Basic Linux Commands
mkdir - make directories
Usage
mkdir [OPTION] DIRECTORY
Options
Create the DIRECTORY(ies), if they do not already exist.
Mandatory arguments to long options are mandatory for
short options too.
-m, mode=MODE set permission mode (as in chmod), not rwxrwxrwx -
umask
-p, parents no error if existing, make parent directories as
needed
-v, verbose print a message for each created directory
-help display this help and exit
-version output version information and exit
cd - change directories
Use cd to change directories.
Type cd followed by the name of a directory to access that
directory.Keep in mind that you are always in a directory and
can navigate to directories hierarchically above or below.
mv- change the name of a directory
Type mv followed by the current name of a directory and the new
name of the directory.
Ex: mv testdir newnamedir
pwd - print working directory
will show you the full path to the directory you are currently
in. This is very handy to use, especially when
performing some of the other commands on this page
rmdir
- Remove an existing directory
rm
-r
Removes directories and files within the directories
recursively.
chown - change file owner and group
Usage
chown [OPTION] OWNER[:[GROUP]] FILE
chown [OPTION] :GROUP FILE
chown [OPTION] --reference=RFILE FILE
Options
Change the owner and/or group of each FILE to OWNER and/or
GROUP. With --reference, change the owner and group of each
FILE to those of RFILE.
-c, changes like verbose but report only when a change is made
-dereference affect the referent of each symbolic link, rather
than the symbolic link itself
-h, no-dereference affect each symbolic link instead of
any referenced file (useful only on systems that can
change the
ownership of a symlink)
-from=CURRENT_OWNER:CURRENT_GROUP
change the owner and/or group of each file only if
its current owner and/or group match those specified here.
Either may be omitted, in which case a match is not required
for the omitted attribute.
-no-preserve-root do not treat `/' specially (the
default)
-preserve-root fail to operate recursively on `/'
-f, -silent, -quiet suppress most error messages
-reference=RFILE use RFILE's owner and group rather than the
specifying OWNER:GROUP values
-R, -recursive operate on files and directories recursively
-v, -verbose output a diagnostic for every file processed
The following options modify how a hierarchy is
traversed when the -R option is also specified. If more
than one is specified, only the final one takes effect.
-H if a command line argument is a symbolic link to a
directory, traverse it
-L traverse every symbolic link to a directory
encountered
-P do not traverse any symbolic links (default)
chmod - change file access permissions
Usage
chmod [-r] permissions filenames
r
Change the permission on files that are in the subdirectories of the
directory that you are currently in.
permission Specifies the
rights that are being granted. Below is the different rights that you
can grant in an alpha numeric format.filenames File or
directory that you are associating the rights with Permissions
u - User who owns the file.
g - Group that owns the file.
o - Other.
a - All.
r - Read the file.
w - Write or edit the file.
x - Execute or run the file as a program.
Numeric Permissions:
CHMOD can also to attributed by using Numeric Permissions:
400 read by owner
040 read by group
004 read by anybody (other)
200 write by owner
020 write by group
002 write by anybody
100 execute by owner
010 execute by group
001 execute by anybody
ls - Short listing of directory contents
-a list hidden files
-d list the name of the current directory
-F show directories with a trailing '/'
executable files with a trailing '*'
-g show group ownership of file in long listing
-i print the inode number of each file
-l long listing giving details about files and
directories
-R list all subdirectories encountered
-t sort by time modified instead of name
cp - Copy files
cp myfile yourfile
Copy the files "myfile" to the file "yourfile" in the current
working directory. This command
will create the file "yourfile" if it doesn't exist. It will
normally overwrite it without warning if it exists.
cp -i myfile yourfile
With the "-i" option, if the file "yourfile" exists, you will be
prompted before it is overwritten.
cp -i /data/myfile
Copy the file "/data/myfile" to the current working directory
and name it "myfile". Prompt before overwriting the file.
cp -dpr srcdir destdir
Copy all files from the directory "srcdir" to the directory "destdir"
preserving links (-poption), file attributes (-p option), and
copy recursively (-r option). With these options, a directory
and all it contents can be copied to another dir
ln - Creates a symbolic link to a file.
ln -s test symlink
Creates a symbolic link named symlink that points to the file
test Typing "ls -i test symlink" will show the two files are
different with different inodes. Typing "ls -l test symlink"
will show that symlink points to the file test.
locate
- A fast database driven file locator.
slocate
-u
This command builds the slocate database. It will take several
minutes to complete this command.This command must be used
before searching for files, however cron runs this command
periodically
on
most systems.locate whereis Lists all files
whose names contain the string "whereis". directory.
more -
Allows file contents or piped output to be sent to the
screen one page at a time
less -
Opposite of the more command
cat
- Sends file contents to standard output. This is a way to list
the contents of short files
to the screen. It works well with
piping.
whereis
-
Report all known instances of a command
wc -
Print byte, word, and line counts
bg
bg jobs
Places the
current job (or, by using the alternative form, the specified
jobs) in the background, suspending its execution so that a new
user prompt appears immediately. Use the
jobs
command to discover the identities of background jobs.
cal month
year
-
Prints a calendar
for the specified month of the specified year.
cat files
-
Prints the
contents of the specified files.
clear
-
Clears the
terminal screen.
cmp file1
file2
-
Compares two
files, reporting all discrepancies. Similar to the
diff
command, though the output format differs.
diff file1
file2
-
Compares two
files, reporting all discrepancies. Similar to the
cmp command, though the output format differs.
dmesg
-
Prints the
messages resulting from the most recent system boot.
fg
fg jobs
-
Brings the
current job (or the specified jobs) to the foreground.
file files
-
Determines and
prints a description of the type of each specified file.
find path -name pattern
-print
Searches the
specified path for files with names matching the specified
pattern (usually enclosed in single quotes) and prints their
names. The
find
command has many other arguments and functions; see the online
documentation.
finger users -
Prints
descriptions of the specified users.
free
-
Displays the
amount of used and free system memory.
ftp hostname
Opens an FTP
connection to the specified host, allowing files to be
transferred. The FTP program provides subcommands for
accomplishing file transfers; see the online documentation.
head files
-
Prints the first
several lines of each specified file.
ispell files
-
Checks the
spelling of the contents of the specified files.
kill
process_ids
kill - signal process_ids
kill -l
Kills the
specified processes, sends the specified processes the specified
signal (given as a number or name), or prints a list of
available signals.
killall
program
killall - signal program
Kills all
processes that are instances of the specified program or sends
the specified signal to all processes that are instances of the
specified program.
mail
-
Launches a simple
mail client that permits sending and receiving email messages.
man title
man section title
-
Prints the
specified man page.
ping host
-
Sends an echo
request via TCP/IP to the specified host. A response confirms
that the host is operational.
reboot
-
Reboots the
system (requires
root
privileges).
shutdown
minutes
shutdown -r
minutes
Shuts down the
system after the specified number of minutes elapses (requires
root
privileges). The -r option causes the system to be
rebooted once it has shut down.
sleep time
-
Causes the
command interpreter to pause for the specified number of
seconds.
sort files
-
Sorts the
specified files. The command has many useful arguments; see the
online documentation.
split file
-
Splits a file
into several smaller files. The command has many arguments; see
the online documentation
sync
-
Completes all
pending input/output operations (requires
root
privileges).
telnet host
-
Opens a login
session on the specified host.
top
-
Prints a display
of system processes that's continually updated until the user
presses the
q
key.
traceroute
host
-
Uses echo
requests to determine and print a network path to the host.
uptime
-
Prints the system
uptime.
w
-
Prints the
current system users.
wall
- Prints a message
to each user except those who've disabled message reception.
Type Ctrl-D to end the message.
