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手册：PPC64/安装/准备磁盘
| PPC64 Handbook |
|---|
| 安装 |
| 关于安装 |
| 选择安装媒介 |
| 配置网络 |
| 准备磁盘 |
| 安装stage3 |
| 安装基本系统 |
| 配置Linux内核 |
| 配置系统 |
| 安装系统工具 |
| 配置系统引导程序Bootloader |
| 收尾安装工作 |
| 使用Gentoo |
| Portage介绍 |
| USE标记 |
| Portage功能特性 |
| 初始化脚本（Initscript）系统 |
| 环境变量 |
| 使用Portage |
| 文件和目录 |
| 变量 |
| 混合使用不同的软件分支 |
| 额外的工具 |
| 定制Portage树 |
| 高级特性 |
| 网络配置 |
| 入门 |
| 高级配置 |
| 模块化网络 |
| 无线 |
| 添加功能 |
| 动态管理 |
块设备简介
块设备
让我们来好好看看Gentoo Linux以及普通Linux中有关磁盘方面的知识，包括Linux文件系统，分区和块设备。一旦磁盘和文件的来龙去脉都了解了，我们将设置分区和文件系统的安装Gentoo Linux。
首先，让我们来看看块设备。最著名的块设备可能是代表Linux系统第一块磁盘的/dev/sda。SCSI和SATA磁盘全标为/dev/sd*；甚至IDE磁盘在libata内核框架下也标为/dev/sd*。当使用老设备框架时，第一个IDE磁盘是/dev/hda。
上面的块设备代表的抽象接口的磁盘。用户程序可以使用这些块设备来与你的磁盘进行交互，而无需担心驱动器到底是IDE，SCSI还是其他什么东西。该程序可以把磁盘当作一系列连续的，可随机访问的512字节块的存储。
Partitions and slices
Although it is theoretically possible to use a full disk to house a Linux system, this is almost never done in practice. Instead, full disk block devices are split up in smaller, more manageable block devices. On most systems, these are called partitions. Other architectures use a similar technique, called slices.
Designing a partition scheme
How many partitions and how big?
The number of partitions is highly dependent on the environment. For instance, if there are lots of users, then it is advised to have /home/ separate as it increases security and makes backups easier. If Gentoo is being installed to perform as a mail server, then /var/ should be separate as all mails are stored inside /var/. A good choice of filesystem will then maximize the performance. Game servers will have a separate /opt/ as most gaming servers are installed there. The reason is similar for the /home/ directory: security and backups. In most situations, /usr/ is to be kept big: not only will it contain the majority of applications, it typically also hosts the Gentoo ebuild repository (by default located at /usr/portage) which already takes around 650 MiB. This disk space estimate excludes the packages/ and distfiles/ directories that are generally stored within this ebuild repository.
It very much depends on what the administrator wants to achieve. Separate partitions or volumes have the following advantages:
- Choose the best performing filesystem for each partition or volume.
- The entire system cannot run out of free space if one defunct tool is continuously writing files to a partition or volume.
- If necessary, file system checks are reduced in time, as multiple checks can be done in parallel (although this advantage is more with multiple disks than it is with multiple partitions).
- Security can be enhanced by mounting some partitions or volumes read-only,
nosuid(setuid bits are ignored),noexec(executable bits are ignored) etc.
However, multiple partitions have disadvantages as well. If not configured properly, the system might have lots of free space on one partition and none on another. Another nuisance is that separate partitions - especially for important mount points like /usr/ or /var/ - often require the administrator to boot with an initramfs to mount the partition before other boot scripts start. This isn't always the case though, so results may vary.
There is also a 15-partition limit for SCSI and SATA unless the disk uses GPT labels.
What about swap space?
There is no perfect value for the swap partition. The purpose of swap space is to provide disk storage to the kernel when internal memory (RAM) is under pressure. A swap space allows for the kernel to move memory pages that are not likely to be accessed soon to disk (swap or page-out), freeing memory. Of course, if that memory is suddenly needed, these pages need to be put back in memory (page-in) which will take a while (as disks are very slow compared to internal memory).
When the system is not going to run memory intensive applications or the system has lots of memory available, then it probably does not need much swap space. However, swap space is also used to store the entire memory in case of hibernation. If the system is going to need hibernation, then a bigger swap space is necessary, often at least the amount of memory installed in the system.
Default: Using mac-fdisk
These instructions are for the Apple G5 system.
Start mac-fdisk:
root #mac-fdisk /dev/sdaFirst delete the partitions that have been cleared previously to make room for Linux partitions. Use d in mac-fdisk to delete those partition(s). It will ask for the partition number to delete.
Second, create an Apple_Bootstrap partition by using b. It will ask what block to start from. Enter the number of the first free partition, followed by a p. For instance this is 2p.
This partition is not a "boot" partition. It is not used by Linux at all; there is no need to place any filesystem on it and it should never be mounted. PPC users don't need an extra partition for /boot.
Now create a swap partition by pressing c. Again mac-fdisk will ask what block to start from. As we used 2 before to create the Apple_Bootstrap partition, enter 3p. When asked for the size, enter 512M (or whatever size needed). When asked for a name, enter swap (mandatory).
To create the root partition, enter c, followed by 4p to select from what block the root partition should start. When asked for the size, enter 4p again. mac-fdisk will interpret this as "Use all available space". When asked for the name, enter root (mandatory).
To finish up, write the partition to the disk using w and q to quit mac-fdisk.
To make sure everything is ok, run mac-fdisk once more and check whether all the partitions are there. If not all created partitions are shown, or it is missing some of the changes that were made, then reinitialize the partitions by pressing i in mac-fdisk. Note that this will recreate the partition map and thus remove all the partitions.
Alternative: Using fdisk
The following instructions are for IBM pSeries, iSeries, and OpenPower systems.
When planning to use a RAID disk array for the Gentoo installation on POWER5-based hardware, first run iprconfig to format the disks to Advanced Function format and create the disk array. Emerge sys-fs/iprutils after the installation is complete.
If the system has an ipr-based SCSI adapter, start the ipr utilities now.
root #/etc/init.d/iprinit startThe following parts explain how to create the example partition layout described previously, namely:
| Partition | Description |
|---|---|
| /dev/sda1 | PPC PReP Boot partition |
| /dev/sda2 | Swap partition |
| /dev/sda3 | Root partition |
Change the partition layout according to personal preference.
Viewing current partition layout
fdisk is a popular and powerful tool to split a disk into partitions. Fire up fdisk on the current disk (in our example, we use /dev/sda):
root #fdisk /dev/sdaCommand (m for help)
If there is still an AIX partition layout on the system, then the following error message will be displayed:
root #fdisk /dev/sda There is a valid AIX label on this disk.
Unfortunately Linux cannot handle these
disks at the moment. Nevertheless some
advice:
1. fdisk will destroy its contents on write.
2. Be sure that this disk is NOT a still vital
part of a volume group. (Otherwise you may
erase the other disks as well, if unmirrored.)
3. Before deleting this physical volume be sure
to remove the disk logically from your AIX
machine. (Otherwise you become an AIXpert).
Don't worry, new empty DOS partition table can be created by pressing o.
This will destroy any installed AIX version!
Type p to display the disk current partition configuration:
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System /dev/sda1 1 12 53266+ 83 Linux /dev/sda2 13 233 981571+ 82 Linux swap /dev/sda3 234 674 1958701+ 83 Linux /dev/sda4 675 6761 27035410+ 5 Extended /dev/sda5 675 2874 9771268+ 83 Linux /dev/sda6 2875 2919 199836 83 Linux /dev/sda7 2920 3008 395262 83 Linux /dev/sda8 3009 6761 16668918 83 Linux
This particular disk is configured to house six Linux filesystems (each with a corresponding partition listed as "Linux") as well as a swap partition (listed as "Linux swap").
Removing all partitions
First remove all existing partitions from the disk. Type d to delete a partition. For instance, to delete an existing /dev/sda1:
Command (m for help):dPartition number (1-4): 1
The partition has been scheduled for deletion. It will no longer show up when typing p, but it will not be erased until the changes have been saved. If a mistake was made and the session needs to be aborted, then type q immediately and hit Enter and none of the partitions will be deleted or modified.
Now, assuming that indeed all partitions need to be wiped out, repeatedly type p to print out a partition listing and then type d and the number of the partition to delete it. Eventually, the partition table will show no more partitions:
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System
Now that the in-memory partition table is empty, let's create the partitions. We will use a default partitioning scheme as discussed previously. Of course, don't follow these instructions to the letter but adjust to personal preference.
Creating the PPC PReP boot partition
First create a small PReP boot partition. Type n to create a new partition, then p to select a primary partition, followed by 1 to select the first primary partition. When prompted for the first cylinder, hit Enter. When prompted for the last cylinder, type +7M to create a partition 7 MB in size. After this, type t to set the partition type, 1 to select the partition just created and then type in 41 to set the partition type to "PPC PReP Boot". Finally, mark the PReP partition as bootable.
The PReP partition has to be smaller than 8 MB!
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System
Command (m for help):nCommand action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-6761, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-6761, default
6761): +8M
Command (m for help):tSelected partition 1 Hex code (type L to list codes): 41 Changed system type of partition 1 to 41 (PPC PReP Boot)
Command (m for help):aPartition number (1-4): 1 Command (m for help):
Now, when looking at the partition table again (through p), the following partition information should be shown:
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 3 13293 41 PPC PReP Boot
Creating the swap partition
Now create the swap partition. To do this, type n to create a new partition, then p to tell fdisk to create a primary partition. Then type 2 to create the second primary partition, /dev/sda2 in our case. When prompted for the first cylinder, hit Enter. When prompted for the last cylinder, type +512M to create a partition 512MB in size. After this, type t to set the partition type, 2 to select the partition just created and then type in 82 to set the partition type to "Linux Swap". After completing these steps, typing p should display a partition table that looks similar to this:
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System /dev/sda1 1 3 13293 41 PPC PReP Boot /dev/sda2 4 117 506331 82 Linux swap
Creating the root partition
Finally, create the root partition. To do this, type n to create a new partition, then p to tell fdisk to create a primary partition. Then type 3 to create the third primary partition, /dev/sda3 in our case. When prompted for the first cylinder, hit Enter. When prompted for the last cylinder, hit enter to create a partition that takes up the rest of the remaining space on the disk. After completing these steps, typing p should display a partition table that looks similar to this:
Command (m for help):pDisk /dev/sda: 30.7 GB, 30750031872 bytes 141 heads, 63 sectors/track, 6761 cylinders Units = cylinders of 8883 * 512 = 4548096 bytes Device Boot Start End Blocks Id System /dev/sda1 1 3 13293 41 PPC PReP Boot /dev/sda2 4 117 506331 82 Linux swap /dev/sda3 118 6761 29509326 83 Linux
Saving the partition layout
To save the partition layout and exit fdisk, type w.
Command (m for help):w
创建文件系统
介绍
现在分区已经创建，该在上面设置文件系统了。下一章节中描述了Linux所支持的众多文件系统。知道使用哪一个文件系统的读者可以继续阅读为分区应用文件系统。剩下的人应该学习可用的文件系统……
文件系统
有一些可以使用的文件系统。有些在ppc64架构上稳定——建议在选择为一个重要分区实验性的选择文件系统前继续阅读。
- btrfs
- 是下一代文件系统，提供了许多高级功能，如快照，通过校验和自我修复、 透明压缩、 子卷和集成 RAID。几个发行版已经开始将它作为一个默认的选项,但它还未为生产工作做好准备。文件系统报告崩溃是常见的。其开发人员敦促人们运行最新的内核版本来解决安全问题,以及老的问题。 这种情况已经很多年了,现在使用它还为时过早。如果出现变更，以及发生了变化，解决错误问题，都很少往旧内核注入补丁。请谨慎使用这个文件系统!
- ext2
- 是经考验证明可靠的Linux文件系统，但是没有元数据日志，这意味这在启动系统时的ext2文件系统的日常检查相当耗时。现在相当一部分的新一代的日志文件系统都可以非常迅速检查一致性，因此比那些非日志文件系统更受欢迎。当你启动系统碰巧遇到文件系统状态不一致时，日志文件系统不会在那里耽搁很长时间。
- ext3
- 是ext2文件系统的带日志版本，提供了元数据日志模式以快速恢复数据。此外还提供了其他增强的日志模式，如完整数据日志模式和有序数据日志模式。它使用了HTree索引，在几乎所有的情况下都能保持高性能。简而言之，ext3是非常好及可靠的文件系统。
- ext4
- 最初创建为ext3的一个分支，EXT4带来了新的功能，性能改进和去除中度更改磁盘格式大小限制。它可以跨越体积高达1的EB并用16 TB最大文件大小。取而代之的是经典的ext2/3位块分配的ext4的使用范围，这对提高大文件的性能，并减少碎片。的Ext4还提供了更为复杂的块分配算法（延迟分配和多嵌段分配）给文件系统驱动更多的方式来优化数据的布局在磁盘上。 EXT4是推荐的通用所有平台的文件系统。
- f2fs
- 这个文件系统最初由三星创建用于NAND闪存，是一种闪存文件系统 从直到2016年第二季度起，这个文件系统仍然被认为不成熟。把Gentoo安装到microSD卡，USB驱动器或其他基于闪存的存储设备时使用它是一个不错的选择。
- JFS
- 是IBM的高性能日志文件系统。JFS是一个轻量级的、快速的和稳定的基于B+树的文件系统，在很多情况下都有很好的表现。
- ReiserFS
- 是基于B+树的文件系统，它有着非常全面的性能，特别时在处理很多小文件的时候，虽然会占用多一点CPU。ReiserFS相比其他文件系统显得受维护的不够。
- XFS
- 是一种带元数据日志的文件系统，它有一个健壮的特性集，并且对可伸缩性进行了优化。XFS似乎对各种各样的硬件问题显得不够宽容。
- vfat
- 也称为FAT32，被支持Linux，但不支持任何权限设置。它主要用于互操作性与其他操作系统（主要是微软的Windows），但也是很有必要的一些系统固件（如UEFI）的支持。
- NTFS
- 这个“新技术”的文件系统是Microsoft Windows的旗舰文件系统。 与上面的vfat类似，它不存储BSD或Linux正常工作所需的权限设置或扩展属性，因此它不能用作根文件系统。 它应该'只'用于与Microsoft Windows系统的互操作性（注意只强调）。
当在一个小的分区（少于8GB）上使用ext2、ext3或ext4，则创建文件系统时必须带适当的选项以保留足够的inode。mke2fs（mkfs.ext2）应用程序使用“字节每inode”设置来计算一个文件系统应该用多少个inode。在小分区，建议增加计算出的inode数量。
对于ext2，可以使用下面的命令来完成：
root #mkfs.ext2 -T small /dev/<device>对于ext3或ext4，添加-j选项来启用日志：
root #mkfs.ext2 -j -T small /dev/<device>这一般将是对于给定的文件系统inode数量的四倍，它的“字节每inode”从16kB每个减少到4kB每个。这个可以在将来通过提供比例进行调整：
root #mkfs.ext2 -i <ratio> /dev/<device>为分区应用文件系统
在一个分区或卷上创建一个文件系统，这里有用于每一个可能的分区的工具。 单击下表中的文件系统名称，了解每个文件系统的更多信息：
| 文件系统 | 创建命令 | 在最小化CD？ | 包 |
|---|---|---|---|
| btrfs | mkfs.btrfs | Yes | sys-fs/btrfs-progs |
| ext2 | mkfs.ext2 | Yes | sys-fs/e2fsprogs |
| ext3 | mkfs.ext3 | Yes | sys-fs/e2fsprogs |
| ext4 | mkfs.ext4 | Yes | sys-fs/e2fsprogs |
| f2fs | mkfs.f2fs | Yes | sys-fs/f2fs-tools |
| jfs | mkfs.jfs | Yes | sys-fs/jfsutils |
| reiserfs | mkfs.reiserfs | Yes | sys-fs/reiserfsprogs |
| xfs | mkfs.xfs | Yes | sys-fs/xfsprogs |
| vfat | mkfs.vfat | Yes | sys-fs/dosfstools |
| NTFS | mkfs.ntfs | Yes | sys-fs/ntfs3g |
比如，在示例分区结构中，有 使用ext2的引导分区（/dev/sda1）和使用ext4的根分区（/dev/sda3），下面的命令将会用到：
root #mkfs.ext2 /dev/sda1root #mkfs.ext4 /dev/sda3现在在新创建的分区（或逻辑卷）上创建文件系统。
激活swap分区
mkswap是用来初始化swap分区的命令：
root #mkswap /dev/sda2要激活swap分区，使用swapon：
root #swapon /dev/sda2使用上面提到的命令创建和激活swap。
挂载 root 分区
现在分区都已初始化并有文件系统，接下来该挂载那些分区了。使用mount命令，但是不要忘记为每一个创建的分区创建需要的挂载目录。比如示例中我们挂载根分区:
root #mount /dev/sda3 /mnt/gentoo如果/tmp/需要放在一个独立分区，确保在挂载后变更它的权限：
root #chmod 1777 /mnt/gentoo/tmp后面的介绍中将挂载proc文件系统（一个内核的虚拟接口）和其它内核伪文件系统。不过我们首先安装Gentoo安装文件。