I'm trying to setup a very small system intended for doing monitoring/logging. It's done on an Intel Atoms in a small box and the idea was to simply run it off a pair of USB flash drives in software RAID 1.
Now the problem is that while the 6.2 DVD installer could go through the entire install process, grub will load then just stop at the prompt. The system will work if I use a SATA hard disk so motherboard compatibility is not an issue.
Attempting the various methods to re-install grub (via rescue mode) or using the grub prompt to setup the disk does not work either. grub just does not seem to be able to find the USB drives. e.g. commands like root (hd0,0) just says device not found. This is despite grub having just loaded from it and despite that grub-install in rescue mode does not report any error.
Same problem even if I just go with one USB drive in a plain vanilla ext3 setup.
It seems that some sites are saying that EL variants just don't seem to be adaptable to installing and running off USB drives. Is this really the case and that I should be looking at using another distribution or am I just missing some crucial steps in the process?
On 04/04/2012 11:46 AM, Emmanuel Noobadmin wrote:
just does not seem to be able to find the USB drives. e.g. commands like root (hd0,0) just says device not found. This is despite grub
hd0,0 represents the bios device id, are you sure thats what your bios thinks the usb disk is at ?
On 4/4/12, Karanbir Singh mail-lists@karan.org wrote:
On 04/04/2012 11:46 AM, Emmanuel Noobadmin wrote:
just does not seem to be able to find the USB drives. e.g. commands like root (hd0,0) just says device not found. This is despite grub
hd0,0 represents the bios device id, are you sure thats what your bios thinks the usb disk is at ?
I can't be sure which is part of the problem. Because when I read the grub documentation, it said that hitting tab at the prompt after typing the command will produce a list of possible devices/drives. However, in my case, nothing happens which seemingly implies grub could not find any device.
I also did try manually doing (hd0,1), (hd1,0) but none of it seemed to be a "findable" device. For what it's worth, the installer did see them as sda and sdb. I also disabled the onboard SATA controller during my attempts in order to eliminate it from showing up as a possible device, since grub doc says the (hdx,x) number usually matches the order in which the devices were discovered.
On Wednesday, April 04, 2012 12:38:03 PM Emmanuel Noobadmin wrote:
I also did try manually doing (hd0,1), (hd1,0) but none of it seemed to be a "findable" device. For what it's worth, the installer did see them as sda and sdb.
The grub order and names and the linux kernel/udev order and names should not be assumed to have any correlation of any kind, since they are discovered differently.
If you can boot a USB live media on this box, you could bring up a grub shell and see how grub sees the disks from that (at a root prompt, type 'grub' and you'll be greeted with the grub shell, and then you can do detection or whatever from that). This also works in the rescue environment given by the install media; you do want to do a 'chroot /mnt/sysimage' in that shell before entering the grub shell, though.
It is completely BIOS dependent as to how the devices show up to grub.
On 4/5/12, Lamar Owen lowen@pari.edu wrote:
The grub order and names and the linux kernel/udev order and names should not be assumed to have any correlation of any kind, since they are discovered differently.
Yes, that is what I understand from the grub manual. However, from that I also understand and expect the first and only device grub could find would be hd0
If you can boot a USB live media on this box, you could bring up a grub shell and see how grub sees the disks from that (at a root prompt, type 'grub' and you'll be greeted with the grub shell, and then you can do detection or whatever from that). This also works in the rescue environment given by the install media; you do want to do a 'chroot /mnt/sysimage' in that shell before entering the grub shell, though.
I've done this previously from the rescue environment but got no closer to resolving this.
I've tried it again with a default install of CentOS 6.2, using default drive layout and all. On first boot, I get the grub shell but I have not been able to find any command that would list valid devices grub can find, apart from the tab button.
Rebooting into the rescue environment, chrooting into the drive, grub-install generates the map to hd(0) which was expected. Runing grub shell and trying root (hd0) also works.
However, rebooting after updating the grub device map always results in "Booting from local disk... Error 21" which indicates grub couldn't find the drive specified.
Any ideas how I can probe/list devices within grub shell? I've done the stupid method of root(hd0,x) all the way up to root(hd8,3) without luck.
In trying to solve this problem, I came across these two articles regarding GRUB and USB booting.
http://vlinux-freak.blogspot.com/2011/01/how-to-create-grub-boot-floppy-usb.... http://bootloader.wikidot.com/linux:boot:usb-grub
The floppy drive issue appears to be the situation as booting the rescue environment from a USB DVD does show up as /dev/fd0.
However, the solutions in those articles did not work. In the first, the GRUB command/options are different, although changing the option from boot-directory to root-directory appear to work, there was no option to force floppy drive.
In the second, the python script thinks the grub install has already been patched for floppy boot so couldn't do anything.
I've also tried editing menu.lst to use (fd0) but also didn't work.
Emmanuel Noobadmin wrote on 04/07/2012 05:51 AM:
Any ideas how I can probe/list devices within grub shell? I've done the stupid method of root(hd0,x) all the way up to root(hd8,3) without luck.
Have you tried the grub "find" command? find /grub/stage1 find /boot/grub/stage1 etc.
http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB
Phil
Emmanuel, I used a totally different approach by using VMware: the trick is to install on a physical device which is the USB drive. When the installation requests a reboot, simply boot on your USB and off you go!
2012/4/10 Phil Schaffner Philip.R.Schaffner@nasa.gov
Emmanuel Noobadmin wrote on 04/07/2012 05:51 AM:
Any ideas how I can probe/list devices within grub shell? I've done the stupid method of root(hd0,x) all the way up to root(hd8,3) without luck.
Have you tried the grub "find" command? find /grub/stage1 find /boot/grub/stage1 etc.
http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB
Phil
CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
--
On 4/10/12, Patrick DERWAEL patrick@derwael.be wrote:
Emmanuel, I used a totally different approach by using VMware: the trick is to install on a physical device which is the USB drive. When the installation requests a reboot, simply boot on your USB and off you go!
That is pretty much what I did. Boot DVD 1 with a USB DVD drive, install to /dev/sda which is the USB flash drive. When the installation requests a reboot, shutdown, remove as well as leave the DVD drive around and reboot... and only grub prompt or Error 21.
Maybe there's a minor but critical step I'm missing so I'll appreciate it if you could outline in greater details how you did it.
I've tried installing grub to both MBR i.e. /dev/sda as well as first partition /dev/sda1 but neither works.
Emmanuel Noobadmin wrote:
On 4/10/12, Patrick DERWAEL patrick@derwael.be wrote:
Emmanuel, I used a totally different approach by using VMware: the trick is to install on a physical device which is the USB drive. When the installation requests a reboot, simply boot on your USB and off you go!
That is pretty much what I did. Boot DVD 1 with a USB DVD drive, install to /dev/sda which is the USB flash drive. When the installation requests a reboot, shutdown, remove as well as leave the DVD drive around and reboot... and only grub prompt or Error 21.
Maybe there's a minor but critical step I'm missing so I'll appreciate it if you could outline in greater details how you did it.
I've tried installing grub to both MBR i.e. /dev/sda as well as first partition /dev/sda1 but neither works.
Two questions: a) are you sure that the USB key is /dev/sda, and b) does your system offer a boot menu, or only go into setup to tell it to boot off the USB key?
Oh, and in fdisk, is the partition flagged bootable?
mark
On 4/10/12, m.roth@5-cent.us m.roth@5-cent.us wrote:
Two questions: a) are you sure that the USB key is /dev/sda,
Yes, I've verified this before and again after you asked that it is seen as /dev/sda, at least through the installation DVD. fdisk also does not find a sdb/c/d if I try that.
and b) does your system offer a boot menu, or only go into setup to tell it to boot off the USB key?
Both, I can set the boot sequence in BIOS, which is currently to boot USB first. And I can also hit F10 to choose.
Oh, and in fdisk, is the partition flagged bootable?
Yes, definitely :D
Usuially, I simply use the default config for about everything; it worked well every time...
I don't remember every detail... sorry for that
-----Original Message----- From: centos-bounces@centos.org [mailto:centos-bounces@centos.org] On Behalf Of Emmanuel Noobadmin Sent: mardi 10 avril 2012 17:32 To: CentOS mailing list Subject: Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.
On 4/10/12, Patrick DERWAEL patrick@derwael.be wrote:
Emmanuel, I used a totally different approach by using VMware: the trick is to install on a physical device which is the USB drive. When the installation requests a reboot, simply boot on your USB and off you go!
That is pretty much what I did. Boot DVD 1 with a USB DVD drive, install to /dev/sda which is the USB flash drive. When the installation requests a reboot, shutdown, remove as well as leave the DVD drive around and reboot... and only grub prompt or Error 21.
Maybe there's a minor but critical step I'm missing so I'll appreciate it if you could outline in greater details how you did it.
I've tried installing grub to both MBR i.e. /dev/sda as well as first partition /dev/sda1 but neither works. _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On 4/10/12, Phil Schaffner Philip.R.Schaffner@nasa.gov wrote:
Have you tried the grub "find" command? find /grub/stage1 find /boot/grub/stage1 etc.
I'm deeply embarrassed and stunned by why I did not stumble across that googling or how I could miss seeing the command in grub shell and doc. I'll try this the next time I get to that machine again.
Thank you very much!
On 4/10/12, Phil Schaffner Philip.R.Schaffner@nasa.gov wrote:
Have you tried the grub "find" command? find /grub/stage1 find /boot/grub/stage1 etc.
I've tried that now but it could not find any of the files be it stage1, grub.conf or menu.lst, also tried both /grub and /boot/grub variants.
The interesting thing is that if I leave the DVD in the DVDROM drive, grub will find it as hd111 with the tab button. So the tab functionality is actually working. Just that as far as grub is concerned, the flash drive it just loaded from just seem to be undetectable.
On a random hunch or sheer desperation, I inserted an old brandless 1GB USB thumbdrive, installed and it booted.
Thinking that the Sandisk Ultra Backup 16GB was incompatible with CentOS/grub for some unknown reason. I switched to a brandless 16GB, installed the same way and it failed at grub prompt again.
Now it is starting to look as if either the newer drives have something on them that prevents booting. Or it's the total size of the drive, regardless of the partition size. I say this because in every case I used a single 1GB ext4 / partition for testing, to reduce the mkfs time.
Since now I have a bootable drive, I started to compare them with fdisk to see if there was any difference.
Bootable 255 heads, 63 sectors/track, 124 cylinders, start sector 63 With a warning that "Partition 1 has different physical/logical endings: phys=(123, 254, 63) logical=(124, 140, 16)"
Unbootable 16GB Sandisk Ultra Backup 54 heads, 48 sectors/track, 12158 cylinders, start sector 2048
Unbootable 8GB Sandisk Blade 20 heads, 4 sectors/track, 195417 cylinders, start sector 2048
Unbootable 16GB Unbranded 171 heads, 40 sectors/track, 4634 cylinders, start sector 2048
It seems that the common issue is starting at sector 2048 so I fdisk the 16GB Sandisk to manually create a 1GB partition started at sector 63. Using this, I installed and was able to boot successfully.
To verify, I use the same 16GB disk to install again, deleting the partition in anaconda and creating a new 1GB partition, ctrl-alt-f2 and fdisk confirms it was again at sector 2048.
As a side note, for some reason, drive geometry changed for the 16GB after a reinsert to varying values such as 6 heads, 33 sectors/track, 159164 cylinders 16 heads, 32 sectors/track, 61551 cylinders
Not sure if this had any significance to why anaconda decides to fdisk the drive starting from sector 2048.
My only guess is that it considers anything bigger than 4GB as a normal HDD drive and does this for hard disk alignment issue? But if grub could boot normally from such a HDD, why would it choke on a USB flash drive?
Should I report this as a bug with anaconda or ?
Emmanuel Noobadmin wrote:
On a random hunch or sheer desperation, I inserted an old brandless 1GB USB thumbdrive, installed and it booted.
Thinking that the Sandisk Ultra Backup 16GB was incompatible with CentOS/grub for some unknown reason. I switched to a brandless 16GB, installed the same way and it failed at grub prompt again.
Now it is starting to look as if either the newer drives have something on them that prevents booting. Or it's the total size of the drive, regardless of the partition size. I say this because in every case I used a single 1GB ext4 / partition for testing, to reduce the mkfs time.
<snip>
It seems that the common issue is starting at sector 2048 so I fdisk the 16GB Sandisk to manually create a 1GB partition started at sector 63. Using this, I installed and was able to boot successfully.
To verify, I use the same 16GB disk to install again, deleting the partition in anaconda and creating a new 1GB partition, ctrl-alt-f2 and fdisk confirms it was again at sector 2048.
As a side note, for some reason, drive geometry changed for the 16GB after a reinsert to varying values such as 6 heads, 33 sectors/track, 159164 cylinders 16 heads, 32 sectors/track, 61551 cylinders
Not sure if this had any significance to why anaconda decides to fdisk the drive starting from sector 2048.
Wonder if it's trying to beat the rush - after weeks of googling, a few weeks ago, I finally found that if I formatted my 3TB drives on a 4k boundry, instead of a 512byte boundry, writes were literally about four times faster, because that's the physical sector on the drives.
It may be trying to do the same, to take care of this invisibly.
Good catch on the USB drive business.
mark
On 4/13/12, m.roth@5-cent.us m.roth@5-cent.us wrote:
Wonder if it's trying to beat the rush - after weeks of googling, a few weeks ago, I finally found that if I formatted my 3TB drives on a 4k boundry, instead of a 512byte boundry, writes were literally about four times faster, because that's the physical sector on the drives.
It may be trying to do the same, to take care of this invisibly.
That is what I think the 2K first sector is supposed to do, align the physical sector be it a 512 or 4K drive. But unfortunately, the check for "is this a 4K HDD" appears to be naive.
-
Emmanuel Noobadmin -
Karanbir Singh -
Lamar Owen -
m.roth＠5-cent.us -
Patrick DERWAEL -
Phil Schaffner