Working with the Unix OS

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Unix Administration 14. UNIX ADMINISTRATION Administration Topics 1. Day-to-Day Tasks 2. File System 3. Backup 4. Startup & Shutdown 5. Cron 6. Printing 7. Networks 8. Mail 9. News A. Accounting B. Performance tuning C. Epilogue Systems Administrator tasks - install & maintain system - install & maintain applications - upgrade software & hardware - monitor hardware operation & performance - support & maintain system software - create new system software - manage file system - monitor system security - backup system data for users - put users on the system solve user problems - establish user groups - educate users - educate operations staff for management - interact with management - state of the system reports advise on technical aspects for network (upto 50% of time) - maintain all network files - caring for network daemons domain name servers - file servers - printer servers - mail servers - monitoring network security Also make all machines run whatever version of UNIX AT&T, BSD, XENIX ===> Standards, POSIX, SVID Day-to-day Administration Between meetings and user interrupts - First tasks of the day: - test local network loading - check life of file servers - check file systems (block & inode limits) - read "root's" mail for error messages - status of system daemons - look for large user files - process console log and restart Critical file systems / # check disk space /usr # contains accounting /usr/spool, /var/spool # log files, prints, etc 187
Unix Administration /tmp, /var/tmp, /usr/tmp # scratch pads fill up fast /usr/spool/console, /usr/adm/messages, ... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ UBUNTU: /usr/spool/ does not exist /usr/adm/ is /var/log/messages ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Other tasks: # cleanup ( find / -type f $ -name core -o -name a.out \ -o name dead.letter $ -atime +1 -exec rm -f {} \; find /usr/spool/console -type f -mtime +7 -exec rm -f {} \; find /usr/preserve -type f -mtime +15 -exec rm -f {} \; find /usr/mail -type -f -atime +28 -exec rm -f {} \; ) > /dev/console 2>&1 ! Performance Watch - buffer cache hit ratios - buffer cache write-behind ratio - kernel time versus user time - page wait - page rate - fullness of process table - fullness of file table - fullness of inode table - fullness of clists ! User Administration - making user directories - creating password and group entries - getting disk space - taking care of all login functions - handling group permissions - changing ownerships and permissions - moving users and user files - updating YP data base source file User password administration on multiple machines without YP requires the creation of a user-ID data base. User-ID from 0 to 100 are reserved for non-humans, User-ID from 101 to 999 are system staff ! Identity Files – not enough info in passwd, group - log name - user ID number - real name - group - group ID number - phone number - location - department number - misc File Systems Disks are split into partitions A partition is then mounted as a subtree of the Unix directory structure Example Configuration Drive 0 Drive 1 / root partition / 2n d root partition /tmp temporary files /usr system libraries swap space /home user directories - root partitions are small and near the outer edge of the drive to reduce risk of failure - 2nd root partition to fix things if drive 0 fails (Harder without swap space) - Essentials are kept on one drive (drive 0) - /tmp can fill up and not interfere with / - /tmp on different drive to user files to reduce disk head seeking when creating temporary files from user files 188
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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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Page 157 and 158: Interprocess Communication } { ptra
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Page 173 and 174: Process Scheduling Page Tables and
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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
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Page 206 and 207: Unix Security $ crypt < exam320.Z >
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Page 210 and 211: Unix Security system(cmdstr); $ ech
Page 212: Unix Security - repairs damaged use
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