Linux Common Command

Linux Commands & Tools

v1.3

j3ffyang at gmail

Environment Setting

BaSH, Bourne Again SHell (Linux default), vs. Korn Shell (on AIX)

Current envenv

System wide/ global/etc/bashrc -> aliases and functions (read always, login-shell and non-login-shell)/etc/profile -> env (read when login- shell)

User base~/.bashrc (/etc/bashrc read first, then ~/.bashrc)~/.profile

/etc/skel -> system level files copied to /home/user when created

Environment Setting

Objective: Run WAS_installdir/bin/setupCmdLine.sh correctly

Solution:#!/bin/sh (symlinked to /bin/bash)source /file (run in current shell). file.sh (same as above)./file.sh (run in child shell process)

pstree

Hardware Specification

Objective: How fast is CPU? How big is RAM? SWAP size?

Solution:cat /proc/cpuinfocat /proc/meminfocat /proc/swaps

System Specification

Objective: How to partition harddisk before installing WebSphere Commerce?

Solution:/boot 100MB/ 10GSWAP =<2 x RAM (usually 1~ 1.2G if RAM=1G)

http://www.redhat.com/docs/manuals/enterprise/RHEL­4­Manual/pdf/rhel­ig­x8664­multi­en.pdf­> page 28

Kernel - Messaging

Objective: Optimize kernel for DB2.

Solution:Display kernel parameteripcs ­l

Display kernel parameterEditing /etc/sysctl.conf

kernel.msgmni = 512kernel.sem=250  128000  32 1024

Activating kernel parameterssysctl ­p

http://www­106.ibm.com/developerworks/linux/library/l­ss3­db2/

System Management

Objective: Want to how the file system being used?

Solution:du -cks $(ls -l | grep '^d' | awk '{print $9}') | sort -nrdu -ksh

System Startup

Objective: Switch between X startup and command line startup.Change the runlevel.

Solution:cat /etc/inittab | grep “id”

System Mgmt - fuser

Objective: Which process holds up the file?

Solution:fuserpid

[root@sevenj root]# fuser /var/log/messages/var/log/messages: 3292

User[root@sevenj root]# fuser -u /var/log/messages/var/log/messages: 3292(root)

Terminate the processes that using filefuser -kimuv /path/filefuser -kxuc /path/file (on AIX)

Port[root@sevenj root]# fuser 22/tcp22/tcp: 3470

System Mgmt - lsof

Objective: Which program is running over a port?

Solution:lsof – LiSt Open File

Which application is using port 22?lsof -i:22[root@summerpalace /]# lsof -i:22COMMAND PID USER FD TYPE DEVICE SIZE NODE NAMEsshd 3803 root 3u IPv4 3387 TCP *:ssh(LISTEN)sshd 30328 root 4u IPv4 2616339 TCP summerpalace.torolab.ibm.com:ssh->9.26.190.11:33875 (ESTABLISHED)

System Mgmt – lsof (cont'd)

What files are opened by PID?

[root@summerpalace /]# lsof -p 3803COMMAND PID USER FD TYPE DEVICE SIZE NODE NAMEsshd 3803 root cwd DIR 3,2 4096 2 /sshd 3803 root rtd DIR 3,2 4096 2 /sshd 3803 root txt REG 3,2 280184 551800 /usr/sbin/sshdsshd 3803 root mem REG 3,2 51924 535486 /lib/libnss_files-2.3.2.sosshd 3803 root mem REG 3,2 1563240 1054615 /lib/tls/libc-2.3.2.sosshd 3803 root mem REG 3,2 5572 292096 /usr/kerberos/lib/libcom_err.so.3.0sshd 3803 root mem REG 3,2 63880 292106 /usr/kerberos/lib/libk5crypto.so.3.0sshd 3803 root mem REG 3,2 385220 292116 /usr/kerberos/lib/libkrb5.so.3.1sshd 3803 root mem REG 3,2 971612 535528 /lib/libcrypto.so.0.9.7asshd 3803 root mem REG 3,2 91368 535470 /lib/libnsl-2.3.2.sosshd 3803 root mem REG 3,2 52584 1216870 /usr/lib/libz.so.1.1.4sshd 3803 root mem REG 3,2 12564 535504 /lib/libutil-2.3.2.sosshd 3803 root mem REG 3,2 76468 535498 /lib/libresolv-2.3.2.sosshd 3803 root mem REG 3,2 14728 535466 /lib/libdl-2.3.2.sosshd 3803 root mem REG 3,2 30448 535533 /lib/libpam.so.0.75sshd 3803 root mem REG 3,2 28452 1216947 /usr/lib/libwrap.so.0.7.6sshd 3803 root mem REG 3,2 106532 535453 /lib/ld-2.3.2.sosshd 3803 root 0u CHR 1,3 66540 /dev/nullsshd 3803 root 1u CHR 1,3 66540 /dev/nullsshd 3803 root 2u CHR 1,3 66540 /dev/nullsshd 3803 root 3u IPv4 3387 TCP *:ssh (LISTEN)

System Mgmt – lsof (cont'd)

What application is holding a dir and files under that dir?

[root@summerpalace /]# lsof +d /var/logCOMMAND PID USER FD TYPE DEVICE SIZE NODE NAMEsyslogd 3676 root 2w REG 3,2 1393576 780963 /var/log/messagessyslogd 3676 root 3w REG 3,2 925 780964 /var/log/securesyslogd 3676 root 4w REG 3,2 430 781130 /var/log/maillogsyslogd 3676 root 5w REG 3,2 10246 781139 /var/log/cronsyslogd 3676 root 6w REG 3,2 0 781134 /var/log/spoolersyslogd 3676 root 7w REG 3,2 0 781138 /var/log/boot.log

System Mgmt – SWAP

Objective: Want to change SWAP size?

Solution:

mkswap /dev/hdaXsyncswapon /dev/hdaX

cat /proc/swaps

System Mgmt – mkfs

Objective: Create a file system?

Solution:

fdisk -lfdisk /dev/hda

mkfs -t ext3 /dev/hdaXmkfs /dev/hdaXtune2fs -j /dev/hdaX (Convert ext2 to ext3. Journaled.)

mount /dev/hdaX /mount/point

Edit /etc/fstab/dev/hdaX /mount/point ext3 defaults 1 2

File - compression

Objective: Compress/ Uncompress? The archive formats?

Solution:Compresszip *.zipjar *.jar (same as zip)tar -czvf *.tar.gzbzip2 *.bz2gzip *.gz / *.Zrar (http://www.rarlab.com/)

Uncompressunzipjar -xvftar -xzvfbunzip2gunzip

File - editor

Objective: Edit the file?

Solution:vikate (Similar to UltraEdit. Install kdebase*.rpm)jedit (http://jedit.org)emacsed

Network

Objective: Get the DHCP IP+ Register hostname in DNSSolution:

/etc/sysconfig/networkdhclient ethX /dhclient.conf (man dhclient.conf -> sample)

YaST or YaST2 (Yet another Setup Tools)/etc/hosts

Edit /etc/sysconfig/network-scripts/ifcfg-ethXAdd DHCP_HOSTNAME=<your_hostname>

Verification:hostname -s / -dnslookup / host / dig

Network - netstat

Objective: Network status.

Solution: TCP/IPnetstat -pant

netstat -pat

Network – http/ftp

Objective: Run ftp client in command line?

Solution:

wget -t3 -c -r -l 10 http://domain.org

-t= retry, -c= continue, -r= recursive, -l= depth (level of subdirectories)

Performance - Process

Objective: The running processes' status?

Solution: How much the CPU usage?ps auxwww | sort +2 -rps -ef | sort +3 -r | head -n 5

How much the MEM usage?ps auxwww | sort +3 -r

The process tree.pstree

Performance – Manage Srvc

Objective: Turn on / off the unnecessary services.

Solution: List all available services.chkconfig --listchkconfig –-list | grep 3:on

Check on / out services. eg.chkconfig iptables on | offchkconfig –level 2345 iptables on

less /etc/init.d/iptablesls /etc/rc.d/rc3.d

Stop a service. eg./etc/init.d/sshd start | stop

Performance - Memory

Objective: System memory usuage.Solution:

vmstat <interval> <length>eg.

vmstat 1 10

[root@summerpalace root]# vmstat 1 10procs memory swap io system cpu r b swpd free buff cache si so bi bo in cs us sy id wa 1 0 0 146512 107140 616064 0 0 4 17 105 30 0 0 99 0 0 0 0 146428 107140 616064 0 0 0 148 130 76 0 4 96 0

r: The number of processes waiting for run time.si / so: Swap in/ outbi / bo: Blocks in/ outus: User timesy: System timeid: Idle

Reference: What's block and character device?http://www.uwsg.iu.edu/usail/concepts/filesystems/everything­is­a­file.html

Performance - top

Objective: Overall system performance.

Solution:

top

s – interval in secondM – sort by memoryP – sort by CPU

RPM

Objective: Manage the packages

Solutions: RPM = RedHat Package Manager. Used by RedHat, SuSE and Mandrake. Debian dpkg converter is available.

Install / Updaterpm -Uvh package.rpm (vs. -ivh)rpm -Uvh package.rpm --nodepsrpm -Uvh –-aid package.rpm (require rpmdb-*.rpm installed)

Uninstallrpm -e package_namerpm -e –-allmatches package (man rpm, search allmatches)

RPM DB Rebuilddb_verify /var/lib/rpm/Packagesrpmdb --rebuilddb

RPM (cont'd)

Solutions:

Find an RPMrpm -qa | grep -i package_name

Which rpm does a file belong to?rpm -qf /path/file

The pre- requisite of an RPM?rpm -q –-requires mozilla

Where is the RPM installed?rpm -qil mozilla

Check RPM's changelogrpm -qi mozilla

MultiMedia :-)

Objective: Have fun in work with Linux :-)Solution:

xmms (Play MP3)grip (Rip wave to MP3)

Make ISO file for burning discmkisofs -r -o file.iso /path/files

Test to mountmount -t iso9660 -o ro,loop=/dev/loop0 file.iso /mnt/tmp

Scan CD writercdrecrd -scanbus

Write ISO to disccdrecord -v speed=8 dev=0,0,0 -data file.iso

GUI CD write -> http://www.xcdroast.org/xcdroast