Real-Time Operating System (RTOS) has become the main category of embedded systems. It is widely used to support tasks requiring real-time response such as printers and switches. The security of RTOS has been long overlooked as it was running in special environments isolated from attackers. However, with the rapid development of IoT devices, tremendous RTOS devices are connected to the public network. Due to the lack of security mechanisms, these devices are extremely vulnerable to a wide spectrum of attacks. Even worse, the monolithic design of RTOS combines various tasks and services into a single binary, which hinders the current program testing and analysis techniques working on RTOS. In this paper, we propose SFuzz, a novel slice-based fuzzer, to detect security vulnerabilities in RTOS. Our insight is that RTOS usually divides a complicated binary into many separated but single-minded tasks. Each task accomplishes a particular event in a deterministic way and its control flow is usually straightforward and independent. Therefore, we identify such code from the monolithic RTOS binary and synthesize a slice for effective testing. Specifically, SFuzz first identifies functions that handle user input, constructs call graphs that start from callers of these functions, and leverages forward slicing to build the execution tree based on the call graphs and pruning the paths independent of external inputs. Then, it detects and handles roadblocks within the coarse-grain scope that hinder effective fuzzing, such as instructions unrelated to the user input. And then, it conducts coverage-guided fuzzing on these code snippets. Finally, SFuzz leverages forward and backward slicing to track and verify each path constraint and determine whether a bug discovered in the fuzzer is a real vulnerability. SFuzz successfully discovered 77 zero-day bugs on 35 RTOS samples, and 67 of them have been assigned CVE or CNVD IDs. Our empirical evaluation shows that SFuzz outperforms the state-of-the-art tools (e.g., UnicornAFL) on testing RTOS.
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Modern IoT device manufacturers are taking advantage of the managed Platform-as-a-Service (PaaS) and Infrastructure-as-a-Service (IaaS) IoT clouds (e.g., AWS IoT, Azure IoT) for secure and convenient IoT development/deployment. The IoT access control is achieved by manufacturer-specified, cloud-enforced IoT access policies (cloud-standard JSON documents, called IoT Policies) stating which users can access which IoT devices/resources under what constraints. In this paper, we performed a systematic study on the security of cloud-based IoT access policies on modern PaaS/IaaS IoT clouds. Our research shows that the complexity in the IoT semantics and enforcement logic of the policies leaves tremendous space for device manufacturers to program a flawed IoT access policy, introducing convoluted logic flaws which are non-trivial to reason about. In addition to challenges/mistakes in the design space, it is astonishing to find that mainstream device manufacturers also generally make critical mistakes in deploying IoT Policies thanks to the flexibility offered by PaaS/IaaS clouds and the lack of standard practices for doing so. Our assessment of 36 device manufacturers and 310 open-source IoT projects highlights the pervasiveness and seriousness of the problems, which once exploited, can have serious impacts on IoT users' security, safety, and privacy. To help manufacturers identify and easily fix IoT Policy flaws, we introduce P-Verifier, a formal verification tool that can automatically verify cloud-based IoT Policies. With evaluated high effectiveness and low performance overhead, P-Verifier will contribute to elevating security assurance in modern IoT deployments and access control. We responsibly reported all findings to affected vendors and fixes were deployed or on the way.
To enable the preset menu feature, you must specify a file to theconfigure script with the option --enable-preset-menu. The filehas the same semantics as normal configuration files(see Configuration).Another point you should take care is that the diskless support(see Diskless) diverts the preset menu. Diskless images embed apreset menu to execute the command bootp (see bootp)automatically, unless you specify your own preset menu to the configurescript. This means that you must put commands to initialize a network inthe preset menu yourself, because diskless images don't set it upimplicitly, when you use the preset menu explicitly.Therefore, a typical preset menu used with diskless support would belike this:# Set up the serial terminal, first of all.serial --unit=0 --speed=19200terminal --timeout=0 serial# Initialize the network.dhcpNode:Security,Next:Images,Previous:Preset Menu,Up:TopProtecting your computer from crackingYou may be interested in how to prevent ordinary users from doingwhatever they like, if you share your computer with other people. Sothis chapter describes how to improve the security of GRUB.One thing which could be a security hole is that the user can do toomany things with GRUB, because GRUB allows to modify its configurationand run arbitrary commands at run-time. For example, the user can readeven /etc/passwd in the command-line interface by the commandcat (see cat). So it is necessary to disable all theinteractive operations.Thus, GRUB provides password feature, so that only administratorscan start the interactive operations (i.e. editing menu entries andentering the command-line interface). To use this feature, you need torun the command password in your configuration file(see password), like this:password --md5 PASSWORDIf this is specified, GRUB disallows any interactive control, until youpress the key and enter a correct password. The option--md5 tells GRUB that PASSWORD is in MD5 format. If itis omitted, GRUB assumes the PASSWORD is in clear text.You can encrypt your password with the command md5crypt(see md5crypt). For example, run the grub shell (see Invoking the grub shell), and enter your password:grub> md5cryptPassword: **********Encrypted: $1$U$JK7xFegdxWH6VuppCUSIb.Then, cut and paste the encrypted password to your configuration file.Also, you can specify an optional argument to password. Seethis example:password PASSWORD /boot/grub/menu-admin.lstIn this case, GRUB will load /boot/grub/menu-admin.lst as aconfiguration file when you enter the valid password.Another thing which may be dangerous is that any user can choose anymenu entry. Usually, this wouldn't be problematic, but you might want topermit only administrators to run some of your menu entries, such as anentry for booting an insecure OS like DOS.GRUB provides the command lock (see lock). This commandalways fails until you enter a valid password, so you can use it, likethis:title Boot DOSlockrootnoverify (hd0,1)makeactivechainload +1You should insert lock right after title, becauseany user can execute commands in an entry, until GRUB encounterslock.You can also use the command password instead oflock. In this case the boot process will ask for the passwordand stop if it was entered incorrectly. Since the passwordtakes its own PASSWORD argument this is useful if you wantdifferent passwords for different entries.Node:Images,Next:Filesystem,Previous:Security,Up:TopGRUB image filesGRUB consists of several images: two essential stages, optional stagescalled Stage 1.5, and two network boot images. Here is a shortoverview of them. See Internals, for more details.stage1This is an essential image used for booting up GRUB. Usually, this isembedded in a MBR or the boot sector of a partition. Because a PC bootsector is 512 bytes, the size of this image is exactly 512 bytes.All stage1 must do is to load Stage 2 or Stage 1.5 from a localdisk. Because of the size restriction, stage1 encodes thelocation of Stage 2 (or Stage 1.5) in a block list format, so it neverunderstand any filesystem structure.stage2This is the core image of GRUB. This does all things but booting upitself. Usually, this is put in a filesystem, but that is not required.e2fs_stage1_5fat_stage1_5ffs_stage1_5jfs_stage1_5minix_stage1_5reiserfs_stage1_5vstafs_stage1_5xfs_stage1_5These are called Stage 1.5, because the purpose is a bridgebetween stage1 and stage2, that is to say, Stage 1.5 isloaded by Stage 1 and Stage 1.5 loads Stage 2. The difference betweenstage1 and *_stage1_5 is that the former doesn'tunderstand any filesystem but the latter does an filesystem(e.g. e2fs_stage1_5 understands ext2fs). So you can move thelocation of Stage 2 to another safely, even after GRUB has beeninstalled.While Stage 2 cannot generally be embedded in a fixed area as the sizeis so large, Stage 1.5 can be installed into the area right after a MBR,or the boot loader area of a ReiserFS or a FFS.nbgrubThis is a network boot image for the Network Image Proposal used by somenetwork boot loaders, such as Etherboot. This is mostly the same asStage 2, but this also sets up a network and loads a configuration filefrom the network.pxegrubThis is another network boot image for the Preboot Execution Environmentused by several Netboot ROMs. This is identical to nbgrub, exceptfor the format. Node:Filesystem,Next:Interface,Previous:Images,Up:TopFilesystem syntax and semanticsGRUB uses a special syntax for specifying disk drives which can beaccessed by BIOS. Because of BIOS limitations, GRUB cannot distinguishbetween IDE, ESDI, SCSI, or others. You must know yourself which BIOSdevice is equivalent to which OS device. Normally, that will be clear ifyou see the files in a device or use the command find(see find).Device syntax: How to specify devicesFile name syntax: How to specify filesBlock list syntax: How to specify block listsNode:Device syntax,Next:File name syntax,Up:FilesystemHow to specify devicesThe device syntax is like this:(device[,part-num][,bsd-subpart-letter])[] means the parameter is optional. device should beeither fd or hd followed by a digit, like fd0. But you can also set device to a hexadecimal or a decimal, whichis a BIOS drive number, so the following are equivalent:(hd0)(0x80)(128)part-num represents the partition number of device, startingfrom zero for primary partitions and from four for extended partitions,and bsd-subpart-letter represents the BSD disklabel subpartition,such as a or e.A shortcut for specifying BSD subpartitions is(device,bsd-subpart-letter), in this case, GRUBsearches for the first PC partition containing a BSD disklabel, thenfinds the subpartition bsd-subpart-letter. Here is an example:(hd0,a)The syntax like (hd0) represents using the entire disk (or theMBR when installing GRUB), while the syntax like (hd0,0)represents using the partition of the disk (or the boot sector of thepartition when installing GRUB).If you enabled the network support, the special drive, (nd), isalso available. Before using the network drive, you must initialize thenetwork. See Network, for more information.Node:File name syntax,Next:Block list syntax,Previous:Device syntax,Up:FilesystemHow to specify filesThere are two ways to specify files, by absolute file name and byblock list.An absolute file name resembles a Unix absolute file name, using/ for the directory separator (not \ as in DOS). Oneexample is (hd0,0)/boot/grub/menu.lst. This means the file/boot/grub/menu.lst in the first partition of the first harddisk. If you omit the device name in an absolute file name, GRUB usesGRUB's root device implicitly. So if you set the root device to,say, (hd1,0) by the command root (see root), then/boot/kernel is the same as (hd1,0)/boot/kernel.Node:Block list syntax,Previous:File name syntax,Up:FilesystemHow to specify block listsA block list is used for specifying a file that doesn't appear in thefilesystem, like a chainloader. The syntax is[offset]+length[,[offset]+length].... Here is an example:0+100,200+1,300+300This represents that GRUB should read blocks 0 through 99, block 200,and blocks 300 through 599. If you omit an offset, then GRUB assumesthe offset is zero.Like the file name syntax (see File name syntax), if a blocklistdoes not contain a device name, then GRUB uses GRUB's rootdevice. So (hd0,1)+1 is the same as +1 when the rootdevice is (hd0,1).Node:Interface,Next:Commands,Previous:Filesystem,Up:TopGRUB's user interfaceGRUB has both a simple menu interface for choosing preset entries from aconfiguration file, and a highly flexible command-line for performingany desired combination of boot commands.GRUB looks for its configuration file as soon as it is loaded. If oneis found, then the full menu interface is activated using whateverentries were found in the file. If you choose the command-line menuoption, or if the configuration file was not found, then GRUB drops tothe command-line interface.Command-line interface: The flexible command-line interfaceMenu interface: The simple menu interfaceMenu entry editor: Editing a menu entryHidden menu interface: The hidden menu interfaceNode:Command-line interface,Next:Menu interface,Up:InterfaceThe flexible command-line interfaceThe command-line interface provides a prompt and after it an editabletext area much like a command-line in Unix or DOS. Each command isimmediately executed after it is entered7. The commands (see Command-line and menu entry commands) are asubset of those available in the configuration file, used with exactlythe same syntax.Cursor movement and editing of the text on the line can be done via asubset of the functions available in the Bash shell:Move forward one character.Move back one character.Move to the start of the line.Move the the end of the line.Delete the character underneath the cursor.Delete the character to the left of the cursor.Kill the text from the current cursor position to the end of the line.Kill backward from the cursor to the beginning of the line.Yank the killed text back into the buffer at the cursor.Move up through the history list.Move down through the history list. When typing commands interactively, if the cursor is within or beforethe first word in the command-line, pressing the key (or) will display a listing of the available commands, and if thecursor is after the first word, the will provide acompletion listing of disks, partitions, and file names depending on thecontext.Note that you cannot use the completion functionality in the TFTPfilesystem. This is because TFTP doesn't support file name listing forthe security.Node:Menu interface,Next:Menu entry editor,Previous:Command-line interface,Up:InterfaceThe simple menu interfaceThe menu interface is quite easy to use. Its commands are bothreasonably intuitive and described on screen.Basically, the menu interface provides a list of boot entries tothe user to choose from. Use the arrow keys to select the entry ofchoice, then press to run it. An optional timeout isavailable to boot the default entry (the first one if not set), which isaborted by pressing any key.Commands are available to enter a bare command-line by pressing (which operates exactly like the non-config-file version of GRUB, butallows one to return to the menu if desired by pressing ) or toedit any of the boot entries by pressing .If you protect the menu interface with a password (see Security),all you can do is choose an entry by pressing , or press to enter the password.Node:Menu entry editor,Next:Hidden menu interface,Previous:Menu interface,Up:InterfaceEditing a menu entryThe menu entry editor looks much like the main menu interface, but thelines in the menu are individual commands in the selected entry insteadof entry names.If an is pressed in the editor, it aborts all the changes madeto the configuration entry and returns to the main menu interface.When a particular line is selected, the editor places the user at aspecial version of the GRUB command-line to edit that line. When theuser hits , GRUB replaces the line in question in the bootentry with the changes (unless it was aborted via ,in which case the changes are thrown away).If you want to add a new line to the menu entry, press if addinga line after the current line or press if before the currentline.To delete a line, hit the key . Although GRUB does not supportundo unfortunately, you can do almost the same thing by justreturning to the main menu.Node:Hidden menu interface,Previous:Menu entry editor,Up:InterfaceThe hidden menu interfaceWhen your terminal is dumb or you request GRUB of hiding the menuinterface explicitly with the command hiddenmenu(see hiddenmenu), GRUB doesn't show the menu interface (see Menu interface) and automatically boots the default entry, unlessinterrupted by pressing .When you interrupt the timeout and your terminal is dumb, GRUB fallsback to the command-line interface (see Command-line interface).Node:Commands,Next:Troubleshooting,Previous:Interface,Up:TopThe list of available commandsIn this chapter, we list all commands that are available in GRUB.Commands belong to different groups. A few can only be used inthe global section of the configuration file (or "menu"); mostof them can be entered on the command-line and can be either usedin the menu or in the menu entries.Menu-specific commands: General commands: Command-line and menu entry commands: Node:Menu-specific commands,Next:General commands,Up:CommandsThe list of commands for the menu onlyThe semantics used in parsing the configuration file are the following:The menu-specific commands have to be used before any others.The files must be in plain-text format.# at the beginning of a line in a configuration file means it isonly a comment.Options are separated by spaces.All numbers can be either decimal or hexadecimal. A hexadecimal numbermust be preceded by 0x, and is case-insensitive.Extra options or text at the end of the line is ignored unless otherwisespecified.Unrecognized commands are added to the current entry, except before entriesstart, where they are ignored. These commands can only be used in the menu:default: Set the default entryfallback: Set the fallback entryhiddenmenu: Hide the menu interfacetimeout: Set the timeouttitle: Start a menu entryNode:default,Next:fallback,Up:Menu-specific commandsdefaultdefault numCommandSet the default entry to the entry number num. Numbering startsfrom 0, and the entry number 0 is the default if the command is notused.You can specify saved instead of a number. In this case, thedefault entry is the entry saved with the commandsavedefault. See savedefault, for more information. Node:fallback,Next:hiddenmenu,Previous:default,Up:Menu-specific commandsfallbackfallback numCommandGo into unattended boot mode: if the default boot entry has any errors,instead of waiting for the user to do anything, immediately startover using the num entry (same numbering as the defaultcommand (see default)). This obviously won't help if the machine wasrebooted by a kernel that GRUB loaded. Node:hiddenmenu,Next:timeout,Previous:fallback,Up:Menu-specific commandshiddenmenuhiddenmenuCommandDon't display the menu. If the command is used, no menu will bedisplayed on the control terminal, and the default entry will bebooted after the timeout expired. The user can still request themenu to be displayed by pressing before the timeoutexpires. See also Hidden menu interface. Node:timeout,Next:title,Previous:hiddenmenu,Up:Menu-specific commandstimeouttimeout secCommandSet a timeout, in sec seconds, before automatically booting thedefault entry (normally the first entry defined). Node:title,Previous:timeout,Up:Menu-specific commandstitletitle name ...CommandStart a new boot entry, and set its name to the contents of the rest ofthe line, starting with the first non-space character. Node:General commands,Next:Command-line and menu entry commands,Previous:Menu-specific commands,Up:CommandsThe list of general commandsCommands usable both in the menu and in the command-line.bootp: Initialize a network device via BOOTPcolor: Color the menu interfacedevice: Specify a file as a drivedhcp: Initialize a network device via DHCPhide: Hide a partitionifconfig: Configure a network device manuallypager: Change the state of the internal pagerpartnew: Make a primary partitionparttype: Change the type of a partitionpassword: Set a password for the menu interfacerarp: Initialize a network device via RARPserial: Set up a serial devicesetkey: Configure the key mapterminal: Choose a terminaltftpserver: Specify a TFTP serverunhide: Unhide a partitionNode:bootp,Next:color,Up:General commandsbootpbootp [--with-configfile]CommandInitialize a network device via the BOOTP protocol. This commandis only available if GRUB is compiled with netboot support. See alsoNetwork.If you specify --with-configfile to this command, GRUB willfetch and load a configuration file specified by your BOOTP serverwith the vendor tag 150. Node:color,Next:device,Previous:bootp,Up:General commandscolorcolor normal [highlight]CommandChange the menu colors. The color normal is used for mostlines in the menu (see Menu interface), and the colorhighlight is used to highlight the line where the cursorpoints. If you omit highlight, then the inverted color ofnormal is used for the highlighted line. The format of a color isforeground/background. foreground andbackground are symbolic color names. A symbolic color name must beone of these:blackbluegreencyanredmagentabrownlight-grayThese below can be specified only for the foreground.dark-graylight-bluelight-greenlight-cyanlight-redlight-magentayellowwhiteBut only the first eight names can be used for background. You canprefix blink- to foreground if you want a blinkingforeground color.This command can be used in the configuration file and on the commandline, so you may write something like this in your configuration file:# Set default colors.color light-gray/blue black/light-gray# Change the colors.title OS-BS likecolor magenta/blue black/magentaNode:device,Next:dhcp,Previous:color,Up:General commandsdevicedevice drive fileCommandIn the grub shell, specify the file file as the actual drive for aBIOS drive drive. You can use this command to create a diskimage, and/or to fix the drives guessed by GRUB when GRUB fails todetermine them correctly, like this:grub> device (fd0) /floppy-imagegrub> device (hd0) /dev/sd0This command can be used only in the grub shell (see Invoking the grub shell). Node:dhcp,Next:hide,Previous:device,Up:General commandsdhcpdhcp [--with-configfile]CommandInitialize a network device via the DHCP protocol. Currently,this command is just an alias for bootp, since the twoprotocols are very similar. This command is only available if GRUB iscompiled with netboot support. See also Network.If you specify --with-configfile to this command, GRUB willfetch and load a configuration file specified by your DHCP serverwith the vendor tag 150. Node:hide,Next:ifconfig,Previous:dhcp,Up:General commandshidehide partitionCommandHide the partition partition by setting the hidden bit inits partition type code. This is useful only when booting DOS or Windowsand multiple primary FAT partitions exist in one disk. See alsoDOS/Windows. Node:ifconfig,Next:pager,Previous:hide,Up:General commandsifconfigifconfig [--server=server] [--gateway=gateway] [--mask=mask] [--address=address]CommandConfigure the IP address, the netmask, the gateway, and the serveraddress of a network device manually. The values must be in dotteddecimal format, like 192.168.11.178. The order of the options isnot important. This command shows current network configuration, if nooption is specified. See also Network. Node:pager,Next:partnew,Previous:ifconfig,Up:General commandspagerpager [flag]CommandToggle or set the state of the internal pager. If flag ison, the internal pager is enabled. If flag is off,it is disabled. If no argument is given, the state is toggled. Node:partnew,Next:parttype,Previous:pager,Up:General commandspartnewpartnew part type from toCommandCreate a new primary partition. part is a partition specificationin GRUB syntax (see Naming convention); type is the partitiontype and must be a number in the range 0-0xff; from andto are the starting and ending sectors, expressed as an absolutesector number. Node:parttype,Next:password,Previous:partnew,Up:General commandsparttypeparttype part typeCommandChange the type of an existing partition. part is a partitionspecification in GRUB syntax (see Naming convention); typeis the new partition type and must be a number in the range 0-0xff. Node:password,Next:rarp,Previous:parttype,Up:General commandspasswordpassword [--md5] passwd [new-config-file]CommandIf used in the first section of a menu file, disable all interactiveediting control (menu entry editor and command-line) and entriesprotected by the command lock. If the password passwd isentered, it loads the new-config-file as a new config file andrestarts the GRUB Stage 2, if new-config-file isspecified. Otherwise, GRUB will just unlock the privileged instructions. You can also use this command in the script section, in which case itwill ask for the password, before continueing. The option--md5 tells GRUB that passwd is encrypted withmd5crypt (see md5crypt). Node:rarp,Next:serial,Previous:password,Up:General commandsrarprarpCommandInitialize a network device via the RARP protocol. This commandis only available if GRUB is compiled with netboot support. See alsoNetwork. Node:serial,Next:setkey,Previous:rarp,Up:General commandsserialserial [--unit=unit] [--port=port] [--speed=speed] [--word=word] [--parity=parity] [--stop=stop] [--device=dev]CommandInitialize a serial device. unit is a number in the range 0-3specifying which serial port to use; default is 0, that correspondsthe port often called COM1. port is the I/O port where the UARTis to be found; if specified it takes precedence over unit. speed is the transmission speed; default is 9600. word andstop are the number of data bits and stop bits. Data bits mustbe in the range 5-8 and stop bits are 1 or 2. Default is 8 data bitsand one stop bit. parity is one of no, odd,even and defaults to no. The option --devicecan only be used in the grub shell and is used to specify thetty device to be used in the host operating system (see Invoking the grub shell).The serial port is not used as a communication channel unless theterminal command is used (see terminal).This command is only available if GRUB is compiled with serialsupport. See also Serial terminal. Node:setkey,Next:terminal,Previous:serial,Up:General commandssetkeysetkey [to_key from_key]CommandChange the keyboard map. The key from_key is mapped to the keyto_key. If no argument is specified, reset key mappings. Note thatthis command does not exchange the keys. If you want to exchangethe keys, run this command again with the arguments exchanged, like this:grub> setkey capslock controlgrub> setkey control capslockA key must be an alphabet, a digit, or one of these symbols:escape, exclam, at, numbersign,dollar, percent, caret, ampersand,asterisk, parenleft, parenright, minus,underscore, equal, plus, backspace,tab, bracketleft, braceleft, bracketright,braceright, enter, control, semicolon,colon, quote, doublequote, backquote,tilde, shift, backslash, bar, comma,less, period, greater, slash,question, alt, space, capslock, FX(X is a digit), and delete. This table describes to whichcharacter each of the symbols corresponds:exclam!at@numbersign#dollar$percent%caret^ampersand&asterisk*parenleft(parenright)minus-underscore_equal=plus+bracketleft[braceleftbracketright]bracerightsemicolon;colon:quote'doublequote"backquote`tildebackslash\barcomma,lessslash/question?space Node:terminal,Next:tftpserver,Previous:setkey,Up:General commandsterminalterminal [--dumb] [--timeout=secs] [--lines=lines] [--silent] [console] [serial] [hercules]CommandSelect a terminal for user interaction. The terminal is assumed to beVT100-compatible unless --dumb is specified. If bothconsole and serial are specified, then GRUB will usethe one where a key is entered first or the first when the timeoutexpires. If neither are specified, the current setting isreported. This command is only available if GRUB is compiled with serialsupport. See also Serial terminal.This may not make sense for most users, but GRUB supports Herculesconsole as well. Hercules console is usable like the ordinary console,and the usage is quite similar to that for serial terminals: specifyhercules as the argument.The option --lines defines the number of lines in yourterminal, and it is used for the internal pager function. If you don'tspecify this option, the number is assumed as 24.The option --silent suppresses the message to prompt you tohit any key. This might be useful if your system has no terminal device. Node:tftpserver,Next:unhide,Previous:terminal,Up:General commandstftpservertftpserver ipaddrCommandCaution: This command exists only for backwardcompatibility. Use ifconfig (see ifconfig) instead.Override a TFTP server address returned by a BOOTP/DHCP/RARP server. Theargument ipaddr must be in dotted decimal format, like192.168.0.15. This command is only available if GRUB is compiledwith netboot support. See also Network. Node:unhide,Previous:tftpserver,Up:General commandsunhideunhide partitionCommandUnhide the partition partition by clearing the hidden bit inits partition type code. This is useful only when booting DOS or Windowsand multiple primary partitions exist in one disk. See alsoDOS/Windows. Node:Command-line and menu entry commands,Previous:General commands,Up:CommandsThe list of command-line and menu entry commandsThese commands are usable in the command-line and in menu entries. Ifyou forget a command, you can run the command help(see help).blocklist: Get the block list notation of a fileboot: Start up your operating systemcat: Show the contents of a filechainloader: Chain-load another boot loadercmp: Compare two filesconfigfile: Load a configuration filedebug: Toggle the debug flagdisplayapm: Display APM informationdisplaymem: Display memory configurationembed: Embed Stage 1.5find: Find a filefstest: Test a filesystemgeometry: Manipulate the geometry of a drivehalt: Shut down your computerhelp: Show help messagesimpsprobe: Probe SMPinitrd: Load an initrdinstall: Install GRUBioprobe: Probe I/O ports used for a drivekernel: Load a kernellock: Lock a menu entrymakeactive: Make a partition activemap: Map a drive to anothermd5crypt: Encrypt a password in MD5 formatmodule: Load a modulemodulenounzip: Load a module without decompressionpause: Wait for a key pressquit: Exit from the grub shellreboot: Reboot your computerread: Read data from memoryroot: Set GRUB's root devicerootnoverify: Set GRUB's root device without mountingsavedefault: Save current entry as the default entrysetup: Set up GRUB's installation automaticallytestload: Load a file for testing a filesystemtestvbe: Test VESA BIOS EXTENSIONuppermem: Set the upper memory sizevbeprobe: Probe VESA BIOS EXTENSIONNode:blocklist,Next:boot,Up:Command-line and menu entry commandsblocklistblocklist fileCommandPrint the block list notation of the file file. See Block list syntax. Node:boot,Next:cat,Previous:blocklist,Up:Command-line and menu entry commandsbootbootCommandBoot the OS/chain-loader which has been loaded. Only necessary ifrunning the fully interactive command-line (it is implicit at the end ofa menu entry). Node:cat,Next:chainloader,Previous:boot,Up:Command-line and menu entry commandscatcat fileCommandDisplay the contents of the file file. This command may be usefulto remind you of your OS's root partition:grub> cat /etc/fstabNode:chainloader,Next:cmp,Previous:cat,Up:Command-line and menu entry commandschainloaderchainloader [--force] fileCommandLoad file as a chain-loader. Like any other file loaded by thefilesystem code, it can use the blocklist notation to grab the firstsector of the current partition with +1. If you specify theoption --force, then load file forcibly, whether it has acorrect signature or not. This is required when you want to load adefective boot loader, such as SCO UnixWare 7.1 (see SCO UnixWare). Node:cmp,Next:configfile,Previous:chainloader,Up:Command-line and menu entry commandscmpcmp file1 file2CommandCompare the file file1 with the file file2. If they differin size, print the sizes like this:Differ in size: 0x1234 [foo], 0x4321 [bar]If the sizes are equal but the bytes at an offset differ, then print thebytes like this:Differ at the offset 777: 0xbe [foo], 0xef [bar]If they are completely identical, nothing will be printed. Node:configfile,Next:debug,Previous:cmp,Up:Command-line and menu entry commandsconfigfileconfigfile fileCommandLoad file as a configuration file. Node:debug,Next:displayapm,Previous:configfile,Up:Command-line and menu entry commandsdebugdebugCommandToggle debug mode (by default it is off). When debug mode is on, someextra messages are printed to show disk activity. This global debug flagis mainly useful for GRUB developers when testing new code. Node:displayapm,Next:displaymem,Previous:debug,Up:Command-line and menu entry commandsdisplayapmdisplayapmCommandDisplay APM BIOS information. Node:displaymem,Next:embed,Previous:displayapm,Up:Command-line and menu entry commandsdisplaymemdisplaymemCommandDisplay what GRUB thinks the system address space map of the machine is,including all regions of physical RAM installed. GRUB'supper/lower memory display uses the standard BIOS interface forthe available memory in the first megabyte, or lower memory, and asynthesized number from various BIOS interfaces of the memory startingat 1MB and going up to the first chipset hole for upper memory(the standard PC upper memory interface is limited to reporting amaximum of 64MB). Node:embed,Next:find,Previous:displaymem,Up:Command-line and menu entry commandsembedembed stage1_5 deviceCommandEmbed the Stage 1.5 stage1_5 in the sectors after the MBR ifdevice is a drive, or in the boot loader area if deviceis a FFS partition or a ReiserFS partition.8 Print the number of sectors whichstage1_5 occupies, if successful.Usually, you don't need to run this command directly. See setup. Node:find,Next:fstest,Previous:embed,Up:Command-line and menu entry commandsfindfind filenameCommandSearch for the file name filename in all of partitions and printthe list of the devices which contain the file. The file namefilename should be an absolute file name like/boot/grub/stage1. Node:fstest,Next:geometry,Previous:find,Up:Command-line and menu entry commandsfstestfstestCommandToggle filesystem test mode. Filesystem test mode, when turned on, prints out data corresponding toall the device reads and what values are being sent to the low-levelroutines. The format is for high-level reads inside apartition, and [disk-offset-sector] for low-level sectorrequests from the disk. Filesystem test mode is turned off by any use of the install(see install) or testload (see testload) commands. Node:geometry,Next:halt,Previous:fstest,Up:Command-line and menu entry commandsgeometrygeometry drive [cylinder head sector [total_sector]]CommandPrint the information for the drive drive. In the grub shell, youcan set the geometry of the drive arbitrarily. The number of thecylinders, the one of the heads, the one of the sectors and the one ofthe total sectors are set to CYLINDER, HEAD, SECTOR and TOTAL_SECTOR,respectively. If you omit TOTAL_SECTOR, then it will be calculatedbased on the C/H/S values automatically. Node:halt,Next:help,Previous:geometry,Up:Command-line and menu entry commandshalthalt --no-apmCommandThe command halts the computer. If the --no-apm optionis specified, no APM BIOS call is performed. Otherwise, the computeris shut down using APM. Node:help,Next:impsprobe,Previous:halt,Up:Command-line and menu entry commandshelphelp --all [pattern ...]CommandDisplay helpful information about builtin commands. If you do notspecify pattern, this command shows short descriptions of most ofavailable commands. If you specify the option --all to thiscommand, short descriptions of rarely used commands (such astestload) are displayed as well.If you specify any patterns, it displays longer informationabout each of the commands which match those patterns. Node:impsprobe,Next:initrd,Previous:help,Up:Command-line and menu entry commandsimpsprobeimpsprobeCommandProbe the Intel Multiprocessor Specification 1.1 or 1.4 configurationtable and boot the various CPUs which are found into a tight loop. Thiscommand can be used only in the Stage 2. Node:initrd,Next:install,Previous:impsprobe,Up:Command-line and menu entry commandsinitrdinitrd file ...CommandLoad an initial ramdisk for a Linux format boot image and set theappropriate parameters in the Linux setup area in memory. See alsoGNU/Linux. Node:install,Next:ioprobe,Previous:initrd,Up:Command-line and menu entry commandsinstallinstall [--force-lba] [--stage2=os_stage2_file] stage1_file [d] dest_dev stage2_file [addr] [p] [config_file] [real_config_file]CommandThis command is fairly complex, and you should not use this commandunless you are familiar with GRUB. Use setup (see setup)instead.In short, it will perform a full install presuming the Stage 2 or Stage1.59 is in its final install location.In slightly more detail, it will load stage1_file, validate thatit is a GRUB Stage 1 of the right version number, install a blocklist forloading stage2_file as a Stage 2. If the option d ispresent, the Stage 1 will always look for the actual diskstage2_file was installed on, rather than using the bootingdrive. The Stage 2 will be loaded at address addr, which must be0x8000 for a true Stage 2, and 0x2000 for a Stage 1.5. Ifaddr is not present, GRUB will determine the addressautomatically. It then writes the completed Stage 1 to the first blockof the device dest_dev. If the options p orconfig_file are present, then it reads the first block of stage2,modifies it with the values of the partition stage2_file was foundon (for p) or places the string config_file into the areatelling the stage2 where to look for a configuration file at boottime. Likewise, if real_config_file is present andstage2_file is a Stage 1.5, then the Stage 2 config_file ispatched with the configuration file name real_config_file. Thiscommand preserves the DOS BPB (and for hard disks, the partition table)of the sector the Stage 1 is to be installed into.Caution: Several buggy BIOSes don't pass a booting driveproperly when booting from a hard disk drive. Therefore, you will haveto specify the option d, whether your Stage2 resides at thebooting drive or not, if you have such a BIOS unfortunately. We knowthese are defective in that:Fujitsu LifeBook 400 BIOS version 31J0103AHP Vectra XU 6/200 BIOS version GG.06.11Caution2: A number of BIOSes don't return a correct LBA supportbitmap even if they do have the support. So GRUB provides a solution toignore the wrong bitmap, that is, the option --force-lba. Don'tuse this option if you know that your BIOS doesn't have LBA support.Caution3: You must specify the option --stage2 in thegrub shell, if you cannot unmount the filesystem where your stage2 fileresides. The argument should be the file name in your operating system. Node:ioprobe,Next:kernel,Previous:install,Up:Command-line and menu entry commandsioprobeioprobe driveCommandProbe I/O ports used for the drive drive. This command will listthe I/O ports on the screen. For technical information,See Internals. Node:kernel,Next:lock,Previous:ioprobe,Up:Command-line and menu entry commandskernelkernel [--type=type] [--no-mem-option] file ...CommandAttempt to load the primary boot image (Multiboot a.out or ELF,Linux zImage or bzImage, FreeBSD a.out, NetBSD a.out, etc.) fromfile. The rest of the line is passed verbatim as the kernelcommand-line. Any modules must be reloaded after using this command.This command also accepts the option --type so that you canspecify the kernel type of file explicitly. The argumenttype must be one of these: netbsd, freebsd,openbsd, linux, biglinux, andmultiboot. However, you need to specify it only if you want toload a NetBSD ELF kernel, because GRUB can automatically determinea kernel type in the other cases, quite safely.The option --no-mem-option is effective only for Linux. If theoption is specified, GRUB doesn't pass the option mem= to thekernel. Node:lock,Next:makeactive,Previous:kernel,Up:Command-line and menu entry commandslocklockCommandPrevent normal users from executing arbitrary menu entries. You must usethe command password if you really want this command to beuseful (see password).This command is used in a menu, as shown in this example:title This entry is too dangerous to be executed by normal userslockroot (hd0,a)kernel /no-security-osSee also Security. Node:makeactive,Next:map,Previous:lock,Up:Command-line and menu entry commandsmakeactivemakeactiveCommandSet the active partition on the root disk to GRUB's root device. This command is limited to primary PC partitions on a hard disk. Node:map,Next:md5crypt,Previous:makeactive,Up:Command-line and menu entry commandsmapmap to_drive from_driveCommandMap the drive from_drive to the drive to_drive. This isnecessary when you chain-load some operating systems, such as DOS, ifsuch an OS resides at a non-first drive. Here is an example:grub> map (hd0) (hd1)grub> map (hd1) (hd0)The example exchanges the order between the first hard disk and thesecond hard disk. See also DOS/Windows. Node:md5crypt,Next:module,Previous:map,Up:Command-line and menu entry commandsmd5cryptmd5cryptCommandPrompt to enter a password, and encrypt it in MD5 format. The encryptedpassword can be used with the command password(see password). See also Security. Node:module,Next:modulenounzip,Previous:md5crypt,Up:Command-line and menu entry commandsmodulemodule file ...CommandLoad a boot module file for a Multiboot format boot image (nointerpretation of the file contents are made, so that user of thiscommand must know what the kernel in question expects). The rest of theline is passed as the module command-line, like thekernel command. You must load a Multiboot kernel image beforeloading any module. See also modulenounzip. Node:modulenounzip,Next:pause,Previous:module,Up:Command-line and menu entry commandsmodulenounzipmodulenounzip file ...CommandThe same as module (see module), except that automaticdecompression is disabled. Node:pause,Next:quit,Previous:modulenounzip,Up:Command-line and menu entry commandspausepause message ...CommandPrint the message, then wait until a key is pressed. Note thatplacing (ASCII code 7) in the message will cause the speaker toemit the standard beep sound, which is useful when prompting the user tochange floppies. Node:quit,Next:reboot,Previous:pause,Up:Command-line and menu entry commandsquitquitCommandExit from the grub shell grub (see Invoking the grub shell). This command can be used only in the grub shell. Node:reboot,Next:read,Previous:quit,Up:Command-line and menu entry commandsrebootrebootCommandReboot the computer. Node:read,Next:root,Previous:reboot,Up:Command-line and menu entry commandsreadread addrCommandRead a 32-bit value from memory at address addr and display it inhex format. Node:root,Next:rootnoverify,Previous:read,Up:Command-line and menu entry commandsrootroot device [hdbias]CommandSet the current root device to the device device, thenattempt to mount it to get the partition size (for passing the partitiondescriptor in ES:ESI, used by some chain-loaded boot loaders), theBSD drive-type (for booting BSD kernels using their native boot format),and correctly determine the PC partition where a BSD sub-partition islocated. The optional hdbias parameter is a number to tell a BSDkernel how many BIOS drive numbers are on controllers before the currentone. For example, if there is an IDE disk and a SCSI disk, and yourFreeBSD root partition is on the SCSI disk, then use a 1 forhdbias.See also rootnoverify. Node:rootnoverify,Next:savedefault,Previous:root,Up:Command-line and menu entry commandsrootnoverifyrootnoverify device [hdbias]CommandSimilar to root (see root), but don't attempt to mount thepartition. This is useful for when an OS is outside of the area of thedisk that GRUB can read, but setting the correct root device is stilldesired. Note that the items mentioned in root above whichderived from attempting the mount will not work correctly. Node:savedefault,Next:setup,Previous:rootnoverify,Up:Command-line and menu entry commandssavedefaultsavedefaultCommandSave the current menu entry as a default entry. Here is an example:default savedtimeout 10title GNU/Linuxroot (hd0,0)kernel /boot/vmlinuz root=/dev/sda1 vga=extinitrd /boot/initrdsavedefaulttitle FreeBSDroot (hd0,a)kernel /boot/loadersavedefaultWith this configuration, GRUB will choose the entry booted previously asthe default entry. See also default. Node:setup,Next:testload,Previous:savedefault,Up:Command-line and menu entry commandssetupsetup [--force-lba] [--stage2=os_stage2_file] [--prefix=dir] install_device [image_device]CommandSet up the installation of GRUB automatically. This command uses themore flexible command install (see install) in the backendand installs GRUB into the device install_device. Ifimage_device is specified, then find the GRUB images(see Images) in the device image_device, otherwise use thecurrent root device, which can be set by the commandroot. If install_device is a hard disk, then embed aStage 1.5 in the disk if possible.The option --prefix specifies the directory under which GRUBimages are put. If it is not specified, GRUB automatically searches themin /boot/grub and /grub.The options --force-lba and --stage2 are just passedto install if specified. See install, for moreinformation. Node:testload,Next:testvbe,Previous:setup,Up:Command-line and menu entry commandstestloadtestload fileCommandRead the entire contents of file in several different ways andcompares them, to test the filesystem code. The output is somewhatcryptic, but if no errors are reported and the final i=X,filepos=Y reading has X and Y equal, then it isdefinitely consistent, and very likely works correctly subject to aconsistent offset error. If this test succeeds, then a good next step isto try loading a kernel. Node:testvbe,Next:uppermem,Previous:testload,Up:Command-line and menu entry commandstestvbetestvbe modeCommandTest the VESA BIOS EXTENSION mode mode. This command will switchyour video card to the graphics mode, and show an endless animation. Hitany key to return. See also vbeprobe. Node:uppermem,Next:vbeprobe,Previous:testvbe,Up:Command-line and menu entry commandsuppermemuppermem kbytesCommandForce GRUB to assume that only kbytes kilobytes of upper memoryare installed. Any system address range maps are discarded.Caution: This should be used with great caution, and shouldonly be necessary on some old machines. GRUB's BIOS probe can pick upall RAM on all new machines the author has ever heard of. It canalso be used for debugging purposes to lie to an OS. Node:vbeprobe,Previous:uppermem,Up:Command-line and menu entry commandsvbeprobevbeprobe [mode]CommandProbe VESA BIOS EXTENSION information. If the mode mode isspecified, show only the information about mode. Otherwise, thiscommand lists up available VBE modes on the screen. See alsotestvbe. Node:Troubleshooting,Next:Invoking the grub shell,Previous:Commands,Up:TopError messages reported by GRUBThis chapter describes error messages reported by GRUB when youencounter trouble. See Invoking the grub shell, if your problem isspecific to the grub shell.Stage1 errors: Errors reported by the Stage 1Stage1.5 errors: Errors reported by the Stage 1.5Stage2 errors: Errors reported by the Stage 2Node:Stage1 errors,Next:Stage1.5 errors,Up:TroubleshootingErrors reported by the Stage 1The general way that the Stage 1 handles errors is to print an errorstring and then halt. Pressing -- willreboot.The following is a comprehensive list of error messages for the Stage 1:Hard Disk ErrorThe stage2 or stage1.5 is being read from a hard disk, and the attemptto determine the size and geometry of the hard disk failed.Floppy ErrorThe stage2 or stage1.5 is being read from a floppy disk, and the attemptto determine the size and geometry of the floppy disk failed. It's listedas a separate error since the probe sequence is different than for harddisks.Read ErrorA disk read error happened while trying to read the stage2 or stage1.5.Geom ErrorThe location of the stage2 or stage1.5 is not in the portion of the disksupported directly by the BIOS read calls. This could occur because theBIOS translated geometry has been changed by the user or the disk ismoved to another machine or controller after installation, or GRUB wasnot installed using itself (if it was, the Stage 2 version of this errorwould have been seen during that process and it would not have completedthe install). Node:Stage1.5 errors,Next:Stage2 errors,Previous:Stage1 errors,Up:TroubleshootingErrors reported by the Stage 1.5The general way that the Stage 1.5 handles errors is to print an errornumber in the form Error num and then halt. Pressing-- will reboot.The error numbers correspond to the errors reported by Stage2. See Stage2 errors.Node:Stage2 errors,Previous:Stage1.5 errors,Up:TroubleshootingErrors reported by the Stage 2The general way that the Stage 2 handles errors is to abort theoperation in question, print an error string, then (if possible) eithercontinue based on the fact that an error occurred or wait for the user todeal with the error.The following is a comprehensive list of error messages for the Stage 2(error numbers for the Stage 1.5 are listed before the colon in eachdescription):1 : Filename must be either an absolute filename or blocklistThis error is returned if a file name is requested which doesn't fit thesyntax/rules listed in the Filesystem.2 : Bad file or directory typeThis error is returned if a file requested is not a regular file, butsomething like a symbolic link, directory, or FIFO.3 : Bad or corrupt data while decompressing fileThis error is returned if the run-length decompression code gets aninternal error. This is usually from a corrupt file.4 : Bad or incompatible header in compressed fileThis error is returned if the file header for a supposedly compressedfile is bad.5 : Partition table invalid or corruptThis error is returned if the sanity checks on the integrity of thepartition table fail. This is a bad sign.6 : Mismatched or corrupt version of stage1/stage2This error is returned if the install command is pointed to incompatibleor corrupt versions of the stage1 or stage2. It can't detect corruptionin general, but this is a sanity check on the version numbers, whichshould be correct.7 : Loading below 1MB is not supportedThis error is returned if the lowest address in a kernel is below the1MB boundary. The Linux zImage format is a special case and can behandled since it has a fixed loading address and maximum size.8 : Kernel must be loaded before bootingThis error is returned if GRUB is told to execute the boot sequencewithout having a kernel to start.9 : Unknown boot failureThis error is returned if the boot attempt did not succeed for reasonswhich are unknown.10 : Unsupported Multiboot features requestedThis error is returned when the Multiboot features word in the Multibootheader requires a feature that is not recognized. The point of this isthat the kernel requires special handling which GRUB is likely unable toprovide.11 : Unrecognized device stringThis error is returned if a device string was expected, and the stringencountered didn't fit the syntax/rules listed in the Filesystem.12 : Invalid device requestedThis error is returned if a device string is recognizable but does notfall under the other device errors.13 : Invalid or unsupported executable formatThis error is returned if the kernel image being loaded is notrecognized as Multiboot or one of the supported native formats (LinuxzImage or bzImage, FreeBSD, or NetBSD).14 : Filesystem compatibility error, cannot read whole fileSome of the filesystem reading code in GRUB has limits on the length ofthe files it can read. This error is returned when the user runs intosuch a limit.15 : File not foundThis error is returned if the specified file name cannot be found, buteverything else (like the disk/partition info) is OK.16 : Inconsistent filesystem structureThis error is returned by the filesystem code to denote an internalerror caused by the sanity checks of the filesystem structure on disknot matching what it expects. This is usually caused by a corruptfilesystem or bugs in the code handling it in GRUB.17 : Cannot mount selected partitionThis error is returned if the partition requested exists, but thefilesystem type cannot be recognized by GRUB.18 : Selected cylinder exceeds maximum supported by BIOSThis error is returned when a read is attempted at a linear blockaddress beyond the end of the BIOS translated area. This generallyhappens if your disk is larger than the BIOS can handle (512MB for(E)IDE disks on older machines or larger than 8GB in general).19 : Linux kernel must be loaded before initrdThis error is returned if the initrd command is used before loading aLinux kernel. Similar to the above error, it only makes sense in thatcase anyway.20 : Multiboot kernel must be loaded before modulesThis error is returned if the module load command is used before loadinga Multiboot kernel. It only makes sense in this case anyway, as GRUB hasno idea how to communicate the presence of location of such modules to anon-Multiboot-aware kernel.21 : Selected disk does not existThis error is returned if the device part of a device- or full file namerefers to a disk or BIOS device that is not present or not recognized bythe BIOS in the system.22 : No such partitionThis error is returned if a partition is requested in the device part ofa device- or full file name which isn't on the selected disk.23 : Error while parsing numberThis error is returned if GRUB was expecting to read a number andencountered bad data.24 : Attempt to access block outside partitionThis error is returned if a linear block address is outside of the diskpartition. This generally happens because of a corrupt filesystem on thedisk or a bug in the code handling it in GRUB (it's a great debuggingtool).25 : Disk read errorThis error is returned if there is a disk read error when trying toprobe or read data from a particular disk.26 : Too many symbolic linksThis error is returned if the link count is beyond the maximum(currently 5), possibly the symbolic links are looped.27 : Unrecognized commandThis error is returned if an unrecognized command is entered into thecommand-line or in a boot sequence section of a configuration file andthat entry is selected.28 : Selected item cannot fit into memoryThis error is returned if a kernel, module, or raw file load command iseither trying to load its data such that it won't fit into memory or itis simply too big.29 : Disk write errorThis error is returned if there is a disk write error when trying towrite to a particular disk. This would generally only occur during aninstall of set active partition command.30 : Invalid argumentThis error is returned if an argument specified to a command is invalid.31 : File is not sector alignedThis error may occur only when you access a ReiserFS partition byblock-lists (e.g. the command install). In this case, youshould mount the partition with the -o notail option.32 : Must be authenticatedThis error is returned if you try to run a locked entry. You shouldenter a correct password before running such an entry.33 : Serial device not configuredThis error is returned if you try to change your terminal to a serialone before initializing any serial device.34 : No spare sectors on the diskThis error is returned if a disk doesn't have enough spare space. Thishappens when you try to embed Stage 1.5 into the unused sectors afterthe MBR, but the first partition starts right after the MBR or they areused by EZ-BIOS. Node:Invoking the grub shell,Next:Invoking grub-install,Previous:Troubleshooting,Up:TopInvoking the grub shellThis chapter documents the grub shell grub. Note that the grubshell is an emulator; it doesn't run under the native environment, so itsometimes does something wrong. Therefore, you shouldn't trust it toomuch. If there is anything wrong with it, don't hesitate to try thenative GRUB environment, especially when it guesses a wrong map betweenBIOS drives and OS devices.Basic usage: How to use the grub shellInstallation under UNIX: How to install GRUB via grubDevice map: The map between BIOS drives and OS devicesNode:Basic usage,Next:Installation under UNIX,Up:Invoking the grub shellIntroduction into the grub shellYou can use the command grub for installing GRUB under youroperating systems and for a testbed when you add a new feature into GRUBor when fix a bug. grub is almost the same as the Stage 2,and, in fact, it shares the source code with the Stage 2 and you can usethe same commands (see Commands) in grub. It is emulated byreplacing BIOS calls with UNIX system calls and libc functions.The command grub accepts the following options:--helpPrint a summary of the command-line options and exit.--versionPrint the version number of GRUB and exit.--verbosePrint some verbose messages for debugging purpose.--device-map=fileUse the device map file file. The format is described inDevice map.--no-floppyDo not probe any floppy drive. This option has no effect if the option--device-map is specified (see Device map).--probe-second-floppyProbe the second floppy drive. If this option is not specified, the grubshell does not probe it, as that sometimes takes a long time. If youspecify the device map file (see Device map), the grub shell justignores this option.--config-file=fileRead the configuration file file instead of/boot/grub/menu.lst. The format is the same as the normal GRUBsyntax. See Filesystem, for more information.--boot-drive=driveSet the stage2 boot_drive to drive. This argument should bean integer (decimal, octal or hexadecimal).--install-partition=parSet the stage2 install_partition to par. This argumentshould be an integer (decimal, octal or hexadecimal).--no-config-fileDo not use the configuration file even if it can be read.--no-cursesDo not use the curses interface even if it is available.--batchThis option has the same meaning as --no-config-file --no-curses.--read-onlyDisable writing to any disk.--holdWait until a debugger will attach. This option is useful when you wantto debug the startup code. Node:Installation under UNIX,Next:Device map,Previous:Basic usage,Up:Invoking the grub shellHow to install GRUB via grubThe installation procedure is the same as under the native Stage2. See Installation, for more information. The commandgrub-specific information is described here.What you should be careful about is buffer cache. grubmakes use of raw devices instead of filesystems that your operatingsystems serve, so there exists a potential problem that some cacheinconsistency may corrupt your filesystems. What we recommend is:If you can unmount drives to which GRUB may write any amount of data,unmount them before running grub.If a drive cannot be unmounted but can be mounted with the read-onlyflag, mount it in read-only mode. That should be secure.If a drive must be mounted with the read-write flag, make sure that anyactivity is not being done on it during running the commandgrub.Reboot your operating system as soon as possible. Probably that is notrequired if you follow these rules above, but reboot is the most secureway. In addition, enter the command quit when you finish theinstallation. That is very important because quit makesthe buffer cache consistent. Do not push .If you want to install GRUB non-interactively, specify --batchoption in the command-line. This is a simple example:#!/bin/sh# Use /usr/sbin/grub if you are on an older system./sbin/grub --batch /dev/nullroot (hd0,0)setup (hd0)quitEOTNode:Device map,Previous:Installation under UNIX,Up:Invoking the grub shellThe map between BIOS drives and OS devicesWhen you specify the option --device-map (see Basic usage),the grub shell creates the device map file automatically unless italready exists. The file name /boot/grub/device.map is preferred.If the device map file exists, the grub shell reads it to map BIOSdrives to OS devices. This file consists of lines like this:device filedevice is a drive, which syntax is the same as the one in GRUB(see Device syntax), and file is an OS's file, which isnormally a device file.The reason why the grub shell gives you the device map file is that itcannot guess the map between BIOS drives and OS devices correctly insome environments. For example, if you exchange the boot sequencebetween IDE and SCSI in your BIOS, it mistakes the order.Thus, edit the file if the grub shell makes a mistake. You can put anycomments in the file if needed, as the grub shell assumes that a line isjust a comment if the first character is #.Node:Invoking grub-install,Next:Invoking grub-md5-crypt,Previous:Invoking the grub shell,Up:TopInvoking grub-installThe program grub-install installs GRUB on your drive by thegrub shell (see Invoking the grub shell). You must specify thedevice name on which you want to install GRUB, like this:grub-install install_deviceThe device name install_device is an OS device name or a GRUBdevice name.grub-install accepts the following options:--helpPrint a summary of the command-line options and exit.--versionPrint the version number of GRUB and exit.--force-lbaForce GRUB to use LBA mode even for a buggy BIOS. Use this option onlyif your BIOS doesn't work in LBA mode even though it supports LBA mode.--root-directory=dirInstall GRUB images under the directory dir instead of the rootdirectory. This option is useful when you want to install GRUB into aseparate partition or a removable disk. Here is an example when you havea separate boot partition which is mounted on /boot:grub-install --root-directory=/boot '(hd0)'--grub-shell=fileUse file as the grub shell. You can append arbitrary options tofile after the file name, like this:grub-install --grub-shell="grub --read-only" /dev/fd0--recheckRecheck the device map, even if /boot/grub/device.map alreadyexists. You should use this option whenever you add/remove a diskinto/from your computer. Node:Invoking grub-md5-crypt,Next:Invoking mbchk,Previous:Invoking grub-install,Up:TopInvoking grub-md5-cryptThe program grub-md5-crypt encrypts a password in MD5 format. This is just a frontend of the grub shell (see Invoking the grub shell). Passwords encrypted by this program can be used with thecommand password (see password).grub-md5-crypt accepts the following options:--helpPrint a summary of the command-line options and exit.--versionPrint the version information and exit.--grub-shell=fileUse file as the grub shell. Node:Invoking mbchk,Next:FAQ,Previous:Invoking grub-md5-crypt,Up:TopInvoking mbchkThe program mbchk checks for the format of a Multibootkernel. We recommend using this program before booting your own kernelby GRUB.mbchk accepts the following options:--helpPrint a summary of the command-line options and exit.--versionPrint the version number of GRUB and exit.--quietSuppress all normal output. Node:FAQ,Next:Obtaining and Building GRUB,Previous:Invoking mbchk,Up:TopFrequently asked questionsHow does GNU GRUB differ from Erich's original GRUB?GNU GRUB is the successor of Erich's great GRUB. He couldn't work onGRUB because of some other tasks, so the current maintainers YoshinoriK. Okuji and Gordon Matzigkeit took over the maintainership, and openedthe development in order for everybody to participate it.Technically speaking, GNU GRUB has many features that are not seen inthe original GRUB. For example, GNU GRUB can be installed on UNIX-likeoperating system (such as GNU/Hurd) via the grub shell/sbin/grub (or /usr/sbin/grub on older systems), itsupports Logical Block Address (LBA) mode that solves the 1024 cylindersproblem, and completes a file name when it's unique. Ofcourse, many bug fixes are done as well, so it is recommended to use GNUGRUB.Can GRUB boot my operating system from over 8GB hard disks?That depends on your BIOS and your operating system. You must makesure that your drive is accessible in LBA mode. Generally, that isconfigurable in BIOS setting utility. Read the manual for your BIOSfor more information.Furthermore, some operating systems (i.e. DOS) cannot access any largedisk, so the problem is not solved by any kind of boot loader. GNU/Hurdand GNU/Linux can surely boot from such a large disk.Can I put Stage2 into a partition which is over 1024 cylinders?Yes, if your BIOS supports the LBA mode.How to create a GRUB boot floppy with the menu interface?The easiest way is: 2ff7e9595c
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