CREATING AND DELETING FILES
cat >
filename
file will be created
cat >> filename
append contents to existing file.
touch file1 file2
no.of
files will be created.
rm filename
file will
be deleted.
CREATING AND REMOVING DIRECTORIES
mkdir dir1 dir2
no.of directories will be created.
rmdir dir1 dir2
no.of empty directories will be deleted
rm –rf dir1
it removes directories with contents.
cd
to change one directory to another
directory
pwd
to know present working directory.
ps –ef
to know all processes.
kill pid
to kill particular process.
kill –9 pid
to kill process forcefully.
vi filename
to edit file in vi.
ls filename
Lists all files and directories.
ls –l
it gives full information of files and
directories.
ls –a
it displays hidden files
ls –p
shows difference b/w files and directories.
ls –i
Displys inode no of files and
directories.
File permissions
We have two ways to
assign permissions to files
1. Numeric mode
2. Symbolic mode or relative mode
Numeric mode
We assign numerics to
permissions like
read 4
write
2
execute
1
chmod 777
filename/dirname
assign full permissions to all users.
chmod 666
filename/dirname
it assigns read and write permissions
to all users
chgrp newgroupname
file/directory
it changes groupname for file or
directory.
chown newownername
file/directory
it changes owner for file or directory.
Symbolic mode or relative mode
Here we assign symbols to users.
owner
u
group
g
others
o
all a
read r
write
w
execute
x
adding permissions +
removing permissions -
To assign permissions
chmod ugo+rwx file/dir.
To remove permissions
chmod ugo-rwx file/dir.
Network communication
In hetrogenous and
homogenous environment
telnet
ipaddress
it connets to remote system
ftp
ipaddress
scp /dir
ipaddress:/dir
it copies date from source system to
target system
ssh
ipaddress:mkdir /dir
it executes commands in remote
system.
Only in homogenous
environment
rlogin ipaddress
rcp /dir
ipaddress:/dir
rsh ipaddress:rm /file
User commads
useradd –u uid –g gid
–G gid –d homedirecory –m –s sh username
it adds user g for primary group
G for secondary
group
d,m for homedirecoty
s for default shell
u user id
su – username
to swith from one user to another
user.
who
displays all users who are currently
logged in system.
who am I
displays detailed information about
current logged in user.
last
displays information about when system
is lastly rebooted,who,time.
finger
information about current logged in
user.
filesystems
df
it displays all filesystems with sizes
df –h
it displays all filesystems with human readable form.
du to know disk utilization
Shutdown commands
shutdown
init 0
like shutdown
init 1
single user mode
init 6
like
reboot
reboot
poweroff
copy or move
To copy a file
cp sourcefile targetfile
To copy empty directory
cp sourcedir targetdir
To copy directory with all contents
cp –r sourcedir targetdir
To move file
mv sourcefile targetfile
To move directory
mv sourcdir targetdir
creating links
To link file or
directory in same filesystem
ln soucefile/dir targerfile/dir
this is called hard mounting
If you link souce
file or dir with another file which is in different file system that is called
soft mounting
ln –s sourcefile/dir targetfile/dir
For help
man command
Pattern search
To seach for a single
word in a file
grep word filename
it
displays all lines which contains this word
To seach multiple
words
egrep word1 | word2 filename
To seach for a text
fgrep text filename
find
searches in current
directory for file or directory.
find . –name
“<file>/<directory>” –type f/d -print
type options:
b block (buffered) special
c character (unbuffered) special
d directory
p named pipe (FIFO)
f regular file
l symbolic link
to search files exact
n th day old from now
find . –name
“<file>/<directory>” –mtime n –print
to search files
morethan n days old from now.
find . –name
“<file>/<directory>” –mtime +n –print
to search files from
n days old from now.
find . –name “<file>/<directory>”
–mtime -n –print
for searched files in
range( from more than 64 days old to 95 days old)
find . -name
"*" -a "(" -mtime +64 -a -mtime -95 ")" -exec ll
{} \;
to know files in
current directory which are more than 10M size.
find . -type f -size +10M -exec ls -l {} \; (for files)
or
find . -xdev -size
+10000000c -exec ls -l {} \; (for files and
directories)
`b' for 512-byte blocks (this is the default if no suffix
used)
`c' for bytes
`w' for two-byte words
`k' for Kilobytes (units of 1024 bytes)
`M' for Megabytes (units of 1048576 bytes)
`G' for Gigabytes (units of 1073741824 bytes)
If
you want to see if you have any directories with world write permission, use:
find . -type d
-perm 777 –print
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