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14 | <HR> |
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15 | <H2><A NAME="FAQ"></A> <A NAME="s6">6. The Most Frequently Asked Questions</A></H2> |
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16 | |
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17 | <P>In this section, the Most Frequently Asked Questions |
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18 | have been placed, together with their answers. |
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19 | You may notice that some questions have the same answer, |
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20 | but the symptoms appear differently. |
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21 | <P>Some of these answers will reference other material in this FAQ, |
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22 | or the LPRng man pages. |
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23 | <H2><A NAME="ss6.1">6.1 Why do I get malformed from address errors?</A> |
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24 | </H2> |
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25 | |
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26 | <P>This is the number one question asked by most LPRng users |
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27 | who try to use LPRng with network printers or other systems |
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28 | supporting |
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29 | <A HREF="#rfc1179">RFC1179</A> printing. |
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30 | For details about LPRng and RFC1179, see |
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31 | <A HREF="LPRng-HOWTO-18.html#rfc1179ref">RFC1179 and LPRng</A>. |
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32 | <P>The |
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33 | <CODE> malformed from address </CODE> error is usually reported when |
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34 | trying to send a print job from LPRng to other BSD LPR or RFC1179 |
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35 | LPR implementations, or with network connected printers |
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36 | that have a built in LPR server. |
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37 | This is due to the following RFC1179 rule: |
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38 | <BLOCKQUOTE> |
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39 | Servers originate a connection from ports in the range 721-731. |
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40 | </BLOCKQUOTE> |
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41 | <P>WHY? These are a subset of the 'reserved' ports in UNIX, and normal users |
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42 | cannot open connections from them. This provides a small amount |
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43 | of security from UNIX users on the host 'spoofing' a server. |
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44 | <P>IMPLICATION: in order to do use a reserved port, the program |
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45 | must have root privileges. This means the LPR, LPD, LPQ, etc., |
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46 | programs must be installed SUID root. This can open up a can |
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47 | of worms with regard to security, but LPRng has been designed to |
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48 | take as much paranoid care as possible to avoid problems. |
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49 | <P>WHAT TO DO:<BR> |
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50 | When installing LPRng, you will need to install the executables |
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51 | SUID root. |
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52 | In the <CODE>src/Makefile</CODE>, you can remove the comment from the line |
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53 | <BLOCKQUOTE><CODE> |
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54 | <PRE> |
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55 | PERMS=SUID_ROOT_PERMS |
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56 | </PRE> |
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57 | </CODE></BLOCKQUOTE> |
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58 | |
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59 | and then do <CODE> make install</CODE>. |
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60 | This will install the executables |
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61 | SUID, and owned by root. |
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62 | <H2><A NAME="ss6.2">6.2 It was working normally, then I get connection refused errors</A> |
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63 | </H2> |
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64 | |
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65 | <P>This message usually appears when you have been sending a large number |
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66 | of jobs to a network printer or a remote system. |
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67 | The reason for this is a combination the above port 721-731 restriction |
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68 | and the TCP/IP timeouts. |
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69 | For details, see |
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70 | <A HREF="LPRng-HOWTO-18.html#rfc1179ref">RFC1179 and LPRng</A>, |
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71 | but here is a quick explanation. |
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72 | <P>A TCP/IP connection is usually specified as between |
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73 | <CODE>srchost:srcport, desthost:destport</CODE>, |
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74 | although in practice the order of source (src) and destination |
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75 | (dest) is not important. |
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76 | <P>When a connection is established, each end of the connection |
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77 | exchanges the necessary flow control and error control information. |
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78 | When a connection is terminated, |
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79 | each end of the connection will not accept another connection from |
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80 | the same <CODE>host:port</CODE> that was previously active |
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81 | for a specified timeout period, |
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82 | usually 10 minutes. |
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83 | <P>Some TCP/IP implementations go further: they will not allow |
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84 | <B>ANY</B> connection to be <B>originated</B> |
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85 | (via the <CODE>bind()</CODE> system call or API) |
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86 | from a port that was active, |
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87 | or accepted on a port that was active for this timeout period. |
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88 | <P>Now let us see what happens when we have a client program, |
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89 | which must originate a connection on port 721-731, connect |
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90 | to the server, which waits for a connection on port 515. |
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91 | We first try to make a connection from host:port |
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92 | <CODE>1.1.1.1:721</CODE> to |
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93 | <CODE>1.1.1.2:515</CODE>. |
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94 | The first time that we make the connection (or the first connection) |
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95 | we succeed. |
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96 | We can transfer a file, etc., and then close the connection. |
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97 | When we try to reconnect from |
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98 | <CODE>1.1.1.1:721</CODE> to |
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99 | <CODE>1.1.1.2:515</CODE> |
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100 | we get an error such as |
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101 | "address already in use" |
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102 | or "connection refused". |
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103 | <P>Luckily, we can use port 722 to originate a connection, |
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104 | and we can connect from |
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105 | <CODE>1.1.1.1:722</CODE> to |
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106 | <CODE>1.1.1.2:515</CODE>. |
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107 | We continue on, until we come to port 731, |
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108 | and then we need to wait for our timeouts. |
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109 | <P>SOLUTION: |
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110 | <P>It appears that most RFC1179 implementations do not check for the exact |
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111 | port |
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112 | range 721-731, but only that the connection originates from a |
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113 | reserved port, |
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114 | i.e. - in the range 1-1023. |
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115 | You can extend the range of ports used by LPRng by changing the |
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116 | <BLOCKQUOTE><CODE> |
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117 | <PRE> |
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118 | originate_port=721 731 |
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119 | </PRE> |
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120 | </CODE></BLOCKQUOTE> |
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121 | |
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122 | value in the defaults (<CODE>LPRng/src/common/defaults.c</CODE>) file or in the <CODE>lpd.conf</CODE> |
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123 | file. I recommend the following: |
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124 | <BLOCKQUOTE><CODE> |
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125 | <PRE> |
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126 | originate_port=512 1022 |
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127 | </PRE> |
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128 | </CODE></BLOCKQUOTE> |
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129 | |
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130 | This is, in fact, now the default in LPRng software. |
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131 | If you get the infamous |
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132 | <CODE>malformed from address</CODE> |
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133 | error message from your spooler, then |
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134 | you will have to set originate_port=721 731, and live with |
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135 | a delayed throughput. |
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136 | <H2><A NAME="ss6.3">6.3 Job is not in print queue, but it gets printed!</A> |
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137 | </H2> |
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138 | |
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139 | <P>In the original BSD LPD implementation, |
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140 | the LPR program copied users files to a special spool queue directory, |
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141 | and then caused the LPD server to peek in the directory and print |
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142 | the files. |
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143 | <P>This type of operation required spool directory space, |
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144 | special SETUID programs, |
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145 | and a slew of headaches in system security and management. |
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146 | <P>The LPR, LPQ, and other user programs in the LPRng suite use TCP/IP |
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147 | connections and transfer jobs directly to a LPD server running on |
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148 | a remote host, |
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149 | or even the local host if appropriate. |
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150 | Note that this type of operation does not require a LPD server to run |
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151 | on each local machine. |
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152 | In fact, you can have a single host system performing all of your |
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153 | printing. |
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154 | This type of operation is very similar to a central mail server versus |
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155 | individual systems, each having their own mail server and queues. |
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156 | <P>However, |
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157 | some users require or want their jobs to be spooled on the local host system, |
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158 | and then transferred to the remote printer. |
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159 | This is usually the case when some type of processing (filtering) |
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160 | is needed in order to print the job correctly. |
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161 | There are several methods that can be used to force this. |
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162 | <P>Method 1: Explicit Printer Address |
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163 | <P>You can force a job to be sent directly to the <CODE> pr </CODE> |
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164 | serviced by the LPD server on |
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165 | <CODE>host</CODE> |
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166 | by using the form: |
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167 | <BLOCKQUOTE><CODE> |
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168 | <PRE> |
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169 | lpr -Ppr@host file |
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170 | </PRE> |
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171 | </CODE></BLOCKQUOTE> |
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172 | <P>You can also set the <CODE>PRINTER</CODE> environment variable to |
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173 | a similar form, and get the same effect: |
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174 | <BLOCKQUOTE><CODE> |
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175 | <PRE> |
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176 | PRINTER=pr@host; export PRINTER; |
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177 | lpr file |
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178 | </PRE> |
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179 | </CODE></BLOCKQUOTE> |
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180 | <P>Method 2: User and Server Printcap Entries |
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181 | <P>If you want to have the benefits of a printcap file, |
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182 | i.e. - you can use aliases or abbreviations for the names of printers, |
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183 | then here is a couple of hints. |
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184 | First, |
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185 | the LPRng software scans the <CODE>/etc/printcap</CODE> file for printcap |
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186 | entries, combining information for the same printer into a single entry. |
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187 | Information found later in the printcap file will override earlier |
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188 | information. |
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189 | In addition, |
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190 | you can tag entries as either being used for all utilities or just |
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191 | for the LPD server. |
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192 | Here are a couple of examples: |
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193 | <BLOCKQUOTE><CODE> |
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194 | <PRE> |
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195 | # for all utilities |
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196 | pr:lp=pr@host |
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197 | # just for LPD |
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198 | pr:server |
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199 | :lp=/dev/lp |
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200 | # more information |
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201 | pr:check_for_nonprintable@ |
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202 | # --- final result for LPR |
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203 | pr:lp=pr@host:check_for_nonprintable@ |
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204 | # --- final result for LPD |
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205 | pr:lp=/dev/lp:check_for_nonprintable@ |
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206 | </PRE> |
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207 | </CODE></BLOCKQUOTE> |
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208 | <P>As you can see, |
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209 | the <CODE>server</CODE> |
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210 | keyword indicates that the printcap entry is only for the printer. |
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211 | The LPR utility will send the job to the host, while the LPD server |
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212 | will print it on <CODE>/dev/lp</CODE>. |
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213 | <P>Note that the <CODE>lp=...</CODE> information overrides the |
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214 | <CODE>:rp:</CODE> (remote printer) |
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215 | and |
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216 | <CODE>:rm:</CODE> (remote machine) fields if they are present. |
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217 | <P>Method 3: Force sending to server on <CODE>localhost</CODE> |
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218 | <P>The |
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219 | <CODE>force_localhost</CODE> |
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220 | printcap or configuration flag forces non-LPD applications to send all |
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221 | requests and print jobs to the server running on the local host. |
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222 | <P>This method is similar to the previous one, |
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223 | but has the benefit that it can be configured as a global (i.e. - |
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224 | applies to all printers) rather than printer specific. |
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225 | You can put this in the <CODE>/etc/lpd.conf</CODE> file for general |
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226 | application, or have a printcap entry of the following form: |
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227 | <BLOCKQUOTE><CODE> |
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228 | <PRE> |
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229 | # for all utilities |
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230 | pr:lp=pr@host:force_localhost |
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231 | </PRE> |
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232 | </CODE></BLOCKQUOTE> |
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233 | <P>The LPD server will ignore the |
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234 | <CODE>force_localhost</CODE> flag, |
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235 | and send jobs to the <CODE>pr</CODE> queue on the <CODE>host</CODE> |
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236 | machine. |
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237 | However, the LPR, LPQ, etc., utilities will send their requests to the |
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238 | server running on the local host. |
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239 | <H2><A NAME="ss6.4">6.4 Job disappears and is never printed, but lpr works</A> |
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240 | </H2> |
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241 | |
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242 | <P>This is a rather disconcerting problem, |
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243 | and usually occurs when sending jobs to either a network printer or |
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244 | a nonconforming |
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245 | <A HREF="#rfc1179">RFC1179</A> |
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246 | print spooler. |
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247 | For details about LPRng and RFC1179, see |
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248 | <A HREF="LPRng-HOWTO-18.html#rfc1179ref">RFC1179 and LPRng</A>, |
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249 | but here is a quick explanation. |
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250 | <P>An LPD job consists of a control file, which contains information |
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251 | about the job, and one or more data files. RFC1179 is silent on the |
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252 | order that jobs are sent; however some implementations REQUIRE that |
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253 | the data files be sent first, followed by the control file. |
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254 | <P>SOLUTION: |
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255 | <P>Set the <CODE>send_data_first</CODE> flag in the printcap for the particular |
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256 | printer, or in the <CODE>lpd.conf</CODE> configuration file. This is: |
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257 | <BLOCKQUOTE><CODE> |
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258 | <PRE> |
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259 | :send_data_first: (printcap) |
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260 | send_data_first (lpd.conf) |
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261 | </PRE> |
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262 | </CODE></BLOCKQUOTE> |
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263 | <P>Note that some printers/servers INSIST on the control file first; |
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264 | You can clear the flag using <CODE>send_job_first@</CODE> if you need to. |
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265 | <H2><A NAME="ss6.5">6.5 I get messages about bad control file format</A> |
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266 | </H2> |
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267 | |
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268 | <P>RFC1179 describes a set of fields that MAY appear in the control file. |
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269 | It is silent if other ones can appear as well. |
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270 | Unfortunately, some implementations will reject jobs unless they contain |
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271 | ONLY fields from a very small set. In addition, RFC1179 is silent |
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272 | about the ORDER the fields can appear. |
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273 | <P>LPRng quite happily will accept jobs from poor or nonconforming RFC1179 |
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274 | spooler programs, |
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275 | and fix them up to be comformant. |
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276 | <P>If you are sending jobs to one of a non-conforming spooler, |
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277 | you can force LPRng to send jobs with only the fields described |
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278 | in RFC1179 by setting the |
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279 | the <CODE> :bk: </CODE> (BacKwards compatible) flag in the |
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280 | printcap for your printer. |
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281 | <H2><A NAME="rfc1179"></A> <A NAME="ss6.6">6.6 What is RFC 1179, the Line Printer Daemon Protocol?</A> |
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282 | </H2> |
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283 | |
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284 | <P>RFC1179 defines a standard method by which print jobs can be transferred |
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285 | using the TCP/IP protocol between hosts. |
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286 | The standard was developed by simply detailing the way that |
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287 | a version of the BSD LPD software did its job. |
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288 | <P>From the RFC Introduction: |
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289 | <BLOCKQUOTE> |
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290 | RFC 1179 describes a print server protocol widely used on |
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291 | the Internet for communicating between line printer daemons (both |
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292 | clients and servers). RFC1179 is for informational purposes only, |
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293 | and does not specify an Internet standard. |
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294 | </BLOCKQUOTE> |
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295 | <P>Having said this, |
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296 | the RFC then goes on to describe the protocol used |
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297 | by a particular implementation of LPD. |
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298 | The problem was that the RFC did not provide |
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299 | any way to put extensions to the operations into the system, |
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300 | and failed to specify such interesting details as the order in which |
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301 | print jobs and their components could be transferred. |
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302 | <P>Comment by Patrick Powell <CODE> <papowell@astart.com> </CODE>: |
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303 | <BLOCKQUOTE> |
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304 | <P>Since 1988, |
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305 | there have been a large number of print spooling systems developed which |
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306 | claim RFC1179 conformance, |
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307 | but which are mutually incompatible. |
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308 | <P>Rather than live with the limited capabilities of the RFC1179 standard, |
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309 | LPRng has extended them by adding capabilities to perform remote control |
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310 | of print spoolers, |
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311 | encrypted and authenticated data transfers, |
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312 | and other operations missing from the RFC1179 specification. |
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313 | However, |
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314 | great effort was made to be backwards compatible with older and other LPD |
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315 | based systems. |
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316 | <P>LPRng was developed in order to be able to both accept and provide |
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317 | interactions with these systems. It does so by allowing various options |
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318 | to be used to <EM>tune</EM> how print jobs would be exchanged. |
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319 | Currently, |
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320 | LPRng can be configured to send and receive print jobs between a vast number |
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321 | of the existing spooling systems. |
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322 | It is flexible enough to act as a gateway between non-compatible systems, |
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323 | and has provisions to transform jobs from one format to another in a dynamic |
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324 | manner. |
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325 | </BLOCKQUOTE> |
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326 | <P>For a detailed explanation |
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327 | about LPRng and RFC1179, see |
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328 | <A HREF="LPRng-HOWTO-18.html#rfc1179ref">RFC1179 and LPRng</A>. |
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329 | <H2><A NAME="ss6.7">6.7 I want to replace lp, lpstat, etc, but my programs need them</A> |
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330 | </H2> |
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331 | |
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332 | <P>LPRng was designed as a replacement the BSD printing system. As such, |
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333 | it inherited its command names and options from the latter. As you |
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334 | might know, System V uses a totally different set of commands, |
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335 | incompatible with the BSD ones. |
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336 | <P>The good news is that the LPRng binaries include an emulation for the |
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337 | System V commands. |
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338 | (See |
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339 | <A HREF="LPRng-HOWTO-4.html#lpsimulation">lp Simulation</A> |
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340 | for details. |
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341 | Briefly, you create links to the appropriate programs, |
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342 | and invoke them by the link names. |
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343 | <EM>Actually, these links are installed by default in recent versions.</EM> |
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344 | <P> |
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345 | <BLOCKQUOTE><CODE> |
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346 | <PRE> |
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347 | ln -s lpr lp |
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348 | ln -s lpq lpstat |
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349 | ln -s lprm cancel |
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350 | </PRE> |
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351 | </CODE></BLOCKQUOTE> |
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352 | <P>If you make these links, calling <CODE>lp</CODE>, <CODE>lpstat</CODE> and |
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353 | <CODE>cancel</CODE> will give you a (partial) SVR4 emulation. They have |
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354 | their own man pages, which you should read if you need the emulation. |
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355 | <P>Since it is a <B>partial</B> emulation, you shouldn't expect everything |
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356 | to work. In particular, I would guess that any script which relies on |
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357 | the output format of one of your system binaries will break. |
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358 | Again, see |
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359 | <A HREF="LPRng-HOWTO-4.html#lpsimulation">lp Simulation</A> |
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360 | for more details or additional suggestions. |
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361 | <H2><A NAME="ss6.8">6.8 What are the drawbacks to LPRng?</A> |
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362 | </H2> |
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363 | |
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364 | <P>There are many reasons to run LPRng, and most of them are related to |
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365 | the extra features it has, compared to vanilla BSD LPR. A short list |
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366 | is given in section |
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367 | <A HREF="LPRng-HOWTO-1.html#secfeatures">What is LPRng?</A>. (A |
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368 | more elaborate description can be found in the LPRng package itself.) |
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369 | <P>On the other hand, there are also reasons <B>not</B> to switch to LPRng: |
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370 | <UL> |
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371 | <LI>Switching from a System V system will require some work. |
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372 | On the other hand, |
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373 | getting System V printing to work correctly for you may be even more work.</LI> |
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374 | <LI>You don't need any of the enhanced features, |
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375 | and are not worried about security issues. |
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376 | On the other hand, |
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377 | you may not have known about them.</LI> |
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378 | <LI>While there are many resources and books devoted to the old BSD |
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379 | printer daemon, documentation for LPRng is rather limited. |
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380 | On the other hand, you get lots of diagnostics and error messages when things |
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381 | go wrong.</LI> |
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382 | </UL> |
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383 | <HR> |
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384 | <A HREF="LPRng-HOWTO-7.html">Next</A> |
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385 | <A HREF="LPRng-HOWTO-5.html">Previous</A> |
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