I'm probably being obtuse but......
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| Author | Content |
|---|---|
| Ridcully Nov 03, 2015 3:00 AM EDT |
What a heck of a complex routine to get something going that is so simple in BIOS. I started to try to read this with enormous interest and then it simply lost me..........I am slowly getting intense dislike for anything that has UEFI somewhere in its background. Is just wiping Win10 and running Ubuntu by itself on a UEFI machine possible ? To be honest, I'd rather have a Linux OS as the basis, then put Win10 into a virtual machine.......if that's possible. Mind you, that means buying a copy of Win10 which revolts me as a principle, but it's a way out I guess. But in any case, I shall be hanging onto my copies of Win7 as long as possible. I don't use them in day to day work, but they are around if I need them. I think I'm getting old.....LOL. |
| gary_newell Nov 03, 2015 4:08 AM EDT |
I don't think it is much more complicated for UEFI than a standard BIOS. Once you get Ubuntu booting from the USB drive the installation is straight forward. The only added difficulty between Windows 10 and Windows 8 is that the boot manager doesn't appear to put Ubuntu as the main bootloader and so you have to force it using efibootmgr. (you can probably use other tools like bootrepair but efibootmgr is fairly straight forward). The main issue with dual booting Ubuntu and Windows on UEFI is that each manufacturer appears to implement UEFI in a different way and so the menu options are different once you get into the UEFI bootloader screens. |
| Ridcully Nov 03, 2015 5:40 AM EDT |
Quoting:The main issue with dual booting Ubuntu and Windows on UEFI is that each manufacturer appears to implement UEFI in a different way and so the menu options are different once you get into the UEFI bootloader screens. And there you have it in a nutshell Gary......I have just discarded a $1000 HP laptop over UEFI and as the local computer repair man indicated, HP has its own way of implementing UEFI and it does NOT play by the normal rules of allowing you to boot in legacy mode - even if it says it does. And I am NOT happy. It was a lovely machine, but totally "bricked" by UEFI and Win8. PS....I will get something back....he's managed to sell the thing; but it is a severe loss as far as I am concerned and I am NOT a happy little camper over UEFI at any price. |
| cybertao Nov 03, 2015 6:06 AM EDT |
UEFI is pretty rad once you get your head around it. You can do things like boot the linux kernel directly without an intermediate bootloader if you set it up right (for what that's worth). All you need is a small FAT partition to put your boot files in and create entries (or /efi/BOOT/BOOTX64.EFI is detected automatically - on any disk including USB). It got a bad rap with Windows 8's use of secure boot, which appeared to be the first exposure of UEFI for some people, Microsoft is still a pain in the arse but always were by overwriting bootsectors with their own bootloader. Apple use their own variation of EFI that I've find to be Linux friendly. The biggest advantage it has over BIOS is GUID partitioning. By default you can have 128 partitions (no fussing around with primary and logical sectors) which can be extended if you want more. Checksums detect errors in the table. Support for disks up to 2 ZiB. Backup tables for recovery...partitioning and repartitioning is much easier. |
| Ridcully Nov 03, 2015 6:24 AM EDT |
I guess my problem is that I want something SIMPLE, effective, easy to implement without recourse to cli editing ......just install, .......like you used to do with BIOS......Guess I am too old to learn something entirely new. Old dog and new tricks ??? |
| cybertao Nov 03, 2015 7:10 AM EDT |
Most users should be able to use it without getting their hands dirty. In the linked story you can see (Boot Into Ubuntu Live Environment) they boot Ubuntu from USB by plugging it in and selecting it from the boot options as it's detected automatically (simple!). No need to select boot order of your disks or confusion over booting the right disk...and you are less likely to bork your installation by choosing the wrong disk or partition. It's easier to work with than GRUB which I thought had a steep learning curve and complexity I struggled when I first started using it. I understand secure boot can still be a bastard on some hardware though. I've never had the misfortune of owning such a device. |
| kikinovak Nov 03, 2015 12:56 PM EDT |
I wouldn't know about Windows (which I haven't used since 2001), but here's how I setup my Asus S300 with UEFI. I'm running Slackware64 14.1 on it. http://www.microlinux.fr/microlinux/Linux-HOWTOs/Asus-S300-H... |
| CFWhitman Nov 03, 2015 1:06 PM EDT |
My desktop machine at home has UEFI with no Secure Boot (I bought the parts separately and assembled the computer myself). At first it acted a little flaky with Linux (would sometimes boot and sometimes hang before it really even got started), but the next iteration of the distribution I was using on it worked fine (Ubuntu Studio). Since then, I have had no issues with running Linux on the machine. I eventually installed Windows 8.1 on a second hard drive so that my brother could play a couple of games that wouldn't run under Wine, but that's the only thing the Windows drive gets used for. |
| NoDough Nov 04, 2015 1:53 PM EDT |
Ridcully wrote: To be honest, I'd rather have a Linux OS as the basis, then put Win10 into a virtual machine.......if that's possible. Mind you, that means buying a copy of Win10 which revolts me as a principle, but it's a way out I guess. My laptop is not a UEFI machine, but that's what I'm doing right now. My primary OS is Linux Mint and Windows 10 is running in VirtualBox. But I didn't have to purchase Win10. I had a Windows 7 key with activations remaining, so I installed that in the VM, then I installed the "Get Windows 10" update (KB3035583) from Windows Updates. Then it was just a matter of allowing the VM to install the Win10 upgrade. Note that you do not want to install the VirtualBox Guest Additions until after the Win10 upgrade has been completed. It will refuse to upgrade otherwise. FWIW, my early impressions of Win10 are that it's far less stable that 7. |
| jdixon Nov 04, 2015 2:34 PM EDT |
> FWIW, my early impressions of Win10 are that it's far less stable that 7. Agreed. Windows 10 users are effectively beta testers for Microsoft. And the automatic updates which seem to happen every week are a royal pain, since they reboot the machine. |
| Ridcully Nov 04, 2015 4:21 PM EDT |
Well, I guess I've been "sorta told"......If you absolutely must use a Win system (and normally I don't) stick with Win7 if you want stability and ease of use. Avoid Win10 like the plague. Make sure Windows updates are either turned off, OR, set to the situation where you as the user have to approve any upgrade. I have gained the impression (from above comments) that UEFI is still in the "shake-down" stages and cli in some form or complexity, seems to be part and parcel of any installation. I have learnt something though, and that usb sticks seem to be used as the installation sources rather than disks (which of course tells you how terribly archaic some of my concepts are). I now have a very nice i5 - 4 core, 64bit laptop running Win7..........and I can replace the hdd and put whatever Linux I want on that new hdd.......and since it runs normal BIOS, I cannot get into trouble - well, I shouldn't and it ought to be very straight forward. I'm going to just sit back and watch. Somehow, I think the UEFI "mess" will become simpler and easier for oldies such as myself to deal with - and I give it a couple of years. Nevertheless, in the back of my mind is always the thought that Microsoft will do anything to block easy Linux uptake and protect its revenue base. I don't care what they say; it's what they do that matters. |
| jdixon Nov 04, 2015 5:32 PM EDT |
> I have gained the impression (from above comments) that UEFI is still in the "shake-down" stages and cli in some form or complexity,,, In theory, it shouldn't be. But then in theory, theory and practice are the same. In practice, they're not. :) As Gary says, each vendor is implementing UEFI differently, and therefore there is no uniform or even semi-uniform setup procedure that works with all of them. |
| Ridcully Nov 04, 2015 9:53 PM EDT |
And that, jdixon, brings me right back to the thread topic, but I feel I am losing my sense of "obtuse-osity". BIOS was pretty much standard in behaviour on every PC/laptop......UEFI isn't. Are the PC makers trying to get "lockin" as well, or are they simply trying to make it as difficult as possible to alter the operating systems on a device that you own and is programmable ? All I see now is UEFI confusion, hence my delight in managing to obtain that i5 laptop with BIOS still intact. |
| cybertao Nov 04, 2015 10:12 PM EDT |
UEFI is standardised. As outlined earlier you can create a EFI partition to hold your boot files which is /efi/BOOT/BOOTX64.EFI by default, and creating entries to boot other EFI apps is also standardised (man efibootmgr). Each vendor has a different front-end, but that is no different from having different front-ends and options in BIOS. UEFI has the advantage of editing the boot entries from the OS without having to enter BIOS, including options such as changing the boot order for the next boot only. EFI actually makes things easier, opening up a wealth of opportunities that BIOS and clunky MBR sectors can't compete. |
| Ridcully Nov 04, 2015 11:49 PM EDT |
But, cybertao, I don't want to edit boot entries, I don't want to change the boot order, I don't want a "wealth of opportunities", I don't want to have to create an EFI partition to hold my boot files. or create entries to boot other EFI apps. They have no appeal. All I want to do is install a clean installation of the OS of my choice on a hdd in a computer that uses UEFI.......and wipe the hdd completely so that only the new OS is present and be able to boot into it - automatically and without any convoluted cli manipulations. And as you might have gathered from an entry way, way above.......I could NOT do that - and got rid of a lovely piece of equipment. Now I have a pretty good one that WILL allow me to do just that. It uses BIOS......I know how it works and why. It suits my needs perfectly. |
| cybertao Nov 05, 2015 12:00 AM EDT |
I've got three UEFI machines all running GNU/Linux, and also have an installation on the family Mac for when I want to use it. Your issue has nothing to do with UEFI but the specific machine you purchased. |
| Ridcully Nov 05, 2015 12:09 AM EDT |
Dear Cybertao........THAT is what I said at the start - go right up the top, the third entry on this thread.......and also what the computer repair man said. My experiences of UEFI have now been coloured by a $1000 brick.......and I am NOT particularly keen on playing in its sandpit again. Manufacturers are playing games and this does NOT mean that the UEFI you will meet in any given PC is standard in its behaviour, thanks to the front ends put in place by various manufacturers. Now this isn't attacking you in any way.... but I treat UEFI with a great deal of suspicion when I encounter it. |
| cybertao Nov 05, 2015 12:37 AM EDT |
I'm not taking it personally, just defending UEFI which has a lot to offer and in itself isn't a problem. Secure Boot features in UEFI aren't even the problem. The problem is hardware vendors who meet the Windows certification requirements by providing Secure Boot without the option to disable it (which many do). In those situations there are still solutions but you are limited to distributions with signed keys such as Red Hat, Ubuntu, and SUSE. Limiting yourself to machines that provide Legacy Boot won't be an effective strategy in the long term - especially laptops. If you want to refer back to your first post: Ridcully wrote:Is just wiping Win10 and running Ubuntu by itself on a UEFI machine possible?Yes, yes it is. Even with Secure Boot enabled. |
| Ridcully Nov 05, 2015 1:26 AM EDT |
I'll leave it at that then, cybertao.......You're happy with UEFI, I'm not, but I do have a solution that suits me and will do me for another 5 or more years. I did get openSUSE loaded onto that UEFI laptop, I'm sure of it.......but it simply would NOT boot up. However, like I indicated above, I think by the time I am ready to seriously look at another replacement laptop, things should have been sorted out. Thanks for the discussion. I've enjoyed it, and I'm pleased I didn't come across as a cranky old so 'n so.. |
| BernardSwiss Nov 05, 2015 2:26 AM EDT |
You know... it strikes me, reading through this thread, how depressingly well this situation around UEFI in personal computers resembles those supposedly "alarmist" warnings previously expressed by the Linux-using community: -- namely that such idiosyncratic (often undocumented or incorrectly documented) implementations, inconsistencies, awkward complications, and arbitrary hurdles for non-Windows OSs would be the entirely predictable consequence (and arguably a major intention behind) the general adoption of UEFI as it was mandated and required by Microsoft. |
| cybertao Nov 05, 2015 2:41 AM EDT |
Ridcully wrote:I've enjoyed it, and I'm pleased I didn't come across as a cranky old so 'n so..."The good lord let's us grow old for a reason: to gain the wisdom to find fault with everything he's made!" - Abe 'Grandpa' Simpson. ;) |
| cybertao Nov 05, 2015 2:49 AM EDT |
BernardSwiss wrote:You know... it strikes me, reading through this thread, how depressingly well this situation around UEFI in personal computers resembles those supposedly "alarmist" warnings previously expressed by the Linux-using community:Yeah, the free-software peeps don't create undocumented or incorrectly documented implementations, inconsistencies, awkward complications, and arbitrary hurdles! Oh... But seriously, the problem is the same as it's always been; proprietary firmware. It's not as though BIOS didn't have similar concerns, though not as integrated with supporting Windows as some vendors' have done in their EFI implementations. It doesn't feel as though any progress has been made regarding firmware for all manner of hardware over the years. I think it's ironic Apple hardware is a good choice when it comes to support for booting other operating systems, although you then run into trouble with other elements such as the wifi and camera. |
| Ridcully Nov 05, 2015 2:58 AM EDT |
Thanks BernardSwiss.....I didn't ever express my thoughts as you have done, but I must admit to feeling depressed about the whole thing and for similar reasons. I really did like that HP laptop. I'll quote myself here from one of my posts above, because it fits your comment perfectly I think: "Nevertheless, in the back of my mind is always the thought that Microsoft will do anything to block easy Linux uptake and protect its revenue base. I don't care what they say; it's what they do that matters." |
| BernardSwiss Nov 05, 2015 3:44 AM EDT |
If it makes you feel any better, a couple of days ago, the barista at my local Starbucks was complaining about the arbitrary problems he'd experienced recently, getting the stock Ubuntu LTS onto his DELL laptop (and though he did eventually succeed, battery-life is still an unresolved issue). |
| Ridcully Nov 05, 2015 4:08 AM EDT |
Ummm.......no........and I am STILL laughing very cynically BernardSwiss.....though I do feel for that poor barista. My new laptop comes from a supplier of ex-Govt. used laptops. They really are very good. My present HP came from there about 8 years ago and it is one of the most reliable computers I think I have ever met. But the reason I am laughing cynically, was that I was actually looking at the Dell offerings before they came up with the present one that I bought that has Win7 and normal BIOS........and is an HP....with an Intel video section. HP with BIOS I am not worried about.....but HP with UEFI.......forgeddit. |
| jdixon Nov 05, 2015 9:14 AM EDT |
> UEFI is standardised. ... Each vendor has a different front-end Which is what we said. So, from an end user perspective, it's not standardized at all. > EFI actually makes things easier, opening up a wealth of opportunities that BIOS and clunky MBR sectors can't compete. EFI makes performing more complicated tasks easier, at the cost of making the entire boot process more complex and opaque. So for the user who simply wants to boot their computer on a <2TB hard drive, it's a net loss. > Your issue has nothing to do with UEFI but the specific machine you purchased. Of course. That's what he said. > I'm not taking it personally, just defending UEFI which has a lot to offer and in itself isn't a problem. Until the user interface issues are fixed, it's a problem. How good the underlying technology is doesn't matter. > Yes, yes it is. Even with Secure Boot enabled. As you note, only with certain distributions. With any generic distribution you pick it may not be. Not all distributions are willing to kowtow to Microsoft. |
| CFWhitman Nov 05, 2015 10:06 AM EDT |
Well, my experience with UEFI points to poor implementations of Secure Boot as the only serious issue. When UEFI first started to become popular, there were a few hiccups in various Linux distributions, with some unable to boot without using legacy mode. That doesn't generally seem to be the case anymore.Yes, UEFI can have different interfaces, but so did BIOS. On my current desktop, which I put together using an MSI mainboard, and with some HP Compaq Pro 4300 machines I have used at work, I have UEFI with no Secure Boot, and I haven't had any problems installing Ubuntu variations starting with some version at least as old as 13.10 (I don't remember for certain which version became problem free for me), Debian 7 or higher, or CentOS 6 or higher. (On the HP machines I could use legacy boot to boot old versions of Linux with no UEFI support as well.) I have also installed Ubuntu variations on a couple of laptops with Secure Boot (one was an HP Slimbook 14; I can't recall what other laptop I encountered it with). So far, I was able to find and disable the Secure Boot setting with no problem, but I did have to search for it. Of course the machines I have dealt with so far were all old enough to require the ability to disable Secure Boot in order to get Windows certification. They seem to have lifted that restriction (and I guess just hoped nobody would notice) with machines certified for Windows 10. Microsoft's strategy seems to be to "gently" force everyone to use Windows 10. They apparently don't want legacy Windows installs around anymore than they want Linux. Their goal seems to be to produce hardware that won't run anything other than Windows 8/8.1 or 10. I can't see this working out for them. I think there will be a backlash of some sort if they keep pushing in that direction. I know I'm not getting any hardware that I can't at least turn Secure Boot off with. I suspect that when some people find they are locked in to Windows 10 on certain hardware, they will not be happy about it. Despite the fact that UEFI without Secure Boot doesn't generally seem to be a problem, my appreciation for the goals of the Coreboot project grows all the time. |
| cybertao Nov 05, 2015 3:16 PM EDT |
jdixon wrote:> UEFI is standardised. ... Each vendor has a different front-endDetermining what key you have to press to bring up the available boot options is hardly a deal breaker, and not a point to claim BIOS was better at. And as previously mentioned, you don't have to use the vendors interface to manually add entries. Apple don't even have an interface beyond holding down the alt/option key at boot-time to bring up the selection of boot options (which includes automatically detecting EFI partitions on media). |
| Ridcully Nov 05, 2015 3:24 PM EDT |
Umm......no cybertao, that's not correct. I quickly found which buttons to press to get into UEFI protocols on that HP brick......the problem was the UEFI complexity from then on. And all the time you were terrified of setting something up that would destroy your ability to use the laptop. It was my first brush with UEFI and it confused the hell out of me. The options made no sense to a person whose only needs to get into BIOS previously were to make sure that the dvd drive was the first place to be accessed during an installation........So I did that and ended up in an endless loop where all the machine did was continually install and re-install and re-install.....Not a good way to start familiarisation with UEFI. |
| cybertao Nov 05, 2015 3:36 PM EDT |
Ridcully wrote:It was my first brush with UEFI and it confused the hell out of me.Of course it did. GRUB didn't when you first encountered it? Linux didn't when you first encountered it? BIOS didn't when you first encountered it? A computer didn't when you first encountered it? |
| Ridcully Nov 05, 2015 3:47 PM EDT |
You are missing the point. I had a $1000 device that I knew I could render useless by making an error. Wouldn't you be unhappy, apprehensive, and deeply concerned under the same circumstances - especially when you had been told it was a cinch to just put it into legacy mode and then it would behave just like a BIOS machine. Oh yeah ? And as I found, it was also a device moreover which was locking me out of options. As regards the rest of your points above, of course there are learning curves, but with this UEFI laptop, it wasn't a curve......it was a 200ft precipice. BIOS was always very clear in what choice you needed to make and I never had any problems understanding what I needed to do. I've never played with GRUB, there was never any need to do so, it all just happened automatically - just the way I like it. Edit.....I can't resist this.......Was I hesitant over my first computer ? Well,flatly, NO !!! It was a dear old Microbee with cassette loading. You simply couldn't hurt it.......and I loved it to death. And had so much fun upgrading it to use a huge floppy disk drive.....remember the 5" paper cover disks ? Lovely. The next step was to drive DOS.....and Win3.1 and batch files.....They've never frightened me.....programming in Fortran, Basic, been there done that. I still cannot forget my first hdd.........a delicious old clunker with 10Megbytes storage and I thought it was 7th heaven. Nope, cybertao, I'm not afraid of new tricks, but the tricks need to be clear, self-explanatory and simple to follow. And I don't want to be under the pressure of just burning a very large amount of money. At least the brick was still operational in Win8.1 when I got rid of it. |
| jdixon Nov 05, 2015 5:00 PM EDT |
>. Determining what key you have to press to bring up the available boot options is hardly a deal breaker, and not a point to claim BIOS was better at. The bios simply loaded the bootloader and expected it to handle all of that for you. > GRUB didn't when you first encountered it? Grub? What's that? :) Not every distro defaults to the latest and greatest you know. And no, it undoubtedly didn't, because the SuSE install handled that for him. > BIOS didn't when you first encountered it? Not really, no. > A computer didn't when you first encountered it? Again, not really. EFI is much more complicated by comparison. |
| cybertao Nov 05, 2015 5:15 PM EDT |
You can't help someone who refuses to help themselves. I feel pity for the jdixons of this world who are unprepared to learn new things in this ever changing world. |
| Ridcully Nov 05, 2015 5:33 PM EDT |
Let's not get even vaguely personal please. |
| penguinist Nov 05, 2015 6:41 PM EDT |
Quoting:I knew I could render useless by making an error. Allow me to offer some tips on that. I've been helping people dual boot their systems for decades now and this is a consistent fear that I encounter. The fear of rendering a system useless by making an error. What I like to do (which completely eliminates that fear) is to capture a full image of the system's disk before doing any mods to it. That way, the worst that can happen is that you simply restore the disk to its original state where every byte is the same as it was before. A lot of Linux people know about the technique, but it probably doesn't hurt to repeat it here for the readers. Procedure: 1. First we want to make sure that there is no disk activity going on. We do this by booting into a Linux livedisk. Take your choice of distributions, they all have livedisks. Put one on a USB stick or a CD/DVD and boot your system into it. Now the main hard drive on your system is unmounted and is totally static. Leave it unmounted, then get to a root prompt for the rest of this procedure. 2. Use lsblk to identify your main drive. On an uncomplicated system your main drive will usually be /dev/sda. Remember what you find. 3. Plug an external hard drive into an available USB port and mount it somewhere. (Mount the external but leave the main drive unmounted.) 4. Use lsblk again and now you can identify your main drive as well as your external drive. Remember what you find. 5. Now you copy the full contents of your main drive into a file on your external drive. You do it with a command like this: dd if=/dev/sdx of=/path_to_external_drive/my_sda.img bs=8M where /dev/sdx needs to be the location of your main drive. That's all there is to it. It may take several hours for a 250GB sized notebook drive to copy, so kick up your feet and enjoy a cup of coffee or a chapter in a good book. Oh, if you want to conserve disk space on that external drive, you can always compress your image. That would look like this: dd if=/dev/sdx bs=8M | gzip | dd of=/path_to_external_drive/my_sda.img.gz Now that you have a perfect image of your system's main hard drive, you can proceed with confidence with a Linux installation or a dual boot. If anything goes wrong you can reverse the above procedure in order to dd that image you made back onto your main drive and every byte will be exactly as you left it. I find this procedure to be a great confidence builder. I've very seldom actually had a problem that needs to be "undone" but it is a comfortable feeling knowing that it is impossible now to render a system useless. |
| cybertao Nov 05, 2015 6:53 PM EDT |
The fear of rendering a Windows certified Secure Boot only UEFI system useless in this instance is that it won't boot anything. Removing the drive from the laptop and imaging/re-imaging on a another machine is probably still a solution. But in the case of a borked installation the device isn't bricked - UEFI will boot a DVD/USB stick with the Windows installer on it at the very least. |
| Ridcully Nov 05, 2015 7:54 PM EDT |
Thanks everybody. But do remember these points: I am NOT a good player with cli; when I hit the UEFI problems I was completely on my own with no prior experience - only what I had been told would/should happen. It didn't. I ended up with something that bore no resemblance to what I wanted and in addition seemed to have destroyed the Windows section as well......and given that there is NO included disk or usb drive with the computer, I simply didn't know whether or not I had "totalled" the machine or whatever. I believe the restore partition was still intact. However, I still come back to something I wrote above: Give UEFI about 5 years to shake itself down with the OEMs etc. etc. and the Linux community. By then, I reckon it will have become a "piece of cake" and even I will be able to simply put onto a UEFI laptop anything I want. But again, thanks all......this has been fascinating and very, very instructive. |
| jdixon Nov 05, 2015 9:33 PM EDT |
> I feel pity for the jdixons of this world who are unprepared to learn new things in this ever changing world. What makes you think I haven't been playing with EFI? It's required for Win8 and above after all. > But in the case of a borked installation the device isn't bricked - UEFI will boot a DVD/USB stick with the Windows installer on it at the very least. AFAICT, the only real danger is that you'll render your system unbootable, not that you'll trash the hard drive itself. Since most machines I've seen have a restore system defaults option, using it should allow the system to boot again. Worst case, simply record all the settings before you start so you can restore them if needed. > However, I still come back to something I wrote above: Give UEFI about 5 years to shake itself down with the OEMs etc. etc. and the Linux community. Agreed. Since the machines I buy tend to be refurbished ones, I haven't needed to worry about it yet with my Linux machines. By the time I do, most of the problems should have been resolved and the remaining ones thoroughly documented. |
| gary_newell Nov 13, 2015 12:30 PM EDT |
Penguinist that is a really good write up. One question I have always wondered is the block size bs=8m in your case above. How did you determine that 8 meg is the correct blocksize and what is the danger of using an incorrect blocksize? For instance say I went for 16 meg or 32 meg. Could that be bad? |
| penguinist Nov 13, 2015 7:40 PM EDT |
Excellent question, Gary. I should have explained that in the writeup. For dd the block size to quite arbitrary. The problem is that its default of 512 bytes is so small as to cause performance problems. In order to make your dd imaging run fast it is convenient to tell it to use a larger block size. 8M or 16M or 32M or 64M are all fine choices. Regardless of the block size chosen, the image is just simply a collection of bytes, a straight unmodified copy of the input from its beginning to its end. It's not a problem if the block size is not an even multiple of the image size. dd knows to stop when it gets to the end of its image even if it has not completely filled the last block. |
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