Busybox and QEMU (20090405)

@spevack	we're about ready to start. I'd like to re-introduce G__81, who is setting a Fedora Classroom record by teaching 3 classes in a row. He'll be starting in the next minute or two, whenever he's ready. Just a reminder that in 75 minutes, we'll have cwickert's class on RPM Packaging	12:13
* spevack hands the microphone to G__81		12:13
... spevack changed the topic of #fedora-classroom to: Fedora Classroom -- Busybox & QEMU		12:13
... join!#fedora-classroom -> marek(n=mmahut@fedora/pyxel)		12:13
G__81	thanks for the introduction spevack and we shall start off	12:15
... signoff!#fedora-classroom -> kkolle(Read error: 110 (Connection timed out))		12:15
G__81	ok today's session focus would be more on how to use busybox and create a basic filesystem	12:16
G__81	and before we get into qemu we would use the created file system and test it with User Mode Linux :) which we had yesterday	12:16
G__81	ok now	12:17
G__81	how many of you know whats busybox	12:17
dash123	g__81: by creating a fs, you mean we'll be creating the same thing folks at nagios.co.uk did for us?	12:17
dash123	not me...did a wiki read of course	12:18
G__81	dash123, thats a fedora file system that we used which has many packages but lets say you just want a basic file system which would boot and you could play with it and which has basic utilities	12:18
... join!#fedora-classroom -> Padhu(n=Padhu@117.97.180.178)		12:18
G__81	so we are going to create a very basic file system and use it with user mode linux. Additions to it could be made later	12:19
dash123	ok	12:19
G__81	not sure whether we could cover everything today but i ll try my level best to cover whatever i could	12:19
G__81	ok busybox is an utility to create embedded file systems with basic utilities installed in the file system	12:20
... join!#fedora-classroom -> xyzz(n=xyzz@norkia.v3.sk)		12:20
G__81	these utilities could be some bash stuff but it basically does not include any compilers, or any other packages which come as additions	12:21
G__81	ok now let us download busybox and compile it	12:21
jcapel	does busybox actually have binaries like /bin/ls, or are these interpreted by the shell?	12:21
dash123	can we jsut yum install busybox it....i saw it exists	12:21
G__81	jcapel, yes it does have	12:22
G__81	dash123, no let us not do that then you would not know how to customize it i am not sure what options you have by default	12:22
G__81	its quite similar to configuring the kernel :)	12:22
dash123	ok...	12:22
G__81	you could download the software from this link	12:22
G__81	http://busybox.net/downloads/busybox-1.13.3.tar.bz2	12:22
linuxguru	so we don't use the one already packaged in fedora ?	12:23
G__81	yes	12:23
G__81	you could its not that we shouldnt	12:23
G__81	but lets take the hard route so that we get to know the options what are available :)	12:24
l0nwlf	busybox downloaded and extracted	12:24
l0nwlf	now what ?	12:24
G__81	good	12:25
... leave!#fedora-classroom -> so_solid_moo("Ex-Chat")		12:25
G__81	now lets first create a raw file	12:25
G__81	an image file	12:25
G__81	you could use qemu img creator for this	12:25
G__81	do you all have qemu image creator installed ?	12:25
lwh	yes	12:26
jcapel	no, but I imagine dd wil also work?	12:26
G__81	yeah fine if you all know about dd fine then	12:26
G__81	lets go the dd way then	12:27
... signoff!#fedora-classroom -> dash123("http://www.mibbit.com ajax IRC Client")		12:27
l0nwlf	no	12:27
l0nwlf	qemu > I think I should get it via Yum	12:27
G__81	any problem ?	12:27
G__81	let me tell you both then :)	12:27
l0nwlf	dd will work i hope ?	12:27
G__81	i ll tell you how to create it using dd and qemu too	12:27
G__81	lets create an empty file for 320k size	12:28
G__81	dd if=/dev/zero of=rootfs.img bs=320k count=1	12:28
G__81	this would create an empty file	12:28
G__81	to know more about dd parameters you could do man dd	12:29
l0nwlf	well inside the Busybox directory	12:29
G__81	no not necessary	12:29
G__81	you could do this inside your home dir	12:29
G__81	is it done?	12:30
* G__81 waits		12:30
openpercept	yes	12:30
lwh	yes	12:30
jcapel	yes	12:30
l0nwlf	yes	12:30
G__81	yeah fine	12:30
G__81	now parallely let me tell you what you would need to do if you want to use qemu image creator	12:30
G__81	example:qemu-img create rootfs.qcow 1G	12:31
l0nwlf	qemu.i386 : QEMU is a FAST! processor emulator	12:31
G__81	the above command would create a rootfs.qcow file system of 1GB size	12:31
G__81	you could use anything you need	12:32
... join!#fedora-classroom -> dash123(i=dce36163@gateway/web/ajax/mibbit.com/x-c69e252ac209cbe4)		12:32
G__81	ok now you have created the rootfs.img	12:32
G__81	now lets format the file system	12:32
... join!#fedora-classroom -> ideamonk(n=ideamonk@117.192.230.66)		12:32
G__81	i mean format the file using ext2 or ext3	12:32
jcapel	the 320k one?	12:33
G__81	yes	12:33
... signoff!#fedora-classroom -> Malformation(Remote closed the connection)		12:33
G__81	mkfs.ext2 i	12:34
G__81	1024 F	12:34
G__81	rootfs.img	12:34
G__81	sorry	12:34
G__81	"mkfs.ext2 -i	12:34
G__81	1024 -F	12:34
G__81	rootfs.img"	12:34
G__81	this is the command for some reason i get line breaks :-o	12:34
G__81	you could either use ext2 or ext3	12:34
G__81	if you want ext3 you could do mkfs.ext3	12:35
* G__81 wait		12:35
* G__81 waits		12:35
jcapel	is there any reason in particular for the -i 1024?	12:35
jcapel	(done, btw)	12:36
lwh	rootfs.img: Linux rev 1.0 ext2 filesystem data	12:36
... join!#fedora-classroom -> mahesh(n=mahesh@116.75.194.100)		12:36
G__81	ok yeah fine	12:36
... join!#fedora-classroom -> Malformation(n=Malforma@tiesda1.lnk.telstra.net)		12:37
l0nwlf	well i do not understood 1 thing	12:37
G__81	as far as i know 1 node is every 1024 bytes and hence you give it but exact reason i could refer and let you know	12:37
openpercept	done, does -i refers to the block size for FS? i guess	12:37
G__81	i am not ablee to recollect it	12:38
l0nwlf	dd if=/dev/zero of=rootfs.img bs=320k count=1 => after this we need to make the FS	12:38
G__81	l0nwlf, yes	12:38
G__81	you need to format it and create a file system	12:38
G__81	the dd command creates an empty file	12:38
l0nwlf	and the command will be "mkfs...."	12:39
lwh	mkfs.ext3 or mkfs.ext2	12:39
G__81	you could use either of those 2	12:39
l0nwlf	ok , i'll go with ext3	12:40
* G__81 waits		12:40
l0nwlf	well i got some odd outputs	12:41
l0nwlf	pasting the log	12:41
l0nwlf	http://www.mibbit.com/pb/mfnGNw	12:41
G__81	its done	12:41
G__81	its not odd thats how you get it	12:42
G__81	if you read through it it says what its doin :)	12:42
... leave!#fedora-classroom -> xyzz()		12:42
l0nwlf	"Filesystem too small for a journal" -> why ?	12:42
l0nwlf	and why will this FS be checked after every 30 mounts/180 days ?	12:43
thomasj	l0nwlf, google will answer that for you, has nothing to do with the class right now.	12:44
linuxguru	that's how ext3 works	12:44
l0nwlf	ok	12:44
G__81	l0nwlf, the ext3 file system is a journalized file system and hence even if you use this mkfs.ext3 as far as i know it still gets you a ext2 file system i believe	12:44
G__81	if i am wrong someone can correct me	12:44
G__81	ok now	12:45
Padhu	excuse me tutor, will you please give me an link of these logx	12:45
G__81	logs ?	12:45
G__81	what logs ?	12:45
mahesh	it will be set in the fedoraproject.org/wiki/classroom later	12:45
Padhu	fedora class room logs	12:45
G__81	yeah now	12:46
G__81	the above steps make sure you have a basic file system	12:46
icarus-c	Padhu: it is on the classroom wiki page	12:46
G__81	now lets dive into Busybox and start playing with it	12:46
icarus-c	Communicate/IRC/Classroom	12:47
G__81	so whats the advantage of busybox	12:47
... nick!Marflow -> marflow_afk		12:47
G__81	or rather why at all should i use busybox	12:47
Padhu	ok thanks	12:47
... nick!marflow_afk -> Marflow		12:48
G__81	if the space requirements are so tight in an embedded device where each MB matters you would need to create a file system which is so light at the same time it has basic utilities and hence you need busybox	12:48
... nick!Marflow -> Marflow_afk		12:49
G__81	ok	12:49
G__81	now	12:49
... nick!Marflow_afk -> marflow_afk		12:49
G__81	let us configure busybox	12:49
G__81	type make menuconfig in the busybox dir	12:49
Padhu	ok	12:50
G__81	you would get a window which is similar to the kernel configuration window	12:50
G__81	now in the window	12:51
G__81	you see lot of options to configure what you want	12:51
G__81	you see Archival utilities, Core Utils, Console Utils, Debian Utils and so on	12:51
Padhu	yes. right now	12:51
G__81	you could select what you want	12:51
jcapel	wow, that's cool :)	12:52
G__81	or you could just select save alternate configuration file option and save the config file as .config	12:52
... signoff!#fedora-classroom -> Malformation(Read error: 104 (Connection reset by peer))		12:52
* G__81 waits		12:53
jcapel	ok, I went for the defaults here :)	12:53
l0nwlf	cat .config	12:53
openpercept	saved to .config	12:53
G__81	ok fine	12:53
G__81	now	12:54
G__81	do make	12:54
... join!#fedora-classroom -> grndplane(n=grndplan@66-215-66-17.dhcp.wsco.ca.charter.com)		12:54
G__81	and let it compile	12:54
* G__81 waits		12:54
Padhu	How can i use as alternate configuration file	12:55
openpercept	Padhu, look at the bottom, there is an option	12:55
l0nwlf	done	12:56
... join!#fedora-classroom -> rjones(n=rjones@87.127.66.208)		12:56
... join!#fedora-classroom -> Malformation(n=Malforma@tiesda1.lnk.telstra.net)		12:57
openpercept	alright compilation done	12:57
G__81	ok	12:57
G__81	now	12:57
G__81	give make install	12:57
Padhu	I got it	12:58
G__81	one sec	12:58
l0nwlf	done : 'You will probably need to make your busybox binary setuid root to ensure all configured applets will work properly.'	12:58
G__81	now	12:58
G__81	after you do make	12:58
G__81	get into _install	12:58
G__81	dir	12:58
jcapel	will make install overwrite the existing system utilities on my system?	12:59
dash123	we need to get into _install before issuing "make install"??	12:59
G__81	no :)	12:59
G__81	jcapel, it will not overwrite	12:59
jcapel	ok :)	12:59
dash123	jcapel:sorry for interrupting	13:00
G__81	dash123, give make and make install and then get into _install directory	13:00
dash123	g__81: ok	13:00
G__81	and now after make install is done get into _install directory and there should be a directory by name sbin	13:00
G__81	and get into it and see for your self what busybox has done for you :)	13:00
* openpercept is already in _install and can see bin sbin linuxrc and usr		13:00
G__81	get into sbin	13:00
jcapel	so much nice tools included in busybox, I must say I'm impressed :)	13:00
G__81	and type ls	13:01
jcapel	s/much/many ><	13:01
jcapel	my resulting binary is 842K though, that probably won't fit on the 320K rootfs :P	13:01
dash123	jcapel: the resulting binary of?	13:02
jcapel	make'ing busybox	13:02
G__81	good question	13:03
G__81	now the reason is	13:03
G__81	we just didnt configure busybox at all :)	13:03
G__81	we just took the default settings	13:03
G__81	you could reduce it	13:03
G__81	how ?	13:03
G__81	let us see	13:03
jcapel	well it's still nice that pretty much all you need fits in under 1MB :)	13:04
G__81	or rather i would take it a little later	13:05
G__81	on reducing the size further	13:05
G__81	i dont want to confuse too much :)	13:05
dash123	mine is 660Kb(busybox binary)? does it depend on system?	13:05
... join!#fedora-classroom -> Padhu_X(i=7561b4b2@gateway/web/ajax/mibbit.com/x-722ed8d27d7b84e2)		13:05
G__81	now let us populate the root file system that we created	13:06
G__81	log in as root in your machine and create a mount point	13:06
G__81	/mnt/rootfs	13:06
G__81	then mount your file system that we created using this	13:07
jcapel	ok, I'll create a slightly bigger rootfs than 320KB then, this won't fit :)	13:07
G__81	you could for sure :)	13:07
G__81	i ll tell you the reason w	13:07
G__81	why we get it a little more is because we used glibc for compilation there is something called as uClibc and if we use that we can still reduce the size to half of what you got	13:08
G__81	we ll look into it separately	13:08
jcapel	cool	13:08
... join!#fedora-classroom -> maploin(n=mapleoin@fedora/maploin)		13:08
jcapel	ready, btw	13:09
G__81	you could probably create something for 3 MB to be on the safest side :)	13:09
jcapel	got 8MB mounted on /mnt now	13:09
G__81	oh good	13:09
G__81	now lets populate the file system with busybox data	13:09
G__81	rsync a	13:09
G__81	busybox/_install/ /mnt/rootfs/	13:09
G__81	chown R	13:09
G__81	root:root /mnt/rootfs/	13:09
G__81	sorry again for some reason	13:10
@spevack	G__81: about 10 minutes left, maybe 15. Next class starts at :30 w/ cwickert	13:10
G__81	the commands dont get pasted	13:10
G__81	"rsync -a	13:10
G__81	busybox/_install/ /mnt/rootfs/	13:10
G__81	chown -R	13:10
G__81	root:root /mnt/rootfs/"	13:10
G__81	give this command	13:10
jcapel	done	13:11
G__81	this will copy/sync the data from the busybox to the fs	13:11
G__81	now type sync to flush all the changes to the fs	13:11
l0nwlf	mount: /mnt/rootfs is not a block device	13:11
jcapel	l0nwlf: mount -o loop /root/rootfs.img /mnt/rootfs	13:11
l0nwlf	oops ok	13:12
G__81	you have to mount it using loop	13:12
G__81	yes	13:12
G__81	now try using this file system for User Mode Linux	13:12
jcapel	ok	13:13
G__81	we gave the Fedora file system as the parameter yesterday instead of that try giving this	13:13
G__81	also make sure you unmount it	13:13
G__81	before you start UML	13:13
G__81	because this file system would be mounted	13:13
jcapel	Kernel panic - not syncing: No init found. Try passing init= option to kernel.	13:13
... signoff!#fedora-classroom -> Padhu_X("http://www.mibbit.com ajax IRC Client")		13:13
G__81	is it the User Mode Linux Kernel ?	13:14
jcapel	yes	13:14
G__81	kernel version ?	13:14
jcapel	./linux ubd0=/root/fs.img mem=128M	13:14
jcapel	2.6.29.1	13:14
l0nwlf	[l0nwlf@l0nwlf-Arena sbin]$ sudo mount -o loop -t ext3 /mnt/rootfs ../../rootfs.img gives : "/mnt/rootfs: Is a directory"	13:14
jcapel	but it's right, it does not have init, I can try init=/bin/sh I guess	13:14
Padhu	jcapel: i think --loop	13:15
linuxguru	l0nwlf, man mount , /mnt/rootfs comes at last	13:15
jcapel	ok and that doesn't work either :p	13:15
l0nwlf	ok	13:15
G__81	jcapel, it works here :o	13:16
G__81	i am on 2.6.28.1	13:16
jcapel	Failed to execute /bin/sh. Attempting defaults. -- using ldd, I see that it depends on ld-linux.so and a libc	13:16
jcapel	my rootfs image doesn't have that	13:16
... join!#fedora-classroom -> kkolle(n=klaus@89.249.9.231)		13:16
lwh	if we weren't here yesterday is there a one-liner to boot using UML?	13:16
... join!#fedora-classroom -> ahmed-araby(n=ahmed@unaffiliated/ahmed-araby)		13:16
G__81	you get the shell now jcapel ?	13:16
jcapel	no, I think I'm missing some libraries	13:16
... join!#fedora-classroom -> padhu_x(i=7561b4b2@gateway/web/ajax/mibbit.com/x-747f0c88c81780d1)		13:17
G__81	anyone getting it ?	13:17
G__81	after its booted	13:17
G__81	the following should be done	13:17
G__81	execute "mkdir /mnt/rootfs/dev"	13:18
G__81	execute "mknod /mnt/rootfs/dev/console c 5 1	13:18
G__81	mknod /"	13:18
G__81	execute "mknod /mnt/rootfs/dev/console c 5 1"	13:18
G__81	execute "mknod /mnt/rootfs/dev/null c 1 3"	13:18
jcapel	I'll try building busybox as a static binary	13:18
G__81	hmmm...	13:18
G__81	but it should work	13:18
jcapel	well it's linked against libc, and I don't have a libc in my rootfs	13:19
G__81	you dont need it	13:19
l0nwlf	I can't mount even : 'mount: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error'	13:19
l0nwlf	'ext3: No journal on filesystem on loop0' -> dmesg output	13:20
G__81	why loop0?	13:20
G__81	the following is the command to mount	13:20
jcapel	but it's fine, I get the idea and will google later; don't let me stall you :)	13:20
G__81	mount o	13:21
G__81	loop rootfs.img /mnt/rootfs	13:21
G__81	there are hyphens missing :o	13:21
G__81	again	13:21
G__81	now mount /proc in the busybox file system	13:21
l0nwlf	ohh i gave '-t ext3' .. now it's fine	13:21
G__81	mount -t proc none /proc	13:22
G__81	and /sys	13:22
G__81	as	13:22
G__81	mount -t sysfs none /sys	13:22
... join!#fedora-classroom -> sattam(n=sattam@unaffiliated/thtoh)		13:22
G__81	and one last step is	13:22
G__81	to create an /etc/inittab file	13:22
G__81	which is the first script which would get executed	13:23
G__81	let me fpaste it	13:23
... join!#fedora-classroom -> qwp0(n=qwp0@adsl-dyn217.78-98-136.t-com.sk)		13:23
G__81	http://fpaste.org/paste/8010	13:23
G__81	this should be the inittab script	13:23
G__81	and once this is done	13:23
G__81	you are all set to play with the busybox FS	13:23
G__81	the other things that could be done are many on top of it	13:24
G__81	you could configure IP addresses, add routes, do test ping etc..........	13:24
G__81	i am not sure whether you all understood it :)	13:24
G__81	and not sure whether i ve conveyed what i wanted to	13:24
G__81	properly	13:24
G__81	:)	13:24
jcapel	I understood :) doesn't work yet, but I'll figure that out later :)	13:25
dash123	g__81: you did say you'll create a wiki for us though:)	13:25
G__81	for busybox ?	13:25
ahmed-araby	sattam:it seems that we came tooo late and missed alot	13:25
... join!#fedora-classroom -> Fzza3a(i=29dd1066@gateway/web/ajax/mibbit.com/x-6ecf413d8a8c2284)		13:25
G__81	ahmed-araby, i guess right time for the next session :D	13:26
jcapel	G__81: thanks, again!	13:26
@spevack	G__81: thanks for teaching this session!	13:26
G__81	yeah i shall create a wiki page too on this	13:26
padhu_x	thank you tutor	13:26
@spevack	we'll take a short break, and cwickert will begin the RPM Packaging session at :30	13:26
padhu_x	you teach me more	13:26
G__81	for busybox i guess it should be useful	13:26
G__81	thanks spevack	13:26
grndplane	Thanks	13:26
dash123	please pass on the link in ML or wherever	13:26
dash123	thanks g__81	13:26
openpercept	thanks G__81	13:26
... leave!#fedora-classroom -> Fzza3a()		13:27
G__81	and thanks to everyone for attending this session	13:27

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