248 lines
8.5 KiB
HTML
248 lines
8.5 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<HTML>
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<HEAD>
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<title>Remote Compilation Using SSH and Make Issue 21</title>
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</HEAD>
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<BODY BGCOLOR="#fff0e8" TEXT="#301400" LINK="#0000FF" VLINK="#0020F0"
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ALINK="#FF0000">
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<!--endcut ============================================================-->
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<H4>
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"Linux Gazette...<I>making Linux just a little more fun!</I>"
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</H4>
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<P> <HR> <P>
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<!--===================================================================-->
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<center>
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<H2>Remote Compilation Using SSH and Make</H2>
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<H4>By John R. Daily,
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<a href="mailto:jdaily@bbn.com">jdaily@bbn.com</a></H4>
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</center>
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<P><HR><P>
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<H3>
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Problem
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</H3>
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<P>
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Occasionally I use my Linux machine at home to write code that I
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intend to compile on a remote machine.
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<P>
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While maintaining open <TT>ftp</TT> and <TT>telnet</TT> connections to
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the remote machine to handle the transfer and compilation steps is a
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manageable solution, I decided to explore <TT><A
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HREF="#ssh">ssh</A></TT> and <TT><A HREF="#make">make</A></TT> to
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develop a more automated method.
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<P>
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The benefits of my solution:
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<UL>
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<LI> No need to remember which files have been modified.
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<LI> Ability to use Emacs' compilation capabilities to move to errors in
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the source. <LI> As mentioned above, no need to use <TT>ftp</TT>
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and <TT>telnet</TT>, and hence no
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benefit to keep an open dialup connection when not compiling.
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<LI> Automate, automate, automate. Laziness is a virtue.
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</UL>
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<H3>
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Overview of Solution
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</H3>
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<P>
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My first step was to set up <TT>ssh</TT> and related tools in order to
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allow
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secure copying of files to my remote system. While setting up a
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<TT>.rhosts</TT>
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file is a (barely) acceptable solution, my IP address and name is
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different each time I dial in, and it would be rather awkward to
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change the remote system's <TT>.rhosts</TT> file each time I dialed
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in.
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<P>
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<TT>ssh</TT> allows me to use a much more secure form of
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authentication to copy
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files and execute remote commands.
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<P>
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Once I had <TT>ssh</TT> behaving properly, I used Emacs' <TT>info</TT> facility to
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explore implicit rules in makefiles, and wrote a simple makefile to
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handle the file transfers and remote compilation.
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<P>
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As an example of the intended effect, assume my remote machine is
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called "remote" (and my local machine "local"), and I've just modified
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a source file called <TT>daemon.c</TT>. I would like to execute the
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following commands in an automated fashion (note that <TT>scp</TT> is
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a secure copy command packaged with <TT>ssh</TT>, and that the
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<TT>-C</TT> option specifies compression, useful for dialup connections):
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<PRE>
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scp -C daemon.c jdaily@remote:~/source-directory
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ssh -C remote "cd source-directory && make"
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</PRE>
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<H3>
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Implementation
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</H3>
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<P>
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First, I needed <TT>sshd</TT> running on the remote system to handle my secure
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connections. Fortunately, <TT>sshd</TT> was already running on the remote
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system in question, but according to the man pages, it can be run as
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any user, and is restricted to handling connections for that user
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(which should be quite sufficient for our needs).
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<P>
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Then, I needed to install the <TT>ssh</TT> toolset on my local machine. Again,
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ideally these would be installed in a public binary directory such as
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<TT>/usr/local/bin</TT>, but any user can install them in his/her
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home directory.
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<P>
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I also wanted a key which would allow me to authenticate myself
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between systems, and which would eliminate the need to type my
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password each time I tried to run one of the <TT>ssh</TT> commands. For this, I
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just ran <TT>ssh-keygen</TT>, and made sure to not give a pass
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phrase, so that
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none would be needed to use my private key to establish the
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connection.
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<PRE>
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[jdaily@local ~]$ ssh-keygen
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Initializing random number generator...
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Generating p: ............++ (distance 186)
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Generating q: ......................................++ (distance 498)
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Computing the keys...
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Testing the keys...
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Key generation complete.
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Enter file in which to save the key (/home/jdaily/.ssh/identity): <CR>
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Enter passphrase: <CR>
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Enter the same passphrase again: <CR>
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Your identification has been saved in /home/jdaily/.ssh/identity.
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Your public key is:
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1024 35 718535638573954[...] jdaily@local
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Your public key has been saved in /home/jdaily/.ssh/identity.pub
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</PRE>
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<P>
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Once I had a public key, I used <TT>scp</TT> to copy it to the remote machine.
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<PRE>
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[jdaily@local ~]$ scp -C ~/.ssh/identity.pub jdaily@remote:~/.ssh/key
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jdaily's password: <entered my remote password>
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</PRE>
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<P>
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Then I logged into the remote host and copied the key file into
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<TT>~/.ssh/authorized_hosts</TT>. If that file already existed, I
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would have
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appended the key file.
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<P>
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Following all this, I could run <TT>ssh</TT> and <TT>scp</TT> without needing either a
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password or a pass phrase to connect to <TT>remote</TT>.
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<P>
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Now I needed a makefile to automate my system. Ideally, the files on
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the remote machine would be checked to see if they were older than the
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files on my local machine, and if so, they would be copied over. To
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simplify matters, I decided to keep a record of the "last transferred
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date" for each file by touching a corresponding file each time I
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copied a source file over.
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<P>
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As an example, when I transferred a newer copy of <TT>daemon.c</TT>
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over, I touched <TT>daemon.ct</TT> in the same directory. Any
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transfer of a <TT>.h</TT> file would be marked by the creation of a
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file with a <TT>.ht</TT> suffix.
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<P>
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After poking around the <TT>info</TT> file for <TT>make</TT>, I came
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up with the following makefile.
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<PRE>
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TRANSFER=scp
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REXEC=ssh
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SSHFLAGS=-C # Compress data
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REMOTE=jdaily@remote:~/source-directory
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FILES=debug.ht messages.ht client.ct daemon.ct queue.ct queue.ht
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%.ht : %.h
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$(TRANSFER) $(SSHFLAGS) $< $(REMOTE)
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touch $@
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%.ct : %.c
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$(TRANSFER) $(SSHFLAGS) $< $(REMOTE)
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touch $@
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all-done: $(FILES)
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$(REXEC) $(SSHFLAGS) remote "cd source-directory && make"
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touch all-done
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</PRE>
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<P>
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This had one limitation in particular; I was unable to specify
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command-line arguments for <TT>make</TT> on the remote machine without writing
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them directly into the makefile on my local system. While this was
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fine for the current application, I decided to generalize it by
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creating a <TT>run-make</TT> shell script, which would handle the remote
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execution of make after calling make on the local system.
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<P>
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Here is my <TT>run-make</TT> shell script:
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<PRE>
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#!/bin/sh
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make
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echo ssh -C remote \"cd source-directory \&\& make $*\"
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ssh -C remote "cd source-directory && make $*"
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</PRE>
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<P>
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I then removed the line from my makefile which remotely ran <TT>make</TT>.
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<P>
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Here's the output from a successful compilation sequence.
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<PRE>
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cd ~/source-directory/
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./run-make
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scp -C debug.h jdaily@remote:~/source-directory
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touch debug.ht
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scp -C messages.h jdaily@remote:~/source-directory
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touch messages.ht
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scp -C client.c jdaily@remote:~/source-directory
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touch client.ct
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scp -C daemon.c jdaily@remote:~/source-directory
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touch daemon.ct
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scp -C queue.c jdaily@remote:~/source-directory
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touch queue.ct
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scp -C queue.h jdaily@remote:~/source-directory
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touch queue.ht
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touch all-done
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ssh -C remote "cd source-directory && make "
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gcc -Wall -Wstrict-prototypes -Wmissing-prototypes -g -c queue.c
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gcc -Wall -Wstrict-prototypes -Wmissing-prototypes -g -DPORT=3000 -o daemon daemon.c queue.o -lsocket -lthread
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gcc -Wall -Wstrict-prototypes -Wmissing-prototypes -g -DPORT=3000 -o client client.c -lsocket
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Compilation finished at Sat Aug 9 01:22:19
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</PRE>
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<H3>
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Tools
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</H3>
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<A NAME="ssh">
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<TT>ssh</TT> is a secure replacement for such tools as <TT>rsh</TT>,
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<TT>rlogin</TT>, and <TT>rcp</TT>. It can be found at
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<A HREF="http://www.cs.hut.fi/ssh">http://www.cs.hut.fi/ssh</A>.
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<P>
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<A NAME="make">
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<TT>make</TT> is a standard Unix utility. GNU's <TT>make</TT> comes with most, if not
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all, Linux distributions.
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<!--===================================================================-->
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<P> <hr> <P>
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<center><H5>Copyright © 1997, John R. Daily<BR>
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Published in Issue 21 of the Linux Gazette, September 1997</H5></center>
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