Linux System Administration phần 6 ppsx

Buy reasonably good quality media. You don't have to buy the best, but definitely buy a tape that is going to stand up to the recurring use. Name−brand tapes are more likely to survive repeated uses than are generic or minor−brand tapes. This applies to CD−Rs as well. For archival CD−R storage, gold/gold media (which appear gold on both sides) and silver/blue (silver on top, blue on bottom) are likely to last longer than are gold/green media. The storage media that work best for you may depend on your tape or CD−R drive; for some drives certain types of tapes last the longest, or certain CD−R brands produce the fewest duds. Pay attention to trends and save your company some money by buying the type the drive likes. • Never pull tapes out while they are active; let the tape finish and rewind. If you've used a nonrewinding device file, let it finish the current process and then rewind the tape with mt. Most tape drives automatically rewind a tape when you insert it in the drive, if it's not already rewound, so removing a nonrewound tape won't save you any time in the long run. Pulling an active tape out of the drive is a good way to damage the tape. • If you get errors when trying to read or write to a tape, try cleaning the drive heads with the appropriate cleaner tape. Often dirty heads cause a tape drive to report write or read errors incorrectly. Don't forget to follow the drive manufacturer's instructions about tape cleaning. • If you get errors when you write a CD−ROM, try a slower write speed or a better quality of media. Also try to reduce the bus load for the appropriate data bus. • Before using a tape drive for real backups, perform a test backup of a lot of static data (such as the contents of the /usr directory tree) and use your tape software's comparison feature (such as tar's −−diff or −−compare commands). If the software reports changes to files that should not have changed, you should track down the source of the problem. One of us once discovered a bizarre incompatibility between a tape drive and an Iomega Zip drive when used on one SCSI host adapter. The problem caused errors when reading data from the tape drive. The incompatibility vanished when both drives were connected to another host adapter. You want to discover such difficulties before you need to use the drive for actual data recovery. • Backing Up the Operating System Preceding sections of this chapter have discussed backup tools and commands, but in practice it's necessary to know what to back up. There are two philosophies concerning backups: minimal and complete. A minimal backup backs up only those files that are unique to your system, such as configuration files and user data. A complete backup backs up the entire computer. Each approach has its pluses and minuses. Minimal Backups The idea behind a minimal backup is that, in the event of a disaster such as a hard disk crash, you can obtain new hardware (if necessary), reinstall Linux from scratch, and restore a small backup from tape, CD−R, or some other medium to recover a working system that's identical or nearly identical to the system you'd been using. Linux is reasonably well−suited to such an approach, because configuration files, user files, and most other system−specific files are confined to specific directories, such as /etc, /home, /usr/local, and /var. Suppose that you want to back up these four directories, leaving the bulk of the Linux system in /usr (aside from /usr/local) "backed up" in the form of the original Linux installation CD−ROM. You might use a command like the following to perform this task using tar and a SCSI tape drive: # tar cvplf /dev/st0 /etc /home /usr/local /var 239 Minimal backups have certain advantages, including speed, a reduced need for tapes, and the capability to recover the system without creating an elaborate disaster recovery plan (you'll reinstall a complete system and then use it to restore your system−specific data). On the down side, you can easily miss something important (including software upgrades installed after the initial system installation), and to work properly, you'll need to take careful notes on what you installed during system installation and afterward, in order to create an initial post−restore configuration that matches your system's state at backup time. On the whole, it's usually better to perform a complete backup, unless you don't have the tape capacity to conveniently back up your entire system. Some systems can benefit from a mixed approach: Use a complete backup on occasion, and minimal backups more frequently. This approach resembles an incremental backup, but is more hit−or−miss. Complete Backups A complete backup backs up everything on the computer, with the possible exception of selected files you know you won't be wanting after a restore—for instance, you might explicitly exclude the /tmp directory's contents. In principle, you can perform a complete backup by backing up the / directory and all its subdirectories, but as described earlier, you want to avoid backing up the /proc filesystem, because it's not a disk−based filesystem at all. This filesystem stores information on the computer's state, so backing it up is a waste of tape at best, and restoring it can cause serious problems, potentially even including a system crash. A complete backup takes more time and tape than a minimal backup, and restoring such a backup after a disaster requires some preparation, as described shortly. On the plus side, once you've recovered such a backup, you won't need to fine−tune your configuration or worry about missed files or program upgrades—if done properly and completely, your recovered system will be a virtual clone of its state before being backed up. Depending upon your software, you may be able to perform a complete backup by backing up / and specifying files or directories to exclude, or by backing up each filesystem independently. For instance, to back up / and exclude /proc using tar, you might issue the following command: # tar cvpf /dev/st0 / −−exclude=proc This particular command omits the leading / from /proc, because tar stores files in its archive in a relative manner by default. If you include the / in /proc, tar will not exclude /proc. The potential for confusion may make it easier to get the correct results by using the −l parameter to tar and specifying each filesystem you want to back up, thus: # tar cvplf /dev/st0 /home / /usr/local /boot This command backs up four filesystems (/home, /, /usr/local, and /boot), but of course you should adjust the filesystems for your computer. You can list the filesystems in any order, but keep in mind that it will be quicker to restore files from the filesystems you list first. This example lists /home first, on the theory that users may accidentally delete files from their home directories and want them restored. Disaster Recovery Techniques Backing up your system regularly and methodically goes a long way toward protecting it, but there are still situations that call for something different. If you forgot to run LILO or can't boot the kernel 240 you just made, you don't need to reinstall, but you do need some sort of disaster recovery. Disaster recovery methods allow you to log onto your system, so that you can fix it or retrieve important files before damaged equipment takes the system down permanently. There are several methods to choose from, depending upon the problem and what you need to do to repair it. Among these are booting in single−user mode, from an emergency boot disk, and in rescue mode. Single−User Mode Single−user mode boots your computer to run level 1. The local filesystems are mounted as usual, and the system's initialization scripts are run, but there is no network access. You are placed in a system maintenance shell where root may use the console but no one else is allowed to log in at all. If your system boots but does not allow you to log in when it has completed booting, try rebooting and entering linux single at the LILO boot prompt: LILO boot: linux single Since this method uses the ailing system's own initialization scripts, any error in these scripts may still be a problem; no daemons run in this mode, however, so problems caused by a daemon's failure to start will likely be fixable in this mode. Single−user mode also uses the system's own kernel, so if the kernel is causing a panic, this won't help either. If a filesystem has problems, single−user mode will attempt to mount it as usual and will probably fail at that point. Single−user mode is great for getting on a system when you've forgotten the root password, allowing you to run LILO when you have forgotten to do so after creating a new kernel image, and to fix some other problems that don't prevent the system from reaching single−user mode. You can take advantage of the fact that no one else can log in to perform functions like installing software, making backups (if the system can stay in single−user mode for a long time without disruption), and doing other standard maintenance functions that benefit from root solitude. Using a Boot Floppy Chapter 2's discussion of installing Linux, as demonstrated on a Red Hat system, noted that creating a boot floppy is a useful installation option. In the early days of Linux, the packaged distributions came with at least one boot and one root floppy. These floppies were required for installation. The boot floppy contained all the files needed for a LILO−initiated bootup of a particular system. The root filesystem was contained on the root floppy. Using this method, you could boot the installed system using the boot floppy and specifying the location of the installed root partition, or you could boot the image on the root floppy. Install Boot Disk There are two flavors of boot disks these days. The first is used to boot into the installation and is typically referred to as an install disk. These days, most CD−ROM distributions provide a bootable CD−ROM, removing the need for a boot disk. Still, if your computer BIOS does not allow booting from a CD−ROM or if your CD−ROM is not functioning, you'll need to create the boot disk by copying the correct boot image to a floppy. If your distribution does not come with a ready−made boot disk, you must create one using one of the boot disk images from your installation CD−ROM. Some bootable CD−ROMs can be used directly in much the same way as an emergency floppy. There are three images that can be used for this disk because different install methods require that different capabilities be built into the kernel. If your distribution came with a premade boot disk, it probably is equivalent to one made from boot.img, since it is the most commonly used boot image. 241 There is also a bootnet.img image to be used for installing from a non−PCMCIA network device. A pcmcia.img image is available for installation via a PCMCIA device like some CD−ROM drives, Ethernet adapters, or hard drives. Since the install disks allow you to boot your system and use a virtual terminal, they can sometimes be used to repair flaws, but some of the same restrictions apply as with single−user mode. The boot disk contains only a kernel image, so all the initialization is performed using the system's own files. There are several ways to create an install floppy. If you have a working Windows system, you may create the disk by using RAWRITE.EXE. This binary is located in the dosutils directory on a Red Hat CD−ROM. To use it, execute the command and tell it which of the images in the images directory you wish to write to floppy and which device to write to. If you are lucky enough to have a Linux or other Unix machine available, you can create the disk using dd with a variation on the following command: # dd if=/mnt/cdrom/images/boot.img of=/dev/fd0 On some systems you'll need to specify the block size. See the man page for the dd command for more details. You may also use the cat command as follows: # cat /mnt/cdrom/images/boot.img >/dev/fd0 You must not use the cp command, because the idea is to transfer the raw image without any formatting, and the cp command requires a formatted disk. Emergency Boot Floppy The second type of boot floppy is a standalone boot image created specifically for your system during an install or by running the command /sbin/mkbootdisk. This disk is typically referred to as an emergency boot floppy. It contains a root filesystem along with customized boot data for the system it was built from rather than the generic data provided with the distribution boot floppy. The standalone boot floppy can be used to boot your system if you cannot or do not wish to run LILO or some other boot manager. It is important to remember that a boot floppy uses files on the existing system when it boots. It needs to find the second−stage boot loader, which is typically /boot/boot.b, the initialization files, and a kernel image on the computer you are booting. If the problem you are trying to fix is in one of these files, you won't be able to boot using a boot floppy. You'll need to use Red Hat's rescue mode. Rescue Mode A Linux distribution's rescue mode boots a small but complete Linux system completely independent of the installed Linux system. From this mode, you can mount the computer's devices, edit configuration files, run a filesystem check, or do a number of other repair functions depending upon the problem. Since both single−user mode and boot disks depend upon files from the installed system itself and certain types of problems cannot be fixed these ways, rescue mode is the only way to fix some problems that you'll encounter. Many distributions' CD−ROMs include the ability to boot into a rescue mode of one sort or another. This section focuses upon Red Hat's rescue mode, but the principles are the same for other distributions. 242 If boot loader has been overwritten by another operating system, you cannot boot from the kernel and initialization files on your hard drive, because there is no way to access them; so you need to use rescue mode. If hardware problems make it impossible to boot using your own initialization scripts, use rescue mode and mount that drive to retrieve whatever you can before it dies. If you've made a mistake in /etc/fstab and incorrectly given the mount point for the / partition, you can use rescue mode to edit the file and reboot. You can even use rescue mode to recover a complete tape backup to a new hard disk after an old one has died. To boot into rescue mode, you need to boot from a Red Hat boot disk or from a floppy containing either the PCMCIA boot image or the bootnet image. When you reach the boot prompt, simply type linux rescue. When the system boots, you will be in rescue mode and will have a Bash # prompt. You will be able to run any of the commands selected as essential by your distribution. For Red Hat 7.3, these are available: Anaconda gzip mkfs.ext2 ps Badblocks head mknod python Bash hwclock mkraid python1.5 cat ifconfig mkswap raidstart chattr init mlabel raidstop Chmod insmod mmd rcp Chroot less mmount rlogin Clock ln mmove rm collage loader modprobe rmmod Cp ls mount route Cpio lsattr mpartition rpm Dd lsmod mrd rsh ddcprobe mattrib mread sed depmode mbadblocks mren sh Df mcd mshowfat sync e2fsck mcopy mt tac Fdisk mdel mtools tail Fsck mdeltree mtype tar fsck.ext2 mdir mv touch fsck.ext3 mdu mzip traceroute ftp mformat open umount gnome−pty−helper minfo pico uncpio Grep mkdir ping uniq Gunzip mke2fs probe zcat If your root filesystem is undamaged, you can mount it and use the chroot command to run commands as if the original root filesystem were your root directory. You can mount all the partitions on this root filesystem and essentially run your own system. Under Red Hat 6.2 and beyond, you are required to create your own devices, so before you can mount /dev/hda1, you'll need to use the mknod command to create /dev/hda, /dev/hda1, and /dev/hda2. # mknod /dev/hda b 3 0 # mknod /dev/hda1 b 3 1 # mknod /dev/hda2 b 3 2 # mkdir /mnt/olddisk 243 # mount /dev/hda1 /mnt/olddisk # mount /dev/hda2 /mnt/olddisk/usr # chroot /mnt/olddisk This example reflects a system that exists as two separate partitions: / and /usr. If you don't know the partitioning scheme of the system you're attempting to fix, you can use fdisk to determine it (after you've created the device file for your hard disk, that is). The fdisk utility will allow you to determine partition types and sizes; this is usually enough information to make a good guess as to the scheme being used. If you are wrong, don't worry; attempting to mount the wrong partition will not harm the system. Third−Party Recovery Software Recently, several third party−vendors have begun marketing recovery packages. In the past, backups were considered by many to be sufficient. Because recovery utilities are common in Windows, users converting from that environment often want to see these tools in Linux. BRU Enhanced Software Technologies (EST) uses the technology behind its BRU backup−and−restore package discussed earlier as the backbone to a line of data recovery products. QuickStart Data Rescue The QuickStart Data Rescue package provides the ability to perform disaster recovery using a single boot disk. Once booted with the QuickStart Data Rescue disk, your system will be able to detect most tape drives. After the tape drive is detected, you will be able to use the graphical interface to reinstall your system with the configuration as it was captured in the original use. Normally, if a system crashes, you need to reinstall the operating system and perform some configuration tasks (to make the system see your tape drive, for instance) before you can even begin to dump the needed elements from tape. With QuickStart Data Rescue, you just boot from the disk and start putting your data back. Undeleting Files It's easy to accidentally delete a file. Part of the purpose of backups is to allow recovery of such files, but if the file hadn't been backed up before its accidental deletion, the backup does no good. Therefore, there are undelete utilities available, and certain window managers use a trash can icon by default, which doesn't immediately delete files, instead storing them in a temporary limbo before deleting them. The rm command does not actually erase the deleted file from the disk but instead removes the file's inode or index pointer, leaving the data in place until that same inode is reused. Because the data still exists, it is often possible to retrieve it. While the ext2 filesystem motivated several undeletion packages/methods, the new ext3 system is much more stable, so the utilities that were being developed, GtkRecover for instance, are no longer being developed. The command−line version of this, Recover, still exists, although not much development activity is presently going on. In Sum Backup is an important topic, and one that covers a lot of territory. Effective backups rely upon an appropriate choice of hardware, selection of a reasonable backup schedule, and use of good backup software. Linux works with most modern backup hardware and provides many choices of 244 backup software. Your backup schedule, of course, is yours to set. Backing up your data is not enough. You must have a good recovery plan in case of disaster. At a minimum, you should be able to boot an emergency recovery disk of some sort in order to restore data from a backup. This same or another recovery disk should allow you to edit your main system's files, in case you accidentally damage some critical file like /etc/fstab. There are also assorted tools available to help you recover data, even without a conventional system backup. All of these tools and techniques play an important role in safeguarding your system's data from accidental loss, or even from sabotage by a cracker. Take a break and obtain your beverage of choice. When you return you'll learn about printers and the spooling subsystem. 245 Part III: Communications and Networking Chapter List Chapter 10: Printers and the Spooling Subsystem Chapter 11: Serial Communications, Terminals, and Modems Chapter 12: TCP/IP Linux Networking Chapter 13: The X Window System Chapter 14: Setting Up Your Mail Server Featuring Understanding serial devices• Configuring terminals and modems• Configuring serial printers• The printing process in Linux and the lpd print spooler• Creating printers in Red Hat• Kernel support for printing• Remote printing• Bash shell scripting• Administrative scripting in other languages• Understanding and configuring TCP/IP networking• File sharing• Internet servers and super servers• Configuring the X Window System• Building a user interface atop X• Setting up a mail server• Protecting against spam• 246 Chapter 10: Printers and the Spooling Subsystem Overview Printers are critical tools for most businesses, and that makes the ability to set up and administer printing a very important system administration task. You will find that many of the emergency calls you receive are from users who cannot print a document they need for an upcoming meeting. Even when something small goes wrong with a printer, it seems like a crisis to anyone who needs that printer at that specific time. A successful system administrator must understand the printing process and be able to successfully troubleshoot basic printing problems. Printing under Linux works somewhat differently than does printing under most non−Unix operating systems. If all works well, these differences are transparent to your users, but you must understand many of Linux's printing details and peculiarities in order to set up and troubleshoot a Linux printing queue. You must also understand how these queues interact with clients if the computer functions as a print server for other computers. This chapter outlines the types of printers commonly used today, the tools Linux provides for controlling printer operation, and basic installation and configuration. Printer Basics Printers are classified both by the way they print and the way they connect to the computer. There are three main types of printers and four types of printer interfaces you may encounter. Familiarity with these printer basics makes you a more capable system administrator and helps your users to trust that you know what you're doing. A brief introduction to types of printers and the ways they interface with the computer will be helpful. If you already know these basics, you can skip ahead to "The Printing Process in Linux." Types of Printers Printers differ radically in the way they create images on paper. Impact printers mechanically strike characters against inked ribbons to transfer an image to paper. These have limited and specialized uses in today's business world; more common are nonimpact printers, which transfer images by other means. Impact printers include line printers, daisy−wheel printers, and dot−matrix printers. Nonimpact printers include laser printers and ink−jet printers. Some of the earliest common printers for mainframe computers were line printers—big, fast, and noisy. Daisy−wheel printers were introduced in 1970, offering the same print quality as typewriters. Soon after, the dot−matrix printer effectively replaced the daisy−wheel. Laser printers hit the scene in 1975 but the cost was prohibitive, so most businesses continued to use dot−matrix printers. In 1976 when the first ink−jet came out, it too was cost−prohibitive. In 1988, Hewlett−Packard released the DeskJet ink−jet printer, which was priced at $1,000. Although many users kept their dot−matrix printers instead of paying for the better capability, this series of printers opened the door to widespread use of ink−jets by home users. Laser printers were still far too expensive and didn't do color like the ink−jets. In 1992, Hewlett−Packard introduced the LaserJet 4, which supported resolutions up to 600×600. Color laser printers were introduced in 1994. The market now is pretty much shared between ink−jet and laser printers. There are, however, a few printer types that are important in niche markets, such as dye sublimation and thermal wax transfer printers, which are popular in graphic arts departments. 247 Dot−Matrix Printers Dot−matrix impact printers have a number of pins (usually between 9 and 24) arranged in a vertical line. The printer shoots some of them into an inked printer ribbon, leaving a number of dots on the paper, which produces a fuzzy, low−quality representation of the intended letter. The fuzziness is due to the mechanical nature of the pins; they simply cannot be made small enough to hide the fact that the letters are made up of dots. To its advantage, however, this type of printer first introduced the possibility of printing graphics since it was not restricted to letters like the daisy−wheel printers that preceded dot−matrix models in the marketplace. Today, dot−matrix printers are rare because they're slow, noisy, and produce lower−quality print than competing ink−jet and laser printers. Nonetheless, they cling to life in certain applications. The primary advantage of these printers is that, because they rely upon impact technology, they can print multipart forms. You'll therefore see dot−matrix printers in use in some retail establishments for printing receipts and invoices. Linux support for dot−matrix printers is quite good. A handful of printer languages, led by Epson's ESC/P, have long dominated the dot−matrix market, and Linux's Ghostscript utility supports these common dot−matrix printer languages. Therefore, if you find yourself needing to support a dot−matrix printer, chances are you can get it working from Linux. Ink−Jet Printers Whereas dot−matrix printers rely on impact through an inked ribbon to create images on the paper, ink−jet printers shoot small drops of ink through nozzles onto the page. Like the pins of a dot−matrix print head, ink−jet nozzles can be arranged to form characters or other images but create smaller dots that are less easily discerned as such. The printing mechanism moves horizontally as the paper is slowly drawn through the printer. Early models produced dots large enough that the print quality was on a par with that of dot−matrix printers, but the technology quickly improved to the point where the images rival laser printers in image quality. Generally cheaper to buy than laser printers, ink−jet printers are more expensive to maintain. The system contains 1–6 ink cartridges, which have to be replaced or refilled when empty. (Each cartridge produces 1–6 colors; all modern ink−jets are color printers, although the earliest models printed only black.) These cartridges can be quite expensive and may print only a few pages before requiring replacement, leading to high per−page costs. Ink−jet printers work best with specially coated paper that prevents the ink from spreading as it dries. Care should be taken when removing a printed sheet from an ink−jet printer, since the ink will smear unless it is allowed sufficient time to dry. Regular printer paper may be used, but the image is often slightly blurred by the way the drops of ink soak into it. NoteYou can buy ink refill kits for most popular ink−jet printer models. These kits can greatly reduce the cost of printing, but refilling can be a messy process and doesn't always work correctly. Printer manufacturers discourage this process, and they may refuse warranty service if they discover you've been refilling, although refill manufacturers claim any such action is illegal. To the best of our knowledge, this claim has never been tested in court. Laser Printers Laser printers offer the best print quality. Introduced commercially by Hewlett−Packard in 1984, they have come to dominate the office market as their price has fallen compared to other printer types. A laser printer transfers a full−page image to paper electrostatically, much like a photocopier. But 248 [...]... the Samba server from other Linux servers and workstations or use a separate 267 printing−only account on the Linux server for printing (users would have to enter this password, not their normal Linux login password, to print from Windows) Printing from Linux to a Windows Printer To print from Linux workstations on a network to a printer attached to a Windows machine, each Linux machine needs a printcap... internal network interface card (NIC) In the first case, the host machine might be a Linux or Unix box or a machine running some version of Microsoft Windows In the second case, the printer runs its own server software that's functionally identical to a Linux/ Unix or Windows print server Linux to Linux In the case of Linux to Linux printing, you'll need to configure printing on both the server (the machine... active Status: printing 'user@speaker+179', file 1 'yacl−egcs.txt', size 4172, format 'l' at 18: 06: 54 Rank Owner/ID Class Job Files Size Time active user@speaker+179 A 179 yacl−egcs.txt 4172 18: 06: 54 2 user@speaker+182 A 182 tweener.txt 4879 18:07:05 3 user@speaker+1 86 A 1 86 kms94.ps 125700 18:07: 16 2 56 Note The output format of LPRng, as shown above, differs from the format of the original lpd's lpq... Because Linux has inherited so many Unix programs, Linux has also inherited the PostScript−centric nature of its printer system Unfortunately, PostScript printers have traditionally been more expensive than otherwise similar non−PostScript printers, and many Linux developers have been unable to afford PostScript printers In order to create more than primitive monospaced text−only output, therefore, Linux. .. http://www.cups.org/ If you want to experiment with an alternative printing system, do so on a test system, at least initially Some packages may not get along well with these new systems, because their lpd compatibility is not perfect Once you've determined that your major applications work with the new system, you can consider installing it on your main systems, possibly including any print servers you maintain Alternative... from one model to another; Linux provides an assortment of printing utilities; and network printing presents an assortment of additional options and challenges Understanding each of these areas and their interactions can help you create a workable Linux printing system There's no point in buying an unsupported printer for use in Linux, for instance Fortunately, each piece of the Linux printing puzzle,... devices are well−supported in Linux USB support varies from one device to another, because Linux requires kernel drivers for particular device types As a general rule, common USB devices, such as mice, keyboards, and printers, are well−supported, but you should check your kernel configuration options, or the Linux USB Web site (http://www .linux usb.org/), for details Linux support for USB 2.0 is still... parameter (An incorrect port type is likely to produce unreliable serial port operation.) Most modern motherboards use 165 50A UARTs, so uarttype would be 165 50A for these boards Very old hardware may use earlier UARTs, such as the 164 50; and some devices use more recent ones, like the 166 50 baud_base speed This parameter sets the speed of the serial port The usual value for speed is 115200, which is the... companion volume in the Craig Hunt Linux Library, Roderick W Smith's Linux Samba Server Administration (Sybex, 2001) There's a brief introduction to Samba in Chapter 12 of this book Briefly, Samba is an open source software suite that provides SMB/CIFS file and print services to clients that might be running any version of Windows, OS/2, or a number of other OSes Samba runs on Linux, other versions of Unix,... in this chapter, the next two sections show how to use con3 Samba to print from a Windows machine to a printer attached to a Linux box and from a Linux machine to a printer attached to a Windows machine Printing from Windows to a Linux Printer Assuming that you have configured a Linux computer to print to a local printer, you have only to set up a Samba share to allow the Windows computers on the LAN . Hat's rescue mode. Rescue Mode A Linux distribution's rescue mode boots a small but complete Linux system completely independent of the installed Linux system. From this mode, you can mount. at 18: 06: 54 Rank Owner/ID Class Job Files Size Time active user@speaker+179 A 179 yacl−egcs.txt 4172 18: 06: 54 2 user@speaker+182 A 182 tweener.txt 4879 18:07:05 3 user@speaker+1 86 A 1 86 kms94.ps. the capability to recover the system without creating an elaborate disaster recovery plan (you'll reinstall a complete system and then use it to restore your system specific data). On the