Vi/Vim commands:
- ?/ (search from bottom to
top)
- /(search from top to
bottom)
- N(press “n ” for next
occurrence of search)
- Dd((Of the current cursor
positiondelete entire line)
- Dd 5((Of the current
cursor position delete five lines)
- Yy(Of the current cursor
position copy the entire line)
- Yy 5(Of the current cursor
position copy 5 entire line)
- P((Of the current cursor
position paste the entire line copied)
- yw(Of the current cursor
position copy the current word)
- p((Of the current cursor
position paste the current word copied)
- dw(Of the current cursor
position delete the current word
copied)
- o(new line below the
current cursor)
- shift + o(Of the current
cursor position newline above empty)
- gg(Of the current cursor
position go to top of file starting at first position of record)
- shift gg(Of the current
cursor position go to bottom of file to first position of record )
- cntrl + o ( to beginning
of file)
- :%s/findwordtoreplace/replacetheexistingword(find
and replace existing word with replace word)
- :wq(write and quit)
- :q!(quit without saving)
- :set nu (sets number for the lines in
vi editor)
MBR--Master
boot record
1.
GRUB-grand unified boot loader
2. Shell:>
init 6 (restart will restart the system in runlevel 6)
3.
configuration files for initialization /etc/initab
4.
service
are in /etc/init.d directory
5.
/etc/rc.d (
for each runlevel there will be a separate directory in which necessary
services are started as If defined )
6. Shell:>last -10(last
10 logins in the system)
7.
Shell:>lastb (last bad login of users)
8.
Shell:>cd /etc/audit(audit directory for the
audit daemon)
9.
auditd.conf(This file controls the
configuration of the audit daemon)
10.
audit.rules
11.
shell:>ausearch --session 1 (the session details with
session id given as “1”)
12.
shell:>aureport(audit report)
13.
shell:>id (gives the current user uid, gid and so on)
14.
shell:>id kumar(gives
the user uid, gid and so on for user
kumar)
15.
shell:> cut -f 1,3,4 -d
: samplepasswd(cut and display the required fields in the file)
16.
shell:> cut -c 1-3
samplepasswd(cut the characters and display)
17.
shell:> grep 'bin/bash' ./samplepasswd(Get the output from
the file which has the lines ‘bin/bash’)
18.
shell:> grep 'bin/bash' ./samplepasswd | cut -d ':' -f 1-6 samplepasswd
19.
shell:> awk [ -F fs ] [ -v var=value ] [ 'prog' | -f progfile ] [
file ... ]
20.
-F = field separator for regular expression fs
21.
-v = Assaigns the value to the variable var
before executing the awk program
22.
Prog =An awk program
23.
-f= awk program in a file to be executed
24.
File = the file name to be operated on.
25.
Shell:> awk ‘print $0,$3,$4’ Deptssaleamounts.txt
26.
Shell:>wc Deptssaleamounts.txt(give the printout of line,
words, bytes count for each file)
27.
Shell:>netstat –r (routing tables)
28.
Shell:>netstat –u (udp
connections),
netstat –t(tcp connections), netstat –l(listening ports),netstat –p (program
name),netstat –g (IPv6,IPv4 group memberships),netstat –I (kernel interface
tables),netstat
–a
29.
Shell:>passwd(change password for current user)
30.
Shell:>cat /home/kumar/.bash_history
| less
31.
Shell:> aulastlog(gives the last login information , need
to be a super user to execute this command)
32.
Shell:>grep -options 'regex' <filename>
33.
Shell:>watch –interval 120 datetime( watch and prints output
on console for a program to for the specified interval)
34.
Shell:>tail –n 5 passwd(prints the output of last 5
lines on the console)
35.
Shell:>adduser kumar (needs
to be super user to execute this command), use passwd to set a password for the
user
36.
Shell:>Lastlog (last logins on the system)
37.
Shell:>Usermod
[options] <login>
Options are –d , - -
home (to change home directory)
38.
Usermod -e (set
expire date)
39.
Usermod –g users kumar
(set a group )
40.
Usermod –a -G
admin Kumar (set Kumar to supplementary, or
secondary groups without disturbing
primary group)
41.
Shell:>
Tty (prints
the file name of tty connected to standard input)
42.
Shell:>Ps --help
43.
Shell:>ps –ef(list all process “–e” running on a system
with full format “ –f” listing.
44.
Shell:>Ps aux(gnu style )(“-a” list w/ tty except session
leaders ,” –u” by effective user id,”-x” processes w/o controlling ttys)
45.
Shell:>Ps T (all
process running on this terminal)
46.
Shell:>Ps –u root, ps –u(list
all the processes by effective user id)
47.
Shell:>ps aux | grep mysqld
48.
Shell:>pgrep sshd
49.
Shell:>pidof bash (find process id of running program)
50.
Shell:>Pidof sshd
//pid -fu samuel
51.
Shell:>kill -9 1540(sshd pid is 1540)
52.
Shell:>free –ml (show high and low”-l” memory
statistics in “-m” mb)
53.
Shell:>fuser –muvf /home/kumar/exportfromhive (identify
process using files or sockets)
54.
Shell:>top (interactive output of linux tasks
/processes running with cpu and memory usage
55.
Shell:>top -u samuel
56.
Shell:>service httpd start(start httpd service which
is webserver)
57.
Shell:>ftp 192.168.50.24 (ftp to address)
58.
Shell:> sftp 192.168.50.2 (sftp
to address)
59.
ftp>mput *.txt (put file from current directory of
type *.txt onto ftp site)
60.
ftp>mget *.txt
61.
Shell:>sort -r filea.txt(reverse the result in descending order)
62.
tar -cvf archive-name.tar /home
63.
tar -xvf archive-name.tar
64.
Shell:>grep Samuel /etc/passwd
(grep Samuel details in /etc/passwd)
65.
Shell:>find / -name /etc
66.
Shell:>ps -ef | grep init
67.
Shell:>kill -9 <pid>
68.
Shell:>rm –I /home/kumar/*temp.txt (prompt before removal)
69.
Shell:>rm –rf /home/kumar (remove with force directory and its contents)
70.
Shell:>lsof -i TCP:22(list open files for tcp on port 22
of any internet address matches ‘-I’)
71.
Shell:>lsof -u samuel (
list open file for user samuel)
72.
Shell:>lsof -i 4(list open file for IPv4)
73.
Shell:>lsof -i 6 list open
file for IPv6)
74.
Shell:>lsof -i TCP:1-1024
//Shell:>lsof –u ^root kumar
75.
Shell:>lsof -i -u samuel
76.
Shell:>lsof -p ^I ,^2 (list
open files for other processors than 1 and 2)
77.
Shell:>kill -9 `losof -t -u samuel`
78.
Shell:>find . -name temp
79.
Shell:>find /home -iname procscript.py(find case
insensitive match)
80.
Shell:>find / -type d -name etc
81.
Shell:>find / -type f -name passwd
82.
Shell:>find / -type f -name '*.php'(find file name)
83.
Shell:>sudo find / -type d -name '*.d' | less( find
directory )
84.
Shell:>history 5(last 5 commands typed)
-------------------- ---------------- -------------------------
System time information and details.
85.
Shell:>cd /usr/share/zoneinfo (find
the zones )
86.
Shell:>cd /etc/sysconfig/clock(
The file which time zone is set for the system)
87.
Shell:>echo
'ZONE="Europe/Copenhagen"' (the display the zone of particular
region)
To remove the current zonetime and set a new time zone
88.
Shell:>rm -f /etc/localtime;(remove the current
localtime)
89.
Shell:> ln -s /usr/share/zoneinfo/Europe/Copenhagen /etc/localtime(set a symbolic
link to zone according to the requirement)
//$ diff -s /etc/localtime /usr/share/zoneinfo/`cat ./etc/timezone`
90.
Shell:>diff -s ./localtime
/usr/share/zoneinfo/US/Michigan(Compare files line by line.)
//dpkg-reconfigure tzdata
-------------------- --------------------------------------
91.
Shell:>tar -tvf sample1-org.tar.bz2
92.
Shell:>tar -xvf sample-org.tar salefile.sh
or
Shell:>tar --extract --file=salefile.sh
93.
Shell:>tar
-zxvf sample-org.tar.gz salefile.sh
or
tar --extract --file=sample-org.tar.gz salefile.sh
94.
Shell:>tar -jxvf sample-org.tar.bz2 salefile.sh
( ‘-j’ option for bzip2)
or
tar --extract --file=sample-org.tar.bz2 salefile.sh
95.
Shell:>tar -xvf sample-org.tar
'salefile.sh' 'orderfile.sh'
96.
Shell:>tar -zxvf sample-org.tar.gz 'salefile.sh' 'orderfile.sh' (‘-z’ required for gzip)
97.
Shell:>tar –jxvf sample-org.tar.bz2 'salefile.sh' 'orderfile.sh'
98.
Shell:>tar -xvf sample-org.tar --wildcards *.sh'
99.
Shell:>tar -rvf sample-org.tar salefile.sh orderfiledir (add files to end of archive)
100.
Shell:>tar xvfw sample-org.tar(not valid for bz2,gzip)(verify
the archive after writing it)
101.
Shell:>uname –a(linux
distribution complete details)
102.
Shell:>id(id under which u are operating as)
103.
Shell:>hostname(hostname given to the IP address)
104.
Shell:>useradd kumar
105.
Shell:>chfn -f 'kumar t' kumar(chfn is
used to change your finger information. This command will display four
pieces of information that can be changed by chfn: your real name, your
work room and phone, and your home phone in RHEL distribution.)
106.
Shell:>usermod kumar
107.
Shell:>/usr/sbin/usermod -p '$1$u??e?z?.....' kumar(use
encrypted password)
108.
Shell:>groupadd devteam
109.
Shell:>groupmod
110.
Shell:> cat /etc/passwd(password
file)
111.
Shell:>cat /etc/groups(group file)
112.
Shell:>cat /etc/shadow (encrypted
password file for users)
113.
Shell:>/etc/shadow/g
114.
Shell:>who
115.
Shell:>whoami
116.
Shell:>chmod u+x demo1(change add file permissions for demo1 file for user
)
117.
Shell:>chmod u-x demo(change remove file permissions for demo file for
user )
118.
Shell:>chmod a=rwx demo((change add file permissions for demo1 file for user
)
119.
Shell:>chmod 744 demo
120.
Shell:>chown kumar:devteam
changescript.sh
chown
[OPTION]... [OWNER][:[GROUP]] FILE
121.
shell:>chgrp -hR devteam
/home/kumar/changedir
122.
shell:>find . type d -exec chmod 755 {} \;
123.
shell:>find . -type f -exec chmod 777 {} \;
124.
shell:>find . -type d -name join* -exec chmod 777 {} \
125.
-------
-------------
----------------------
DNS
126.
Shell:>Bind:bekerly intenet name system
127.
Shell:>Dig (cat /etc/resolv.conf to IP address of known domain servers)Dig is Dns lookup utility)
128.
Use a Specific DNS server Using dig
@dnsserver. By default dig uses the DNS servers defined in your
/etc/resolv.conf file. If you like to use a different DNS server to perform the
query, specify it in the command line as @dnsserver
129.
Shell:>cat /etc/hosts (list
of computers on your network)
130.
Shell:> cat /etc/nsswitch.conf (
watch the file to see exactly where the user passwords and other important information being
persisted with different options of local file system , dns , database or
anywhere else.Indicates the system where to look for host system related information.)
----
----------------------------------
-------------------------------
131.
MTA(mail transfer agents) sendmail, pop, Imap
132.
MUA(mail user agent) Evolution(supported
by Linux to draft a email) , mail, netscape
133.
MDA(mail delivery agent)Lda,
local,(procmail)
134.
mail program is used to transfer mails
135.
shell:>cd /var/spool/mail (
is where the sent or received mails are stored for each individual user in the
directory as specified)
136.
bashshell:>mail usrname
< user.txt
137.
shell:>cd etc/mail( mail program location)
138.
sendmail.cf configuration file
139.
sendmail.mc macro for sendmail.cf(sendmail.cf
file for use with sendmail)
140.
bashshell:>m4 etc/mail/sendmail.mc > /etc/mail/sendmail.cf (m4 is a
macro processor . Process macros in
FILEs. If no FILE or if FILE is ‘-’,
standard input is read.) esyscmd()
tells m4 to run the given shell command and insert its output at the given
location.define command defines the macro. ifdef checks if a macro has been
defined.
-----------------
-----------------------------------------------------
webserver
141.
shell:>/etc/rc.d/init.d/httpd start(location of httpd
program location .httpd is the webserver program)
142.
shell:> service httpd start
143.
shell:>chkconfig --level 5 httpd on (automatically start the httpd daemon)
144.
or
145.
shell:>redhat-config-services(It is stated
that you can get to Services via, System → Administration → Services or by
typing system-config-services at shell. To install use yum install
redhat-config-services to install with dependencies)
146.
shell:> less /etc/httpd/conf/httpd.conf(configuration
directory for httpd service)
The httpd.conf file has lot of
information regarding serverroot, listening for traffic, addons to apache web
server called modules, extended status is on or off, user and group running
apache web server who is owner and which group can run, servername ,log files
storing ,log files information format, document root, restricting access to
webserver using <Directory “/”> saying allow or deny for the folder/directory, saying which host machine can access it ).Different
options directives can be set such as Indexed,
includes, FollowSymlinks, Exec CGI, Multi views, these option directives
can be set as “all/none” with restricting access to them with “allow/deny” qualifiers. Allow override
directive for directory by directory can be given in httpd.conf file to restrict access. “.htaccess “ file should be created in each directory in apache webserver
directories based on access rights set using allow override directives on those directories in httpd.conf file .
Sample snippet : order deny , allow
Deny from all
And you can
also restrict access to directories by
setting passwords by using command such as
htppasswd –c
webusers kumar( to add more
users to file webusers password file use” htppasswd webusers Samuel”) . And the
apache to use this kind of
authentication to restrict access you should change the settings in conf file
as “Auth Name SecretStuff
AuthType
Basic
Auth User file
<path-to>/webusers
Require valid-user “
147. shell:> yum search system-config-services
148. shell:>redhat-config-services (redhat graphical user
interface tool can be used to configuration service)
149.
apache
web server main packages(install all the
below rpm’s to get the full functionality of apache web server)
httpd, httpd-devel(development
tools for apache web server),redhat-config-httpd(Graphical user interface help
to configure web server), httpd-manual(documentation for the
web server where it is located in directory at
/var/www/html/manual)
mod-perl(perl lanquage
interperters for apache web server),mod-python(python lanquage interperters for
apache web server),mod-ssl(for encryptions so you can use protocols like secure
http),autoconf(to create scripts),automake(make files),libtool(generic library
tools for apache)
-------------------
---------------------------------------------------
150.
Shell:>mount nandgama.example.com:/misc/export /misc/local
(this command mounts the nfs share with server:directory
details to the local machine directory. This command is used as a set up for
one time use only)
151.
fstab(file system table configuration file)
example : /dev/mapper/VolGroup-lv_root
/ ext4
defaults,noatime,discard,acl,usrquota
1 1(a entry in fstab file to
set user quota)
152.
nfs –server configuration “/etc/exports” is a
configuration file . Command is
“directory host(options) [host (options)]”
Option asnyc is write to cache memory and then once it is
full then write /sync Is force write to disk ,“no_root_squash” options is set to specify no added privileges for client user on the
server machine to make any changes to dir/files, options “ro/rw” is read only access and rw read write access.
153.
This is the entry in Fstab to
mount the /usr/local/bin on nfs server to local /bin directory everytime the
system starts up. “server:/usr/local/bin /bin nfs rsize=8192,wsize=8192,timeo=14,intr”(
the rsize and wsize of data the client and server exchange with each other)
154.
webmin interface( GUI interface to add nfs sever
share point to local file system, which is better to do to in correct format
instead of using emacs or VI)
155.
Bonnie,Bonnie++, IOzone benchmark testing tools(
Benchmark programs used between nfs server and client to determine the rsize and wsize ) You want to experiment with rsize and wsize
that works and is fast as possible
156.
From the client machine type “time dd if=/dev/zero of= /mnt/home/testfile bs=16k
count 16384” and time
it and find the best time it works. “time” : times a transaction, “dd” convert and copy a
file dd of option: write to file instead
of stdout, dd if options reads from file instead
of standard input, bs options reads and writes bytes at a time, count options count
only BLOCKS input blocks. And after the above procedure read it back to the client machine “time dd if=
/mnt/home/testfile of=/dev/null bs=16k”. Average the time and
figure out the best rsize and wsize.
157.
Shell:>mount –l(shows the mount including with labels)
158.
rmp -ivh package_name(install options install,
verbose and hash options)
159.
rpm –qa vsftpd* (verify options,query all)
160.
rpm -e vsftpd-2.0.5.10.e15(erase options/uninstall)
161.
rpm -ivh --nodep --force (to
force and install without any dependency check.
162.
rpm -Uvh package_name(update
it with option “-U”)
163.
rpm –Fvh package_name(freshen it up with
option “-F”)
164.
rpm -qip /home/kumar/Desktop/teradata-connector-1.4.1-h(query
about the connector with option “-q”, -p package, -I info.
165.
[kumar@localhost ~]$ rpm -qpl
/home/kumar/Desktop/teradata-connector-1.4.1-hadoop2.x.noarch.rpm(check
the rpm file with more detailed info , -l list )
166.
[kumar@localhost ~]$ rpm -qf /var/ftp/pub
166.(check the file is created
in which step)
167.
rpm –Va package_name (verify –V, -a all)
-------------------
----------------------------------------------------------------
168. monolithic vs modular kernel's(manolithic kernel has
everything inside of it , where as modular you install the necessary modules
based on the need)
169. Initial RAMDISK (iscis initiators)(initial
ramdisk is a disk image in memory . Most of the usage of the initial ramdisk is
because the hard disks are scsi disks , the scsi drivers are not part of
initial load of kernels modules, so you need a initial ram disk to boot of the
system properly with scsi drivers.
170. In symmetric multiple processors machines you should install SMP
kernel version for compatibility.
New
RHEL5 based kernel uses different flavors naming:
- UP kernel is no longer provided
- SMP kernel comes without any flavor (like old UP)
- entnosplit kernel comes as PAE
- enterprise kernel comes as ent
- ovzkernel.x86_64 for 64-bit
171. to create a checksum for any file
shell:>md5sum <filename>
172. go to grub.conf and
find the boot section and find the title to figure out how many kernel versions
are installed on the machine.
173. Download the kernel in /tmp directory.
And install the kernel with “RPM –i /temp/
kernel-2.4.19-3.i386.rpm”
174. To see which processor u have go to
shell:> cat
/proc/cpuinfo and see the details of
the processor . Based on cpu info you must download the kernel and install the
kernel. “uname –a ”
175. There are two distributions of kernels
available one in source code and one in
binary. The source code distribution of kernel version is denoted by
kernel-****src.rpm and other with binary
version which is compiled ready to install. The src distribution should be
compiled to binary before installation.
176. shell:>cd /boot
and do a listing ls
command directory to see the different files such as config-***(configuration
file) ,initrd-***(intial ram disk ), modules files , system map, actual kernel
for each distribution of kernel installed on the machine.
177. To install
a kernel you need the following package
RPM’s Kernel-source-*,
glibc-kernel-headers-*(library
for kernel headers),
glibc-devel-*(developmental
c library),
cpp-*(c language
preprocessor),
binutils-*(binary configuration utilities),
gcc-*(gnu c compiler),
tcl-*(scripting lanquage needed
to run binutil configuration utility to run ), tk-*(scripting cd lanquage
needed to run binutil configuration utility to run ).
178. shell:> cd
/usr/src/linux-2.*(change to this directory to run the kernel
operations) . And under the /usr/src/linux-2.*/configs/ directory you will see
configuration template files. Based on cpu of the machine sample kernel
configuration template file needs to be edited to your requirement/customize
179. Configure a custom kernel
procedure(we need source code, c language compiler, libraries.
In
dir path /usr/src/linux-2.* Shell:>make mrpoper
make command is nothing but a script
execution named "MakeFile" in which it goes to the particular
section given and executes it. “Make mrproper” command
execute and proceed with caution. if you did a custom configuration on your
system then you find a configuration file .config on your system , copy it to
seperate directory and change the file name to different name and load it back
to the Linux directory /usr/src/linux-2.4/.
Otherwise if you a run the command “Make mrproper” then that command
will delete the old .config file in the directory /usr/src/linux-2.4 which is
your custom configuration file for kernel.
To make a configuration file
.config you can use “make config(text based tool)/”make menuconfig”(it
is still a text based installation but you can make changes if you do something
wrong in the process) commands. To use make menuconfig you need to
have two more important packages installed on the system which are ncurses4-*,
ncurses-devel-*
180. (Redhat recommended installation process
method for new kernel.)Run bashshell>Make xconfig
to configure your linux system which is recommended by red hat.After
completion of this step run the below commands
make dep command
will check for dependencies. Make clean will
prepare the source tree for source compilation
Make bzImage
to build the kernel. Run Make Modules to
make modules . Make
modules_install will install the
modules. Make
install will copy the new kernel to
all the associated directories and will create the ramdisk file by running the
scripts.) Run the above commands shown above one after another to install the
kernel with correct configuration.
NOT NEEDED{genisoimage \\\mkisofs -o
file.iso -b isolinux.bin -c boot . cat
-no-emul-boot -boot-load-size 4
-boot-info-table -R -J -v -T isolinux
mkisofs is effectively a pre-mastering program to generate an ISO9660/JOLIET/HFS hybrid filesystem.
{ An emulator typically enables
the host system to run software or use peripheral devices designed for the
guest system)
( -o filename Specify the output
file for the the ISO9660 filesystem
image.
-b
eltorito_boot_image Specifies the path
and filename of the boot image to
be used when making
an El Torito bootable CD for x86 PCs.
–c boot_catalog Specifies
the path and filename of the boot catalog, which is
required for an El Torito bootable CD
-boot-load-size load_sectors Specifies the number of "virtual"
(512-byte) sectors to load in
no-emulation mode. The default is to
load the entire boot file. Some BIOSes may have problems if this is not a multiple
of 4.
-boot-info-table Specifies that a 56-byte table with
information of the
CD-ROM layout will be patched in
at offset 8 in the boot file
- -R Generate SUSP and RR records using the
Rock Ridge protocol
to further describe the files on the ISO9660 filesystem.
- -J Generate Joliet directory records in
addition to regular ISO9660 filenames.
-T Generate a file TRANS.TBL in each directory
on the CD-ROM, which can be used on
non-Rock Ridge-capable systems to help establish the correct filenames }
181. use kernel version ”bigmem " distribution for i686 machines with more
than 4gb of memory
182. shell:>umount (to un mount a device)
183. bashshell:>/sbin/mkbootdisk 2.4.20-69(The iso option instructs
mkbootdisk to make a bootable ISO image on the hard disk that can later be used
with a CD writer to create a bootable CDROM . The boot floppy created by
mkbootdisk contains five files: boot.msg, initrd.img, ldlinux.sys, syslinux.cfg
and vmlinuz. vmlinuz is the compressed Linux kernel executable, and it is
bootable.)The general syntax for mkbootdisk is
mkbootdisk
[options] kernel
usage: mkbootdisk [--version]
[--noprompt] [--device <devicefile>]
[--verbose -v] [--iso] [--kernelargs
<args>] [--size
<size>] <kernel>
(ex:
mkbootdisk --device
/dev/fd1 2.0.31)2.0.31(kernel version) – -
device (use device file)
183. An entry in shell:>cd /etc/fstab file {/etc/fstab(/dev/mapper/VolGroup-lv_root / ext4
defaults,noatime,discard,acl,usrquota 1 1)
184. shell:>quotacheck --help
185. shell:>quotacheck -avcm (-a
:all, c:create new quota files, -m :do not remount filesystem read-only)
186. shell:> edquota <user-name>(ex: edquota kumar)
187. shell:> cat /etc/warnquota.conf(will go with
warnquota script)
188. sudo(super user do)
189. shell:>cd /etc/sudoers | less (read the sudoers file and watch for sections of
user_Alias( Runas_Alias
Host_Alias
Cmnd_Alais
Next comes the main part: which
users can run what software on which machines (the sudoers file can be shared
between multiple systems).
Syntax: user
MACHINE=COMMANDS
The COMMANDS
section may have other options added to it.
Example :Allow root to run any commands
anywhere
root ALL=(ALL) ALL
kumar ALL=(ALL) ALL
190. use visudo(to edit sudoers file)
191. the sudo entries will be /var/log/secure file . shell:>
cat /var/log/secure
192. useradd –D (print or change default useradd configuration)
193. shell:> cd /etc/skel directory (where the default files will be stored such as bash_logout .bash_profile
.bashrc .gnome2 .mozilla, so that whenever a new user is
created these defaults are assaigned to every user )shell:> ls
–la /etc/skel
193. shell:>usermod -p <passwd> siri
194. shell:>userdel –r
kumar(remove home directory and mail spool of user kumar)
195. shell:>userdel kumar
196. IN /etc/passwd file
where the system related login information is stored
197. In /etc/shadow file
where the encrypted passwords for logins are stored
198. In /etc/group file where the group information is stored
199. rhel-config-users/system-config-users( A graphical
user interface to add user operation and group operations in large)
200. [root@localhost etc]# find
/ -name system-config-users
Results of the
above command(notice the graphical system-config-users is in different paths
/usr/bin/system-config-users
/usr/share/gnome/help/system-config-users
/usr/share/system-config-users
/usr/share/system-config-users/system-config-users
/usr/share/omf/system-config-users
/etc/pam.d/system-config-users
/etc/sysconfig/system-config-users
/etc/security/console.apps/system-config-users
201. webmin a progam to install on linux which can be
used to administer the machine or cluster (a script to create users in batch)
202. shell:> cat /etc/bashrc (A file in which fucntions and aliases go in /etc/bashrc)
System wide functions and aliases
203. shell: >cat /etc/profile(system wide env and
startup programs,for login setup)
shell will run 1st /etc/profile
2nd local .bash_profile(when logged
in . Local env go in here)
3rd in .bash_profile
runs a .bashrc (.bashrc: User specific aliases and functions)
4th .bashrc runs a
/etc/bashrc
Hint: It's better to create a custom.sh shell script in #
/etc/profile.d/ to make custom changes to your environment, as this will prevent the need for merging in future
updates.
-----------
------------------------------------------------------
204. shell:> fsck (file
system check) (fsck on root and /boot is avoided at most times)
Usage:
fsck.ext4 [-panyrcdfvtDFV] [-b superblock] [-B blocksize]
[-I
inode_buffer_blocks] [-P process_inode_size]
[-l|-L
bad_blocks_file] [-C fd] [-j external_journal]
[-E
extended-options] device
205. shell:>fdisk(create partition)( is a advanced program used to experienced users to
create a partition by specifying options on the command line while running it.
It will create /erase the old one if any mistakes are done which will have a
loss of data)
Usage: fdisk
[options] <disk> change partition table
Fdisk
[options] -l <disk> list partition table(s)
fdisk
-s <partition>
give
partition size(s) in blocks
203. e2label(changing labels on partition) usage: e2label device [newlabel]
204. sync(save changes to disk)
205. shell:>ls /lib/modules(where all the modules of the
kernel are present)
206. shell:> sbin/mkbootdisk(to make a boot partition
command)
207. shell:> yum install dvd+rw-tools
>
dvd+rw-format -force /dev/sr0
(to format a dvd)
cdrecord dev=/dev/sr0 blank=fast(wodim is
used to record data or audio Compact Discs on an Orange Book CD-Recorder or to write DVD media on a
DVD-Recorder. Usage : wodim [options] track1...trackn)
Usage: dvd+rw-format
[-force[=full]]
[-lead-out|-blank[=full]]
[-ssa[=none|default|max|XXXm]] /dev/dvd
208. shell:>/sbin/mkbootdisk --device /dev/sr0 2.6.32-431.29.2.el6.i686
(it check for
file named 2.6.32* on the current directory and writes on device /dev/sr0 as
boot disk)
209. If Linux is unable to boot for some
errors , put the installation floppy inside the dvd device and do a rescue
operation. Three options available in rescue mode when running by a disc to do
a rescue operation
-select f5 or type linux rescue to
go into rescue mode
once in rescue
mode you have three options “continue”, ”readonly”,
”skip”.
The entire file
system will be mounted under /mnt/SYSimage if you choose continue,read-only.
210. shell:>fdisk –l (gives the information of the mount
filesystem on the machine)
211. shell:>e2fsck /dev/sda1(can be checked
only when the file system is not mounted because the /dev/sda1 is the /boot
partition.)
212. shell:>e2label /dev/sda1
/boot
213. shell:>Mount /dev/sda2 /tmpMount/
214. sync(run it three times recommended by redhat)( sync - flush
file system buffers)
215. shell:>umount /tmpmount
----------------
-------------------------------------------------
216. RPM(redhat package manager)
i-install,e-erase,-U
upgrade,-q query, -V verify
217. shell:>rpmbuild --rebuild webmin-1.110-1.src.rpm(To build
a binary file from source file)
218. shell:>redhat-config-packages
219. redhat network,Erata,Schedule,rhn.redhat.com(one
more way to do a update of packages on the system by using rhn.redhat.com(login
into rhn.redhat.com and follow the links)
All updates and errata for Red Hat
Enterprise Linux are available via
Red Hat
Network (RHN) and can be downloaded and installed with
up2date. The
up2date is a utility provided
with Red Hat Enterprise Linux 4
rhn_register(To register your
system with Red Hat Network (RHN)
To list all updates
available for your system:up2date –l
To download and install all
updates: up2date –U
To download only all updates(these are stored in
/var/spool/up2date directory): up2date -u –d
By default, all kernel updates are on the "Skip List"
and will not be installed. To force up2date to install
any kernel updates you need to include
the -f option: up2date -uf
220. shell:>/root/rpmbuild/RPMS/noarch/webmin-1.801-1.noarch.rpm(noarch
is no architecture distribution can be installed on any machine)
-------
----------------------------------------------------------
221: desktop environments distributions for Linux (Gnome, KDE)
222. Window
Managers(clients are displayed ,moved, resized,.... functionality is taken
care by window managers)
Metacity
,sawfish,windowmaker(for Gnome)
kwin(for
kde)
222. display managers-initial login screen(the
display managers where the windows are managed to display without any
additional functionality)
gdm(gnome display
manager),kdm ,Display managers(gdm,kdm)
223. /etc/gnome/ (path where gnome related files
present), ~/.gnome where “.gnome2” is present at home of every user
which is his customized desktop option.
224. display manager is a xClient,
default Display manager is gdm, in path/etc/X11/perfdm shell
script sets default as scripted, Display manager starts
a session manager( xsm - X Session Manager )xsm session manager once it started it takes care
of xClient. Gdm (usr/sbin/gdm)
same with gdm with gnome.
225. startx will excute X windows on the console . where
X windows is a child process of shell
226. (dm vs startx)
==gnome-control-center(in
path /usr/bin/gnome-control-center)
==to change window manager go to ~/.bash_profile edit it with export
window_manager
="sawfish" and save it .
==switchdesk gnome , switchdesk kde(will switch between gnome and
kde desktop environments)
==gnome-"press
tab" twice(to find more gnome programs)
In the typical client/server relationship, the
client application runs on the local machine and the server application can run
on either the local machine or a
remote machine
(i.e., any other computer on the network). In X, however. this relationship is
inverted in that each local machine contains X server software and can access X
client programs that run either on the same machine or on a remote machine.
This has the advantage of eliminating the need for the application programs to
be aware of the details of the graphics cards, monitors and other hardware,
thereby simplifying the development of such programs and facilitating their
servicing of multiple users on the network simultaneously.
Any application program that runs in a GUI provided
by X, which is virtually every GUI used on
Linux and other
Unix-like operating systems,
is an X client. Thus OpenOffice, Apache, gedit, gFTP, the GIMP, rCalc and Xpdf
are all X clients when used on such operating systems.
--------------------------
-----------------------------------------------------------
----------------------------------
227. xFree86(is a command line tool for X windows)( XFree86 was an
implementation of the X Window System.)
228. xclient -display <hostname:0.0> -geometry
Xsize x Ysize, +X offset,+Y offset {using
xclient command setting for the windown X SIZE and Y size(with –geomety option)
for the hostname given in “–display” option}
229. run xf86config is a program that generates XF86Config file
230. XF86Config is the configuration file for xFree86
231. shell:>info XF86config
232. shell:>X & (to
start X windows)
== X server(x server to work
perfectly need x font server running) An X server is a program in
the X Window System that runs on local machines (i.e., the computers
used directly by users) and handles all access to the graphics cards, display
screens and input devices (typically a keyboard and mouse) on those computers
233. X font server (xfs service), XF86config, fonts must exits in path /usr/x11R6/lib/X11/fonts
xfs [ -config configuration_file
] [ -daemon ] [ -droppriv ] [ -inetd ] [ -ls listen_socket
] [ -nodaemon ] [ -port tcp_port ] [ -user username
]
xfs is the X Window System
font server. It supplies fonts to X Window System display servers. The server
is usually run by a system administrator, and started via init (8) or inetd
(8) . Users may also wish to start private font servers for specific sets of fonts.
234. GUI Tools to configure x windows is redhat-config-xfree86(old tool is Xconfiguration)
235. alternatively run xf86config in /etc/X11 (be
careful)
236. apropos xf86config, apropos gnome(The apropos command
displays a list of all topics in the man pages)
237. xwindows
is working with desktop environment and a window manager to give the
look and feel
238. shell:>/sbin/init 3 (to run in runlevel 3)
239. After starting at logon page press control +alt +f1 to get text based logon screen
==xterm -display localhost:0.0 & (to display x client), and press Alt+f7 to get
xterminal window in xsession.
==cd /usr/X11R6/bin(is where window
programs are present)
240. xclock -display localhost:0.0
-geometry 50X50-0-0& (display
xclock window program as with geometry option)
-----------------------
-------------------------------------------------------
-----------------------------------------
------------------------
For example, if you're using iptables,
you could allow traffic on these ports and eth1 (the private network interface) with these commands:(
iptables — administration tool for IPv4 packet filtering and NAT)
241. Shell:>sudo iptables -A
INPUT -i eth1 -p udp
-m multiport --dports 5404,5405,5406 -m conntrack --ctstate NEW,ESTABLISHED
-j ACCEPT
{-i: Name of an
interface via which a packet was received (only
forpackets entering the
INPUT, FORWARD and PREROUTING chains),
-A:append,-p:protocol, -m :match, -d:address, -j: This specifies the target of
the rule; i.e., what to do if the
packet matches it, --ctstate:satelist is a comma separated
list of the connection states to match.
Possible states are listed below}
Iptables is
used to set up, maintain, and
inspect the tables of IPv4 packet filter
rules in the Linux kernel. Several
different tables may be defined.
Each table contains a number of
built-in chains and may also contain user-defined chains. Each chain is a list
of rules which can match a set of
packets. Each rule specifies
what to do with a packet that matches.
This is called a‘target’, which may be a jump to a user-defined chain in
the same
ta-ble.
242. Shell:>sudo iptables -A OUTPUT -o eth1 -p udp -m multiport –s ports 5404,5405,5406 -m conntrack
--ctstate ESTABLISHED -j
ACCEPT--match -m match extended match (may load extension)
--proto -p
proto protocol: by number or name, eg. `tcp'
--source -s address [/mask][...]
source specification
--destination -d
address[/mask][...] destination
specification
--in-interface -i
input name[+] network interface name ([+] for wildcard)
--jump -j target target for rule (may load target
extension)
--out-interface
-o output name[+] network interface name ([+] for wildcard)
---------------------------
--------------------------------------------
-----------------------------------------------------------
243. Shell:>less /root/install.log (
the installation log entries in /root/install.log directory)
244. Shell:>kudzu is a hardware indentification package.
kudzu detects
and configures new and/or changed hardware on a
system.
When started, kudzu detects the current
hardware, and checks it against
a
database stored in /etc/sysconfig/hwconf, if one exists. It then
determines if any hardware has been
added or removed from the system.
If
so, it gives the users the opportunity to configure any added hard-
ware, and unconfigure
any removed hardware.
It then updates
the
database in /etc/sysconfig/hwconf.
If
no previous database
exists, kudzu attempts
to determine what
devices have already been configured, by
looking at /etc/modprobe.conf,
/etc/sysconfig/network-scripts/, and
/etc/X11/xorg.conf.
245. Shell:>cd /var/log> cat dmesg(dmesg is a system startup log)
246. Shell:>dmesg | less (www.linuxgazette.com/issue59/nazario.html is a explanation of dmesg file verbose output)
247. Shell:>/usr/bin/setup is program
called text mode setup utility which actually to run )( setup - A text mode
system configuration tool)
248. Shell:>authconfig-tui,system-config-firewall,ntsysv,
timeconfig{(authconfig, authconfig-tui - an interface
for configuring system authentication resources.
Use system-config-authentication GUI application or the
command line options instead.)( ntsysv - simple interface
for configuring runlevels)(timeconfig provides a
simple method of configuring both /etc/syscon-fig/clock and
/etc/localtime which is compatible with both the standard
Red Hat startup scripts
and timeconfig(8).)}
Authconfig
[options]
{--update|--updateall|--test|--probe|--restorebackup
<name>|--savebackup
<name>|--restorelastbackup}
ntsysv [--back] [--level <levels>]
timeconfig [--utc]
[--arc] [--back] [--test] [timezone]
249. Shell:>system-config-authentication
250. Shell:>redhat-config-network
251. Shell:>redhat-config-services
-------------------------
-----------------------------------------
--------------------------------------------------------------
252. Shell:>Disk Druid(to setup the partitions and raid setup)
==Do not do a
raid set up for /boot partition because the /boot should be at a single
partition only
==And for other software raid
partitions do not set up a mount point . Do setup a mount point after the set
up of raid.
253. Shell:>fdisk –L (text based implantation of raid)(
Partition table manipulator for Linux)
fdisk
[-uc] [-b sectorsize] [-C cyls] [-H heads] [-S sects] device
fdisk -l [-u] [device...]
fdisk -s partition...
fdisk -v
fdisk -h
==select RAID button on the
partitioning window and do the necessary steps to attach
the above software raid member
partiions in this step to create MAKE A RAID DEVICE working with a mount point
==Text based
setup of raid and graphical setup of Raid(disk druid)
254. Shell:>LVM(logical volume Management) new
to redhat 8.0,pv(physical volume, logical volume group, logical volumes to
mount point with each volume.
==to do a logical
volume from a physical volume.
==Using Disk Druid through
graphical representation we can do physical volume to logical volume.
==lvm,pv,lv,lvg and so on.(logical
volume management, physical volume, logical volume,logical volume group)
255. shell:>info lvm (location of lvm directory /etc/lvm/lvm.conf, and location lvm of
specific for user $HOME/.lvm_history
256. shell:>lvextend -L +100 /dev/volume00/logvol00(to
extend 100 megabytes)( lvextend: Add space to a logical volume
==Raid levels(0,1,5),Hardware
raid, software raid, Lvm (www.sistina.com)
----------------------------------------
--------------------------------------------------------------------
network installation issues:
257. Network installation, kickstart,
Grub, Lilo boot loader.
258. In path /images we will have bootnet.img file to do a installation through
network.
259. client machine(minumum installation),server
machine(make access to this machine from any client machine so that network
installation is done without problems)
260. shell:>mount -t iso9660 /dev/cdrom /mnt/cdrom(To mount the cdrom to
the server machine under /mnt/cdrom)
261. shell:>df -h( to report filesystem disk space usage)
262. shell:>mkdir /rhinstall , cp –av /mnt/cdrom /rhinstall ( copy the contents of installtaion
disk cdrom to the directory on /rhinstall directory on server machine)
==go to /etc directory
on the server machine and do some change to export file emacs /etc/exports
/rhinstall * (ro)
and save the exports file.
263. shell:>mount -t iso9660 /dev/cdrom /mnt/cdrom
(do the mount on client machine ),copy "bootnet.img" to the
client machine by using "dd" command,
==dd if
=/mnt/cdrom/bootnet.img of=/dev/fdo
(use dd when ur copying .img files )
==put the floppy
disc and start the machine it will prompt a boot:where you type linux askmethod
"boot:linux
askmethod"
==nfs,ftp,http(enter client and
server information to install linux after prompt of boot:linux askmethod"
264. shell:>kickstart (using kickstart method to
automate the installation of linux installation), using ks.cfg to
automate,(use anaconda-ks.cfg in /root, edit sample.ks to get to required, use ksconfig GUI
to do the required in /usr/sbin)
==boot: linux
ks=floppy"
==boot: linux ks=nfs:192.168.0.100:/ks/ks.cfg"
==boot: linux ks=ftp://192.168.0.100:/ks/ks.cfg"
==boot: linux ks=http://192.168.0.100:/ks/ks.cfg"
==more anaconda-ks.cfg
( to see different options)
==grub, lilo
(linux loader)
-----------------------------------------
--------------------------------------
265. Disk Druid only available at installation
266. shell:>DD more user friendly,fdisk, sfdisk,fdisk allows
actions to be scripted.
==DD is only available at
installation , but after installation you want to partition then you got to use
fdisk.
==tab to move to
next option available and space bar to select .
--------------------------------------------
----------------------------------------
---------------------------------------
267. Business perspective, user perspective, technical issues.(while
installation of Linux)
==business &
end user perspective, Main system or supplemental, Starting fresh or migrating?
------------------
Types of problems
268. Hardware, operating system (kernel),application software,
configuration, user
269. Kernels are denoted by x.y.z (“y”
should be even number instead of odd number) stable
release is a y
with a even
number.
270. change and check in /etc for system wide
problems , .filename problems with user specific
problems.
==Plan of attack Observer problem
first hand (Recreate the problem), and work on it, formulate a guess as to
cause, attempt to fix (keep records), Go back to step1 until fixed.
==preventative measures buy supported
hardware, stay away from untested software, and don’t overclock
271. shell:>cd /var/log/ ;
/var/log:>cat boot.log, maillog,
maillog.1(boot.log in location of path /var/log/boot.log)
272. shell:>cd /etc/ , shell:>cat rsyslog.conf | less (rsysconf in /etc directory)
Bugprirority:debug,info,notice,warning,warn(depreciated),err,error(depreciated),crit,alert,emerg,panic(depreciated)
273. shell:>cat syslog.conf | less
Check the output , and
you find few lines about paths of log
files locations.
==mail.* /var/log/maillog, ==authpriv* /var/log/secure, ==cron* /var/log/cron, ==*.emerg *(to
display to everybody) , ==kern.* /dev/console,
==*.info;mail.non;authpriv.none;cron.none /var/log/messages
274. shell:>dmesg (displays log files recorded when starting )(
dmesg - print or control the kernel ring buffer)
275. shell:>ifconfig etho (ifconfig - configure a network interface)
SYNOPSIS
ifconfig
[interface]
ifconfig interface [aftype] options | address
...
{Ifconfig
is used to configure the kernel-resident
network interfaces. It is used at
boot time to set up interfaces as necessary.
After that, it is usually only needed when debugging
or when system
tuning is needed. If no arguments are
given, ifconfig displays the status of the currently active interfaces.
276. shell:>route (specficies the routes used by eth0 and
eth1)( route - show / manipulate the IP routing table)
277. Shell:>df /boot (report file system disk space usage)
278, shell:>du *, du / , du /boot(du - estimate file space
usage)
279. shell:>fsck (check and repair a Linux file system)
fsck.ext4
[-panyrcdfvtDFV] [-b superblock] [-B blocksize]
[-I
inode_buffer_blocks] [-P process_inode_size]
[-l|-L
bad_blocks_file] [-C fd] [-j external_journal] [-E extended-options] device
280. shell:>lpq(lpq - show printer queue status)
281. Shell:>top (top - display Linux tasks)
top
-hv | -abcHimMsS -d delay -n iterations [-u user | -U user] -p pid [,pid ...]
-a sort by
memory usage
-b batch mode
operation
-M detect memory
units
-s secure mode
operation
282. shell:>cd /etc/init.d (
where all process scripts are present)
283. lock files(sometimes when the process is killed
by a kill -9 option then the process lock file will prevent the service to get restared
with a restart command. SO in that case search the process lock file and delete
it and restart the process. The lock file will get generated when the process
starts.)
284. when the process is already running any configuration
changes for it to take effect will have to get restarted. But if you are restarting
when it is in use the users will get effected , so make changes to process conf
file and use kill
-1 <pid>where -1 option for kill is sighup.sighup is saying that when the process is again restarted
anytime soon please apply the necessary configuraition change without killing
it.
Use start and
stop scripts in etc/init.d directory to proper stop and start scripts of
processes.
285. shell:>kill -l ( to see
all the signals of the kill command type kill –l)
286. shell:> ip (show
/ manipulate routing, devices, policy routing and tunnels)
ip [
OPTIONS ] OBJECT { COMMAND | help }
OBJECT := { link | addr |
addrlabel | route | rule | neigh | tunnel | maddr | mroute | monitor } OPTIONS := { -V[ersion] | -s[tatistics] |
-r[esolve] | -f[amily] { inet| inet6 | ipx | dnet | link } | -o[neline]}
287. Shell:>ip addr ,
shell:> ip link, shell:> ip -s link
(For statistics use)
288. shell:>cancel (cancel cancels existing print jobs. The -a
option will remove all jobs from the specified destination, check these
commands lp , lpr, lprm,lpstat
---------------------
------------------------------------------------------------------------
