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1<?xml version='1.0'?> 1<?xml version='1.0' encoding="UTF-8"?>
2<?xml-stylesheet href="/xsl/guide.xsl" type="text/xsl"?> 2<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/uml.xml,v 1.25 2005/12/16 15:54:54 swift Exp $ -->
3 3
4<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> 4<!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
5 5
6<guide link="/doc/uml.html"> 6<guide link="/doc/en/uml.xml">
7<title>Gentoo Linux Developer's guide to system testing with User-Mode Linux</title> 7<title>Gentoo Linux Developer's guide to system testing with User-Mode Linux</title>
8
9<author title="Editor">
8<author title="Editor"><mail link="g2boojum@gentoo.org">Grant Goodyear</mail></author> 10 <mail link="g2boojum@gentoo.org">Grant Goodyear</mail>
11</author>
12<author title="Editor"><!-- zhen@gentoo.org -->
13 John Davis
14</author>
15<author title="Editor">
16 <mail link="swift@gentoo.org">Sven Vermeulen</mail>
17</author>
18<author title="Editor">
19 <mail link="bennyc@gentoo.org">Benny Chuang</mail>
20</author>
9 21
10<abstract> 22<abstract>
11 This guide shows Gentoo Linux developers how to set up and use 23This guide shows Gentoo Linux developers how to set up and use
12 user-mode linux for testing potentially system-breaking changes. 24user-mode linux for testing potentially system-breaking changes.
13</abstract> 25</abstract>
14 26
27<!-- The content of this document is licensed under the CC-BY-SA license -->
28<!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
29<license/>
30
15<version>0.05</version> 31<version>0.13</version>
16<date>5 Mar 2002</date> 32<date>2005-12-16</date>
17 33
18<chapter> 34<chapter>
19<title>Obtaining User-Mode Linux</title> 35<title>Obtaining User-Mode Linux</title>
20<section> 36<section>
21<body> 37<body>
38
39<p>
22<p>As the user-mode linux website 40As the user-mode linux website
23(<uri>http://user-mode-linux.sourceforge.net</uri>) 41(<uri>http://user-mode-linux.sourceforge.net</uri>) states, user-mode linux
24states, user-mode linux
25allows a user to "run Linux inside itself". Specifically, 42allows a user to "run Linux inside itself". Specifically,
26user-mode linux provides a virtual machine on which a user can "[r]un buggy 43user-mode linux provides a virtual machine on which a user can "[r]un buggy
27software, experiment with new Linux kernels or distributions, and poke around 44software, experiment with new Linux kernels or distributions, and poke around
28in the internals of Linux, all without risking your main Linux setup." Changes 45in the internals of Linux, all without risking your main Linux setup."
29to Gentoo core packages such as <e>sys-apps/baselayout</e> or <e>sys-libs/glibc</e> 46Experimental changes to Gentoo core packages such as <e>sys-apps/baselayout</e>
30have the potential to break the system and render it unbootable; with user-mode 47or <e>sys-libs/glibc</e> have the potential to break the system and render it
31linux we can test these changes without having to worry about breaking the live 48unbootable; with user-mode linux we can test these changes without having to
32system. 49worry about breaking the live system.
33</p>
34<p> 50</p>
35Installing user-mode linux is essentially identical to a normal kernel 51
36install. First install the kernel sources (appropriately patched for
37user-mode linux), and then configure the user-mode linux kernel in the
38usual fashion:
39</p> 52<p>
53Most 2.6 kernels have UML support. Although you can use your current kernel
54sources, it might be wiser to keep the UML kernel tree(s) separate. After all,
55you'll be building a new kernel with a different configuration and you might
56want to have heterogenous systems on your main Linux system (several different
57UML kernels).
58</p>
59
40<pre> 60<p>
41# <i>emerge sys-kernel/usermode-sources</i> 61So download a nice kernel tree (like the vanilla one from <uri
62link="http://www.kernel.org">kernel.org</uri>) and extract it to some local
63development location.
64</p>
65
66<p>
67Next, configure this UML kernel as you would do for any other system, but append
68<e>ARCH=um</e> so that the kernel build software knows that the kernel
69is meant to run as a guest process on the main system.
70</p>
71
72<pre caption="Building the UML kernel">
42# <i>cd /usr/src/uml/linux</i> 73# <i>cd /srv/aegis/src/uml-linux</i>
43# <i>make menuconfig <comment>ARCH=um</comment></i> 74# <i>make menuconfig <comment>ARCH=um</comment></i>
44# <i>make linux <comment>ARCH=um</comment></i> 75# <i>make linux <comment>ARCH=um</comment></i>
45# <i>cp linux /usr/local/bin/linux</i> 76# <i>cp linux /usr/local/bin/linux</i>
46</pre> 77</pre>
78
79<warn>
47<warn>The <e>ARCH=um</e> fragment is <e>extremely</e> important!</warn> 80The <e>ARCH=um</e> fragment is <e>extremely</e> important!
48<impo> 81</warn>
82
83<p>
84Make sure that <path>/usr/local/bin</path> is in your path. Edit
85<path>/etc/env.d/00basic</path> to that the PATH variable contains
86<path>/usr/local/bin</path> and rerun <c>env-update</c>:
87</p>
88
89<pre caption="Editing 00basic">
90# <i>nano -w /etc/env.d/00basic</i>
91# <i>env-update</i>
92# <i>source /etc/profile</i>
93</pre>
94
95<p>
49For the user-mode linux kernel to properly boot a Gentoo system the 96For the user-mode linux kernel to properly boot a Gentoo system the
50kernel needs to be configured to <e>not</e> automatically mount 97kernel needs to be configured to <e>not</e> automatically mount
51<path>/dev</path> (devfs) by default. 98<path>/dev</path> (devfs) by default. Also, you will almost certainly
52Also, you will almost certainly
53want to make sure that you have <e>tmpfs</e> (the "Virtual Memory 99want to make sure that you have <e>tmpfs</e> (the "Virtual Memory
54Filesystem") compiled in, since by default the Gentoo linux bootscripts 100Filesystem") compiled in, since by default the Gentoo linux bootscripts
55store their information in a small tmpfs partition. 101store their information in a small tmpfs partition.
56(The binary kernels available 102(The binary kernels available from the user-mode website do automatically
57from the user-mode website do automatically mount <path>/dev</path>, 103mount <path>/dev</path>, and they don't have tmpfs compiled in; don't bother
58and they don't have tmpfs compiled in; don't bother with them.) 104with them).
59</impo> 105</p>
106
107<p>
60<p>I highly recommend reading the user-mode linux documentation, but the 108I highly recommend reading the user-mode linux documentation, but the
61basic idea is that running the <path>/usr/local/bin/linux</path> program 109basic idea is that running the <path>/usr/local/bin/linux</path> program
62boots the user-mode kernel and tries to bring up the system stored in 110boots the user-mode kernel and tries to bring up the system stored in
63the file <path>root_fs</path> that should be located in the current working 111the file <path>root_fs</path> that should be located in the current working
64directory.</p> 112directory.
113</p>
114
115<p>
65<p>It won't hurt to also install the user-mode linux tools.</p> 116It won't hurt to also install the user-mode linux tools.
66<pre> 117</p>
118
119<pre caption="Installing UML tools">
67# <i>emerge sys-apps/usermode-utilities</i> 120# <i>emerge sys-apps/usermode-utilities</i>
68</pre> 121</pre>
122
123<p>
69<p>These tools facilitate networking (among other things) 124These tools facilitate networking (among other things) between the user-mode
70between the user-mode linux virtual system 125linux virtual system and the host Linux system.
71and the host Linux system.</p> 126</p>
127
72</body> 128</body>
73</section> 129</section>
74</chapter> 130</chapter>
75 131
76<chapter> 132<chapter>
77<title>Creating <path>root_fs</path></title> 133<title>Creating root_fs</title>
78
79<section> 134<section>
80<title>Making the Gentoo chroot</title> 135<title>Making the Gentoo chroot</title>
81<body> 136<body>
137
82<p> 138<p>
83The <path>root_fs</path> file needed for user-mode linux is 139The <path>root_fs</path> file needed for user-mode linux is
84a single file that contains an entire Gentoo Linux filesystem. 140a single file that contains an entire Gentoo Linux filesystem.
85To generate this file you will need to have Loopback device 141To generate this file you will need to have Loopback device
86support enabled in the host (non-user-mode) kernel. 142support enabled in the host (non-user-mode) kernel.
87</p> 143</p>
144
145<p>
88<p>Generating the <path>root_fs</path> file itself will be 146Generating the <path>root_fs</path> file itself will be
89our last step. First we will generate a Gentoo filesystem in 147our last step. First we will generate a Gentoo filesystem in
90an ordinary chroot. We need the build tarball available, which 148an ordinary chroot. We need the stage tarball available, which
91could be downloaded separately, extracted from a build cd, or 149could be downloaded separately, extracted from an Installation CD, or
92extracted from a build .iso. 150extracted from an Installation CD .iso.
93</p> 151</p>
152
94<pre caption="Mounting a build .iso"> 153<pre caption="Mounting an Installation CD .iso">
95# <i>mkdir /mnt/loop</i> 154# <i>mkdir /mnt/loop</i>
96# <i>mount -o loop /path/to/build-&lt;TAB&gt;.iso /mnt/loop</i> 155# <i>mount -o loop /path/to/install-&lt;TAB&gt;.iso /mnt/loop</i>
97</pre> 156</pre>
157
98<p> 158<p>
99Setting up the chroot is essentially identical to an ordinary Gentoo 159Setting up the chroot is essentially identical to an ordinary Gentoo
100Linux build. 160Linux build.
101</p> 161</p>
102<pre> 162
163<pre caption="Creating the Gentoo chroot mount">
103# <i>mkdir /mnt/gentoo</i> 164# <i>mkdir /mnt/gentoo</i>
104# <i>cd /mnt/gentoo</i> 165# <i>cd /mnt/gentoo</i>
105# <i>tar xvjpf /path/to/build-&lt;TAB&gt;.tar.bz2</i> 166# <i>tar xvjpf /path/to/stage&lt;TAB&gt;.tar.bz2</i>
106</pre> 167</pre>
168
107<p> 169<p>
108Go ahead and unmount the .iso. You don't need it anymore. 170Go ahead and unmount the .iso. You don't need it anymore.
109</p> 171</p>
110<pre> 172
111# <i>cp /etc/resolv.conf /mnt/gentoo/etc/</i>
112# <i>mount -o bind /proc /mnt/gentoo/proc</i>
113# <i>mkdir -p /mnt/gentoo/usr/portage/distfiles</i>
114# <i>mkdir -p /mnt/gentoo/usr/portage/packages</i>
115# <i>mount -o bind /usr/portage/distfiles /mnt/gentoo/usr/portage/distfiles</i>
116# <i>mount -o bind /usr/portage/packages /mnt/gentoo/usr/portage/packages</i>
117# <i>chroot /mnt/gentoo /bin/bash</i>
118# <i>env-update</i>
119# <i>source /etc/profile</i>
120</pre>
121<p>
122By bind-mounting <path>/usr/portage/distfiles</path> and
123<path>/usr/portage/packages</path> we avoid having to download
124or build packages that are already present on the Gentoo host.
125</p> 173<p>
174Build the system in the usual fashion: chroot into <path>/mnt/gentoo</path> and
175follow the Gentoo installation instructions.
126<p> 176</p>
127Bootstrap and build the system in the usual fashion: 177
128</p>
129<pre>
130# <i>emerge rsync</i>
131# <i>cd /usr/portage</i>
132# <i>nano -w /etc/make.conf</i>
133# <i>nano -w /etc/make.profile/packages</i>
134# <i>nano -w /usr/portage/profiles/package.mask</i>
135# <i>scripts/bootstrap.sh &amp;&amp; emerge --usepkg system</i>
136</pre>
137<warn>
138The <path>/etc/make.profile/packages</path> file needs to be
139edited to remove grub from the default system (just remove the "*"
140from the beginning of the "*sys-apps/grub" line). The grub ebuild
141tries to mount the /boot partition, which will fail in our chroot.
142</warn>
143<note>
144Make sure you examine <path>/etc/make.profile/packages</path>
145and <path>/usr/portage/profiles/package.mask</path> to be sure that
146any to-be-tested packages that you want to install aren't masked out.
147As currently written, <path>scripts/bootstrap.sh</path> will compile
148the bootstrap packages from source. To use already-existing packages,
149add <c>alias emerge="emerge --usepkg"</c> somewhere near the top of
150the bootstrap script.
151</note>
152<p> 178<p>
153Add any additional packages you desire. Feel free to give your virtual 179Add any additional packages you desire. Feel free to give your virtual
154Gentoo system a hostname, if you so desire. In <path>/etc/fstab</path> 180Gentoo system a hostname, if you so desire. In <path>/etc/fstab</path>
155you will want <path>/dev/ROOT</path> to be <path>/dev/ubd/0</path>, with 181you will want <path>/dev/ROOT</path> to be <path>/dev/ubda</path>, with
156a fs type of either ext2, ext3, or reiserfs. Set <path>/dev/SWAP</path> 182a fs type of either ext2, ext3, or reiserfs. Set <path>/dev/SWAP</path>
157to be <path>/dev/ubd/1</path>, and comment out <path>/dev/BOOT</path>. 183to be <path>/dev/ubdb</path>, and comment out <path>/dev/BOOT</path>.
184</p>
185
158</p> 186<p>
187At this point, remember to set your root password.
188</p>
189
190<pre caption="Setting root password">
191# <i>passwd</i>
192</pre>
193
194<p>
195Now we need to make some changes to the boot scripts. Remove consolefont and
196keymaps from the boot runlevel:
197</p>
198
199<pre caption="Removing unneeded initscripts">
200# <i>rc-update del consolefont boot</i>
201# <i>rc-update del keymaps boot</i>
202</pre>
203
159<p> 204<p>
160Exit the chroot, unmount all of the bind mounts, 205Exit the chroot, unmount all of the bind mounts,
161tar up the new Gentoo distro, and clean up: 206tar up the new Gentoo distro, and clean up.
162</p> 207</p>
163<pre> 208
164# <i>exit</i> 209<pre caption="Finalising the installation">
165# <i>umount /mnt/gentoo/usr/portage/distfiles</i>
166# <i>umount /mnt/gentoo/usr/portage/packages</i>
167# <i>umount /mnt/gentoo/proc</i>
168# <i>du -ks /mnt/gentoo</i> 210# <i>cd /mnt/gentoo</i>
169261744 /mnt/gentoo
170# <i>tar cvjpf ~/gentoo.tbz2 *</i> 211# <i>tar cvjpf ~/gentoo.tbz2 *</i>
171# <i>cd</i> 212# <i>cd</i>
172# <i>rm -rf /mnt/gentoo</i> 213# <i>rm -rf /mnt/gentoo</i>
173</pre> 214</pre>
174</body>
175</section>
176 215
216</body>
177<section> 217</section>
218<section>
178<title>Making <path>root_fs</path></title> 219<title>Making root_fs</title>
179<body> 220<body>
221
180<p> 222<p>
181Our Gentoo chroot is nearly 300 MB in size, so 223Our Gentoo chroot is nearly 300 MB in size, so
182<path>root_fs</path> needs to be at least that size. 224<path>root_fs</path> needs to be at least that size.
183We'll choose 0.5 GB as a reasonable size. 225We'll choose 0.5 GB as a reasonable size.
184</p> 226</p>
185<pre> 227
228<pre caption="Creating UML files">
186# <i>dd if=/dev/zero of=root_fs seek=500 count=1 bs=1M</i> 229# <i>dd if=/dev/zero of=root_fs seek=500 count=1 bs=1M</i>
187# <i>mke2fs -F root_fs</i> 230# <i>mke2fs -F root_fs</i>
188# <i>mount -o loop root_fs /mnt/loop</i> 231# <i>mount -o loop root_fs /mnt/loop</i>
189# <i>tar xvjpf gentoo.tbz2 -C /mnt/loop</i> 232# <i>tar xvjpf gentoo.tbz2 -C /mnt/loop</i>
190# <i>umount /mnt/loop</i> 233# <i>umount /mnt/loop</i>
191</pre> 234</pre>
235
192<p> 236<p>
193It would also be nice to have a 0.5 GB swap partition. 237It would also be nice to have a 0.5 GB swap partition.
194</p> 238</p>
195<pre> 239
240<pre caption="Create swap partition">
196# <i>dd if=/dev/zero of=swap_fs seek=500 count=1 bs=1M</i> 241# <i>dd if=/dev/zero of=swap_fs seek=500 count=1 bs=1M</i>
197# <i>mkswap -f swap_fs</i> 242# <i>mkswap -f swap_fs</i>
198</pre> 243</pre>
244
199<p> 245<p>
200Now see if it works! 246Now see if it works!
201</p> 247</p>
202<pre> 248
249<pre caption="Start UML kernel thread">
203# <i>linux ubd0=root_fs ubd1=swap_fs</i> 250# <i>linux ubd0=root_fs ubd1=swap_fs</i>
204</pre> 251</pre>
205<note> 252
253<p>
206User-mode linux uses xterms for the virtual consoles that 254User-mode linux uses xterms for the virtual consoles that
207are run at boot time, so you need to make sure that the 255are run at boot time, so you need to make sure that the
208terminal from which you run user-mode linux has $DISPLAY 256terminal from which you run user-mode linux has $DISPLAY
209properly set (along with proper xhost/xauth permissions). 257properly set (along with proper xhost/xauth permissions).
210</note> 258</p>
259
211<p> 260<p>
212With any luck you should be able to log into your user-mode linux 261With any luck you should be able to log into your user-mode linux
213Gentoo system. The only thing keeping this user-mode linux version 262Gentoo system. The only thing keeping this user-mode linux version
214of Gentoo from being fully functional is networking from the virtual 263of Gentoo from being fully functional is networking from the virtual
215machine to the host. Such networking is supposed to be trivial, 264machine to the host.
216but I have yet to get it to work for me. Should you find a workable
217solution, please let me know!
218</p> 265</p>
266
219</body> 267</body>
220</section> 268</section>
221</chapter> 269</chapter>
222 270
223<chapter> 271<chapter>
224<title>Networking</title> 272<title>Networking</title>
225
226<section> 273<section>
274<title>Using an Existing Network</title>
227<body> 275<body>
228<p> 276
229Thanks to Martin Schlemmer (Azarah), I now know how
230to get networking to function from within a user-mode
231system. The idea is that we set up a private network
232consisting of the user-mode system and the host system,
233and then the user-mode system routes all of its packets
234to the host, which then forwards packets to the net.
235Make sure that the host kernel has
236Networking --> IP: Netfilter Configuration --> IP tables support
237--> Full NAT --> MASQUERADE target support and
238Network Device Support --> Ethertap network tap
239compiled as modules; then do the following on the
240<e>host</e> machine:
241</p> 277<p>
278Make sure that the host kernel has the following settings compiled as modules:
279</p>
280
281<pre caption="Host kernel configuration">
282Networking --&gt;
283 IP: Netfilter Configuration --&gt;
284 IP tables support --&gt;
285 Full NAT --&gt;
286 &lt;M&gt; MASQUERADE target support
287
288 Network Device Support --&gt;
289 &lt;M&gt; TUN/TAP Support
242<pre> 290</pre>
291
292<p>
293Run the following commands on the <e>host</e> machine:
294</p>
295
296<pre caption="Setup networking">
243# <i>modprobe ethertap</i> 297# <i>modprobe tun</i>
298<comment>(If you receive a FATAL error here, try deleting /dev/net/tun and retry)</comment>
244# <i>modprobe iptable_nat</i> 299# <i>modprobe iptable_nat</i>
245# <i>iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE</i> 300# <i>iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE</i>
246# <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i> 301# <i>echo 1 > /proc/sys/net/ipv4/ip_forward</i>
247</pre> 302</pre>
303
248<p> 304<p>
249The iptables line sets up IP Masquerading between the private 305The iptables line sets up IP Masquerading between the private
250network that our user-mode system will be on and the internet 306network that our user-mode system will be on and the internet
251(reachable via <c>eth0</c> in our case). The echo line then 307(reachable via <c>eth0</c> in our case). The echo line then
252turns on packet forwarding between the private network and the 308turns on packet forwarding between the private network and the
253interface that the default gateway is on (eth0 for us). 309interface that the default gateway is on (eth0 for us).
254</p> 310</p>
311
255<p> 312<p>
256Now we bring up the user-mode system and see if networking 313Now we bring up the user-mode system and see if networking
257is functional. 314is functional.
258</p> 315</p>
259<pre> 316
317<pre caption="Get UML up and running">
260# <i>linux ubd0=root_fs ubd1=swap_fs eth0=ethertap,tap0,,192.168.0.254</i> 318# <i>linux ubd0=root_fs ubd1=swap_fs eth0=tuntap,,,192.168.0.254</i>
261<comment>(login to user-mode system)</comment> 319<comment>(login to user-mode system)</comment>
262# <i>ifconfig eth0 192.168.0.1 up</i> 320# <i>ifconfig eth0 192.168.0.1 up</i>
263# <i>ping -c 2 192.168.0.254</i> 321# <i>ping -c 2 192.168.0.254</i>
264PING 192.168.0.254 (192.168.0.254): 56 octets data 322PING 192.168.0.254 (192.168.0.254): 56 octets data
26564 octets from 192.168.0.254: icmp_seq=0 ttl=255 time=0.8 ms 32364 octets from 192.168.0.254: icmp_seq=0 ttl=255 time=0.8 ms
26664 octets from 192.168.0.254: icmp_seq=1 ttl=255 time=0.6 ms 32464 octets from 192.168.0.254: icmp_seq=1 ttl=255 time=0.6 ms
267 325
268--- 192.168.0.254 ping statistics --- 326--- 192.168.0.254 ping statistics ---
2692 packets transmitted, 2 packets received, 0% packet loss 3272 packets transmitted, 2 packets received, 0% packet loss
270round-trip min/avg/max = 0.6/0.7/0.8 ms 328round-trip min/avg/max = 0.6/0.7/0.8 ms
271<i>route add default gw 192.168.0.254</i> 329# <i>route add default gw 192.168.0.254</i>
272<i>netstat -rn</i> 330# <i>netstat -rn</i>
273Kernel IP routing table 331Kernel IP routing table
274Destination Gateway Genmask Flags MSS Window irtt Iface 332Destination Gateway Genmask Flags MSS Window irtt Iface
275192.168.0.0 0.0.0.0 255.255.255.0 U 40 0 0 eth0 333192.168.0.0 0.0.0.0 255.255.255.0 U 40 0 0 eth0
2760.0.0.0 192.168.0.254 0.0.0.0 UG 40 0 0 eth0 3340.0.0.0 192.168.0.254 0.0.0.0 UG 40 0 0 eth0
277<i>scp user@192.168.0.254:/etc/resolv.conf /etc/resolv.conf</i> <comment>(if needed)</comment> 335# <i>scp user@192.168.0.254:/etc/resolv.conf /etc/resolv.conf</i> <comment>(if needed)</comment>
278<i>ping -c 2 www.gentoo.org</i> 336# <i>ping -c 2 www.gentoo.org</i>
279PING www.gentoo.org (207.170.82.202): 56 octets data 337PING www.gentoo.org (207.170.82.202): 56 octets data
28064 octets from 207.170.82.202: icmp_seq=0 ttl=240 time=119.6 ms 33864 octets from 207.170.82.202: icmp_seq=0 ttl=240 time=119.6 ms
28164 octets from 207.170.82.202: icmp_seq=1 ttl=240 time=92.0 ms 33964 octets from 207.170.82.202: icmp_seq=1 ttl=240 time=92.0 ms
282 340
283--- www.gentoo.org ping statistics --- 341--- www.gentoo.org ping statistics ---
2842 packets transmitted, 2 packets received, 0% packet loss 3422 packets transmitted, 2 packets received, 0% packet loss
285round-trip min/avg/max = 92.0/105.8/119.6 ms 343round-trip min/avg/max = 92.0/105.8/119.6 ms
286</pre> 344</pre>
345
287<p> 346<p>
288On the user-mode system we assign the user-mode eth0 interface 347On the user-mode system we assign the user-mode eth0 interface
289the private IP address 192.168.0.1 and bring up the interface. The 348the private IP address 192.168.0.1 and bring up the interface. The
290host has private IP address 192.168.0.254, and we ping it to make sure 349host has private IP address 192.168.0.254, and we ping it to make sure
291that our networking is, indeed, up. The route line adds a default 350that our networking is, indeed, up. The route line adds a default
293<path>/etc/resolv.conf</path> (if necessary), and we ping www.gentoo.org 352<path>/etc/resolv.conf</path> (if necessary), and we ping www.gentoo.org
294to make sure that name resolution (and general access to the internet) 353to make sure that name resolution (and general access to the internet)
295is working from our user-mode system. Now the user-mode system can 354is working from our user-mode system. Now the user-mode system can
296<c>emerge</c> at will! 355<c>emerge</c> at will!
297</p> 356</p>
357
358</body>
359</section>
360<section>
361<title>Using a Virtual Network</title>
362<body>
363
364<p>
365Before you get all too excited, this is not a virtual private network. It is a
366network that is only accessible by the UML instances. The
367<c>usermode-utilities</c> package provides a tool called <c>uml_switch</c> which
368defines the end points of the switch.
369</p>
370
371<pre caption="Activating end points of a UML switch">
372<comment>(If the switch information should stay in the foreground:)</comment>
373$ <i>uml_switch -unix ~/tmp/switch.sock</i>
374
375<comment>(If it should be backgrounded:)</comment>
376$ <i>uml_switch -unix ~/tmp/switch.sock &amp;&gt; ~/tmp/switch.log &amp;</i>
377</pre>
378
379<p>
380To start the UML instances on the switch, run the next command. Your
381(virtual) network interface will be connected to the <c>uml_switch</c> process
382and will be using the given MAC address.
383</p>
384
385<pre caption="Running first UML instance">
386$ <i>linux ubd0=first_rootfs ubd1=first_swapfs eth0=daemon,10:00:01:02:00:00,,~/tmp/switch.sock</i>
387</pre>
388
389<p>
390You can still connect the system to the existing network, or have a second
391process attached to both the virtual one and the existing one:
392</p>
393
394<pre caption="Running second UML instance">
395$ <i>linux ubd0=second_rootfs ubd1=second_swapfs eth0=daemon,10:00:01:02:00:01,,~/tmp/switch.sock \
396 eth1=tuntap,,,192.168.1.43</i>
397</pre>
398
399<p>
400More information about the tuntap setting can be found in the previous section.
401</p>
402
298</body> 403</body>
299</section> 404</section>
300</chapter> 405</chapter>
301
302<chapter> 406<chapter>
303<title>Testing the .iso</title> 407<title>Testing the .iso</title>
304
305<section> 408<section>
306<body> 409<body>
410
307<p> 411<p>
308Perhaps the true ideal of Gentoo Linux testing would be 412Perhaps the true ideal of Gentoo Linux testing would be
309to boot the .iso with user-mode linux and do the complete 413to boot the .iso with user-mode linux and do the complete
310Gentoo install from within the user-mode linux virtual system. 414Gentoo install from within the user-mode linux virtual system.
311</p> 415</p>
416
312<p> 417<p>
313Booting the .iso, or actually the initrd from the .iso, is pretty 418Booting the .iso, or actually the initrd from the .iso, is pretty
314straightforward. 419straightforward.
315</p> 420</p>
316<pre> 421
422<pre caption="Booting the ISO">
317# <i>mount -o loop /path/to/build-&lt;TAB&gt;.iso /mnt/loop</i> 423# <i>mount -o loop /path/to/install-&lt;TAB&gt;.iso /mnt/loop</i>
318# <i>cp /mnt/loop/isolinux/rescue.gz .</i> 424# <i>cp /mnt/loop/isolinux/gentoo.igz .</i>
319# <i>linux load_ramdisk=1 prompt_ramdisk=0 ramdisk_size=22000 \</i> 425# <i>linux load_ramdisk=1 prompt_ramdisk=0 ramdisk_size=22000 \</i>
320&gt; <i>initrd=rescue.gz root=/dev/ram0 ubd0=root_fs ubd1=swap_fs \</i> 426&gt; <i>initrd=rescue.gz root=/dev/ram0 ubd0=root_fs ubd1=swap_fs \</i>
321&gt; <i>ubd2=/dev/cdroms/cdrom0 eth0=ethertap,tap0,,192.168.0.254</i> 427&gt; <i>ubd2=/dev/cdroms/cdrom0 eth0=tuntap,,,192.168.0.254</i>
322</pre> 428</pre>
429
430<p>
323<p>Now you can follow the Gentoo install doc essentially verbatim, 431Now you can follow the Gentoo install doc essentially verbatim,
324although you'll need to know that the root filesystem will be 432although you'll need to know that the root filesystem will be
325<path>/dev/ubd/0</path>, the swap "partition" 433<path>/dev/ubd/0</path>, the swap "partition"
326will be <path>/dev/ubd/1</path>, and the CD rom 434will be <path>/dev/ubd/1</path>, and the CD rom
327will be <path>/dev/ubd/2</path>.</p> 435will be <path>/dev/ubd/2</path>.
436</p>
437
328</body> 438</body>
329</section> 439</section>
330</chapter> 440</chapter>
331 441
442<chapter>
443<title>Resources</title>
444<section>
445<body>
446
447<ul>
448 <li>
449 <uri link="http://edeca.net/articles/bridging/index.html">Bridging with
450 UML</uri>
451 </li>
452 <li>
453 <uri link="http://user-mode-linux.sourceforge.net/">UML Homepage</uri>
454 </li>
455 <li>
456 <uri link="http://www.theshore.net/~caker/uml/">Caker's UML Notes</uri>
457 </li>
458 <li>
459 <uri link="http://sourceforge.net/mailarchive/forum.php?forum_id=3647">UML
460 Mailinglist archives</uri>
461 </li>
462</ul>
463
464</body>
465</section>
466</chapter>
332 467
333</guide> 468</guide>

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