FakeRaid指南
出自Ubuntu中文
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FakeRaid 指南
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翻译人员：npnufn2006_yan
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如何配置Ubuntu来存取fakeRAID硬件设备
在当初Breezy预览版发布的时候，我花了一个星期的时间将Breezy安装在我的Via SATA fakeRAID上，并最终在用两块万转36G西数Rapter硬盘组建的RAID-0系统上实现了Winxp和Ubuntu linux的双启动。所以，我想我应该把我如何做得写下来，以便于他人能得益于我的工作，并同样添加一些相关的内容。
本页描述了如何让linux将RAID看做一块硬盘并由其上启动。在我的例子中，我是使用的RAID-0结构，但我所介绍的内容应当也适用于RAID-1，和RAID-5(参见文末的说明)。考虑到一些没有做过类似操作的朋友，我在此给出的介绍比较详细，所以不要被这篇文章的长度所吓倒，其实都很直白。
什么是fakeRAID?
在前一两年，市场上出现了自称是IDE或者SATA RAID控制器的硬件设备。这类硬件出现在一些桌面或工作站的主板上。实际上，这些设备都不是真正的RAID控制器。它们其实只是简单的多通道磁盘控制器，只不过是可以借助于特殊的BIOS和驱动来协助操作系统实现软件层面的RAID功能。由于RAID设置是用的BISO设置界面而且系统可以从RAID上启动，所以这种功能就可以给用户一个像是硬件RAID的外表。
在windows下，我们必须为其安装驱动才能操作RAID。而在linux环境下，由于系统内置了软RAID功能可以对这些设备进行预处理，这些硬件可以就按照它们本来的面目来看待，多硬盘驱动器或者多通道IDE/SATA控制器。也就是，"fakeRAID"。
如果你已经在internet上研究了这个题目并看到了这里，你一定已经知道通常对于这个问题的反映是，我不知道你是否可以做到，但是没必要苦恼，因为linux已经内置了软raid的功能。而且，我们也不知道在linux放弃内置的软raidn功能而选择使用fakeRaid是否真的能带来系统性能上的提升。cpu最后仍然要作这些工作。不过，这不是问题的重点。重点在于，有windows用户可能会希望将linux也安装在同一个硬盘组上。对于那些喜欢尝试各种系统，或者因为工作需要或其他原因必须使用windows的用户来说，多重启动是很常见的。这类用户没必要为了使用linux就添加一块硬盘。另外，一些人说RAID-0不安全。不过这要视个人需要而言，看你是更看重安全还是效率。这些问题都不是本文的重点问题，因此我们就假定您需要这么做并告诉您如何去做。
在RAID阵列上安装Ubuntu
安装dmraid
标准的LiveCDs（光盘版系统）和可选择安装CD现在还不支持fakeRAID. 我用LiveCDs(光盘版系统）来启动，然后通过包管理器从通用库（要开启Synaptic中的设置为"Universe"或修改 /etc/apt/sources.lst)中下载dmraid包。
注意：Ubuntu 6.06对dmraid的支持已经增强，所以下面的一些步骤理论上说也不是必须的。如果你从Live CD安装，请在启动安装程序（Ubiquity）之前从通用库中选择安装dmraid包。并且要确保你的RAID设备在/dev/mapper下，而不是随意地以/dev/sd*代替。到目前为止，我听一位用户说Ubiquity在安装整个系统时一切正常。
然而，这显然只是一小部分，对大部分用户（包括我自己）来说，Ubuquity安装失败了。也许对于较为稳定的6.06来说，这些烦闷的步骤不再需要。然而，在这一过程中，不要气馁，你会对你的系统更加了解。
如果Ubiquity(Ubuquity?）不能自动完成安装，你可以按照下面说明中的步骤手动完成。有一点要特别注意，一些步骤对Ubuntu 6.06不再需要，这些会被标记为"Ubuntu 5.10"。
所以，再次提醒，如果你安装的是Ubuntu 6.06或更新版本，请跳过标记为"Ubuntu 5.10"的步骤。
将RAID阵列分区
在我们创建文件系统（Windows用户称作"格式化"）之前，必须要把磁盘切成分区来存放我们的文件系统。
如果你喜欢，可以使用gparted来创建和删除分区或文件系统，但我们并不推荐这样做，因为：
a）使用gparted，在对分区表修改后不能对它进行更新，所以你不得不修改分区，然后退出gparted，从命令行运行dmraid -ay来探测新分区，然后再次启动gparted，在这之后，你才能格式化这些分区。
b）它会生成大量的出错信息，这样很容易导致混乱，很难知道这些操作是否成功。
c）一些朋友看到上面两条很容易就退缩了。
While it IS possible to use gparted for this, until it improves, we recommend command-line utilities for partitioning and the creation of filesystems:
fdisk: partitioning (and creation of filesystems on some platforms) parted: partitioning and creation of filesystems mkfs: creation of filesystems
Familiarize yourself with the tools my using the man pages (i.e., "man fdisk", "man parted", "man mkfs"). Work with partitions and filesystems as root (sudo) or the kernel may not be able to re-read the partition table until you reboot.
In my case, I first needed to resize my existing NTFS partition to make space for Ubuntu. (If you don't need to do this, skip to the next paragraph.) Gparted currently can not do this on the mapper device so I had to use the ntfsresize program from the command line. Note that ntfsresize only resizes the filesystem, not the partition, so you have to do that as a following step. Use ntfsresize to shrink the filesystem, note the new size of the filesystem in sectors, then fire up fdisk. Switch fdisk to sector mode with the 'u' command. Use the 'p' command to print the current partition table. Delete the partition that you just resized and recreate it with the same starting sector. Use the new size of the filesystem in sectors to compute the ending sector of the partition. Don't forget to set the partition type to the value it was before. Now you should be able to create a new partition with the free space.
Create the partitions (the actual commands will vary depending on your choice of tool(s)):
sudo fdisk /dev/mapper/via_hfciifae p ?
At a minimum, this should include a root partition and a swap partition (this configuration is recommended for new users). For a multi-user desktop, you may want root, swap, and home. In my case, I wanted to isolate my Windows and Linux files at the primary partition level, so I created an extended partition to hold several logical linux partitions. Also, I wanted a separate /boot partition as a security measure, so I created logical partitions for root, boot, and swap. Also, since you can only have four primary partitions on a DOS-labeled disk, using an extended partition gives me the flexibility to add more linux partitions later if I want them. If I decide to serve web apps or something, I might want logical partitions for boot, root, swap, tmp, var, usr, and home.
在RAID阵列上建立文件系统
Now "format" each partition (create filesystems). In my case I used fdisk and ran a mk2fs on /dev/mapper/via_hfciifae5 and mkreiserfs on /dev/mapper/via_hfciifae7. You can also do this with parted. Or you can exit your partitioning tool and use mkfs (e.g., "mkfs.ext3" and "mkfs.reiserfs") to create the filesystems. Create swap with "mkswap /dev/mapper/etc." and "swapon /dev/mapper/etc.". (Use the man pages.)
The command dmraid -r will show how the partitions have been mapped in RAID: In my case:
via_hfciifae -- the raw raid volume via_hfciifae1 -- the NTFS partition via_hfciifae5 -- /boot via_hfciifae6 -- swap via_hfciifae7 -- /
挂载临时文件结构
Next, I created a temporary file structure to hold my new installation while I construct it, I and mounted two sets of directories to it: a) Mounted the new partitions I had created for / and /boot (so could install packages to them). b) Mounted the currently running, /dev, /proc, and /sys filesystems, so I could use these to simulate a running system within my temporary file structure.
mkdir /target mount -t reiserfs /dev/mapper/via_hfciifae7 /target mkdir /target/boot mount -t ext2 /dev/mapper/via_hfciifae5 /target/boot mkdir /target/dev mount --bind /dev /target/dev mkdir /target/proc mount -t proc proc /target/proc mkdir /target/sys mount -t sysfs sysfs /target/sys
安装基本系统
Now we install the base system. debootstrap installs all base packages and does it setup. Afterwards you need to install some additional packages:
cd /target apt-get install debootstrap debootstrap breezy /target ## instead of breezy can be any distribution selected cp /etc/apt/sources.list etc/apt cp /etc/resolv.conf /target/etc cp /etc/hosts /target/etc chroot /target apt-get update apt-get install dmraid apt-get install grub apt-get install linux-k7 apt-get install ubuntu-base ubuntu-desktop
- Temporary Note to other editors: when I tested this howto with 6.06 LTS on 1 June 2006, the install of dmraid failed (--configure), indicating it was unable to start the dmraid initscript. This may have been some kind of error on my part. I was able to fix this with
dpkg-reconfigure dmraid, so I add it here as a possibily useful tip should this turn out to be systemic problem that others encounter. Also, install dmraid first, then the kernel, in order to use the initramfs scripts that are now part of the 6.06 distrubution. This is based on one 6.06 test -- please correct/edit this as appropriate.** - 18 June 2006: another user reported this same problem. dpkg-reconfigure did not work for him, but he reports that after reinstalling dmraid "like ten times" it magically worked. To help reduce the likelihood of this occuring, I have separated the package installs to separate lines (above) to help ensure things are completed in what I'm guessing to be the best order.
- Please contribute your lessons learned regarding this error and how to overcome it.
- Temporary Note to other editors: when I tested this howto with 6.06 LTS on 1 June 2006, the install of dmraid failed (--configure), indicating it was unable to start the dmraid initscript. This may have been some kind of error on my part. I was able to fix this with
为RAID安装启动器
Now that you have the debian core, ubuntu-base, linux kernel, dmraid, grub, and ubuntu-desktop installed, you can proceed with the bootloader. If you haven't completed these successfully, don't attempt to proceed, you will just exacerbate any problem you have at this point.
We will demonstrate the installation of GRUB (Grand Unified Bootloader), but there are several alternatives (e.g., LILO). The key information here is how the normal process for use of the bootloader had to be modified to accomodate the RAID mappings, so this general process should be useful regardless of your choice of bootloader.
安装启动器包
Now you need to run the grub shell. In a non-RAID scenario, one might use grub-install, but we cannot because it cannot see the RAID device mappings and therefore cannot set up correct paths to our boot and root partitions. So we will install and configure grub manually as follows:
First, make a home for GRUB and put the files there that it needs to get set up:
mkdir /boot/grub cp /lib/grub/<your-cpu-arch>-pc/stage1 /boot/grub/ cp /lib/grub/<your-cpu-arch>-pc/stage2 /boot/grub/ cp /lib/grub/<your-cpu-arch>-pc/<the staging file for your boot partition's filesystem>
The "staging files" look like: "e2fs_stage1_5" (for ext2 or 3); "reiserfs_stage1_5" (for reiserfs); "xfs_stage1_5" (and so on). It is safe to copy them all to your /boot/grub.
Next, go into the grub shell:
grub
You should now see the grub prompt.
Next, tell GRUB which device is the boot device:
device (hd0) /dev/mapper/via_hfciifae
In my case, it was the RAID array mapped as /dev/mapper/via_hfciifae.
Next, tell GRUB where all the stuff is that is needed for the boot process:
root (hd0,4)
CAUTION: This is one of the most common sources of error, so we will explain this in excruciating detail. From GRUB's perspective, "root" is whatever partition holds the contents of /boot. For most people, this is simply your linux root (/) partition. E.g., if / is your 2nd partition on the RAID you indicated above as hd0, you would say "root (hd0,1)". Remember that GRUB starts counting partitions at 0. The first parition is 0, the second is 1, and so on. In my case, however, I have a separate boot partition that GRUB mounts read-only for me at boot time (which helps keep it secure). It's my 5th partition, so I say "root (hd0,4)"
Optional: IF GRUB complains about bad cylinder numbers (i.e, if it did not complain, skip this part about fdisk and geometry):
You may need to tell it about the device's geometry (cylinders, heads, and sectors per track. You can find this information out by using fdisk (quit GRUB) with the command: fdisk (fdisk -l /dev/mapper/via_hfciifae)
...then reenter the GRUB shell and use the command: geometry (hd0) 9001 255 63
Next, now that you've successfully established the "device" and "root", you can go ahead and instantiate GRUB on the boot device. This sets up the stage 1 bootloader in the device's master boot record and the stage 2 boot loader and grub menu in your boot partition:
setup (hd0) quit
配置启动器
Now run update-grub:
update-grub
This adds your newly installed linux kernel, and the associated initial ram disk image, to the boot options menu that grub presents during start-up. You will find this menu in the boot/grub directory. We need to edit this menu.lst file as follows. (CAUTION: Get this right - this is a common source of error and mistakes result in kernel panic upon reboot, so no typos.):
a) "root=": Correct the path that points to the linux root (in several places). update-grub configures hda1 as root because, not being dmraid-aware, it can't find your current root-device. Put the correct device mapping for your linux root. So put your equivalent of:
root=/dev/mapper/via_hfciifae7
every place you see "root=" (only where you see root and the equal sign). This goes in all the places where update-grub defaulted to root=/dev/hda1 or just left it blank like root= .
Make sure you change this in the Automagic defaults section as well as in each of the multiple alternatives sections that follow. (Important: the Automagic defaults section is nested and therefore uses ## to indicate comments and # to indicate the actual defaults that is uses. So don't "un-comment" the default lines when you edit them. In other words, leave the #). When you update your kernel later on, update-grub will use these defaults so it won't ignorantly "assume hda1" and send your system into a kernel panic when you boot. This ought to end up looking something like:
b) "groot": If necessary, correct the grub root. In places, you will see other lines that also refer to "root" (or "groot") but use syntax such as root (hd0,1) instead of a path. As described earlier, these refer to the "root" for grub's purposes, which is actually your /boot. Also, remember grub's syntax uses partition numbering beginning with zero. So, if you have a separate /boot partition, these lines should instead show something like:
root (hd0,4)
(The same information we used while working with grub interactively earlier.) Change this both for the Automagic defaults as well as for each alternative, including the memtest option.
c) An additional edit is required IF you are using a separate /boot partition. The path pointing to the linux root must be RELATIVE to the grub "root" (your /boot). So if you are using a separate boot partition, the paths in grub's menu.lst file that help grub locate the linux kernel and initrd will not begin with "/boot", and you should delete that portion of the path. For example, {{update-grub</nowiki></pre> initially spat out this:
title Ubuntu, kernel 2.6.15-29-amd64-k8 root (hd0,0) kernel /boot/vmlinuz-2.6.15-29-amd64-k8 root= ro quiet splash initrd /boot/initrd.img-2.6.15-29-amd64-k8 savedefault boot
... and because I have a separate boot parition and opted not to use a grub splash image (which you can learn about elsewhere), my editing looked like this...
title Ubuntu, kernel 2.6.15-29-amd64-k8 root (hd0,4) kernel /vmlinuz-2.6.15-29-amd64-k8 root=/dev/mapper/via_hfciifae ro quiet initrd /initrd.img-2.6.15-29-amd64-k8 savedefault boot
IMPORTANT: Note that I removed "savedefault". If you leave this in, you will get a "file not found" error when you try to boot (you also can't set use default=saved up top as it shows in the menu.lst file's example). Again, if you are not using a separate boot partition, you can leave /boot in the paths.
d) To add a static boot stanza for Windows, you can use and change the example in the menu.lst file or the following:
title Windows XP rootnoverify (hd0,0) chainloader +1Put it at the bottom, below where it says
### END DEBIAN AUTOMAGIC KERNELS LIST. Or if for some unforgivable reason you want your computer to boot Windows by default, you can put it up front above where it says### BEGIN DEBIAN AUTOMAGIC KERNELS LIST
e) Close the gaping security hole! First, set a password where the example shows it. This will be required for any locked menu entries, for the ability to edit the bootlines, or to drop to a command prompt. To do this, in the console type:
grub-md5-crypt
When it prompts you "Password:", it's asking what you want to be the GRUB password (not your user password, the root password, or anything else). You will be prompted to enter it twice, then it will spit out the MD5 hash that you need to paste into menu.lst. This line should end up looking something like:
password --md5 $1$gLhU0/$aW78kHK1QfV3P2b2znUoe/
- Then, to keep your "recovery mode" boot alternative(s) locked each time update-grub runs, set
lockalternative=true.
Unless you do this, anybody will be able to seize root simply by rebooting your computer (e.g., cutting power to it) and selecting your "recovery mode" menu entry when it reboots, or editing the normal bootline to include 'single' mode.
f) Test automagic kernels settings (also completes the locking of alternatives). It is better to find errors now than a month from now when you've forgotten all this stuff and the kernel gets updated.
- first, make a backup of menu.lst
- then run update-grub again
- watch for errors and re-examine menu.lst for discrepancies
- correct as needed.
为RAID 重新配置Initramfs (Ubuntu 5.10)
Reminder: Sections Ubuntu 5.10 should be skipped if you are installing Ubuntu 6.06.
In recent years there has been a trend to try and pull a bunch of code out of the kernel and into EarlyUserspace. This includes stuff like nfsroot configuration, md software RAID, lvm, conventional partition/disklabel support, and so on. Early user space is set up in the form of an initramfs which the boot loader loads with the kernel, and this contains user mode utilities to detect and configure the hardware, mount the correct root device, and boot the rest of the system.
Hardware fakeRAID falls into this category of operation. A device driver in the kernel called device mapper is configured by user mode utilities to access software RAIDs and partitions. If you want to be able to use a fakeRAID for your root filesystem, your initramfs must be configured to detect the fakeRAID and configure the kernel mapper to access it.
So we need to add dmraid to the initramfs. Debian and Ubuntu supports this by way of a set of shell scripts and configuration files placed in /etc/mkinitramfs/. We must tailor these to include dmraid by plugging in two simple scripts and adding a one-line entry to a configuration file. The only real challenge here is to make sure you don't inadvertently screw up the syntax with a typo.
Note that in Ubuntu 6.06, this is taken care of by the dmraid package itself.
在Ubuntu 5.10中配置mkinitramfs
First, create a new file as /etc/mkinitramfs/scripts/local-top/dmraid .
(If you are lazy or don't like to keyboard, you can open this how-to in the browser and copy the text.)
PREREQ="udev"
prereqs()
{
echo "$PREREQ"
}
case $1 in
prereqs)
prereqs
exit 0
;;
esac
modprobe -q sata_nv
modprobe -q dm-mod
/sbin/dmraid -ay
Second, create another new file as /etc/mkinitramfs/hooks/dmraid.
(Again for the lazy, you can copy it from your browser. Also, it's only slightly different, so if you are manually typing it for some reason, you may want to start with a copy of the first script.)
PREREQ=""
prereqs()
{
echo "$PREREQ"
}
case $1 in
prereqs)
prereqs
exit 0
;;
esac
. /usr/share/initramfs-tools/hook-functions
copy_exec /sbin/dmraid /sbin
exit 0
Third, mark both of these new initramfs scripts as executable:
chmod +x /etc/mkinitramfs/hooks/dmraid chmod +x /etc/mkinitramfs/scripts/local-top/dmraid
Last, add the line dm-mod to the file /etc/mkinitramfs/modules. Make sure the file ends with a newline. If you use a RAID-1 (mirror), include dm-mirror as well.
升级initrd (Ubuntu 5.10)
Now the big moment -- use initramfs to update the initrd file. Below, I show the kernel I installed at that time, but stuff following "img-" and following "-c -k " must reflect the version YOU are using (e.g., "2.6.15-29-amd64-k8-smp" or whatever).
Two commands
rm /boot/initrd.img-2.6.12-9-k7 update-initramfs -c -k 2.6.12-9-k7
Now you are ready to set up the new system.
像通常一样预配置新系统
Ensure that you are still operating as root within the new (temporary) system (i.e., your prompt will be root@ubuntu#. If not, chroot /target again:
sudo chroot /target
(The process from here forward is the same as any bootstrap / network installation, and there are other sources to refer to for more detail.)
UBUNTU 5.10: Enter the command base-config new to configure system defaults.
- UBUNTU 6.06: base-config is deprecated in Dapper Drake. The correct procedure needs to be inserted here, so please contribute. Theoretically, one could do what base-config does manually.
While it is not absolutely necessary, it may be useful to also copy the live hosts and interfaces files into your temporary system before rebooting (after exiting your chroot:
cp /etc/hosts /target/etc/hosts cp /etc/network/interfaces /target/etc/network/interfaces).
It will also be helpful to configure your fstab file at this point. One easy way to do this is:
cat /etc/mtab
(select and copy everything)
nano /target/etc/fstab
(paste everything)
Then delete everything except the proc line, and the lines that refer to your RAID partitions. It might end up something like this (yours will vary - people asked for examples):
proc /proc proc rw 0 0 /dev/mapper/via_hfciifae5 /boot ext3 defaults 0 2 /dev/mapper/via_hfciifae7 / reiserfs notail,noatime 0 1 /dev/mapper/via_hfciifae6 none swap sw 0 0
or
/dev/mapper/nvidia_bggfdgec2 /boot ext3 defaults 0 1 /dev/mapper/nvidia_bggfdgec3 none swap sw 0 0 proc /proc proc rw 0 0
Finally you are ready to reboot. This first time, select the "recovery mode" option. When it asks, you want to "perform maintenance". Set the root password:
passwd
Suggested early set-up tasks: adduser yourself (create a regular user) nano /etc/group (create an admin group) visudo (duplicate the root line except with %admin where root was) reboot, and you should be able to log in a normal user through gdm, and continue normally with sudo privileges.
(more is needed here, or a reference to whatever replaces the howto that describes a general debootstrap install)
升级到Ubuntu 6.06 (Dapper Drake)
The dmraid package in Ubuntu 6.06 has the necessary scripts included (under /usr). After upgrading the dmraid package, you can therefore delete the old scripts that you've made (under /etc). To be sure the package scripts are baked into the initrd, update the initrd again by reconfiguring dmraid:
sudo rm /etc/mkinitramfs/hooks/dmraid sudo rm /etc/mkinitramfs/scripts/local-top/dmraid sudo dpkg-reconfigure dmraid
RAID 5的特别说明
While trying to install dmraid for a Raid 5 Nvidia setup received a error 139 forced exit and upon further investigation in the TODO doc in /usr/share/doc/dmraid found that dmraid doesn't support raid modes above 1 yet. Here's the exact wording from the TODO,"higher RAID levels above 1; main restriction to support these is the need for device-mapper targets which map RAID3,4,5."
EDIT: Further research has lead me to dmraid 1.0.0.rc10, which in it's changelog notes Raid5 support for nvidia. Current Ubuntu version is 1.0.0.rc9 which explains the lack of Raid5 support. Will update with more info on how well it works.
NOTE: The kernel device mapper ( which dmraid depends on ) does not yet support raid 5. There are some early development patches availible, so they might get merged into Linus's kernel in time for Dapper+1, but I'd say it's not all that likely.
