This document provides solutions to common Linux commands and tasks. It covers topics such as environment setting, hardware and system specifications, file editing and compression, networking, performance monitoring, package management with RPM, and multimedia. Solutions are provided for tasks like changing the startup runlevel, monitoring swap size, editing files, getting the network IP and registering the hostname, and burning discs.

1. Linux Commands & Tools
v1.3
j3ffyang at gmail

2. Environment Setting
BaSH, Bourne Again SHell (Linux default), vs. Korn Shell (on
AIX)
Current env
env
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

3. 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

4. Hardware Specification
Objective:
How fast is CPU? How big is RAM? SWAP size?
Solution:
cat /proc/cpuinfo
cat /proc/meminfo
cat /proc/swaps

5. System Specification
Objective:
How to partition harddisk before installing WebSphere
Commerce?
Solution:
/boot 100MB
/ 10G
SWAP =<2 x RAM (usually 1~ 1.2G if RAM=1G)
http://www.redhat.com/docs/manuals/enterprise/RHEL­4­Manual/pdf/rhel­ig­x8664­multi­en.pdf
­> page 28

6. Kernel - Messaging
Objective:
Optimize kernel for DB2.
Solution:
Display kernel parameter
ipcs ­l
Display kernel parameter
Editing /etc/sysctl.conf
kernel.msgmni = 512
kernel.sem=250 128000 32 1024
Activating kernel parameters
sysctl ­p
http://www­106.ibm.com/developerworks/linux/library/l­ss3­db2/

7. System Management
Objective:
Want to how the file system being used?
Solution:
du -cks $(ls -l | grep '^d' | awk '{print $9}') | sort -nr
du -ksh

8. System Startup
Objective:
Switch between X startup and command line startup.
Change the runlevel.
Solution:
cat /etc/inittab | grep “id”

9. System Mgmt - fuser
Objective:
Which process holds up the file?
Solution:
fuser
pid
[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 file
fuser -kimuv /path/file
fuser -kxuc /path/file (on AIX)
Port
[root@sevenj root]# fuser 22/tcp
22/tcp: 3470

10. 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:22
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 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)

11. System Mgmt – lsof (cont'd)
What files are opened by PID?
[root@summerpalace /]# lsof -p 3803
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 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/sshd
sshd 3803 root mem REG 3,2 51924 535486 /lib/libnss_files-2.3.2.so
sshd 3803 root mem REG 3,2 1563240 1054615 /lib/tls/libc-2.3.2.so
sshd 3803 root mem REG 3,2 5572 292096 /usr/kerberos/lib/libcom_err.so.3.0
sshd 3803 root mem REG 3,2 63880 292106 /usr/kerberos/lib/libk5crypto.so.3.0
sshd 3803 root mem REG 3,2 385220 292116 /usr/kerberos/lib/libkrb5.so.3.1
sshd 3803 root mem REG 3,2 971612 535528 /lib/libcrypto.so.0.9.7a
sshd 3803 root mem REG 3,2 91368 535470 /lib/libnsl-2.3.2.so
sshd 3803 root mem REG 3,2 52584 1216870 /usr/lib/libz.so.1.1.4
sshd 3803 root mem REG 3,2 12564 535504 /lib/libutil-2.3.2.so
sshd 3803 root mem REG 3,2 76468 535498 /lib/libresolv-2.3.2.so
sshd 3803 root mem REG 3,2 14728 535466 /lib/libdl-2.3.2.so
sshd 3803 root mem REG 3,2 30448 535533 /lib/libpam.so.0.75
sshd 3803 root mem REG 3,2 28452 1216947 /usr/lib/libwrap.so.0.7.6
sshd 3803 root mem REG 3,2 106532 535453 /lib/ld-2.3.2.so
sshd 3803 root 0u CHR 1,3 66540 /dev/null
sshd 3803 root 1u CHR 1,3 66540 /dev/null
sshd 3803 root 2u CHR 1,3 66540 /dev/null
sshd 3803 root 3u IPv4 3387 TCP *:ssh (LISTEN)

12. System Mgmt – lsof (cont'd)
What application is holding a dir and files under that dir?
[root@summerpalace /]# lsof +d /var/log
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
syslogd 3676 root 2w REG 3,2 1393576 780963 /var/log/messages
syslogd 3676 root 3w REG 3,2 925 780964 /var/log/secure
syslogd 3676 root 4w REG 3,2 430 781130 /var/log/maillog
syslogd 3676 root 5w REG 3,2 10246 781139 /var/log/cron
syslogd 3676 root 6w REG 3,2 0 781134 /var/log/spooler
syslogd 3676 root 7w REG 3,2 0 781138 /var/log/boot.log

13. System Mgmt – SWAP
Objective:
Want to change SWAP size?
Solution:
mkswap /dev/hdaX
sync
swapon /dev/hdaX
cat /proc/swaps

14. System Mgmt – mkfs
Objective:
Create a file system?
Solution:
fdisk -l
fdisk /dev/hda
mkfs -t ext3 /dev/hdaX
mkfs /dev/hdaX
tune2fs -j /dev/hdaX (Convert ext2 to ext3. Journaled.)
mount /dev/hdaX /mount/point
Edit /etc/fstab
/dev/hdaX /mount/point ext3 defaults 1 2

15. File - compression
Objective:
Compress/ Uncompress? The archive formats?
Solution:
Compress
zip *.zip
jar *.jar (same as zip)
tar -czvf *.tar.gz
bzip2 *.bz2
gzip *.gz / *.Z
rar (http://www.rarlab.com/)
Uncompress
unzip
jar -xvf
tar -xzvf
bunzip2
gunzip

16. File - editor
Objective:
Edit the file?
Solution:
vi
kate (Similar to UltraEdit. Install kdebase*.rpm)
jedit (http://jedit.org)
emacs
ed

17. Network
Objective: Get the DHCP IP+ Register hostname in DNS
Solution:
/etc/sysconfig/network
dhclient ethX /dhclient.conf (man dhclient.conf -> sample)
YaST or YaST2 (Yet another Setup Tools)
/etc/hosts
Edit /etc/sysconfig/network-scripts/ifcfg-ethX
Add DHCP_HOSTNAME=<your_hostname>
Verification:
hostname -s / -d
nslookup / host / dig

18. Network - netstat
Objective:
Network status.
Solution:
TCP/IP
netstat -pant
netstat -pat

19. 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)

20. Performance - Process
Objective:
The running processes' status?
Solution:
How much the CPU usage?
ps auxwww | sort +2 -r
ps -ef | sort +3 -r | head -n 5
How much the MEM usage?
ps auxwww | sort +3 -r
The process tree.
pstree

21. Performance – Manage Srvc
Objective:
Turn on / off the unnecessary services.
Solution:
List all available services.
chkconfig --list
chkconfig –-list | grep 3:on
Check on / out services. eg.
chkconfig iptables on | off
chkconfig –level 2345 iptables on
less /etc/init.d/iptables
ls /etc/rc.d/rc3.d
Stop a service. eg.
/etc/init.d/sshd start | stop

22. Performance - Memory
Objective: System memory usuage.
Solution:
vmstat <interval> <length>
eg.
vmstat 1 10
[root@summerpalace root]# vmstat 1 10
procs 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/ out
bi / bo: Blocks in/ out
us: User time
sy: System time
id: Idle
Reference: What's block and character device?
http://www.uwsg.iu.edu/usail/concepts/filesystems/everything­is­a­file.html

23. Performance - top
Objective:
Overall system performance.
Solution:
top
s – interval in second
M – sort by memory
P – sort by CPU

24. RPM
Objective: Manage the packages
Solutions:
RPM = RedHat Package Manager. Used by RedHat, SuSE and Mandrake.
Debian dpkg converter is available.
Install / Update
rpm -Uvh package.rpm (vs. -ivh)
rpm -Uvh package.rpm --nodeps
rpm -Uvh –-aid package.rpm (require rpmdb-*.rpm installed)
Uninstall
rpm -e package_name
rpm -e –-allmatches package (man rpm, search allmatches)
RPM DB Rebuild
db_verify /var/lib/rpm/Packages
rpmdb --rebuilddb

25. RPM (cont'd)
Solutions:
Find an RPM
rpm -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 changelog
rpm -qi mozilla

26. MultiMedia :-)
Objective: Have fun in work with Linux :-)
Solution:
xmms (Play MP3)
grip (Rip wave to MP3)
Make ISO file for burning disc
mkisofs -r -o file.iso /path/files
Test to mount
mount -t iso9660 -o ro,loop=/dev/loop0 file.iso /mnt/tmp
Scan CD writer
cdrecrd -scanbus
Write ISO to disc
cdrecord -v speed=8 dev=0,0,0 -data file.iso
GUI CD write -> http://www.xcdroast.org/
xcdroast