Working with the Unix OS

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Unix Administration fi done echo $status Compression tar cf dirname.tar dirname; compress dirname.tar (tar cf- dirname ) | compress > dirname.tar.Z tar xvi dirname.tar uncompress dirname.tar cat dirname.tar.Z | uncompress | tar xvfzcat dirname.tar.Z | tar tf - Networks NFS or RFS Network File System or other TCP/IP Services TCP Transmission Control Protocol Transport - data packaging IP Internet Protocol Network Layer - routing Ethernet Link Layer - Ethernet Address Physical Hardware Distributed Filesystems NFS and RFS provide facilities for distributed filesystems. This means that users can have a host on their desk but still access shared disks Backups and software updates can be more reliably administered in one place. Super User permissions do NOT work across remote mounted filesystems - prevents broke security propagating over the network. Electronic Mail (E-mail) Mail is spooled in a queue area and then if necessary sent to other hosts. Communications with these hosts may be either immediate (for close neighbors) or until some regular time specified in /etc/crontab. To: fred@water.fit.qut.edu.au Subject: I need help ... sendmail.cf - is the configuration file for BSD elm & pine - are agents that create and queue requests in /usr/mail or /usr/spool/mail News - (available via VAX/VMS locally) - Keep up to date with industry as it happens - Ask your problem to THE experts world wide - Heaps of free software - Public domain Unix news readers: "tin" Network Domains Used throughout the Internet: fred@water.fit.qut.edu.au Australian domain Education sub-domain QUT sub-domain Faculty sub-domain Host "water" User name Domains & sub-domains are used to prevent naming conflicts with other domains. So we can invent our own host names without worrying about host names at other sites. Things to Remember Don't be superuser more than necessary. Always re-read what you type when using commands like: 197
Unix Administration rm -rf /tmp/ *, a typo could involve several hours Optimizing Performance ! Rebuilding the filesystem Over time, files on the system become fragmented and spread their data over distant parts of the filesystem. To optimize system performance, the system should ideally be copied onto tape and rebuilt from scratch to enhance performance. The drives should also be reformatted to enhance reliability. (Only if you know what you're doing!!) ! Super User - login as "root" - "su" - preferred ! AT&T System V sar - system activity reporter (-a all) crash ! BSD iostat uptime vrnstat pstat - number of chars (kbytes) read, written to term, disk, and cpu time as user mode, niced, in-system mode, idle mode. - display time, system up time, number of users, number of jobs - virtual memory statistics - procs, memory, page, faults, cpu - process statistics ! Tunable Parameters NBUF - number of system buffers 250 (3 x number of ttys) NHBUF - number of hash buffers 64 NPROC - number of process table entries/slots 250 MAXUP - number of process a user can have 20 MAXPROC - maximum number of system processes NCLIST - character minibuffers are called clists. TEXT NSWAP FILES MOUNTS CALLS - number of slots in text table - swap device should be at least size of memory - each process has 3: stdin, stdout and stderr - size of mount table - callout table - so that UNIX can operate in as close to real time as possible for applications Accounting Unix provides facilities for monitoring system performance, network traffic etc. The administrator may need to tune the system by reorganising filesystems or network links. utmp & wtmp - used by accounting struct utmp { char ut_user[8]; /* user login name */ char ut_id[4]; /* /etc/line id */ char ut_line[12]; /* device name (console) */ short ut-pid; /* process id */ short ut_type; /* type of entry */ struct exit_status { short e_terrnrnination; /* process termination status */ short e_exit; /* process exit status */ } ut_exit; time_t ut_time /* time entry was made*/ } od -c /etc/utmp | more 198
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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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Processes II /* client loop */ mesg
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I/O Subsystem Drivers frequently sl
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Page 157 and 158: Interprocess Communication } { ptra
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Page 167 and 168: Interprocess Communication ! Compar
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Page 173 and 174: Process Scheduling Page Tables and
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Page 178 and 179: Process Scheduling Clock - restart
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Page 182 and 183: Figure 62. Sequence of Swapping Ope
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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
Page 196 and 197: Unix Administration Load /Unix kern
Page 198 and 199: Unix Administration for (i=0; i&i d
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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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Working with the Unix OS

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