Running Linux phần 2 pdf

Chapter 3. Installation and Initial Configuration 59 Command (m for help): m Command action a toggle a bootable flag d delete a partition l list known partition types m print this menu n add a new partition p print the partition table q quit without saving changes t change a partition's system id u change display/entry units v verify the partition table w write table to disk and exit x extra functionality (experts only) Command (m for help): The n command is used to create a new partition. Most other options you won't need to worry about. To quit fdisk without saving any changes, use the q command. To quit fdisk and write the changes to the partition table to disk, use the w command. This is worth repeating: so long as you quit with q without writing, you can mess around as much as you want with fdisk without risking harm to your data. Only when you type w can you cause potential disaster to your data if you do something wrong. The first thing you should do is display your current partition table and write the information down for later reference. Use the p command to see the information. It is a good idea to copy the information to your notebook after each change you have made to the partition table. If, for some reason, your partition table is damaged, you will not access any data on your hard disk any longer, even though the data itself is still there. But by using your notes, you might be able to restore the partition table and get your data back in many cases by running fdisk again and deleting and re-creating the partitions with the parameters you previously wrote down. Don't forget to save the restored partition table when you are done. Here is an example of a printed partition table, where blocks, sectors, and cylinders are units into which a hard disk is organized: Command (m for help): p Disk /dev/hda: 16 heads, 38 sectors, 683 cylinders Units = cylinders of 608 * 512 bytes Device Boot Begin Start End Blocks Id System /dev/hda1 * 1 1 203 61693 6 DOS 16-bit >=32M Command (m for help): In this example, we have a single Windows partition on /dev/hda1, which is 61693 blocks (about 60 MB). 2 This partition starts at cylinder number 1 and ends on cylinder 203. We have a total of 683 cylinders in this disk; so there are 480 cylinders left on which to create Linux partitions. To create a new partition, use the n command. In this example, we'll create two primary partitions (/dev/hda2 and /dev/hda3) for Linux: 2 A block, under Linux, is 1024 bytes. Chapter 3. Installation and Initial Configuration 60 Command (m for help): n Command action e extended p primary partition (1-4) p Here, fdisk is asking which type of the partition to create: extended or primary. In our example, we're creating only primary partitions, so we choose p: Partition number (1-4): fdisk will then ask for the number of the partition to create; because partition 1 is already used, our first Linux partition will be number 2: Partition number (1-4): 2 First cylinder (204-683): Now, we enter the starting cylinder number of the partition. Because cylinders 204 through 683 are unused, we'll use the first available one (numbered 204). There's no reason to leave empty space between partitions: First cylinder (204-683): 204 Last cylinder or +size or +sizeM or +sizeK (204-683): fdisk is asking for the size of the partition we want to create. We can either specify an ending cylinder number, or a size in bytes, kilobytes, or megabytes. Because we want our partition to be 80 MB in size, we specify +80M. When specifying a partition size in this way, fdisk will round the actual partition size to the nearest number of cylinders: Last cylinder or +size or +sizeM or +sizeK (204-683): +80M If you see a warning message such as this, it can be ignored. fdisk prints the warning because it's an older program and dates back before the time that Linux partitions were allowed to be larger than 64 MB. Now we're ready to create our second Linux partition. For sake of demonstration, we'll create it with a size of 10 MB: Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 3 First cylinder (474-683): 474 Last cylinder or +size or +sizeM or +sizeK (474-683): +10M At last, we'll display the partition table. Again, write down all this information — especially the block sizes of your new partitions. You'll need to know the sizes of the partitions when creating filesystems. Also, verify that none of your partitions overlaps: Chapter 3. Installation and Initial Configuration 61 Command (m for help): p Disk /dev/hda: 16 heads, 38 sectors, 683 cylinders Units = cylinders of 608 * 512 bytes Device Boot Begin Start End Blocks Id System /dev/hda1 * 1 1 203 61693 6 DOS 16-bit >=32M /dev/hda2 204 204 473 82080 83 Linux native /dev/hda3 474 474 507 10336 83 Linux native As you can see, /dev/hda2 is now a partition of size 82080 blocks (which corresponds to about 80 MB), and /dev/hda3 is 10336 blocks (about 10 MB). Note that most distributions require you to use the t command in fdisk to change the type of the swap partition to "Linux swap," which is numbered 82. You can use the L command to print a list of known partition type codes, and then use the t command to set the type of the swap partition to that which corresponds to "Linux swap." This way the installation software will be able to automatically find your swap partitions based on type. If the installation software doesn't seem to recognize your swap partition, you might want to rerun fdisk and use the t command on the partition in question. In the previous example, the remaining cylinders on the disk (numbered 508 to 683) are unused. You may wish to leave unused space on the disk, in case you want to create additional partitions later. Finally, we use the w command to write the changes to disk and exit fdisk: Command (m for help): w # Keep in mind that none of the changes you make while running fdisk takes effect until you give the w command, so you can toy with different configurations and save them when you're done. Also, if you want to quit fdisk at any time without saving the changes, use the q command. Remember that you shouldn't modify partitions for operating systems other than Linux with the Linux fdisk program. You may not be able to boot Linux from a partition using cylinders numbered over 1023. Therefore, you should try to create your Linux root partition within the sub-1024 cylinder range, which is almost always possible (e.g., by creating a small root partition in the sub-1024 cylinder range). If, for some reason, you cannot or do not want to do this, you can simply boot Linux from floppy. Some Linux distributions require you to reboot the system after running fdisk to allow the changes to the partition table to take effect before installing the software. Newer versions of fdisk automatically update the partition information in the kernel, so rebooting isn't necessary. To be on the safe side, after running fdisk you should reboot from the installation medium before proceeding. Chapter 3. Installation and Initial Configuration 62 3.1.4 Creating Swap Space If you are planning to use a swap partition for virtual RAM, you're ready to prepare it. 3 In Section 6.2 in Chapter 6, we discuss the preparation of a swap file, in case you don't want to use an individual partition. Many distributions require you to create and activate swap space before installing the software. If you have a small amount of physical RAM, the installation procedure may not be successful unless you have some amount of swap space enabled. The command used to prepare a swap partition is mkswap, and it takes the following form: mkswap -c partition where partition is the name of the swap partition. For example, if your swap partition is /dev/hda3, use the command: # mkswap -c /dev/hda3 With older versions of mkswap, you had to specify the size of the partition, which was dangerous, as one typo could destroy your disk logically. The -c option tells mkswap to check for bad blocks on the partition when creating the swap space. Bad blocks are spots on the magnetic medium that do not hold the data correctly. This occurs only rarely with today's hard disks, but if it does occur, and you do not know about it, it can cause you endless trouble. Always use the -c option to have mkswap check for bad blocks. It will exclude them from being used automatically. If you are using multiple swap partitions, you need to execute the appropriate mkswap command for each partition. After formatting the swap space, you need to enable it for use by the system. Usually, the system automatically enables swap space at boot time. However, because you have not yet installed the Linux software, you need to enable it by hand. The command to enable swap space is swapon, and it takes the following form: swapon partition After the mkswap command shown, we use the following command to enable the swap space on /dev/hda3: # swapon /dev/hda3 3 Again, some distributions of Linux prepare the swap space for you automatically, or via an installation menu option. Chapter 3. Installation and Initial Configuration 63 3.1.5 Creating the Filesystems Before you can use your Linux partitions to store files, you must create filesystems on them. Creating a filesystem is analogous to formatting a partition under Windows or other operating systems. We discussed filesystems briefly in Section 2.2.3 in Chapter 2. Several types of filesystems are available for Linux. Each filesystem type has its own format and set of characteristics (such as filename length, maximum file size, and so on). Linux also supports several "third-party" filesystem types, such as the Windows filesystem. The most commonly used filesystem type is the Second Extended Filesystem, or ext2fs. The ext2fs is one of the most efficient and flexible filesystems; it allows filenames of up to 256 characters and filesystem sizes of up to 32 terabytes. In Section 6.1.1 in Chapter 6, we discuss the various filesystem types available for Linux. Initially, however, we suggest you use the ext2fs filesystem. To create an ext2fs filesystem, use the command: mke2fs -c partition where partition is the name of the partition. For example, to create a filesystem on /dev/hda2, use the command: # mke2fs -c /dev/hda2 If you're using multiple filesystems for Linux, you need to use the appropriate mke2fs command for each filesystem. If you have encountered any problems at this point, see Section 3.3 later in this chapter. 3.1.6 Installing the Software Finally, you are ready to install the software on your system. Every distribution has a different mechanism for doing this. Many distributions have a self-contained program that steps you through the installation. On other distributions, you have to mount your filesystems in a certain subdirectory (such as /mnt) and copy the software to them by hand. On CD-ROM distributions, you may be given the option to install a portion of the software on your hard drive and leave most of the software on the CD-ROM. This is often called a "live filesystem." Such a live filesystem is convenient for trying out Linux before you make a commitment to install everything on your disk. Some distributions offer several different ways to install the software. For example, you may be able to install the software directly from a Windows partition on your hard drive instead of from floppies. Or you may be able to install over a TCP/IP network via FTP or NFS. See your distribution's documentation for details. For example, the Slackware distribution requires you to do the following: Chapter 3. Installation and Initial Configuration 64 1. Create partitions with fdisk. 2. Optionally create swap space with mkswap and swapon (if you have 16 MB or less of RAM). 3. Run the setup program to install the software. setup leads you through a self- explanatory menu system. The exact method used to install the Linux software differs greatly with each distribution. You might be overwhelmed by the choice of software to install. Modern Linux distributions can easily contain a thousand or more packages spread over several CD-ROMs. There are basically three methods for selecting the software package: Selection by task This is the easiest means of selection for beginners. You don't have to think about whether you need a certain package. You just pick whether your Linux computer should act as a workstation, a development machine, or a network router, and the installation program will pick the appropriate packages for you. In all cases, you can then either refine the selection by hand or come back to the installation program later. Selection of individual packages by series With this selection mechanism, all the packages are grouped into series like "Networking," "Development," or "Graphics." You can go through all the series and pick the individual packages there. This requires more decisions than if you choose selection by task, because you have to decide whether you need each package; however, you can skip an entire series when you are sure that you are not interested in the functions it offers. Selection of individual packages sorted alphabetically This method is useful only when you already know which packages you want to install; otherwise you won't see the forest for the trees. Choosing one selection method does not exclude the use of the others. Most distributions offer two or more of the aforementioned selection mechanisms. It might still be difficult to decide which package to pick. Good distributions show a short description of each package on screen to make it easier for you to select the correct ones, but if you are still unsure, our advice is this: when in doubt, leave it out! You can always go back and add packages later. Modern distributions have a very nifty feature, called dependency tracking. Some packages work only when some other packages are installed (e.g., a graphics viewer might need special graphics libraries to import files). With dependency tracking, the installation program can inform you about those dependencies and will let you automatically select the package you want along with all the ones it depends on. Unless you are very sure about what you are doing, you should always accept this offer, or the package might not work afterward. Chapter 3. Installation and Initial Configuration 65 Installation programs can help you make your selection and avoid mistakes in other ways. For example, the installation program might refuse to start the installation when you deselect a package that is absolutely crucial for even the most minimal system to boot (like the basic directory structure). Or, it might check for mutual exclusions, such as cases in which you can only have one package or the other, but not both. Some distributions, such as SuSE, come with a large book that, among other things, lists all the packages together with short descriptions. It might be a good idea to at least skim those descriptions to see what's in store for you, or you might be surprised when you select the packages and are offered the 25 th text editor. 3.1.7 Creating the Boot Floppy or Installing LILO Every distribution provides some means of booting your new Linux system after you have installed the software. In many cases, the installation procedure suggests you create a boot floppy, which contains a Linux kernel configured to use your newly created root filesystem. In order to boot Linux, you could boot from this floppy; control is transferred to your hard drive after you boot. On other distributions, this boot floppy is the installation floppy itself. Many distributions give you the option of installing LILO on your hard drive. LILO is a program that resides on your drive's master boot record. It boots a number of operating systems, including Windows and Linux, and allows you to select to which boot at startup time. In order for LILO to be installed successfully, it needs to know a good deal of information about your drive configuration: for example, which partitions contain which operating systems, how to boot each operating system, and so on. Many distributions, when installing LILO, attempt to "guess" at the appropriate parameters for your configuration. Occasionally, the automated LILO installation provided by some distributions can fail and leave your master boot record in shambles (however it's very doubtful that any damage to the actual data on your hard drive will take place). In particular, if you use OS/2's Boot Manager, you should not install LILO using the automated procedure; there are special instructions for using LILO with the Boot Manager, which will be covered in Chapter 5. In many cases, it is best to use a boot floppy until you have a chance to configure LILO yourself, by hand. If you're exceptionally trusting, though, you can go ahead with the automated LILO installation if it is provided with your distribution. In Section 5.2.2 in Chapter 5, we'll cover in detail how to configure and install LILO for your particular setup. There are also other boot loaders besides LILO, including the Grand Unified BootLoader (GRUB). Most distributions use LILO, though. If everything goes well, congratulations! You have just installed Linux on your system. Go have a cup of tea or something; you deserve it. Chapter 3. Installation and Initial Configuration 66 In case you ran into trouble, Section 3.3, later in this chapter, describes the most common sticking points for Linux installations, and how to get around them. 3.1.8 Additional Installation Procedures Some distributions of Linux provide a number of additional installation procedures, allowing you to configure various software packages, such as TCP/IP networking, the X Window System, and so on. If you are provided with these configuration options during installation, you may wish to read ahead in this book for more information on how to configure this software. Otherwise, you should put off these installation procedures until you have a complete understanding of how to configure the software. It's up to you; if all else fails, just go with the flow and see what happens. It's doubtful that anything you do incorrectly now cannot be undone in the future (knock on wood). 3.2 Post-Installation Procedures After you have completed installing the Linux software, you should be able to reboot the system, log in as root, and begin exploring the system. (Each distribution has a different method for doing this; follow the instructions given by the distribution.) Before you strike out on your own, however, there are some tasks you should do now that may save you a lot of grief later. Some of these tasks are trivial if you have the right hardware and Linux distribution; others may involve a little research on your part, and you may decide to postpone them. 3.2.1 Creating a User Account In order to start using your system, you need to create a user account for yourself. Eventually, if you plan to have other users on your system, you'll create user accounts for them as well. But before you begin to explore you need at least one account. Why is this? Every Linux system has several preinstalled accounts, such as root. The root account, however, is intended exclusively for administrative purposes. As root you have all kinds of privileges and can access all files on your system. However, using root can be dangerous, especially if you're new to Linux. Because there are no restrictions on what root can do, it's all too easy to mistype a command, inadvertently delete files, damage your filesystem, and so on. You should log in as root only when you need to perform system administration tasks, such as fixing configuration files, installing new software, and so on. See Section 5.1 in Chapter 5 for details. 4 For normal usage, you should create a standard user account. Unix systems have built-in security that prevents users from deleting other users' files and corrupting important resources, such as system configuration files. As a regular user, you'll be protecting yourself from your own mistakes. This is especially true for users who don't have Unix system administration experience. 4 A side note: on a Windows 95/98/ME system, the user is always the equivalent to a root user, whether that power is needed or not. Chapter 3. Installation and Initial Configuration 67 Many Linux distributions provide tools for creating new accounts. These programs are usually called useradd or adduser. As root, invoking one of these commands should present you with a usage summary for the command, and creating a new account should be fairly self-explanatory. Most modern distributions provide a generic system administration tool for various tasks, one of which is creating a new user account. Again, other distributions, such as SuSE Linux, Red Hat Linux, or Caldera Open Linux, integrate system installation and system administration in one tool — e.g., yast or yast2 on SuSE Linux, and lisa on Caldera Open Linux. If all else fails, you can create an account by hand. Usually, all that is required to create an account is: 1. Edit the file /etc/passwd to add the new user. (Doing this with vipw — instead of editing the file directly — will protect you against concurrent changes of the password file, but vipw is not available on all distributions.) 2. Optionally edit the file /etc/shadow to specify "shadow password" attributes for the new user. 3. Create the user's home directory. 4. Copy skeleton configuration files (such as .bashrc) to the new user's home directory. These can sometimes be found in the directory /etc/skel. We don't want to go into great detail here: the particulars of creating a new user account can be found in virtually every book on Unix system administration (see the Bibliography for suggested reading). We also talk about creating users in Section 5.7 in Chapter 5. You should be able to find a tool that takes care of these details for you. Keep in mind that to set or change the password on the new account, you use the passwd command. For example, to change the password for the user duck , issue the following command: # passwd duck This will prompt you to set or change the password for duck. If you execute the passwd command as root, it will not prompt you for the original password. In this way, if you have forgotten your old password, but can still log in as root, you can reset it. 3.2.2 Getting Online Help Linux provides online help in the form of manual pages. Throughout this book, we'll be directing you to look at the manual pages for particular commands to get more information. Manual pages describe programs and applications on the system in detail, and it's important for you to learn how to access this online documentation in case you get into a bind. To get online help for a particular command, use the man command. For example, to get information on the passwd command, type the following command: $ man passwd Chapter 3. Installation and Initial Configuration 68 This should present you with the manual page for passwd. Usually, manual pages are provided as an optional package with most distributions, so they won't be available unless you have opted to install them. However, we very strongly advise you to install the manual pages. You will feel lost many times without them. In addition, certain manual pages may be missing or incomplete on your system. It depends on how complete your distribution is and how up-to-date the manual pages are. Linux manual pages also document system calls, library functions, configuration file formats, and kernel internals. In Section 4.12 in Chapter 4, we'll describe their use in more detail. Besides traditional manual pages, there are also so-called Info pages. These can be read with the text editor Emacs, the command info, or one of many graphical info readers available. Many distributions also provide documentation in HTML format that you can read with any web browser, such as Konqueror, as well as with Emacs. Finally, there are documentation files that are simply plain text. You can read these with any text editor or simply with the command more. If you cannot find documentation for a certain command, you can also try running it with either the -h or - -help option. Most commands then provide a brief summary of their usage. 3.2.3 Editing /etc/fstab In order to ensure that all your Linux filesystems will be available when you reboot the system, you may need to edit the file /etc/fstab, which describes your filesystems. Many distributions automatically generate the /etc/fstab file for you during installation, so all may be well. However, if you have additional filesystems that were not used during the installation process, you may need to add them to /etc/fstab in order to make them available. Swap partitions should be included in /etc/fstab as well. In order to access a filesystem, it must be mounted on your system. Mounting a filesystem associates that filesystem with a particular directory. For example, the root filesystem is mounted on /, the /usr filesystem on /usr, and so on. (If you did not create a separate filesystem for /usr, all files under /usr will be stored on the root filesystem.) We don't want to smother you with technical details here, but it is important to understand how to make your filesystems available before exploring the system. For more details on mounting filesystems, see Section 6.1.2 in Chapter 6, or any book on Unix system administration. The root filesystem is automatically mounted on / when you boot Linux. However, your other filesystems must be mounted individually. Usually, this is accomplished with the command: # mount -av in one of the system startup files in /etc/rc.d or wherever your distribution stores its configuration files. This tells the mount command to mount any filesystems listed in the file [...]... fd1 (floppies 1 and 2) fd2, fd3 (floppies 3 and 4) I/O address 3f8 2f8 3e8 2e8 378 - 37f 27 8 - 27 f 3f0 - 3f7 370 - 377 IRQ 4 3 4 3 7 5 6 10 DMA n/a n/a n/a n/a n/a n/a 2 3 3.3 .2. 2 Problems recognizing hard drive or controller When Linux boots, you see a series of messages on your screen, such as the following: Console: colour VGA+ 80x25 Floppy drive(s): fd0 is 1.44M ttyS00 at 0x03f8 (irq = 4) is a 16550A... the problem Table 3 -2 is a list of IRQ and DMA channels used by various "standard" devices found on most systems Almost all systems have some of these devices, so you should avoid setting the IRQ or DMA of other devices to these values Table 3 -2 Common device settings Device ttyS0 (COM1) ttyS1 (COM2) ttyS2 (COM3) ttyS3 (COM4) lp0 (LPT1) lp1 (LPT2) fd0, fd1 (floppies 1 and 2) fd2, fd3 (floppies 3 and... from a floppy by entering: boot: linux root=partition at the boot menu, where partition is the name of the Linux root partition, such as /dev/hda2 SuSE Linux offers a menu entry early in the installation program that boots your newly created Linux system from the installation boot floppy Consult the documentation for your distribution for details 3.3.4 .2 Problems booting Linux from the hard drive If you... reinstall the Linux software can solve the problem Don't beat your head against the wall any longer than you have to! Also, if Linux unexpectedly hangs during installation, there may be a hardware problem of some kind See Section 3.3 .2 for hints 3.3.4 Problems after Installing Linux You've spent an entire afternoon installing Linux In order to make space for it, you wiped your Windows and OS /2 partitions... system to hang See Section 3.3 .2, for a discussion of hardware incompatibilities Section 10 .2 in Chapter 10 lists the currently supported video chipsets, which are a major issue in running graphics on Linux • System reports out-of-memory errors while attempting to boot or install the software This problem relates to the amount of RAM you have available Keep in mind that Linux itself requires at least... numbered above 1 023 BIOS limits the number of cylinders to 1 024 , and any partition using cylinders numbered above this won't be accessible from the BIOS As far as Linux is concerned, this affects only booting; once the system has booted, you should be able to access the partition Your options are to either boot Linux from a boot floppy, or boot from a partition using cylinders numbered below 1 024 See Section... when installing the Linux software If not, the system will still boot Windows (or whatever other operating system you may have) when you attempt to boot from the hard drive In order to boot Linux from the hard drive, you need to install LILO (see the section Section 5 .2. 2 in Chapter 5) o • On the other hand, if you did install LILO, and another operating system boots instead of Linux, you have LILO... option (usually just linux) to boot Linux If you wish to select Linux as the default operating system to boot, you will need to reinstall LILO It also may be possible that you attempted to install LILO, but the installation procedure failed in some way See the previous item on installation 3.3.4.3 Problems logging in After booting Linux, you should be presented with a login prompt: Linux login: At this... hard drive After installing the Linux software, you can install LILO, allowing you to boot from the hard drive At that time, you can specify the drive geometry to the LILO 75 Chapter 3 Installation and Initial Configuration installation procedure, making it unnecessary to enter the drive geometry each time you boot See Section 5 .2. 2 in Chapter 5 for more about LILO 3.3 .2. 3 Problems with SCSI controllers... not relevant to the discussion here In this example, the root filesystem is on /dev/hda1, the /home filesystem is on /dev/hdb2, and the swap partition is on /dev/hdb1: # /etc/fstab # device # /dev/hda1 /dev/hdb2 /dev/hdb1 /proc directory type options / /home none /proc ext2 ext2 swap proc defaults defaults sw defaults The lines beginning with the "#" character are comments Also, you'll notice an additional . 608 * 5 12 bytes Device Boot Begin Start End Blocks Id System /dev/hda1 * 1 1 20 3 61693 6 DOS 16-bit >=32M /dev/hda2 20 4 20 4 473 820 80 83 Linux native /dev/hda3 474 474 507 10336 83 Linux. 3 -2. Common device settings Device I/O address IRQ DMA ttyS0 (COM1) 3f8 4 n/a ttyS1 (COM2) 2f8 3 n/a ttyS2 (COM3) 3e8 4 n/a ttyS3 (COM4) 2e8 3 n/a lp0 (LPT1) 378 - 37f 7 n/a lp1 (LPT2) 27 8. lp1 (LPT2) 27 8 - 27 f 5 n/a f d0, fd1 (floppies 1 and 2) 3f0 - 3f7 6 2 f d2, fd3 (floppies 3 and 4) 370 - 377 10 3 3.3 .2. 2 Problems recognizing hard drive or controller When Linux boots, you