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Local Area Network Management,Design and Security Linux –Kap.9 i kursboken

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1 Local Area Network Management,Design and Security Linux –Kap.9 i kursboken

2 Linux ”facts” SB Linus Thorvalds Helsingfors universitet. Utgick från Minix, skapat av Professor Andrew S. Tanenbaum, för att skapa ett eget operativsystem för Intel-processor. Blev inledningen på det största gemensamhetsprojektet i vår tid. Kernel (2.6.x stabil / 2.5.x instabil) GNU is Not Unix av Free Software Foundation (FSF) GNU General Public License (GPL). Allt ska vara fritt även källkod, men är också Copyrighted till skaparen. Fritt att använda och att vidare- distribuera men allt nytt som skapas utifrån ”källan” ska också var under GPL- licensiering.

3 LINUX Core (Kärna) LINUX shell command interpreter Tools and Help functions Linux structure Word Editors “Normal” commands + more bash sh

4 Låga krav på hårdvaran i386->, + många andra processortyper >64 MByte RAM om GUI 2 GByte HDD om GUI Dual boot möjligt och vanligt Partitionering av HDD med fdisk, disk druid eller FIPS (The First nondestructive Interactive Partition Splitting program). Installation från CD eller FTP. (även HTTP eller över share används)

5 Kernel (Kärnan) SB

6 File system NFS SB Network file system (NFS) Nätverkstjänsterna tillhandahåller även ett filsystem över nätverk. Denna tjänst (NFS), utvecklad av Sun, lurar applikationerna till att tro att filsystemet finns lokalt, emedan det egentligen finns någon annanstans. Det finns egentligen ingen begränsning på var datorn/hårddisken finns. T.ex. har KTH en filserver här hos Umdac. Det upplevs inte som segt så länge förbindelsen är snabb.

7 File system layout FSSTDN SB Mount points for other filesystems: /homeAnvändarnas hemkataloger /usrVanliga unix-program /varLog-filer,köer mm Ex. mount jupiter:/export/appl /usr ”Partition”

8 Filesystem, lite djupare SB /”root-directory” som innehåller alla andra ”directoryn”. /binGrundläggande kommandon Commands needed during bootup that might be used by normal users /devDevice files – Kräver lite extra uppmärksamhet. UNIX känner igen två olika typer av device: - ”random-access block device”(hårddisk t.ex. /hda1) - ”character-device”(serieport/parallellport). Ett device i UNIX representeras av en speciell fil i /dev. Parallellport 1 (dos - lpt1:) representeras av /dev/par0 i UNIX. För att ”accessa” denna parallellport behövs inget speciellt program. Man kan skriva ut en fil på skrivaren på detta sätt, (om man har skrivrättigheter på den filen dvs): >cat filen > /dev/par0 (> = skicka resultatet till) Normalt finns det dock user-level program som tar hand om skrivning/läsning på device. För utskrifter är det lpr som gör jobbet, på ett mycket smartare sätt dessutom. Normalt installeras alla device-filer i /dev fastän det inte finns just de devicen. Det blir enklare sen om man vill installera något senare. /sbinLike /bin but the commands are not intended for normal users.

9 File system, lite djupare /etc SB /etcConfiguration files specific to the machine. (Viktiga inställningsfiler) --x11Inställningar X-windows --ftpdInställningar för FTP-server --init.dInnehåller startupscript 1/tjänst --mailInställningar MAIL --rc0.d Runlevel0 scriptanropHalt, förbereder avstängning --rc1.d Runlevel1 scriptanropSingle user, kör inga demoner --rc2.d Runlevel2 scriptanropMultiuser, normal --rc3.d Runlevel3 scriptanrop Multiuser, normal --rc4.d Runlevel4 scriptanrop Multiuser, normal --rc5.d Runlevel5 scriptanrop Multiuser, normal --rc6.d Runlevel6 scriptanropReboot, som 0 fast med omstart passwdfil med användare shadowfil med lösenord, endast root har rättigheter. groupfil med definition av grupper lilo.conf grub.conf >init 0

10 File system, mer SB /homeHemkataloger /usrStandardkatalog för applikationer /varLog-filer,köer mm /boot Files used by bootstrap loader e.g. LILO. (Kärnan + bootinformation) LILO/GRUB (Linux loader/GRand Unified Boot loader ) i MBR (Master Boot Record ) /tmpTemporary files. Raderas vid uppstart (Programs running after bootup should use /var/tmp) /libShared libraries needed by programs on the root filesystem /lib/modulesLoadable kernel modules, especially those that are needed to boot the system when recovering from disasters (e.g.,network and filesystem drivers) /lost+foundFörlorade filer hamnar här vid diskcheck /mntMount point for external temporary mounts by system administrator.mount jupiter:/export/swap /mnt /optMånga kommersiella program vill installera sig här jmf. /usr /rootHome for user root /procI primärminne. Se nedan !

11 /proc (i minnet) SB

12 RPM RedHat Packet Manager Installera bara dom komponenter som du behöver, RPM gör det enkelt att komplettera senare. rpm –i package.rpm  installera package rpm –e package  ta bort package (-q visa status, –qa alla) Vanliga ”installationsalternativ”: –Printer support –X-windows GUI –Mail/WWW/News –Networked workstation –SMB (Samba) –Web-server (Apache) –Emacs/Vi (Text editor) –C Development –Extra documentation (Man-sidor, nås med >man filnamn) –+ more

13 Att visa innehållet i en fil >cat filnamn.ext  Hela filen filnamn.ext visas >more filanmn.ext  Stannar för varje ”fönster” >less filnamn.ext  som more men du kan scrolla >tail filnamn.ext  visar slutet, bra för loggfiler där sista raderna är senaste händelserna. >cat filnamn.ext|grep ”…”  visa bara rader som innehåller: ”…” text-editor  du kan även redigera innehållet Några kommandon för att hantera filer/Kataloger mkdir, rmdir  Skapa, ta bort katalog ls  Lista kataloginnehåll cd,cd..,cd /  ”Byt” katalog cp  copy file mv  move file rm  remove file

14 > useradd john >chfn -f "John Tonnessen" -p john >passwd john New UNIX password:tr5fgty Retype new UNIX password:tr5fgty >cat /etc/passwd|grep john john:3lnEkcBOE:537:537:John Tonnessen,, :/home/john:/bin/bash >userdel john Skapa en user/grupp userdel john  användaren tas bort userdel –r john  hemkatalog tas också bort >groupadd employees (editing of group-file with an editor: Vi or Emacs) >cat /etc/group|grep employees employees:x:538:john,mark,ken,louise,julia,paul Det finns ”parametrar” att använda!

15 Process handling >ps PID TTY STAT TIME COMMAND 3626 p1 S 0:00 su john 3627 p1 S 0:00 bash 3768 p0 S 0:00 /bin/login -h oppringt-3.tisip.no -p 3769 p0 S 0:00 -bash 3782 p0 R 0:00 ps PID – Process ID, identifierar varje process unikt. TTY – Vilken terminal som startat processen STAT – Aktuell status Sleep/Running >kill 3782

16 >top 10:15am up 305 days, 19:03, 3 users, load average: 0.02, 0.01, processes: 51 sleeping, 1 running, 0 zombie, 0 stopped CPU states: 1.3% user, 2.6% system, 0.0% nice, 96.1% idle Mem: 63152K av, 60436K used, 2716K free, 26216K shrd, 30336K buff Swap: 66492K av, 0K used, 66492K free 16852K cached top – ger systemets status kontinuerligt var 5:e sekund top (kommando)

17 Processer SB Bootsekvens: Kärnan hittar periferienheter (eg tgb, mm) Monterar root-filsystem Startar processen Init Init: Aktiverar swap Kontrollerar root-filsystemet Monterar root-fs Laddar eventuella moduler Kontrollerar övriga filsystem Monterar lokala filsystem Konfigurerar upp nätverket Monterar nätfilsystem Vanliga processer forkTar en kopia och kör den ExecKör waitVänta daemonProgram i bakgrunden (demon) shellDin ”prompt” (Du kan ha flera igång samtidigt, Multitasking) shell: ”Parent”-process läser kommando från terminal Skapar ”child”process mha fork child använder exec för att utföra kommandot parent använder wait och väntar på exit från child parent går tillbaka till läge 1

18 Andra Processer SB SYSLOGKärnan och många systemprogram skapar fel, varning och andra meddelanden. Syslog finns tillhanda för att ta emot och arkivera dessa meddelanden. CRON OCH AT program för att köra program periodiskt. –Cron – körs periodisk på en viss tidpunkt. –At – kör program en gång på en viss tid. >shutdown - ! Stäng av (>shutdown now) >logout eller >exit - loggar ut.

19 Windows systems/protocols (X Windows) regler för GUI Windows handlers (fvwm2, windowmaker) använder X-system/X-protocol Libraries (GNOME, KDE) program som körs i fönster GUI Graphical User Interface

20 Applikationer för Linux X-term – ”commandoprompt” flera samtidigt Text editor – Vi, Emacs, Pico(editor i pine) Pine – text/meny baserat Word – StarOffice/WordPerfect/ApplixWare Development – gcc/g++/gdb/gdd/Perl/Python/Java Webserver – Apache server – sendmail/imap Samba – Kommunikation med windowsvärlden + många fler

21 Samba SB smbd (the SMB daemon) nmbd (Provides NetBIOS nameserver support to clients) configuration file = /etc/smb.conf log file = /var/log/samba-log.%m lock directory = /var/lock/samba. (/usr/bin or /usr/local/samba/bin)smbstatus (Lists the current SMB connections for the local host)

22 WEBMIN SB Webmin is a web-based interface for system administration for Unix. Using any browser that supports tables and forms (and Java for the File Manager module), you can setup user accounts, Apache, DNS, file sharing and so on. Webmin consists of a simple web server, and a number of CGI programs which directly update system files like /etc/inetd.conf and /etc/passwd. The web server and all CGI programs are written in Perl version 5, and use no non-standard Perl modules. (WWW.webmin.com)WWW.webmin.com

23 Approaching LDAP Migration Approaching LDAP Migration By: Brian K. Jones Topics: LDAP, Administration LDAP is not your father's naming and directory service. Application vendors large and small, commercial and open source alike, have embraced LDAP as a centralized service for authentication and 'white pages' type information. These days, if you're not wearing a 'got root?' t-shirt and yelling at the suits to get LDAP, you're probably the suits wondering if LDAP is right for your environment. With features for security and integration far beyond that of other services, LDAP is probably something you should spend at least a bit of time discovering. Let's get started!Brian K. JonesLDAPAdministrationLDAP I've asked a number of friends (including consultants, administrators, and managers) about the idea of migrating to LDAP. Generally they get a look on their face like I just asked them to quit smoking or stop eating fast food. The look says, "I know it's probably the direction I should be going, but I dunno." Then they usually ask something like "Where do I start?" or "Will it work with (insert name of application or platform here)?". This, the first of a new series of weekly columns on Linux.com for system managers, offers a few things to consider before beginning the migration, and lays out some steps you can follow to get you moving. Why Move to LDAP? Let's start by taking a look at some of the reasons behind a migration to LDAP: Sun will discontinue NIS and NIS+ Sun reportedly will not bundle NIS server or client software in the next release of Solaris. NIS+ will stay around for another version, but even Sun's NIS+ clients have been advised that they should begin migrating, as NIS+ will also be going away sometime after the release of Solaris 10. If you're unfamiliar with NIS and NIS+, have a look here for a 5-minute crash course, or see the Sun docs on NIS and NIS+.hereSun docs on NISNIS+ It probably comes as no surprise that what Sun is recommending as an alternative to these solutions is their own SunONE Directory software (formerly iPlanet Directory server), which is conveniently bundled with Solaris 9. Some of the reasons Sun recommends LDAP are the same reasons I'll discuss here.

24 servers.linux.com/article.pl?sid=04/02/03/ Security I don't like to expound upon things about which I have little knowledge, so my security comparison will be NIS-specific -- though the facts I give you about LDAP should be readily available for comparison with whatever naming or directory system you currently use. Due to the fact that LDAP is not a database, but rather a standardized protocol for accessing your directory's data, LDAP makes a fitting gatekeeper for your environment's information. There are clear and visible lines between the implementation of the protocol and the implementation of the data storage mechanism. (The two parts can be configured separately.) As such, the data storage mechanism can concentrate on storing data, while the access protocol can be configured to secure it. LDAP is designed for very granular security. This is at least partially attributable to LDAP's data model, which looks similar to an object/attribute hierarchy rather than a flat file full of strings. For example, the fields of a user entry stored on a Linux box in /etc/passwd as a single string would be quite different in LDAP, which identifies a user as a single object in the directory, and all of the other /etc/passwd fields (login shell,home directory, GECOS, etc.) become attributes of that object. This means you can restrict access at the attribute level -- the equivalent of being able to restrict access to individual fields in any given NIS map. Furthermore, access can be configured using access control lists (ACLs) that restrict not only which pieces of data can be accessed, but the operations that can be performed on the data. For example, you may allow anybody to read the list of user names on a system, but not allow them to read the encrypted password string for individual users. And while a user can certainly be granted read access to all of the data pertinent to himself or herself, you may decide to standardize things like the GECOS (optional information about the user) field, and deny write access to it, reserving that right only for administrators.

25 servers.linux.com/article.pl?sid=04/02/03/ Integration I don't think the powers-that-be would be silly enough to try to push administrators toward a NIS/NIS+ replacements that won't give them at least the same level of integration as these two services. Over the years, naming and directory services tend to become dependencies for most applications in the environment in which they're working. Although there are still a few areas where LDAP support is not where it should be, for many environments LDAP works with everything NIS does, and then some. A couple of quick examples: Apache can use LDAP to perform authentication. Sendmail can use LDAP for authentication, mail routing information,and alias lookups. Samba can use LDAP as a backend authentication mechanism. Autofs can retrieve automounter maps from LDAP. FreeRADIUS can authenticate against LDAP Wow! And these examples are just the tip of the iceberg. In addition to system services, many companies use LDAP as a corporate "white pages" solution, because so many and calendar applications are LDAP-compatible. Netscape, Mozilla, Evolution, Outlook, KMail, and many more clients have robust support for LDAP, and even text-based clients like Mutt and Pine can do address completion based on an LDAP search.

26 >chmod 777 minutes txt >chown root minutes txt >chgrp othergroup minutes txt >ls –l -rwxrwxrwx 1 root othergroup 562 Jun 20 09:09 minutes txt d r w x r w x r w x File type ”-” means file d means directory User u Group g Others o Rights i UNIX >chmod g+w minutes txt >ls -l -rw-rw-r-- 1 john employees 562 Jun 20 09:09 minutes txt r - Read w - Write x - Execute >chmod 664 minutes txt >ls -l -rw-rw-r-- 1 john employees 562 Jun 20 09:09 minutes txt chown  Ändra user chgrp  Ändra grupp chmod  Ändra rättigheter 10 Byte Sätter rättigheter för ugo! för ugo, +/- lägger till/tar bort rättigheter(rwx)


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