ipchains is always invoked with one of the following commands: -A chain rules, –append chain rules Append new rules to chain. -I chain number rules, –insert
-o name Name module name instead of attempting to name it from the object file’s name. -x Do not export: do not add any external symbols from the module to the kernel’s symbol table. install install [options] [file] directories System administration command. Used primarily in makefiles to update files. install copies files into user- specified directories. It will not overwrite a file. Similar to cp but attempts to set permission modes, owner, and group. Options -d, –directory Create any missing directories. -g group, –group group Set group ID of new file to group (privileged users only). -m mode, –mode mode Set permissions of new file to mode (octal or symbolic). By default, the mode is 0755. -o [owner], –owner [owner] Set ownership to owner or, if unspecified, to root (privileged users only). -s, –strip Strip symbol tables. ipchains ipchains command [options] System administration command. Edit IP firewall rules in the 2.2 Linux kernel. A 2.2 Linux kernel compiled with firewall support will examine the headers of all network packets and compare them to matching rules to see what it should do with the packet. A firewall rule consists of some matching criteria and a target, a result to be applied if the packet matches the criteria. The rules are organized into chains. You can use these rules to build a firewall or just reject certain kinds of network connections. Firewall rules are organized into chains, an ordered checklist that the kernel works through looking for matches. There are three built-in chains input, output, and forward. Packets entering the system are tested against the input chain. Those exiting the system are checked against the output chain. If an incoming packet is destined for some other system, it is checked against the forward chain. Each of these chains has a default target, a policy, in case no match is found. User-defined chains can be created and used as targets for packets, but they have no default policies. If no match can be found in a user-defined chain, the packet is returned to the chain from which it was called and tested against the next rule in that chain. ipchains only changes the rules in the running kernel. When the system is powered off, all those changes are lost. You can use the ipchains-save command to make a script you can later run with ipchains-restore to restore your firewall settings. Such a script is often called at boot up and many distributions have an ipchains initialization script that uses the output from ipchains-save. Commands
–vi-keys Use vi-like key bindings. init init [option] [runlevel] System administration command. Option -t seconds When changing runlevels, send SIGKILL seconds after SIGTERM. Default is 20. Files init is the first process run by any Unix machine at boot time. It verifies the integrity of all filesystems and then creates other processes, using fork and exec, as specified by /etc/inittab. Which processes may be run are controlled by runlevel. All process terminations are recorded in /var/run/utmp and /var/log/wtmp. When the runlevel changes, init sends SIGTERM and then, after 20 seconds, SIGKILL to all processes that cannot be run in the new runlevel. Runlevels The current runlevel may be changed by telinit, which is often just a link to init. The default runlevels vary from distribution to distribution, but these are standard: 0 Halt the system. 1, s, S Single-user mode. 6 Reboot the system. q, Q Reread /etc/inittab. Check the /etc/inittab file for runlevels on your system. insmod insmod [options] file [symbol=value …] System administration command. Load the module file into the kernel, changing any symbols that are defined on the command line. If the module file is named file.o or file.mod, the module will be named file. Options -f Force loading of module, even if some problems are encountered. -m Output a load map.
Turn on socket-level debugging and print debugging information to stdout. Files /etc/inetd.conf Default configuration file. /var/run/inetd.pid inetd’s process ID. info info [options] [topics] GNU hypertext reader: display online documentation previously built from Texinfo input. Info files are arranged in a hierarchy and can contain menus for subtopics. When entered without options, the command displays the top-level info file (usually /usr/local/info/dir). When topics are specified, find a subtopic by choosing the first topic from the menu in the top-level info file, the next topic from the new menu specified by the first topic, and so on. The initial display can also be controlled by the -f and -n options. Options -d directories, –directory directories Search directories, a colon-separated list, for info files. If this option is not specified, use the INFOPATH environment variable or the default directory (usually /usr/local/info). –dribble file Store each keystroke in file, which can be used in a future session with the –restore option to return to this place in info. -f file, –file file Display specified info file. -n node, –node node Display specified node in the info file. -o file, –output file Copy output to file instead of displaying it at the screen. –help Display brief help. –restore file When starting, execute keystrokes in file. –subnodes Display subtopics. –version Display version.
File containing X-specific variables. Library.tmpl File containing library rules. Server.tmpl File containing server-specific rules. .cf The .cf files are the vendor-specific VendorFiles that live in Imake.vb. A .cf file contains platform- specific definitions, such as version numbers of the operating system and the compiler and workarounds for missing commands. The definitions in .cf files override the defaults, defined in Imake.params. The Imakefile The Imakefile is a per-directory file that indicates targets to be built and installed and rules to be applied. imake reads the Imakefile and expands the rules into Makefile target entries. An Imakefile may also include definitions of make variables and list the dependencies of the targets. The dependencies are expressed as cpp macros, defined in Imake.rules. Whenever you change an Imakefile, you need to rebuild the Makefile and regenerate header file dependencies. For more information on imake, see Software Portability with imake by Paul DuBois. imapd imapd TCP/IP command. The Interactive Mail Access Protocol (IMAP) server daemon. imapd is invoked by inetd and listens on port 143 for requests from IMAP clients. IMAP allows mail programs to access remote mailboxes as if they were local. IMAP is a richer protocol than POP because it allows a client to retrieve message-level information from a server mailbox instead of the entire mailbox. IMAP can be used for online and offline reading. The popular Pine mail client contains support for IMAP. inetd inetd [option] [configuration_file] TCP/IP command. Internet services daemon. inetd listens on multiple ports for incoming connection requests. When it receives one, it spawns the appropriate server. When started, inetd reads its configuration information from either configuration_file, or from the default configuration file /etc/inetd.conf. It then issues a call to getservbyname, creates a socket for each server, and binds each socket to the port for that server. It does a listen on all connection-based sockets, then waits, using select for a connection or datagram. When a connection request is received on a listening socket, inetd does an accept, creating a new socket. It then forks, dups, and execs the appropriate server. The invoked server has I/O to stdin, stdout, and stderr done to the new socket, connecting the server to the client process. When there is data waiting on a datagram socket, inetd forks, dups, and execs the appropriate server, passing it any server program arguments. A datagram server has I/O to stdin, stdout, and stderr done to the original socket. If the datagram socket is marked as wait, the invoked server must process the message before inetd considers the socket available for new connections. If the socket is marked nowait, inetd continues to process incoming messages on that port. The following servers may be started by inetd: bootpd, bootpgw, fingerd, ftpd, imapd, popd, rexecd, rlogind, rshd, talkd, telnetd, and tftpd. Do not arrange for inetd to start named, routed, rwhod, sendmail, listen, or any NFS server. inetd rereads its configuration file when it receives a hangup signal, SIGHUP. Services may be added, deleted, or modified when the configuration file is reread. Option -d
Use string as delimiter in file, instead of # DO NOT DELETE THIS LINE — make depend depends on it. -v Verbose. List all files included by main source file. -Dname Define name with the given value (first form) or with value 1 (second form). -Idir Add directory dir to the list of directories searched. -Ydir Search only dir for include files. Ignore standard include directories. mkdirhier dir… Create directory dir and all missing parent directories during file installation operations. xmkmf [option] [topdir] [curdir] Bootstrap a Makefile from an Imakefile. topdir specifies the location of the project root directory. curdir (usually omitted) is specified as a relative pathname from the top of the build tree to the current directory. The -a option is equivalent to the following command sequence: % xmkmf % make Makefiles % make includes % make depend Configuration files Following is a list of the imake configuration files: Imake.tmpl Master template for imake. Imake.tmpl includes all the other configuration files, plus the Imakefile in the current directory. Imake.params Contains definitions that apply across sites and vendors. Imake.rules Contains cpp macro definitions that are configured for the current platform. The macro definitions are fed into imake, which runs cpp to process the macros. Newlines (line continuations) are indicated by the string @@ (double at sign, backslash). site.def Contains site-specific (as opposed to vendor-specific) information, such as installation directories, what set of programs to build, and any special versions of programs to use during the build. The site.def file changes from machine to machine. Project.tmpl
-Ddefine Set directory-specific variables. This option is passed directly to cpp. -e Execute the generated Makefile. Default is to leave this to the user. -f filename Name of per-directory input file. Default is Imakefile. -Idirectory Directory in which imake template and configuration files may be found. This option is passed directly to cpp. -s filename Name of make description file to be generated. If filename is a — , the output is written to stdout. The default is to generate, but not execute, a Makefile. -Ttemplate Name of master template file used by cpp. This file is usually located in the directory specified with the - I option. The default file is Imake.tmpl. -v Print the cpp command line used to generate the Makefile. Tools Following is a list of tools used with imake: makedepend [options] files Create header file dependencies in Makefiles. make- depend reads the named input source files in sequence and parses them to process #include, #define, #undef, #ifdef, #ifndef, #endif, #if, and #else directives so it can tell which #include directives would be used in a compilation. makedepend determines the dependencies and writes them to the Makefile. make then knows which object files must be recompiled when a dependency has changed. makedepend has the following options: — options — Ignore any unrecognized options following a double hyphen. A second double hyphen terminates this action. Recognized options between the hyphens are processed normally. -a Append dependencies to any existing ones instead of replacing existing ones. -ffilename Write dependencies to filename instead of to Makefile. -m Print a warning when encountering a multiple inclusion. -sstring
irq addr Set the device’s interrupt line. metric n Set routing metric of the interface to n. Default is 0. mtu num Set the interface’s Maximum Transfer Unit (MTU). multicast Set the multicast flag. netmask mask (inet only.) Specify how much of the address to reserve for subdividing networks into subnetworks. mask can be specified as a single hexadecimal number with a leading 0x, with a dot notation Internet address, or with a pseudonetwork name listed in the network table /etc/networks. pointopoint/-pointopoint [address] Enable/disable point-to-point interfacing, so that the connection between the two machines is dedicated. up Mark an interface “up” (ready to send and receive). trailers/-trailers Request/disable use of a “trailer” link-level encapsulation when sending. address Either a hostname present in the hostname database (/etc/hosts), or an Internet address expressed in the Internet standard dot notation. imake imake options C preprocessor (cpp) interface to the make utility. imake (for include make) solves the portability problem of make by allowing machine dependencies to be kept in a central set of configuration files, separate from the descriptions of the various items to be built. The targets are contained in the Imakefile, a machine-independent description of the targets to be built, written as cpp macros. imake uses cpp to process the configuration files and the Imakefile, and to generate machine-specific Makefiles, which can then be used by make. One of the configuration files is a template file, a master file for imake. This template file (default is Imake.tmpl) #includes the other configuration files that contain machine dependencies such as variable assignments, site definitions, and cpp macros, and directs the order in which the files are processed. Each file affects the interpretation of later files and sections of Imake.tmpl. Comments may be included in imake configuration files, but the initial # needs to be preceded with an empty C comment: /**/# For more information, see cpp and make. Also check out the Nutshell Handbook Software Portability with imake, by Paul DuBois. Options
icmpinfo icmpinfo [options] TCP/IP command. Intercept and interpret ICMP packets. Print the address and name of the message’s sender, the source port, the destination port, the sequence, and the packet size. By default, provide information only about packets that are behaving oddly. Options -k Kill the syslogd process begun by -l. -l Record via syslogd. Only a privileged user may use this option. -n Use IP addresses instead of hostnames. -p Suppress decoding of port number: do not attempt to guess the name of the service that is listening at that port. -s Include IP address of interface that received the packet, in case there are several interfaces on the host machine. -v Verbose. Include information about normal ICMP packets. You may also specify -vv and -vvv for extra verbosity. id id [options] [username] Display information about yourself or another user: user ID, group ID, effective user ID and group ID if relevant, and additional group IDs. Options -g, –group Print group ID only. -G, –groups Print supplementary groups only. -n, –name With -u, -g, or -G, print user or group name, not number. -r, –real With -u, -g, or -G, print real, not effective, user ID or group ID. -u, –user
hwclock hwclock [options] System administration command. Read or set the hardware clock. This command maintains change information in /etc/adjtime, which can be used to adjust the clock based on how much it drifts over time. hwclock replaces the clock command. The single-letter options are included for compatibility with the older command. Options You may specify only one of the following options: -a Adjust the hardware clock based on information in /etc/adjtime and set the system clock to the new time. –adjust Adjust the hardware clock based on information in /etc/adjtime. –date date Meaningful only with the –set option. date is a string appropriate for use with the date command. –debug Print information about what hwclock is doing. -r, –show Print the current time stored in the hardware clock. -s, –hctosys Set the system time in accordance with the hardware clock. –set Set the hardware clock according to the time given in the –date parameter. –test Do not actually change anything. This is good for checking syntax. -u, –utc The hardware clock is stored in Universal Coordinated Time. –version Print version and exit. -w, –systohc Set the hardware clock in accordance with the system time.