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System Administration

Learning Objectives:

1. To understand the procedure of using externalstorage medium in Unix System

2. To learn the method of retrieving hardwares

information in Unix System

3. To understand the method of setting up /managing users account in Unix System

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Lecture A2 / Slide 2

System Administration

Table of Content

Using Floppies / CD-Rom (Sun)

Using Floppies / CD-Rom (Linux)

Disks

User Accounts

User Groups

Shutdown

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Lecture A2 / Slide 3

Using floppies/CDROM (Sun)

Preparing PC format diskette in a Sun computer$ fdformat -v -U -b myfiles

Formatting 1.44 M in /vol/dev/rdiskette0/unformatted

Press return to start formatting floppy. [ Return ]

-v Verifies whether the diskette was formatted correctly.

-U Unmounts the diskette if it is mounted.

-e Ejects the diskette when done formatting.

-b label Name for the diskette. (

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Lecture A2 / Slide 4

Using floppies (Linux)

Default mount options of file systems stored in /etc/fstab$ cat /etc/fstab

LABEL=/ / ext2 defaults 1 1

LABEL=/data /data ext2 defaults 1 2

/dev/cdrom /mnt/cdrom iso9660 noauto,owner,ro 0 0

/dev/fd0 /mnt/floppy auto noauto,owner 0 0none /proc proc defaults 0 0

none /dev/pts devpts gid=5,mode=620 0 0

/dev/hda5 swap swap defaults 0 0

Mounting and dismounting a diskette (Linux)

$ mount /dev/fd0

mount: block device /dev/fd0 is write-protected, mounting read-only

$ ls /mnt/floppy

install.bat readme.txt utility

$ umount /dev/fd0umount removable device before

taking them out to flush all data

If a diskette is write protected

Device file name, mount point, file system type, mount options, dump opt, mount order

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Lecture A2 / Slide 5

Using CDROM (Linux)

Usually CDROMs are in standard ISO9660 format and

therefore readable in all computer systems (but

probably not for floppies and hard disks file systems)

$ mount /dev/cdrom

$ ls /mnt/cdrom

95OR98.EXE INSTALLG.DOC README.TXT SETUP.FR VERSION.TXT

$ eject

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Lecture A2 / Slide 6

Disks Usage Statistics

df display free blocks and # of files in each file system$ df | head

/proc (/proc ): 0 blocks 934 files

/ (/dev/dsk/c0t3d0s0 ): 226544 blocks 280996 files

/dev/fd fd ): 0 blocks 0 files

/var (/dev/dsk/c0t3d0s3 ): 1480320 blocks 252851 files/cache (/dev/dsk/c0t3d0s4 ): 308472 blocks 243243 files

/home (/dev/dsk/c0t3d0s7 ): 1408858 blocks 284098 files

/tmp (swap ): 2903968 blocks 10169 files

/var/mail(mail:/mail ):14054672 blocks 1097254 files

/var/spool/uucp (mail:/var/spool/uucp): 3450734 blocks 350809 files

du display disk usage statistics (in number of 512k blocks)$ du | head -5

282 ./zmodem

14 ./gzip-0.7/msdos

2 ./gzip-0.7/os2

662 ./gzip-0.7

du shows disk usage of

directories in 512k blocks

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Lecture A2 / Slide 7

User Accounts (1)

Creating user accounts (root super-user only)useradd [-c comment] [-d home_dir]

[-e expire_date] [-f inactive_time]

[-g initial_group] [-G group[,...]]

[-m [-k skeleton_dir] | -M] [-p passwd]

[-s shell] [-u uid [ -o]] [-n] [-r] login

useradd -D [-g default_group] [-b default_home]

[-f default_inactive] [-e default_expire_date]

[-s default_shell]

$ su

Password:$ useradd wujun

Viewing user account settings$ ypcat passwd | grep wujun

wujun:##wujun:30152:1501:Wu_Jun,,=EXP.2001.07.31=DEMTER=PC.yes=RMACCESS.yes:/homes/wujun:/bin/tcsh

-D changing defaults

su change to another user (default= root)

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Lecture A2 / Slide 8

User Accounts (2)

Changing password (user may change own password)$ passwd john

Changing password for user john

New UNIX password:

BAD PASSWORD: it is based on a dictionary word

Retype new UNIX password:passwd: all authentication tokens updated successfully

Changing user account setting (super-user only)$ usermod

usage: usermod [-u uid [-o]] [-g group] [-G group,...][-d home [-m]] [-s shell] [-c comment] [-l new_name]

[-f inactive] [-e expire ] [-p passwd] [-L|-U] name

$ usermod -p secret john

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Lecture A2 / Slide 9

User Accounts (3)

Deleting a user account

userdel [ -r ] login

The userdel utility deletes a user's login from the system

and makes the appropriate login-related changes to the sys-tem file and file system.

OPTIONS

The following options are supported:

-r Remove the user's home directory from the system.This directory must exist. The files and direc-

tories under the home directory will no longer be

accessible following successful execution of the

command.

$ userdel john

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Lecture A2 / Slide 10

User Groups (1)

Adding a new group (super-user only)$ groupadd

usage: groupadd [-g gid [-o]] [-r] [-f] group

$ groupadd comp111

Adding users to a group (super-user only)

$ usermod -G comp111 kwchiu

$ usermod -G comp111 john

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Lecture A2 / Slide 11

User Groups (2)

View users of a group$ ypcat group | grep comp111

comp111:*:40000:kwchiu,john

usage: groupmod [-g gid [-o]] [-n name] group

Renaming a group (super-user only)$ groupmod

usage: groupmod [-g gid [-o]] [-n name] group

$ groupmod -n cs111 comp111

Deleting a group

$ groupdel

usage: groupdel group

$ groupdel cs111

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Lecture A2 / Slide 12

Shutdown

An executable shell script that calls the init program to shutdown the system.Recommended for servers because users are notified of the impending shutdown as are the systems that are mounting resources from the server beingshut down.

Usage: /usr/sbin/shutdown [ -y ] [ -g grace-period ]

[-i init-state ] [ message ]

$ shutdown -i S -g 120 "===== disk replacement ====="

Shutdown started. Tue Jun 7 14:51:40 PDT 1994

Broadcast Message from root (pts/1) on foo Tue Jun 7 14:51:41...

The system will be shut down in 2 minutes

===== disk replacement =====

Broadcast Message from root (pts/1) on foo Tue Jun 7 14:52:41...

The system will be shut down in 1 minutes

===== disk replacement =====

Broadcast Message from root (pts/1) on foo Tue Jun 7 14:53:41...

The system will be shut down in 30 seconds

===== disk replacement =====

Do you want to continue? (y or n):