Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
2013/7/2 Grant Edwards grant.b.edwa...@gmail.com On 2013-07-01, Grant Edwards grant.b.edwa...@gmail.com wrote: I've just recently run into a problem where sometimes when a machine boots, the kernel can't find init. This appears to be because my grub configuration line says root=/dev/sda5 and _sometimes_ the drive that contains my root partition is sdb instead of sda. AFAICT, for the past 30 years the linux kernel was 100% consistent in the order that hard drives were labelled -- but recently that has seems to have changed. I still haven't figured out why my drives suddenly started getting discovered in varying orders. I think that the SATA drives are always in the same order with respect to each other, but sometimes the external firewire drive gets discovered before the SATA drives and sometimes after the SATA drives. It looks like my options are: 1) Keep hitting the reset button until it works. 2) Unplug or power down the firewire drive when booting. 3) Set up an initrd for the sole purpose of finding the actual root parition via filesystem label. [I find this idea rather offensive.] 4) Build the firewire drive as a module instead of building it into the kernel. That would delay the discovery of the firewire drive until after root has been mounted. 5) For the drive with the root parition on it switch from a DOS parition table to a GPT partition table and use the root=PARTUUID=whatever kernel option. You don't need to switch to GPT for that. I have a DOS partitioned disk and blkid prints the LABEL and UUID for each partition. 6) Fix the kernel so it can find root by looking at filesystem labels. Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a bit out of scope for the momement. The early code in the kernel obviously knows how to read partition tables and also knows about the relevent file system, so I'm a bit baffled why it can't look at the file system label. Changing the firewire driver to be a module is probably the simplest solution, but it's a kludgy work-around for what is, in my opinion, a kernel bug: if you are going to require people to specify an absolute disk drive index for the root partition, then you'd better index drives in a consistent order from one boot to the next. Switching to a GPT partition table sounds like the cleanest solution, but I need to figure out if the grub (legacy) ebuild includes GPT support or not. I know it's supported by grub2, but I don't really feel like switching to grub2 ATM. -- Grant Edwards grant.b.edwardsYow! But was he mature at enough last night at the gmail.comlesbian masquerade? -- Mit freundlichen Grüßen / Best regards Randolph Maaßen
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
2013/7/2 Grant Edwards grant.b.edwa...@gmail.com: It looks like my options are: snip 5) For the drive with the root parition on it switch from a DOS parition table to a GPT partition table and use the root=PARTUUID=whatever kernel option. Switching to a GPT partition table sounds like the cleanest solution, but I need to figure out if the grub (legacy) ebuild includes GPT support or not. I know it's supported by grub2, but I don't really feel like switching to grub2 ATM. I'm not exactly sure about your system's setup, but msdos partition tables can also hold partition UUIDs, which can be seen by running blkid. So, such a solution does not necessarily imply a GPT-based setup... you can experiment with it a bit, having fun tweaking kernel parameters :)
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On 07/02/2013 07:23 AM, Grant Edwards wrote: On 2013-07-01, Grant Edwards grant.b.edwa...@gmail.com wrote: 2) Unplug or power down the firewire drive when booting. I had this problem on my Intel motherboard, and found out you can disable booting from external drives. Boot to removable devices or similar in the BIOS. Failing that, changing the boot order so that the firewire/USB device is at the very end of the boot list may help your situation. Number 6 (fixing the kernel) is The Right Thing To Do(tm), but it's a bit out of scope for the momement. The early code in the kernel obviously knows how to read partition tables and also knows about the relevent file system, so I'm a bit baffled why it can't look at the file system label. Is CONFIG_EDD set? CONFIG_EDD: Say Y or M here if you want to enable BIOS Enhanced Disk Drive Services real mode BIOS calls to determine which disk BIOS tries boot from. This information is then exported via sysfs. Dan
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
2013/7/2 Grant Edwards grant.b.edwa...@gmail.com On 2013-07-02, Randolph Maa?en r.maasse...@gmail.com wrote: 2013/7/2 Grant Edwards grant.b.edwa...@gmail.com It looks like my options are: [...] 5) For the drive with the root parition on it switch from a DOS parition table to a GPT partition table and use the root=PARTUUID=whatever kernel option. You don't need to switch to GPT for that. I have a DOS partitioned disk and blkid prints the LABEL and UUID for each partition. And you can pass those values to the kernel via the root= parameter? Yep. The G in GPT just means that the type of the partition is stored as GUID/UUID. The partition ID is a separate value. -- Grant Edwards grant.b.edwardsYow! NEWARK has been at REZONED!! DES MOINES has gmail.combeen REZONED!! -- Mit freundlichen Grüßen / Best regards Randolph Maaßen
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, Jul 02, 2013 at 02:42:15PM +, Grant Edwards wrote: You don't need to switch to GPT for that. I have a DOS partitioned disk and blkid prints the LABEL and UUID for each partition. And you can pass those values to the kernel via the root= parameter? That still requires an initrd/initramfs, iirc. -- Happy Penguin Computers ') 126 Fenco Drive ( \ Tupelo, MS 38801 ^^ supp...@happypenguincomputers.com 662-269-2706 662-205-6424 http://happypenguincomputers.com/ A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing in e-mail? Don't top-post: http://en.wikipedia.org/wiki/Top_post#Top-posting
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, 2 Jul 2013 15:16:15 + (UTC), Grant Edwards wrote: The PARTUUID= parition specifier format is handled directly by kernel code, so I don't see why it should require an initrd (unless the UUID values for MBR partitions aren't actually something the kernel knows about and are something made up from whole cloth by the blkid program) MBRs don't have PARTUUIDs do they? Don't confuse them with filesystem UUIDs as used in fstab. -- Neil Bothwick Oops. My brain just hit a bad sector. signature.asc Description: PGP signature
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, 2 Jul 2013 15:09:28 + (UTC), Grant Edwards wrote: I had this problem on my Intel motherboard, and found out you can disable booting from external drives. Boot to removable devices or similar in the BIOS. Failing that, changing the boot order so that the firewire/USB device is at the very end of the boot list may help your situation. The problem isn't that the BIOS is booting the wrong drive. The BIOS is booting the correct drive, grub is starting, grub is loading the correct kernel. When the _kernel_ runs it (sometimes) identifies disk drives in the wrong order and tries to mount the root directory from the wrong drive. And the BIOS order can affect the order in which the kernel sees the drives, so it is worth trying. I'd go for the firewire-as-a-module approach and add the module to /etc/conf.d/modules to make sure it is loaded ASAP. Yes, it is a kludge, but it is the simplest solution from a practical POV. -- Neil Bothwick Processor: (n.) a device for converting sense to nonsense at the speed of electricity, or (rarely) the reverse. signature.asc Description: PGP signature
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, 2 Jul 2013 16:57:26 + (UTC), Grant Edwards wrote: IOW, it appears that the blkid program is either just making stuff up or its the filesystem UUID rather than the partition UUID. I suspect the latter, since I notice that blkid doesn't print a UUID for paritions that don't have filesystems. UUIDs are for filesystems, PARTUUIDs ae for partitions - blkid prints both, but only if both are present, which requires a GPT partition table. -- Neil Bothwick A man needs a mistress - just to break the monogamy signature.asc Description: PGP signature
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, Jul 2, 2013 at 11:57 AM, Grant Edwards grant.b.edwa...@gmail.com wrote: All the references Google can find for me say that you have to use a GPT partition table if you want to specify a boot partition using root=PARTUUID=partition-uuid. Does the root=PARTUUID option work for you? Can you point to some documentation on how you can use root=PARTUID=partition-uuid with an DOS/MBR partition table? As Neil alluded to, you can use UUID with MBR (instead of PARTUUID and GPT). I have DOS/MBR partition table and my kernel commandline looks like: root=UUID=1d21fa55-0fa9-4d43-8d41-8b4193900efa ro log_buf_len=1M quiet rootfstype=ext4 raid=noautodetect (along with an initramfs)
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
2013/7/2 Grant Edwards grant.b.edwa...@gmail.com On 2013-07-02, Neil Bothwick n...@digimed.co.uk wrote: On Tue, 2 Jul 2013 15:16:15 + (UTC), Grant Edwards wrote: The PARTUUID= parition specifier format is handled directly by kernel code, so I don't see why it should require an initrd (unless the UUID values for MBR partitions aren't actually something the kernel knows about and are something made up from whole cloth by the blkid program) MBRs don't have PARTUUIDs do they? Don't confuse them with filesystem UUIDs as used in fstab. No, blkid does not print a PARTUUID value with an MBR. In only prints UUID values, which as you noted, are _filesystem_ UUIDs. If you want to use a filesystem UUID to locate the root partition, you need an initramfs/initrd which contains an 'init' program that finds the filesystem with the specified UUID, mounts that filesystem, and then does a root_pivot. -- Grant Edwards grant.b.edwardsYow! Hello. Just walk at along and try NOT to think gmail.comabout your INTESTINES being almost FORTY YARDS LONG!! SCREW ME! Still messing around with these IDs. Sorry for disturbance. -- Mit freundlichen Grüßen / Best regards Randolph Maaßen
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, Jul 2, 2013 at 3:27 PM, Grant Edwards grant.b.edwa...@gmail.com wrote: Can you point to some documentation on how you can use root=PARTUID=partition-uuid with an DOS/MBR partition table? As Neil alluded to, you can use UUID with MBR (instead of PARTUUID and GPT). I have DOS/MBR partition table and my kernel commandline looks like: root=UUID=1d21fa55-0fa9-4d43-8d41-8b4193900efa ro log_buf_len=1M quiet rootfstype=ext4 raid=noautodetect (along with an initramfs) Yes, we've already discussed that if you have an initrd (or initramfs), and an 'init' program that handles it, you can use filesystem labels and filesystem uuids. The option we were discussing in the posting to which you replied is that of using the root=PARTUUID method which is handled directly by the kernel. Ah, sorry, I missed that detail. I thought I was helping to clear up confusion, when in fact I was the confused one! :)
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Tue, 2 Jul 2013 20:40:20 + (UTC), Grant Edwards wrote: Next time I do an install, I think I'll try GPT... I can't think why any sane person would do otherwise. Who in their right mind would want to use a 30+year old format where any more than four partitions is a fragile kludge? :-O -- Neil Bothwick Eat shit - 50 million flies can't be wrong Use Microsoft . . . . . signature.asc Description: PGP signature
Re: [gentoo-user] Re: Can't find init due to inconsistent drive order
On Jul 1, 2013 9:45 PM, Grant Edwards grant.b.edwa...@gmail.com wrote: On 2013-07-01, Alan McKinnon alan.mckin...@gmail.com wrote: On 01/07/2013 23:52, Grant Edwards wrote: I've just recently run into a problem where sometimes when a machine boots, the kernel can't find init. This appears to be because my grub configuration line says root=/dev/sda5 and _sometimes_ the drive that contains my root partition is sdb instead of sda. AFAICT, for the past 30 years the linux kernel was 100% consistent in the order that hard drives were labelled -- but recently that has seems to have changed. I use partition labels in my fstab, so that's not a problem, but after all these years, the kernel still doesn't know how to grok parition labels. Are we really expected now to set up an initrd just so that the kernel can find the root partition?? Where have you been for the past 6 months? Did you miss the entire clusterfuck debate about latest udev tricks? No. Those names depend only on the order in which devices are discovered, and that process has always been indeterminate. Really? I've been running Linux on a lot of machines for 30 years -- often on machines with a half-dozen hard drives -- and I never saw drive order change from one reboot to the next until today. That's quite a lucky streak. Since Linus started writing Linux in 1991 (22 years ago), I want to know which time machine did you use. Regards. -- Canek Peláez Valdés
