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1Unix Administration CSIE.NCKU

email As System Administrators it is important that you

learn how to use electronic forms of communication. Start checking your e-mail regularly.

Mail server: sendmailsendmail daemon Mail client: elm, pine, mail, etc Where is my mail stored in the mail server?

– /var/spool/mail/username

mail notification: command: biff y or biff n


email Forwarding Electronic Mail

– file .forward: address@machine

finger: find a person in a machine– .plan and .project files

archie:– http://archie.ncu.edu.tw


Usenet News

– http://sunsite.unc.edu/usenet-i/hier-s/comp.unix.html

Newsgroup comp.admin.policycomp.unix.??? comp.unix.admincomp.os.linux.???

comp.os.linux.announcecomp.os.386bsd.???

comp.unix.ultrix

aus.computers.linux

Purpose discussion of adm policy whole list of Unix newsgroups discussion of Unix admgeneral help and questions:Linux major announcements for Linux whole list of groups about

386BSD about the Ultrix operating system.

Australian Linux group


Compression compress

– compress filename.*

– compress -d filename.*.Z

zcat – zcat filename.*

– uncompress filename.*.z

gzip– gzip filename.*

– gunzip or gzip -d filename.*.gz

bzip


Compression tar cf - fromdir | (cd todir; tar xfp -)

– tar a directory to standard tape device • tar cv /home/mi85 (/dev/rmt0 by default)

– tar a directory to /tmp/mi85.tar• tar cv /tmp/mi85.tar /home/mi85 or• tar cvf AFile.tar AFile

– untar a tar file in current directory• tar xvf /tmp/mi85.tar

– copy everything in a directory to another one• tar cf - fromdir |(cd todir; tar xfp -)

– cpdir: (cd $1; tar cf - .) | (cd $2; tar xvf -)$ cpdir fromdir todir


Some commands printing a document

– lpr -Php -h test.ps – enscript -2rG -h -Php test.c – Ghostview or gsview on Unix and Win96 to

print and read PS files – lpq -Php, – lprm -Php 123– psselect (sun or solaris):

• psselect -p1-10 test.ps >t.ps


Some commands List all the Unix commands you know which can

be used to display the contents of a file. – tail, head, vi, joe, more, cat, cut,

Using wildcards construct a Unix file spec that all files have 10 characters in the filename, where the third character is any character between a and s, and the last three characters are either doc or tmp. – ??[a-s]????[dt][om][pc]


Some commands ls | wc -l : count # of lines given by the output of

ls command. Should count # of files/directories in the current directory

rm ??? : delete all files with three letter filename who | wc -l : count # of lines output by the who

command, counts # of people on the system. mv progs/* /usr/steve/backup : move all the files

from progs sub-directory into the directory /usr/steve/backup. When you are moving multiple files the destination must be a directory.


Some commands ls *.c | wc -l : similar to a) should count the

number of files with filenames which end in .c who | sort : sort the output of who command into

ascending order. cd ; pwd : changes into the users home directory

(cd) and then prints the working directory (pwd) cp memo1 .. : make a copy of the file memo1 in

the parent directory (..) ls -l | sort +4n : sorts the output of ls -l on the

fourth field. Sorted byusing numeric order (n)


Some commands grepgrep and regular expresssionsregular expresssions List those lines from the /etc/passwd file that have

a username that starts with j. – grep '^j' /etc/passwd

Show the usernames of all the people using bash as their login shell (Login shell is the last field on each line of the file /etc/passwd.) – grep '/bash$' /etc/passwd

List those lines from the /etc/passwd that have a username starting with j and have bash login shell. – grep '^j.*/bash$ /etc/passwd


Some commands List all lines from the /etc/passwd file that

have users with uid's less than 100. User id:the 3rd field. – grep '[^:]*:[^:]*:[0-9]:' /etc/passwd – grep '[^:]*:[^:]*:[0-9][0-9]:' /etc/passwd – [^:]* says match any number of characters that

aren't colons. Have to do it twice to take into account UIDs less then 10 and UIDs between 10 and 100.


ls command A Little big man -- Unix 101 by Mo Budlong http://www.sunworld.com/swol-09-1998/swol-09-unix101.html

ls -AFC |more, ls -Afxd l* ls -b l* ;for special characters


ls command (cont.) ls -l: long listing

– -rwxrwxrwx+ 1 smith dev 10876 May 16 9:42 part2 1 2 3 4 5 6 7 8

• 1: types of files

• 2: file permission

• 3: # of links to the file

• 4: owner or user’s name

• 5: group name of the user

• 6: file size or major and nimor # of a device file

• 7: date and time

• 8: file name

• +: ACL (Access Control List)


ls command (cont.)– File types:

• -: an ordinary file;(rm, editor/cp..)

• d: is a directory; (md, rd)

• l: a symbolic link; (ln, rm)

• b: a block special file; (mknod, rm)

• c: a character special file; (mknod, rm)

• s: Unix domain socket

• p or |: a fifo (or "named pipe") special file;


ls command (cont.)– Permissions

• r: the file is readable

• w: the file is writable

• x: the file is executable

• -: the indicated permission is not granted

• l: mandatory locking occurs during access (the set-group-ID bit is on and the group execution bit is off) /usr/bin/ls

• L: mandatory locking occurs during access (the set-group-ID bit is on and the group execution bit is off) /usr/xpg4/bin/ls


ls command (cont.)– Permissions

• s the set-user-ID or set-group-ID bit is on, and the corresponding user or group execution bit is also on

• S undefined bit-state (the set-user-ID bit is on and the user execution bit is off)

• t the 1000 (octal) bit, or sticky bit, is on (see chmod(1)), and execution is on

• T the 1000 bit is turned on, and execution is off (undefined bit-state)


ls command (cont.) example: -rwsr-xr-x

– readable, writable, and executable by owner,

– readable and executable by group and others,

– allows its user-ID to be assumed, during execution, by the user presently executing it.

-rw-rwl---– readable and writable only by the user,

– the group and can be locked during access.


chmod command Absolute mode: chmod nnnn file

– n is a octal number from 0 to 7.

– 4000: Set user ID on execution.

– 20#0:• Set group ID on execution if # = 7/5/3/1.

• Enable mandatory locking if # is 6, 4, 2, 0.

• For directories, files are created with BSD semantics for propagation of the group ID. With this option, files and subdirectories created in the directory inherit the group ID of the directory, rather than of the current process. It may be using symbolic mode.


chmod command Absolute mode: chmod nnnn file

– 1000: Turn on sticky bit. See chmod(2).– 0400: Allow read by owner.– 0200: Allow write by owner.– 0100: Allow execute (search in dir) by owner.– 0700: Allow read, write, and execute

(search) by owner.– 0040:0020,0010,0070,0004,0002,– 0001,0007


chmod command Symbolic Mode

– chmod <symb-mode-list> file– <sym-mode-list> [who] operator [permissions]– who: 0 or more of the characters u, g, o, or a

• u: user's permissions,• g: group's permissions• o: others' permissions• a: all permissions (user, group, and other)• omitted: default to all


chmod command Symbolic Mode

– operator: either +, -, or =– In a directory which has the set-group-ID bit set

(reflected as either -----s--- or -----l--- in the output of 'ls -ld'), files and subdirectories are created with the group-ID of the parent directory- not that of current process.

– Error messages:• chmod g+x,+l file• chmod g+s,+l file

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