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Unix/Linux

Unix/Linux. Contents. Unix file system introduction Unix Common commands useful tips sharing snoop tool / tcpdump Set env. variables trouble shooting/diagnose (solaris) Diff b/w Linux and unix. Unix system structure. / (root). lib. tmp. bin. var. dev. lib. usr. root. boot.

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Unix/Linux

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  1. Unix/Linux

  2. Contents • Unix file system introduction • Unix Common commands • useful tips sharing • snoop tool / tcpdump • Set env. variables • trouble shooting/diagnose (solaris) • Diff b/w Linux and unix

  3. Unix system structure

  4. / (root) lib tmp bin var dev lib usr root boot src etc scott lib alice n321 man mail bin sbin local bin sbin bob home public_html share UNIX File system Hierarchy

  5. Unix common commands • Files commands grep,find,tail,ln,diff,tar/gzip,chmod,chown • System commands df,du,ifconfig,netstat,route,mount/umount,swap • Process commands ps,top,kill,bg,nohup,crontab

  6. grep/egrep/fgrep–display lines that match • grep [options] regexp [files...] e.g. grep '^\.' myfile.txt grep –i “exception” */* find . |xargs grep -i “exception" # ls –al|grep ‘^d’ # List the directory in currect path: • fgrep --It does not use regular expressions; instead, it does direct string comparison to find matching lines of text in the input. • egrep --Search a file for a pattern using full regular expressions

  7. find--find files matching a type or pattern • find directory [options] [actions] [...] • e.g. • find . -name hello -print # • find . –mtime +7 –print # list the files modified 7days ago • find . –size +2000m –print #list the files larger than 2000m • find /tmp –user b123 –print#print the files belong to b123 user under tmp. • find . -name "*.php" –exec/ok rm {} \;# find and remove this php files or find . –name “*.php” |xargs rm

  8. tail/ln/diff • tail --display the last few lines (or parts) of a file. tail [options] file e.g tail –f filename #display last 10 lines tail –5f filename # display last 5 lines • ln--link the source_file to the target ln [options] source target • diff --compare the two files and display the differences (text files only) diff file1 file2

  9. File Archiving, Compression--- Tar/gzip/gunzip • tar [options] [directory file] gzip [options] file gunzip[options] file • Extract from an archive gunzip backup.tar.gz or tar -xvf backup.tar • Create an archive: tar -cvf backup.tar /etc #backup.tar gzip -q backup.tar #backup.tar.zip • tar –tf backup.tar #list the files in archive

  10. File Permissions

  11. chmod/chown/chgrp • chmod --- change file permissions chmod nnn [argument list] numeric mode chmod [who]op[perm] [argument list] symbolic mode chmod u+xrw file chmod g+x file chmod o-rw file chmod 750 file • chown change the ownership of a file chown[options] user[:group] file • chgrp change the group of the file

  12. df,du • df --summarize disk block and file usage df [options] [resource] Common Options -l local file systems only -k report in kilobytes • du report disk space in use du [options] [directory or file]

  13. ps,top,kill, nohup • ps --Show status of active processes ps –ef|grep ems • Kill --terminate a process kill [-signal] processID kill –l #displays the available kill signals kill -9 processID #kill the processId of process • Top/topas/prstat --display all running processes • nohup --Runs a command even if the session is disconnected or the user logs out nohup find -name '*' -size +1000k > log.txt

  14. crontab • Crontab -- List of files that you want to run on a regular schedule. crontab –l ; crontab -e • All crontab files are maintained in the /var/spool/cron/crontabs in solaris. • These first five fields are separated by spaces and indicate when the command will be executed. 10,20 3 * * 0 /usr/sbin/log/adm

  15. ifconfig--allows the operating system to setup network interfaces and allow the user to view information about the configured network interfaces • ifconfig eth0 # View the network settings on the first Ethernet adapter installed in the computer. • ifconfig –a #display into on all network interfaces on server, active or inactive. • ifconfig eth0 down #If eth0 exists would take it down causing it cannot send or receive any information. • ifconfig eth0 up #If eth0 exists and in the down state would return it back to the up state allowing to to send and receive information. • ifconfig eth0 192.168.1.102 netmask 255.255.255.0 broadcast 192.168.1.255 #Assign eth0 with the above values for IP, netmask and broadcast address.

  16. netstat -- Shows network status. • netstat #Displays generic net statistics of the host you are currently connected to. • netstat –an #Shows all connections to the server including the source and destination ips and ports if you have proper permissions. • netstat –rn #Displays routing table for all ips bound to the server. • netstat -an |grep :80 |wc –l #Display the amount of active connections on port 80. Removing the pipe and wc command would display each connection. • netstat –natp #Display active Internet connections.

  17. route -- Show / manipulate the IP routing table • route –n #Shows routing table for all IPs bound to the server. (linux) • route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0 #adds a route to the network 192.56.76.x via "eth0". The Class C netmask modifier is not really necessary here because 192.* is a Class C IP address. The word "dev" can be omitted here. • route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0 #This is an obscure one documented so people know how to do it. This sets all of the class D (multicast) IP routes to go via eth0". This is the correct normal configuration line with a multicasting kernel.

  18. mount/umount,swap • Mount --- mount a partition mount -F hsfs -o ro /dev/dsk/c0t6d0s0 /cdrom mount -F pcfs /dev/diskette0 /floppy mount /dev/dsk/c0t0d0s0 /tmp/xxx • umount -- Unmount a partition umount /cdrom • swap mkfile 10G /home/swapfile /usr/sbin/swap -a /home/swapfile /usr/sbin/swap –l /usr/sbin/swap –d /home/swapfile rm -rf /home/swapfile

  19. Redirection <, >, >>,|,; • Pipe | :The output of the first command is sent as the input to the second command, and so on, who | more • ; Grouping commands %pwd; cal 1 2000; date • >> append the results of the command to the existing file. • > The results of the command will be sent to the specified file

  20. Set env. variables • .profile /etc/profile /root/.bash_profile /home/abc/.bash_profile • Commands set –local variable env –global variable • add variables to .profile MOT_NSM_HOME=/opt/EMS export MOT_NSM_HOME • Re-logon, the variable will take effect.

  21. Other useful commands tips • converts Unix text file line to Dos unix2dos : sed –e ‘s/$/\r/’ file1 > file2 dos2unix : sed –e ‘s/.$//’ file1 > file2 • How to remove ^M in the file • # cat test.dat | tr -d '\015' > test.out • or #dos2unix test.dat test.out • watch –n N command(linux) # • init 0 ～6 • init 0 shutdown server • init 6 restart server • vi filename1 filename2 … :n #edit next file :e# # edit prev file :1,$s/ABC/abc/g #abc to replace ABC in file

  22. Snoop(solaris) –xcapturing and Inspecting Network Packets • to see what happens when one system uses the ping command to communicate with another system. • %snoop sys41 sys42 sys41 -> sys42 ICMP Echo request sys42 -> sys41 ICMP Echo reply • Use the -a option to enable audible clicks, which notify you of any network traffic. %snoop -a dhcp • shows how to turn on audible clicks for all network traffic related to a Dynamic Host Configuration Protocol (DHCP) boot.

  23. Touble shooting/diagnose (1) • 1.  How to setup solaris network. We usually meet the following problem 1.1 how to config the IP,gateway, router,netmask, both dynamicly and staticly? Please add a file named S* in /etc/rc2.d/,such as S99router The content of this file is a command to exec 1.2 how to add multi virtual IP to a single interface? • #ifconfig bge0:100 plumb • #ifconfig bge0:100 11.14.33.100 netmask 255.255.255.0 up • #ifconfig bge0:100 unplumb 1.3 how to disable certain network interface for test? • ifconfig eth0 down

  24. Touble shooting/diagnose (2) • 2. root user can't telnet on a remote client. Edit /etc/default/login and comment out “CONSOLE=/dev/console” • 3. root user can't ftp on a remote client Edit /etc/ftpd/ftpusers and comment out “root” • 4. how to monitor the performance of the Solaris/Linux, including MEM,CPU,disk I/O, network I/O

  25. Touble shooting/diagnose (3) • 5. Certain Solaris command cannot be used     1) Check disk space to confirm whether there is the capacity of any filesystem is 100% #df –h     2) Check the permission of some important directories. The directories must exist and have “x” permission./usr, /etc/ssh, /bin, /usr/bin • 6. forget the root passwd #boot cdrom -s #mount /dev/dsk/c0t0d0s0 /mnt #cd /mnt/etc #vi shadow #umount /mnt 

  26. Touble shooting/diagnose (4) • 7. If we meet system issues, such as the whole system can't boot. how to sovle? and how to collect the important saloris info(explorer) • 8. Why some user can't excute command cron and at to schedule a task? • 9. what's the difference between halt/reboot/shutdown/init #(# refers to a run level). what's the right step to reboot a system?

  27. Touble shooting/diagnose (5) • 10. how to kill a service in solaris 10? (SMF related) Please use “svcs disable “, not the “kill -9” • 11. how to delete temp file effectively? the following two commands are useful for programmers to delete certain files     #find $HOME/. -name *.txt -ok rm {} \      #find . \( -name a.out -o -name '*.o' -o -name 'core' \) -exec rm {} \ • 12. what's the difference between the two command "#./set_env" and "#. ./set_env"? • The parent shell can get the env set by the child shell

  28. Touble shooting/diagnose (6) • 13. Nov 20 15:25:04 unix /usr/lib/snmp/snmpdx: [ID 702911 daemon.error] unable to get my IP address: gethostbyname(unix) failed [h_errno: host not found(1)] • Please add the hostname to hosts file • #nodename unix • #vi /etc/hosts127.0.0.1       localhost       unix    loghost • 14. Nov 20 15:36:32 unix ip: [ID 482227 kern.notice] ip_arp_done: init failed • Don’t use the interface name as the hostname

  29. Touble shooting/diagnose (7) • 15. Nov 20 15:37:21 unix sendmail[318]: [ID 702911 mail.crit] My unqualified host name (localhost) unknown; sleeping for retry • You should edit /etc/hosts like this, please note the FQDN and loghost 192.168.224.251 outer   outer.c204.comloghost • svcs disable /network/smtp:sendmail

  30. Touble shooting/diagnose (8) • 16. When use “crontab -e” to add a cronjob, we can’t see the content of the cron table #EDITOR=vi #export EDITOR • 17. When connect via console, and edit a file with vi, we can only see part of the file $ TERM=VT100 $ export TERM

  31. Diff b/w linux and unix • Linux –free and open source, just kernel, based on UNIX standards, runs on many hardware platforms. • Unix --compete operating system, commercial application (if you wanted to buy one) typically costs much more for a commercial UNIX , a typical UNIX is proprietary-hardware-bonded.

  32. System Configuration and System Storage

  33. The Linux Proc File System • The proc file system does not store data, rather, its contents are computed on demand according to user file I/O requests • Proc is organized in virtual directories and subdirectories, provide hardware information, such as /proc/cpuinfo, /proc/meminfo, and /proc/interrupts. The files under /proc/sys are related to kernel configuration parameters. • The /proc special directory provides full detailed information about the inner workings of Linux and lets you fine-tune many aspects of its configuration. If you spend some time learning all the possibilities of this directory, you'll be able to get a more perfect Linux box.

  34. Lunix file system architeture

  35. Linux versions/study website • Redhat http://www.redhat.com • Fedora (cover many features of windows) http://fedora.redhat.com • 红旗LINUX (China) htt://www.redflag-linux.com • SUSE Linux http://www.opensuse.org • Mandrake Linux http://www.mandriva.com

  36. Thank you

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