Working with the Unix OS

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Unix Administration Load /Unix kernel - swapper (process 0) - init (process 1) Set date - date mmddhhmm[yy] - TZ=EST10 Go into single user - init s Check filesystems - fsck /dev/root Go into multi-user - init 2 Boot ROM passes control over to the UNIX kernel - find the root file system - start the init process then go to run-level 2, i.e. multi-user The init process has ID = 1, has no parent. It reads the /etc/inittab configuration file. Look at the /etc/inittab file on "water". id:runstate:action:process where "action" is either: - initdefault - set default run-level - boot - bootwait - wait - respawn - when process dies run it again - process - off Run-level 2 entries include /etc/rc initialization script and letc/getty for each terminal line. /etc/rc - speed up startup - check filesystem - start system accounting - start daemons - recover files after crash - start printer spooler System Shutdown Shutdown vs Reboot - users logged on - how quickly need system down shutdown uses kill -14 on processes reboot uses kill –9 on processes sync writes memory out to disk File System Consistency Only use "fsck -y" on the root partition. Phase: 1. Checks Blocks and Sizes i.e. checks inode types, examines the inode block numbers for bad or duplicate blocks, and checks the inode format. 2. Checks Pathnames Removes directory entries pointing to files or directories modified by Phase 1. 3. Checks Connectivity Cleans up after Phase 2 - making sure that there is at least one directory entry for each inode and that multiple links make sense. 4. Checks Reference Counts List errors from unreferenced files, missing or full "lost+found" directories, incorrect link count, bad or duplicate blocks, or incorrect sum for free inode count. 5. Checks Free List 193
Unix Administration Compares free block count with free block list. 6. Salvage Free List Only if Phase 5 error. If any errors occur for root file system then **** BOOT UNIX (NO SYNC) **** i.e. do a cold start by pressing restart button. ncheck -i inode_number /dev/dsk/2s6 There should be a "lost+found" directory for each mounted file system. mklost+found - creates a "slotted directory" : if [ $# -lt 1 ]; then echo "usage: mklf /path/dirname" exit 1 fi if [ -d $1 ] ; then N_SLOTS=254 cd $1 mkdir lost+found cd lost+found i=0 while [ 'expr $i' do -le $N_SLOTS ] do >$i # create $i rm $i i='expr $i + 1' done else echo "$(1) is not a legitimate directory" exit 1 fi /* mklf.c - makes lost+found */ #include #include #include #include main(int argc, char *argv[]){ int i, fd; char f_name[128]; if (argc != 3 ){ fprintf(stderr,"usage: mklf /path/dirname /dev/special\n"); exit(1); } if ((mknod (argv[1], S_IFDIR|0700, argv[2])) == -1) { fprintf(stderr, "mklf: can't make directory %s\n", argv[1]); exit(2); } for (i=0; i
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UNIVERSITY OF ATHENS DEPARTMENT OF
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Figure 27. Driver Entry Points.....
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Introduction to Unix ! Execution ma
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Introduction to Unix It works in th
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Introduction to Unix * matches 0 or
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Introduction to Unix vi file-name s
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Introduction to Unix 1,$s/^/>>/ 1,$
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Introduction to Unix ! Special Devi
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Introduction to Unix Working with F
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Introduction to Unix ! Communicatio
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Unix Shells 2. UNIX SHELLS Back Quo
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Unix Shells ! CASE Statement case t
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Unix Shells two lines !Y@Y@Z@Z@ZY c
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Unix Shells if $append then tee -a
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C Programming - Basics main() { int
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C Programming - Basics e.g. i += 2
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External Variables A C program cons
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C Programming - Basics main.c #incl
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C Programming - Basics default: pri
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C Programming - Basics struct tnode
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Unix Tools 4. UNIX TOOLS Tools of t
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Unix Tools Korn shell ! .profile HI
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Unix Tools grep "$name" $PHONEBOOK
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Unix Tools awk '$3 > 0 { print $1,
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Unix Tools END { print max, maxline
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Unix Tools Let an example input fil
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Unix Tools Brown eqn 1 # output Jon
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Development Tools Make looks at the
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Development Tools /* compute size o
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Development Tools #endif #line cons
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Development Tools 1.1 5 lines Retri
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Development Tools In Emacs, you may
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Development Tools */ %{ #define YYS
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C Libraries 6. C LIBRARIES Input an
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C Libraries } while (!feof(fp1)) pu
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C Libraries } free(p); /* what is w
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C Libraries } if ((fp->flag&( _READ
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C Libraries /* dirwalk: apply fcn t
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C Libraries } switch (pid=fork()){
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C Libraries What is curses? - libra
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C Libraries } if ((fd=fopen(argv[1]
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Introduction to kernel 7. INTRODUCT
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82 Introduction to kernel Programs
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Introduction to kernel } { printf("
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Introduction to kernel The kernel r
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Introduction to kernel UNIX Interna
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Introduction to kernel File System
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Introduction to kernel Every proces
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Processes I Process States 1. Execu
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Processes I } printf("%d %s\n", cnt
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Processes I dup (and other similar
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Processes I The u area contains - p
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Processes I The Context of a Proces
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Processes I Process Control use and
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Processes I Although the processes
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Processes I Handling Signals - proc
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Processes I USER=neville PATH=/user
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Processes I ! Shadow Password /etc/
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struct timeval { long tv_sec; /* se
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Processes I F_SETFL set status flag
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Processes I process is the child pr
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Processes I Rules about sharing of
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Processes II 9. PROCESSES (II) FORK
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Processes II /* background.c */ #in
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Processes II } while (1){ printf("p
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Processes II } /* child */ signal (
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Processes II int readline(int fd, c
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Processes II { } char process_name[
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Processes II - Pipe in a single pro
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Processes II System V IPC - message
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Processes II int msgctl(int msqid,
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Processes II For every semop operat
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Page 157 and 158: Interprocess Communication } { ptra
Page 159 and 160: Interprocess Communication T ID KEY
Page 161 and 162: Interprocess Communication }; int m
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Page 167 and 168: Interprocess Communication ! Compar
Page 169 and 170: … connect(sockfd,(struct sockaddr
Page 171 and 172: Interprocess Communication Address
Page 173 and 174: Process Scheduling Page Tables and
Page 176 and 177: Figure 49. Tie breaker rule Process
Page 178 and 179: Process Scheduling Clock - restart
Page 180 and 181: Process Scheduling Figure 57. Mappi
Page 182 and 183: Figure 62. Sequence of Swapping Ope
Page 184 and 185: Buffer Cache The kernel takes buffe
Page 186 and 187: Buffer Cache The kernel places the
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Page 190 and 191: Unix Administration 14. UNIX ADMINI
Page 192 and 193: Unix Administration Example output
Page 194 and 195: Unix Administration *) IN=-mtime -2
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Page 200 and 201: Unix Administration fi done echo $s
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Page 204 and 205: Unix Security Example: group name:g
Page 206 and 207: Unix Security $ crypt < exam320.Z >
Page 208 and 209: Unix Security - exported filesystem
Page 210 and 211: Unix Security system(cmdstr); $ ech
Page 212: Unix Security - repairs damaged use
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