Testbed for Predicate Routing in DTN over MANET User Manual
Contents
1. check if etc apt sources list contains http ftp us debian org debian check if etc securetty contains echo tty0 gt gt etc securetty echo ttys 0 gt gt etc securetty modify etc inittab like this 1 2345 respawn sbin getty 38400 tty0 2 23 respawn sbin getty 38400 tty2 3 23 respawn sbin getty 38400 tty3 4 23 respawn sbin getty 38400 tty4 0 0 5 23 respawn sbin getty 38400 tty5 6 23 respawn sbin getty 38400 tty6 10 8 Since the testbed uses a Debian distribution every time an instance of the Operating System is generated with UML an user would need to enter lo gin and password To speed up the process of instantiating many nodes in the testbed and since there are no real security issues in the virtualization the user might consider an autologin funtionality One package which pro vides the autologin is the package mingetty After installing the package as follows root host apt get install mingetty the user needs to modify etc inittab like this 1 2345 respawn sbin mingetty a respawn respawn 2 3 4 5 6 23 223 2253 223 223 respawn respawn respawn sbin ge sbin ge tty tty sbin getty sbin getty sbin getty 38400 38400 38400 38400 38400 tty2 tty3 tty4 LEYS tty6 utologin root tty0O 4 4 How to Install the DTN Reference Implementation At this stage we need to install the DTN R2. init The script contains the following instructions bin bash script init groupadd tun useradd ubuntu G tun chown tun dev net tun chmod gtrw dev net tun Then we need to start the virtual interface tap lt X gt as many as the number of nodes in the emulation Calling the following script as root root host tap_up lt numbers_of_nodes gt which exactly does for seven interfaces bin bash tunctl u ubuntu t tapO b ifconfig tap up tunctl u ubuntu t tapl b 21 ifconfig tapl up tunctl u ubuntu t tap2 b ifconfig tap2 up tunctl u ubuntu t tap3 H ifconfig tap3 up tunctl u ubuntu t tap4 b ifconfig tap4 up tunctl u ubuntu t tapo b ifconfig tap5 up tunctl u ubuntu HE tape p ifconfig tap6 up tunctl u ubuntu t tap7 b ifconfig tap7 up In order to start more than one terminal for each emulated node with command as user for example for the first emulated machine with number 1 the following command shall be used user host node lt number_of_nodes gt Where node is the following script bin bash echo echo node S 1 starting echo A S 1 1 B S A 4 xterm T nodeS 1 e linux ubd0 cow_uml1SA root_fs eth0 tuntap tapSA ethl tuntap tap SB amp Notice that the command cow_umlX makes a local copy of the general filesystem root fs 6 1 Configur
3. was conflicting with VPN We solved the problem bringing down the network interfaces associated with the virtual machine vmnet8 and vmnet shutting down VMware disconnecting the VPN and starting again the virtual machine then the VMware network con figuration file needed to be run again of course a user can reset manually the network interfaces that need to be up again Notice also that whenever a change in the VMware network configuration setting is done for example from NAT to bridge the virtual machine needs to be rebooted and it does not do automatically If the user wish to use virt manager to run ubuntu here below are listed some of the not intuitive instructions to create the virtual machine e Create a new virtual system and load the ISO image e We suggest to be safe in the space allocation or not to assign the storage space in advance unless the user is confident about how much is needed for the purpose of the experiments e Connect to host Network via virtual network if the host is disconnected connected via wireless or dynamically configured with NetworkManager or via shared physical device if the host is statically connected to the wired ethernet to gain the ability to migrate the virtual system e Allocate properly the memory and the cpu to the virtual machine e It is common to get error of unable complete install the virDominCreateLinux failed QEMU quits during console startup Sometimes this error can be
4. D C0 Hj lj hj lj D C0 install nets into taps 18 A8 A8 A8 A8 2F 2F 2F 2F Assign network objects to TAP agents Sal network Sa2 network Sa3 net Sa4 net work work Assign TAP Srawl Sraw2 Sraw3 Sraw4 agents to ns 2 nodes Sns_ attach agent node 0 Sal Sns_ attach agent node_ 1 S a2 Sns_ attach agent node_ 2 a3 Sns_ attach agent node_ 3 S a4 puts loading scenario source val sc puts scenario loaded Sns_ at Sval stime stop Sns_ at Sval stime puts NS EXITING Sns_ halt proc stop global ns_ Sns_ flush Stracefd close Srawl Sraw2 Sraw3 Sraw4 puts Sns_ CL o ru C el Cc ose lose ose lose key n tracefd rawl raw2 raw3 raw4 trace 5 3 Create the Virtual Tnterface tap lt X gt One of the possible transport mechanisms for User Mode Linux is the TAP virtual Ethernet device To use the TAP devices the TUN TAP driver should be included in the kernel configuration If the kernel does not have this option one can download a patch from the TUN TAP home page 10 The user needs also the tunctl tool which is used to configure TUN TAP devices This is included in 19 the uml utilities package in the Debian based system root host apt get install uml utilities Now we can set up TAP devices for User Mode Linux machines and prepare
5. Testbed for Predicate Routing in DTN over MANET User Manual Flavio Esposito and Gabriele Ferrari Aggradi Boston University Email flavio gfa cs bu edu September 11 2008 Abstract This guide describes how to rebuild a User Mode Linux UML based testbed we have used to test our Predicate Routing for DTN over MANET 5 Following these instructions a number of UML virtual machines can be set up to emulate DTIN MANET nodes connected by a simulated network through ns 2 19 1 Installing Ubuntu on a Virtual Machine The testbed has been installed on an Ubuntu Linux distribution A user can follow herein the instructions for installing the testbed even with a different oper ating system or a different Linux distribution given a virtual machine support In this case an image of Ubuntu has to be installed The version we used is Ubuntu 7 10 Gutsy Gibbon and the image we mounted has been ubuntu 7 10 desktop i386 iso downloadable from 7 Examples of virtual machines are VMware 17 or the free KVM 6 that has to be used with QEMU 3 in particular the management tool needed to run the OS image with KVM is called virt manager In any case the user who wishes to use a virtual machine has to make sure the network adaptor is configured to share the host s internet connection NAT We found that both virtual machines work well except when we used VMware together with a Virtual Private Network VPN running the NAT protocol
6. The tap agents then use this mapping table to determine the destination network address within the simulation To test the installation the user can use the example in 11 with the command as normal user fuser host nse ns2emulation tcl If launched at this stage the script will generate an error since there are no tap interfaces installed yet An exemplifying script is the following bin nse An example script for the usage of ns 2 in emulation mode Uses 1 Network Raw agents to access to a network device at level 2 Tap Raw agents to map between real MAC addresses and NS 2 IP addresses 3 In memory compression of the trace file to reduce disk write operations during simulation Common variables set scriptname routingdemo set val chan Channel WirelessChannel set val prop Propagation TwoRayGround set val netif Phy WirelessPhy set val mac Mac 802_11 gt set val ifq Queue DropTail PriQueue set val ll LL A set val ant Antenna OmniAntenna gt set val ifqlen 50 set val x 800 set val y 600 R set val rp DumbAgent A set val nn 4 15 set val stime 180 0 set val stime 360000 0 set val sc set ns_ new mobility tcl Simulator Sns_ use sch duler RealTime use this for file trace set tracefd set namtrace use this to set namtrace use this to set tracefd set na
7. arning Can not write log openpty failed dev pts not mounted root root_fs apt get install tcl8 4 root root_fs apt get install tcl8 4 dev root root_fs apt get install libxerces28 root root_fs apt get install libxerces28 dev root root_fs apt get install libdb4 5 root root_fs apt get install libdb4 5 dev root root_fs apt get install libdb4 5 root root_fs apt get install libdb4 5 dev root root_fs apt get install libdb4 5 tcl root root_fs cd dtn lt version gt root root_fs configure root root_fs make root root_fs make install From the version dtn 2 5 0 released in October 2007 the user can also use the binary debian package for the stable release etch as well as the source files through the apt package management system The user needs to add the following lines to etc apt sources list deb http www dtnrg org debian etch contrib deb src http www dtnrg org debian etch contrib and finally run root host apt get install dtn 4 5 Install the AODV Kernel Module The routing protocol is a kernel module that needs to run as a daemon dur ing our emulation We have implemented our predicate routing starting from the AODV UU implementation of University of Uppsala In order to reproduce the testbed the first thing to do is therefore to install that module on the guest filesys tem The module
8. can be found at 1 12 After downloading the user needs to modify the Makefile in the main direc tory and in the directory Inx in particular the version of the kernel the install directory and the uninstall directory The default options is the directory ib mod ules of the host but we need it in the same directory of the guest since we are running the kernel in the guest After changing the makefile the installation of the AODV kernel module will run with root host make ARCH um root host make install ARCH um As a final stage of the testbed installation since the installation of the kernel mod ules writes the AODV modules in the lib modules lt kernel_version gt of the host system the user again shall copy this directory in the same place in the guest filesystem 5 Configuring the Testbed Having created the testbed i e having installed the kernel filesystem let us give instructions on how to configure the host machine This section will explain how to create the virtual network structures and how to connect these with the network simulator ns 2 5 1 Create User and Group We need to create a group to have access to the virtual network interface on the host machine To do so in the terminal as root root host groupadd lt group_name gt Then we need to add the user to the group created previously This user will be able to use network emulation in ns 2 in the terminal as root root h
9. control network has been created to remotely con trol the application on the emulated nodes during a testbed execution A Linux software bridge with the IP address 10 0 1 254 connects all guest control network interfaces to the host system and to each other The user who wishes to implement the set of elements described has to make a choice 1 To download a pre compiled kernel for User Mode Linux with a filesystem configured to work with that kernel 9 or 2 To compile the kernel from source and to create the filesystem following the instructions in the sections below Even though the first choice seems the easiest one the associated tree sources of the kernel have to be configured to support the addition of external modules For example for our DTN over MANET testbed we had to install in addition the kaodv module User Mode Linux User Mode Linux User Mode Linux User Mode Linux Figure 1 Proposed testbed each emulated node shall have an AODV daemon running some of the emulated nodes will be DTN nodes running a DTN reference implementation A machine will host the ns 2 simulator for simulating wireless connectivity and mobility of emulated nodes A control network is also estab lished to remotely control the application on the emulated nodes during scenario execution Some references to a pre compiled kernel with a filesystem that suits our needs are UML home page 2 VNUML website 13 and the Nagafix website 8 3 User M
10. eference Implementation code on the root_fs to do so the user shall mount the filesystem root_fs and download the latest reference code from the official website 14 Then the packages Tcl Tk Xerces and BerkeleyDB need to be installed Before doing that in order to run our convergence layer the user may need also to install the perl packages root host libdbi perl libclass autouse perl libhtml template perl libmime perl liburi perl libcon libhtm libmailt libwww per too s per l libio st tringy perl apt get install libdatetime perl libdbd mysql perl libmd5 perl libdigest shal perl libimage size perl libmime lite perl npress zlib perl tagset perl libnet dns perl libhtml parser perl libwww perl libgd gd2 perl libunicode maputf8 per libxml simple perl libdigest hmac perl And likewise for the optional modules root host apt get install libgd graph perl libproc process perl librpc xml perl 11 libsoap 1lite perl Libxmlrss perl libxml atom perl libn libcrypt dh per per libstring crc32 perl nath bigint gmp perl liburi fetch perl magick libclass accessor perl libclass trigger libmail gnupg perl libtext vcard perl per libclass data inheritable perl libgnupg interf During your installation the user can ignore the w
11. igure an ns 2 node initially proc setup_node id x y z color global ns node_ set node_ id Sns_ node Snode_ Sid set X_ Sx Snode_ Sid set Y_ Sy Snode_ Sid set Z_ z Snode_ Sid color S color Sns_ at 0 Snode_ id setdest x Sy 0 Se oH HEHE SHE SHR HE 17 Sns_ at 0 Snode_ i setup_node setup_node setup_node setup_node for set i global ns_ set node_ Snode_ i Sns_ at 0 ens Snode_ Sid random motion 0 d 100 2 50 350 500 e w N FP 0 node_ i 300 300 300 300 oO a S CO i lt 3 color S CO bo black green blue cyan incr i Sns_ node random motion 0 start Snode_ i at Sval stime Snode_ i Snode Snode Snode Snode col col or or black green color blue color cyan Network reset objects to access the TAP devices at the link layer set set set set Srawl rawl raw2 raw3 raw4 open new new new new tap Network Raw Network Raw Network Raw Network Raw 0 readwrite Sraw2 Sraw3 Sraw4 Tap Agent open open open tapl tap2 tap3 readwrite readwrite readwrite for each node Agent Tap set maxpkt_ 3100 set set set set puts al a2 a3 I a4 ew ew ew ew Agent Tap Raw FE Agent Tap Raw FE Agent Tap Raw FE Agent Tap Raw FE D C0 D C0
12. ing Emulated Nodes In order to configure the emulated nodes in each virtual machine UML the user shall execute the following commands root vm init node lt number_of_node gt this script is the MAC address must be the same as in the ns2emulation tcl con figuration file 22 bin bash echo configure node S 1 hostname nodes 1 ifconfig ethO 10 0 0 S 1 netmask 255 255 255 0 hw ether FE FD C0 A8 2F 0 1 up ifconfig ethl 10 0 1 1 netmask 255 255 255 0 up echo node S 1 configured At this stage we need to initialize the AODV kernel module and to run the AODV daemon root vm aodv this script is bin bash modprobe kaodv aodvd d i ethO 1 r 3 Where the option d means that it will run in daemon mode the option i ethO means that the interface eth0 will be used the option enables the logging in the file var log aodv log the option r 3 enables the logging every 3 seconds of the routing table in the file var log aodv rtlog We also need to initialize the database of the DIN node and we do so calling root vm init dtn This script is bin bash dtnd init db To run the DTN daemon for running the node as a DTN node root vm dtn and this script is bin bash dtnd d o var log dtn log t 23 where the option d means that it will run in daemon mode the option o var log din log means that the log file will be in var log dt
13. l for User Mode root host apt get update root host apt get upgrade root host apt get install ncurses dev root host cd linux lt version gt root host make defconfig ARCH um root host make menuconfig ARCH um 2We do not guarantee that all of them have been compiled enabling the addition of new mod ules such as kaodv The option ARCH um is vitally important while building UML since it causes the kernel built to work as a separate Linux architecture In the rest of this section the options that we used in our testbed are listed The user may need to enable or disable others in order to build a fully function ing kernel We report the options that we have set after running the system call menuconfig Load module support Enable To add modules or external modules to the kernel and to permit the automatic load UML Specific Options Host Processor Type Features Generic x86 support Disable UML Specific Options Host Processor Type Features Process Family Choose your processor Networking Amateur Radio Disable Networking IRDA infrared Subsystem Support Disable Networking Blue tooth Subsytem Support Disable Enable the Block Layer Block Devices Virtual block devices En able Character devices stderr console Enable Character devices virtual serial line Enable Character devices port channel support Enab
14. le Character devices pty channel support Enable Character devices tty channel support Enable Character devices xterm channel support Enable File systems To make the kernel build faster enable the filesystems that you would need ext3 was one of them SCSI support Disable Multi device support RAID and LVM Multiple devices driver support RAID and LVM Disable e Memory Technology Devices MID Memory Technology Device MID support Disable e Kernel Hacking Show timing information on printks Enable e Kernel Hacking Kernel debugging Enable e Kernel Hacking Compile the Kernel with Debug Info Enable e Netfilter Options Networking Networking Options Network Packet Filtering replaces ipchains IP Netfilter configuration You have to enable all the options to lt M gt to use the modularized features We suggest to follow the instructions in the original source 16 If the source is no longer available we also report the same page at 4 Beginning with kernel 2 6 20 the Netfilter kernel configuration was com pletely changed It is split into Core Netfilter Configuration and IP Net filter Configuration Netfilter configuration is needed to use some network modules in the kernel as AODV in our use case At this stage after having complete the previous setting we suggest to backup the config file root host cp config config bkp Now
15. llowing subsections explain how to install the AODV kernel module the DTN reference implementation and finally how to create mount and configure the filesystem 4 1 Create the Filesystem Among all the common distributions we used the Debian 12 following the user mode linux tradition To begin the user shall initialize the files using the system call dd Assuming that the user image files are root_fs in the directory home lt user gt in terminal as root we type root host dd if dev zero of home lt user gt root_fs bs 1024K count 1000 With the call above we have created a filesystem of 1024 Mb Of course the user might need a different size The next step is to initialize the filesystems inside of each of these files We will be using ext3 as our root filesystem If the system does not recognize root_fs as a block special device proceed anyway root host mkfs ext3 home lt user gt root_fs Now the user needs to mount the root filesystem before calling debootstrap root host mkdir mnt uml root host mount o loop home lt user gt root_fs mnt uml Next step is to install debootstrap and bootstrap a base Debian installation This is a barebones installation that is less than 200 megabytes We used the latest testing distribution whose codename is lenny root host apt get install debootstrap root host debootstrap arch i386 lenny mnt uml http ftp us debian org debian 4 2 Mo
16. mtrace Sns_ trace al open gzip gt S scriptname tr gz w open gzip gt S scriptname nam gz w pipe the namtrace to nam only do this in X open nam r 0 1 w disable tracing open dev null w open dev null w 1 Stracefd Sns_ namtrac all wireless Snamtrace val x S val y set trO new BaseTrace ShmGZ test tr gz 16 400 104857600 Procedure n proc NamTime Send time to global ns_ na set now S ns_ set next exp puts Snamtrac flush Snamtra Sns_ at Snext Sns_ at 1 0 proc UniformE set err Serr unit Serr set Serr ranv ded when running nam in real time t 1 nam periodically mtrace now r Snow 0 05 e T t Snow ce NamTime NamTime EE tad A new ErrorModel packet rate_ 0 01 ar new RandomVariable Uniform 16 err drop target new Agent Null return Serr set topo new Topography Stopo load_flatgrid val x Sval y Create GOD set god create god val nn Create channel set chan 1l new Sval chan Configure node parameters Sns_ node config adhocRouting val rp 11Type eval ii macType val mac ifqType Sval ifq ifgLen val ifglen antType Sval ant propType val prop phyType Sval netif topolInstance topo agentTrace OFF routerTrace OFF macTrace ON movementTrace OFF channel Schan_1_ IncomingErrProc UniformErr Procedure to conf
17. n log option needed if you use the option d and the option f clears the database and initializes the tables on startup We are now ready to run the ns2 simulations on the testbed having only the AODV routing protocol 24 References 1 AODV Module Uppsala University Sweden http core it uu se core index php AODV UU 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 ht ht tp user mode linux sf net tp bellard org gemu http cs people bu edu flavio kernelConfiguration4Testbed htm ht ht tp csr bu edu preda tp kvn tp rel htt ht Pa tp uml ge ht ht ht ht n gumranet com kvmwiki HOWTO1 leases ubuntu com 7 10 l nagafix co uk tp user mode linux sourceforge net tp vtun sourceforge net tun tp www ivs cs uni magdeburg de EuK forschung ojekte nse p www debian org tp www dit upm es vnumlwiki index php Main_ tp www dtnrg org wiki Code tp www kernel org tp www shorewall net kernel htm tp www vmaware com Jef Dike User Mode Linux Bruce Perens Open Source Series Prentice Hall 2006 19 Daniel Mahrenholz and Svilen Ivanov Real time network emulation with ns 2 In In Proc of DS RT pages 29 36 2004 25
18. ode Linux This section provides compiling instructions for the kernel when a user wish to use the User Mode Linux virtualization Moreover how to install the necessary kernel module needed is explained Before starting we report the definition of UML from 18 User Mode Linux UML is an extended Linux kernel that works as a guest virtual machine on a Linux host machine It is possible to assign a root filesystem and other physical resources different from the host machine Technically UML is a port of Linux to Linux Linux has been ported to many different processors including the ubiqui tous x86 Sun s SPARC IBM and Motorola s PowerPC DEC s then Compaq s and HP s Alpha and a variety of others UML is a port of Linux in exactly the same sense as these The difference is that it is a port to the software interface defined by Linux rather than the hardware interface defined by the processor and the rest of the physical computer 3 1 How To Compile the Kernel For UML This section explains how to compile and configure the kernel for User Mode Linux We underline again that we considered compiling our own kernel because we think is the better way to have full control on the testbed features The first thing to do is to get the latest version source of the kernel tree from the Linux Kernel Archives 15 Then follow the instructions Unpack the tree as root root host bunzip2 linux lt version gt tar bz2 Configure the kerne
19. ost useradd lt user_name gt G lt group_name gt 5 2 Install NS2 Emulation on the Host Since the node whose mobility is simulated by ns 2 are emulated the modified version of ns 2 ns2emulation shall be used Ns 2 acts like a bridge between the virtual Ethernet interfaces TAP It reads packets from a source TAP device it passes them through a simulated wireless network and it writes them back to the TAP device destination Each ns 2 in the 13 simulated network represents an UML virtual machine in the real network Even in this case there are two ways to install ns 2 in the host machine with emulated extension the first one is to build it from the source the second one is to use a Debian package Here we used simply one of the two the Debian package downloading from the website of the original project 11 and adding the following lines to the reposito ries list in etc apt source list deb http bode cs uni magdeburg de aherms debian sid ns2 deb src http bode cs uni magdeburg de aherms debian sid ns2 to install from the new repository you have to update the packages list in terminal as root type root host apt get update root host apt get install nsemulation root host apt get source nsemulation The ns 2 emulation is made from network objects and tap agents The network objects are used to send and receive packets to and from a network The ns 2 network object a
20. solved just by pressing the finish button again some other time the user needs to add his username to the kvm group log off and log in again To solve execute sudo adduser username kvm Alternatively the user can create an image and the QEMU system call as fol lows The Network Address Translator protocol allows multiple nodes in this case one node would be the host machine and the other is the virtualized machine to share a single internet or local network IP address pathi qemu hda path2 NameImage img m 256 for 256 Mbyte of RAM allocated to the virtualized system If the user is not the installer of QEMU path1 should be usr bin 2 The Testbed The architecture of the Linux based testbed we used can be described with a set containing the following components e User Mode Linux to emulate more than one machine node e The DTN Reference Implementation Code so that every emulated node is a DTN node e A Mobile Ad hoc NETwork MANET Routing Protocol Implementation necessary to run the routing protocol at MANET level e The network simulator ns 2 ns emulation version useful to simulate the mobility of both DTN and MANET nodes In Figure 1 four emulated nodes are configured to communicate with the host machine For each emulated node we need two network interfaces one to in terconnect the hosts creating a control network and the other one to interconnect with the ns 2 simulator The
21. t the link layer uses the pcap library to read packets from a network device The emulation version of ns 2 implements a new network object to read and write packets to a network device at the link layer using the Linux packet sockets for this purpose The network object for link layer access is called Network Raw It supports the commands open and close with the following syntax lt Network Object gt open lt Interface Name gt readwrite readonly writeonly lt Network Object gt close The user can use it for example in the following way set raw0 new Network Raw Sraw0 open tap0 readwrite s eran Sraw0 close The tap agents are connected to network objects and to ns 2 nodes obtaining network packets from the network objects and sending them through the sim ulated network In the emulation version of ns 2 the new tap agent is called Agent Tap Raw It implements additionally address mapping between MAC addresses of the virtual machines and IP addresses of ns 2 nodes Each Agent is assigned to one virtual network interface via a network object Network Raw 14 The only difference in using Agent Tap Raw is that at the creation the user has to specify the MAC address of the machine that the agent corresponds to For example set a0 new Agent Tap Raw FE FD 0A 00 00 01 In this case the tap agent registers in a common mapping table that it is re sponsible for receiving frames with the specified MAC address
22. them for the network emulation If the device deu net tun does not exist create it in terminal as root root host mkdir dev net root host mknod dev net tun c 10 200 Create the permissions to read write for the group created previously In terminal as root root host chown tun dev net tun root host chmod gtrw dev net tun The general command to create a virtual interface is root host tunctl b u lt user_name gt t tap lt X gt and to destroy a virtual interface is root host tunctl d tap lt xX gt 5 4 Create the Bridge A network bridge is needed to create a control network to control the nodes during the test by a ssh session In terminal as root type root host bridge_up this script is bin bash proti addbr Bro proti stp Bro off brctl addif br0 tap4 brctl addif br0 tap5 brctl addif br0 tap6 brctl addif br0 tap7 ifconfig brO 10 0 1 254 netmask 255 255 255 0 up 20 with this netmask configuration the control network will be 10 0 1 z To destroy the bridge at the end of the test in terminal as root root host bridge_down this script is bin bash ifconfig brO down bretl delbr Pro 6 Howto Run the Testbed Having installed and configured the testbed we can finally play with it This section describes the scripts needed to run it First of all we need to initialize the machine in terminal as root root host
23. unt the filesystem This section lists the commands the user needs to execute in the filesystem In terminal as root root host cd mnt root host mkdir uml root host cd uml root host mkdir proc root host mount o loop lt path gt lt filesystem gt mnt uml root host mount t proc none mnt uml proc root host chroot mnt uml At this stage the user has access to the filesystem as root and can use com mands like apt get update apt get upgrade apt get install lt name_of_package gt For the sake of completeness we report also how to unmount the filesystem In terminal as root root host umount mnt uml proc root host umount mnt uml 4 3 Configure the Filesystem In order to configure the filesystem the user needs to edit the following files in order to have your system in a valid configuration as follows e etc fstab e etc hostname e etc hosts e etc network interfaces e etc apt sources list e etc securetty e etc inittab e deb ubd0 check if etc fstab contains dev ubd0 ext3 defaults 0 1 proc proc proc defaults 0 0 check if etc hostname contains lt umluser gt it will be the name of the user who will start the emulated node of the testbed check if etc hosts or etc hosts allow contains 127 0 0 1 localhost check if etc network interfaces contains auto lo iface lo inet loopback
24. we can start with the compilation of the kernel To do so we use the com mand root host make ARCH um 3 2 How to Install the Kernel Modules The following two commands are needed to install the modules of the kernel and also to install the external modules root host make modules ARCH um root host make modules_install ARCH um After these commands the modules will be loaded in the lib nodules lt kernel_version gt of the host system At this point the user shall copy this directory in the same place in the guest file system after having mounted it Notice that in the directory ib modules the user might have two different kernel versions one for the host for example 2 6 22 14 generic and one for the emulated system for example 2 6 26 The latter is the kernel version to use 7 4 About the Filesystem At the end of this section the software necessary for the testbed will be com pleted A User Mode Linux instance requires a kernel and a root filesystem in order to run The filesystem is stored in a file on the host system The UML ker nel uses an user block device ubd mapped to this file to access its root filesys tem The UML can also use the copy on write COW feature of the ubd driver to share a single filesystem among a number of virtual machines the root filesystem in this case is used as a read only file and all the writes are done on a separate copy on write file for each virtual machine The fo
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