]

TCP/IP command. IPv4 Trivial File Transfer Protocol server. in.tftpd is normally started by inetd and operates at the port indicated in the tftp Internet service description in /etc/services. Only publicly readable files may be accessed. By default, only files that already exist and are publicly writable can be written. In addition, if any directories are specified, access is restricted to files in those directories. The version of tftp described here is tftp-hpa.

Options

-a [address] [:port]

Specify the address and port to listen to when run in standalone mode with -l. By default, use the address and port in /etc/services.

-B size

Do not transmit blocks larger than size, a number between 512 and 65464.

-c

Allow new files to be written. The default permissions allow anyone to read and write the files. Use -p or -U to set other permissions.

-l

Run tftpd in standalone mode, not from inetd. This mode ignores -t.

-m file

Remap filenames based on rules specified in file. Each line in this file should contain an operation, an egrep-style regular expression (regex), and, optionally, a replacement pattern. If the regex matches any part of a filename, the operation is performed. The operation is specified as any of the letters shown in the next section, alone or in combination. Comment lines begin with #. See filename remapping rules below.

-p

Use only normal system access controls for the user specified with -u (the tftpd username).

-r option

Never accept the specified RFC 2347 option. The possible options are blksize, blksize2 (not based on a standard; like blksize but the block size must be a power of 2), tsize (transfer size), and timeout.

-s

On startup, change root directory to the directory specified as directory on the command line. With -s, only one directory should be specified. Recommended for security and compatibility with certain boot ROMs.

-t timeout

Specify how long in seconds the server should wait for a new connection before terminating. Default timeout is 900 (15 minutes). If terminated, inetd spawns a new server when it receives a new request.

-T timeout

Wait timeout microseconds before retransmitting the first packet.

-u username

Specify the name of the tftpd user. The default user is nobody.

-U umask

Set the umask for newly created files. Without -p, the default is 0. With -p, it is inherited from the calling process.

-v

Increase verbosity. Specify multiple times for greater verbosity.

-V

Print version and configuration information, and exit.

Filename remapping rules

Use one or more of the following characters to create a single remapping operation.

a

If this rule matches, refuse the request and send an "access denied" error to the client.

e

If this rule matches, execute it and then end rule processing.

g

Repeat the rule until it no longer matches. Used with r.

G

Apply this rule to GET (RRQ) requests only.

i

Use case-insensitive regex matching. The default is for case-sensitive matching.

P

Apply this rule to PUT (WRQ) requests only.

r

Replace the matching substring with the replacement pattern.

s

If this rule matches, execute it and then restart rule processing with the first rule.

~

Invert the regular expression so operation affects filenames that do not match.

The replacement pattern can include the following escape sequences:

\0

The entire string matching the regex.

\1...\9

The strings matched by each of the first nine substrings in the regex.

\e

Cancel the effect of \U or \L.

\i

The IP address of the requesting host, in dotted-quad notation.

\L

Convert letters following this sequence to lowercase.

\U

Convert letters following this sequence to uppercase.

\x

The IP address of the requesting host, in hexadecimal notation.

\\

Literal backslash.

\whitespace

Literal whitespace.

\#

Literal hash mark.


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