gnome-control-center: open system settings from terminalxclip -selection clipboard: to copy output directly to clipboard
| Command | Usage |
|---|---|
ssh | ssh (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine. |
ls | List information about the FILEs (the current directory by default). |
cd | Change Directory |
cat | Concatenate files and print on the standard output |
file | determine file type |
du | estimate file space usage |
find | search for files in a directory hierarchy |
grep | print lines that match patterns |
sort | sort lines of text files |
uniq | report or omit repeated lines |
strings | print the sequences of printable characters in files |
base64 | base64 encode/decode data and print to standard output |
tr | Translate, squeeze, and/or delete characters from standard input, writing to standard output. |
tar | an archiving utility |
gzip | compress or expand files |
bzip2 | a block-sorting file compressor |
xxd | make a hexdump or do the reverse. |
mkdir | make directories |
cp | copy files and directories |
mv | move files and directories |
telnet | The telnet command is used for interactive communication with another host using the TELNET protocol |
nc | netcat is a simple unix utility which reads and writes data across network connections, using TCP or UDP protocol. |
openssl | OpenSSL command line tool |
s_client | The s_client command implements a generic SSL/TLS client which connects to a remote host using SSL/TLS. It is a very useful diagnostic tool for SSL servers. |
nmap | Network exploration tool and security / port scanner |
diff | compare files line by line |
bash | Bash is an sh-compatible command language interpreter |
screen | Screen is a full-screen window manager that multiplexes a physical terminal between several processes |
tmux | tmux is a terminal multiplexer: it enables a number of terminals to be created, accessed, and controlled from a single screen. |
bg | background a process |
fg | foreground a process |
jobs | list processes running in background |
& | run a command in background |
cron | daemon to execute scheduled commands |
crontab | maintain crontab files for individual users |
crontab(5) | tables for driving cron |
more | file perusal filter for crt viewing |
less | opposite of more |
vi | vim - Vi IMproved, a programmer's text editor |
id | print real and effective user and group IDs |
pwd | print working directory |
git | the stupid content tracker |
locate | find files by name, quickly |
man | an interface to the system reference manuals |
which | locate a command |
type | lets you query the type of each command. |
ps | report a snapshot of the current processes. |
kill | send a signal to a process |
uname | print system information |
chmod | change file mode bits |
chown | change file owner and group |
chgrp | change group ownership |
tail | output the last part of files |
ln | make link between files |
cat ./-(./ - stands for current directory) : cat a file with name "-"cat ./-filename: cat a file whose name starts with "-"cat \spaces \in \this \filename.txt(Original filename:spaces in this filename.txt) - cat a file name with spacesbase64 -d data.txt- base64 decode a filestrings filename- output human readable text from non-humanreadable file:echo "acbdlksjfla KHLKJfdlsfasd" | tr 'A-Za-z' 'N-ZA-Mn-za-m'- rotate a text with all lowercase and uppercase by 13 positions:openssl s_client -connect <host>:<port>: connect a host with ssl encryptiondiff fileone filetwo: check differencetail -n <number of lines> <path & file name>: print last n lines of a fileln -s tmp/files/take-the-command-challenge take-the-command-challenge: Create a symbolic link named take-the-command-challenge that points to the file tmp/files/take-the-command-challenge.find . -delete: Delete all of the files in this challenge directory including all subdirectories and their contents.grep -rl 500:-rfor Recursive, read all files in given directory and subdirectories &-lfor Print the name of each file which contains a match.
Note: These are my notes for personal reference!
date: displays the current time and date
┌──(shreyas㉿kali)-[~] └─$ date Tuesday 04 January 2022 03:39:43 PM IST cal: displays a calendar of the current month
┌──(shreyas㉿kali)-[~] └─$ cal January 2022 Su Mo Tu We Th Fr Sa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 df: the current amount of free space on our disk drives
┌──(shreyas㉿kali)-[~] └─$ df Filesystem 1K-blocks Used Available Use% Mounted on udev 1953436 0 1953436 0% /dev tmpfs 399160 1168 397992 1% /run /dev/sda1 130538556 11247868 112613492 10% / tmpfs 1995784 0 1995784 0% /dev/shm tmpfs 5120 0 5120 0% /run/lock tmpfs 399156 68 399088 1% /run/user/1000 free: display the amount of free memory
┌──(shreyas㉿kali)-[~] └─$ free total used free shared buff/cache available Mem: 3991568 672232 2753624 8864 565712 3079888 Swap: 998396 0 998396 pwd: print working directory
┌──(shreyas㉿kali)-[~] └─$ pwd /home/shreyas cd: change directory
┌──(shreyas㉿kali)-[~] └─$ cd practise ┌──(shreyas㉿kali)-[~/practise] └─$ pwd /home/shreyas/practise ┌──(shreyas㉿kali)-[~/practise] └─$ ls hackthebox cdshortcuts
| Shortcut | Result |
|---|---|
| cd | Changes the working directory to your home directory. |
| cd - | Changes the working directory to the previous working directory. |
| cd ~user_name | Changes the working directory to the home directory of user_name. For example, typing cd ~bob will change the directory to the home directory of user “bob.” |
ls: List directory contents
ls -l: output in long formatls -t: the t option to sort the result by the file’s modification time.ls -lt --reverse: --reverse to reverse the order of the sort.
┌──(shreyas㉿kali)-[~] └─$ ls BugBounty Documents Music practise Templates Desktop Downloads Pictures Public Videos ┌──(shreyas㉿kali)-[~] └─$ ls /usr bin games include lib lib32 lib64 libexec libx32 local sbin share src ┌──(shreyas㉿kali)-[~] └─$ ls practise /usr practise: hackthebox /usr: bin games include lib lib32 lib64 libexec libx32 local sbin share src ┌──(shreyas㉿kali)-[~] └─$ ls -l total 176 drwxr-xr-x 3 shreyas shreyas 4096 Jan 1 17:38 BugBounty drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Desktop drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Documents drwxr-xr-x 3 shreyas shreyas 4096 Dec 29 15:32 Downloads drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Music drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Pictures drwxr-xr-x 3 shreyas shreyas 4096 Dec 26 21:40 practise drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Public drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Templates drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Videos ┌──(shreyas㉿kali)-[~] └─$ ls -lt total 40 drwxr-xr-x 3 shreyas shreyas 4096 Jan 1 17:38 BugBounty drwxr-xr-x 3 shreyas shreyas 4096 Dec 29 15:32 Downloads drwxr-xr-x 3 shreyas shreyas 4096 Dec 26 21:40 practise drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Desktop drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Documents drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Music drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Pictures drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Public drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Templates drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Videos ┌──(shreyas㉿kali)-[~] └─$ ls -lt --reverse 2 ⨯ total 40 drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Videos drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Templates drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Public drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Pictures drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Music drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Documents drwxr-xr-x 2 shreyas shreyas 4096 Dec 14 19:34 Desktop drwxr-xr-x 3 shreyas shreyas 4096 Dec 26 21:40 practise drwxr-xr-x 3 shreyas shreyas 4096 Dec 29 15:32 Downloads drwxr-xr-x 3 shreyas shreyas 4096 Jan 1 17:38 BugBounty file filename: the file command will print a brief description of the file’s contents
┌──(shreyas㉿kali)-[~/practise/hackthebox] └─$ file flag.txt flag.txt: ASCII text, with no line terminators ┌──(shreyas㉿kali)-[~/practise/hackthebox] └─$ file pack.ovpn pack.ovpn: ASCII text less: allows us to scroll forward and backward through a text file.Note: less is more. Means both commands are same
┌──(shreyas㉿kali)-[~/practise/hackthebox] └─$ cat example | less ┌──(shreyas㉿kali)-[~/practise/hackthebox] └─$ less example | Command | Action |
|---|---|
PAGE UP or b | Scroll back one page |
PAGE DOWN or space | Scroll forward one page |
Up arrow | Scroll up one line |
Down arrow | Scroll down one line |
G | Move to the end of the text file |
1G or g | Move to the beginning of the text file |
/characters | Search forward to the next occurrence of characters |
n | Search for the next occurrence of the previous search |
h | Display help screen |
q | Quit less |
- Wildcards:
| Wildcards | Meaning |
|---|---|
* | Matches any character |
? | Matches any single character |
[characters] | Matches any character that is a member of the set characters |
[!characters] | Matches any character that is not a member of the set characters |
[:class:]] | Matches any character that is member of the specified class |
- List of most commonly used character classes
| Character class | Meaning |
|---|---|
[:alnum:] | Matches any alphanumeric character |
[:alpha:] | Matches any alphabetic characters |
[:digit:] | Matches any numerical |
[:lower:] | Matches any lowercase letter |
[:upper:] | Matches any uppercase |
- Wildcard examples:
| Pattern | Matches |
|---|---|
* | All files |
g* | Any file beginning with g |
b*.txt | Any file beginning with b followed by any characters and ending with .txt |
Data??? | Any file beginning with Data followed by exactly three characters |
[abc]* | Any file beginning with either an a, a b, or a c |
BACKUP.[0-9][0-9][0-9] | Any file beginning with BACKUP. followed by exactly three numerals |
[[:upper:]]* | Any file beginning with an uppercase letter |
[![:digit:]]* | Any file not beginning with a numeral |
*[[:lower:]123] | Any file ending with a lowercase letter or the numerals 1, 2, or 3 |
Wildcards can be used with any command that accepts filenames as arguments
mkdir- make directorymkdir dir- single directorymkdir dir1 dir2 dir3- multiple directories
┌──(shreyas㉿kali)-[~/practise] └─$ mkdir commandline ┌──(shreyas㉿kali)-[~/practise] └─$ ls commandline hackthebox ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ mkdir dir1 dir2 dir3 ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ ls dir1 dir2 dir3 cp- copy files and directoriescp item1 item2: copy single file item1 into item2cp item... directory: copies multiple items (either files or directories) into a directory.
| Option | Meaning |
|---|---|
-a,--archive | Copy the files and directories and all of their attributes, including ownerships and permissions. |
-i, --interactive | Before overwriting an existing file, prompt the user for confirmation. |
-r, --recursive | Recursively copy directories and their contents. This option (or the -a option) is required when copying directories. |
-u, --update | When copying files from one directory to another, only copy files that either don’t exist or are newer than the existing corresponding files in the destination directory. This is useful when copying large numbers of files as it skips files that don’t need to be copied |
-v, --verbose | Display informative messages as the copy is performed. |
mvis same ascp
rm file: remove files and directories
| Option | Meaning |
|---|---|
-i, --interactive | Before deleting an existing file, prompt the user for confirmation. |
-r, --recursive | Recursively delete directories. This means that if a directory being deleted has subdirectories, delete them too. To delete a directory, this option must be specified. |
-f, --force | Ignore nonexistent files and do not prompt. This overrides the --interactive option. |
-v, --verbose | Display informative messages as the deletion is performed. |
ln: create linksln file link: create a hard linkln -s item link: creates a symbolic link
type: is a shell builtin that displays the kind of command the shell will execute
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ type ls ls is an alias for ls --color=auto ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ type ssh ssh is /usr/bin/ssh ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ type cd cd is a shell builtin which: Display an Executable’s Location
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ which ls ls: aliased to ls --color=auto ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ which pwd pwd: shell built-in command ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ which cd cd: shell built-in command ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ which gedit /usr/bin/gedit ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ which firefox /usr/bin/firefox man: Display a Program’s Manual Page
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ man ls LS(1) User Commands LS(1) NAME ls - list directory contents SYNOPSIS ls [OPTION]... [FILE]... DESCRIPTION List information about the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor --sort is specified. Mandatory arguments to long options are mandatory for short options too. -a, --all do not ignore entries starting with . -A, --almost-all do not list implied . and .. --author with -l, print the author of each file Manual page ls(1) line 1 (press h for help or q to quit) apropos- Display Appropriate Commands
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ apropos copy cifsdd (8) - convert and copy a file over SMB COPY (7) - copy data between a file and a table cp (1) - copy files and directories cpgr (8) - copy with locking the given file to the password or group file cpio (1) - copy files to and from archives cppw (8) - copy with locking the given file to the password or group file dd (1) - convert and copy a file debconf-copydb (1) - copy a debconf database git-checkout-index (1) - Copy files from the index to the working tree gvfs-copy (1) - Deprecated equivalent of gio copy install (1) - copy files and set attributes mariadb-hotcopy (1) - a database backup program mysqlhotcopy (1) - a database backup program ntfscp (8) - copy file to an NTFS volume. objcopy (1) - copy and translate object files ptrepack (1) - Copy any PyTables Leaf, Group or complete subtree into anothe... rcp (1) - OpenSSH secure file copy rsync (1) - a fast, versatile, remote (and local) file-copying tool scp (1) - OpenSSH secure file copy ssh-copy-id (1) - use locally available keys to authorise logins on a remote ma... svnversion (1) - Produce a compact version identifier for a working copy. vfs_shadow_copy (8) - Expose snapshots to Windows clients as shadow copies. vfs_shadow_copy2 (8) - Expose snapshots to Windows clients as shadow copies. x86_64-linux-gnu-objcopy (1) - copy and translate object files whatis: Display One-line Manual Page Descriptions
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ whatis rm rm (1) - remove files or directories ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ whatis ls ls (1) - list directory contents ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ whatis sudo sudo (8) - execute a command as another user info: Display a Program’s Info Entry
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ info ls Next: dir invocation, Up: Directory listing 10.1 ‘ls’: List directory contents ================================== The ‘ls’ program lists information about files (of any type, including directories). Options and file arguments can be intermixed arbitrarily, as usual. For non-option command-line arguments that are directories, by default ‘ls’ lists the contents of directories, not recursively, and omitting files with names beginning with ‘.’. For other non-option arguments, by default ‘ls’ lists just the file name. If no non-option argument is specified, ‘ls’ operates on the current directory, acting as if it had been invoked with a single argument of ‘.’. By default, the output is sorted alphabetically, according to the locale settings in effect.(1) If standard output is a terminal, the output is in columns (sorted vertically) and control characters are output as question marks; otherwise, the output is listed one per line and control characters are output as-is. -----Info: (coreutils)ls invocation, 56 lines --Top------------------------------------ Follow xref: gument is specified, ‘ls’ operates on the current directory, acting asif alias: Creating Our Own Commands with aliastrick: It’s possible to put more than one command on a line by separating each command with a semicoloncommand1; command2; command3...
[me@linuxbox ~]$ cd /usr; ls; cd - bin games include lib local sbin share src /home/me [me@linuxbox ~]$ [me@linuxbox ~]$ type foo bash: type: foo: not found [me@linuxbox ~]$ alias foo='cd /usr; ls; cd -' [me@linuxbox ~]$ foo bin games include lib local sbin share src /home/me [me@linuxbox ~]$ [me@linuxbox ~]$ type foo foo is aliased to `cd /usr; ls; cd -' [me@linuxbox ~]$ unalias foo [me@linuxbox ~]$ type foo bash: type: foo: not found <command> > <file>: Redirecting Standard Output
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ ls -l /usr/bin > ls-output.txt ┌──(shreyas㉿kali)-[~/practise/commandline] └─$ ls -l total 180 drwxr-xr-x 2 shreyas shreyas 4096 Jan 4 17:21 dir1 drwxr-xr-x 2 shreyas shreyas 4096 Jan 4 17:21 dir2 drwxr-xr-x 2 shreyas shreyas 4096 Jan 4 17:21 dir3 -rw-r--r-- 1 shreyas shreyas 171639 Jan 4 18:21 ls-output.txt command >> file- append redirected output to a file instead of overwriting the file
[me@linuxbox ~]$ ls -l /usr/bin >> ls-output.txt 0>OR<: redirecting standard input>: redirecting standard output2>: redirecting standard error
[me@linuxbox ~]$ ls -l /bin/usr 2> ls-error.txt ls -l /bin/usr > ls-output.txt 2>&1ORls -l /bin/usr &> ls-output.txt: Redirecting Standard Output and Standard Error to One Filels -l /bin/usr 2> /dev/null: Disposing unwanted output
command1 | command2: Pipelinewc: Print line, Word, and Byte countsgrep: print line matching patternhead -n <number of lines> ls-output.txt: print initial lines of filetail -n <number of lines> ls-output.txt: print last lines of filestee: Read from Stdin and Output to Stdout and Files
┌──(shreyas㉿kali)-[~/practise/commandline] └─$ wc ls-output.txt 2557 24294 171639 ls-output.txt [me@linuxbox ~]$ head -n 5 ls-output.txt total 343496 -rwxr-xr-x 1 root root 31316 2017-12-05 08:58 [ -rwxr-xr-x 1 root root 8240 2017-12-09 13:39 411toppm -rwxr-xr-x 1 root root 111276 2017-11-26 14:27 a2p -rwxr-xr-x 1 root root 25368 2016-10-06 20:16 a52dec [me@linuxbox ~]$ tail -n 5 ls-output.txt -rwxr-xr-x 1 root root 5234 2017-06-27 10:56 znew -rwxr-xr-x 1 root root 691 2015-09-10 04:21 zonetab2pot.py -rw-r--r-- 1 root root 930 2017-11-01 12:23 zonetab2pot.pyc -rw-r--r-- 1 root root 930 2017-11-01 12:23 zonetab2pot.pyo lrwxrwxrwx 1 root root 6 2016-01-31 05:22 zsoelim -> soelim echo: Display a line of textecho *: works same aslsecho D*: Display files/directories which starts with Decho *s: Display files/drectories which ends with secho [[:upper:]]*: Display files/directories that starts with uppercase lettersecho /usr/*/share: display all directories between /usr/ & /shareecho ~: tilde expansion
┌──(shreyas㉿kali)-[~] └─$ echo hello there my name is shreyas hello there my name is shreyas ┌──(shreyas㉿kali)-[~] └─$ echo * BugBounty Desktop Documents Downloads Music Pictures practise Public Templates Videos ┌──(shreyas㉿kali)-[~] └─$ echo D* Desktop Documents Downloads ┌──(shreyas㉿kali)-[~] └─$ echo *s Documents Downloads Pictures Templates Videos ┌──(shreyas㉿kali)-[~] └─$ echo [[:upper:]]* BugBounty Desktop Documents Downloads Music Pictures Public Templates Videos ┌──(shreyas㉿kali)-[~] └─$ echo /usr/*/share /usr/local/share ┌──(shreyas㉿kali)-[~] └─$ echo ~ /home/shreyas - Arithmetic Expansion:
$((expression))
┌──(shreyas㉿kali)-[~] └─$ echo $((2 + 2)) 4 ┌──(shreyas㉿kali)-[~] └─$ echo $(($((5**2)) * 3)) 75 | Operator | Description |
|---|---|
+ | Addition |
- | Subtraction |
* | Multiplication |
/ | Division (but remember, since expansion supports only integer arithmetic, results are integers) |
% | Modulo, which simply means “remainder” |
** | Exponentiation |
- Brace Expansion: create multiple text strings from a pattern containing braces
┌──(shreyas㉿kali)-[~] └─$ echo Front-{A,B,C}-Back Front-A-Back Front-B-Back Front-C-Back ┌──(shreyas㉿kali)-[~] └─$ echo Number_{1..5} Number_1 Number_2 Number_3 Number_4 Number_5 ┌──(shreyas㉿kali)-[~] └─$ echo {01..15} 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 ┌──(shreyas㉿kali)-[~] └─$ echo a{A{1,2},B{3,4}}b aA1b aA2b aB3b aB4b - Parameter expansion:
echo $var - Command Substitution
echo $(ls)ls -l $(which cp)file $(ls -d /usr/bin/* | grep zip)
- Quoting:
- Double Quotes: If we place text inside double quotes, all the special characters used by the shell lose their special meaning and are treated as ordinary characters. The exceptions are $ (dollar sign), \ (backslash), and ` (backtick).
- Single Quotes: If we need to suppress all expansions, we use single quotes.
- Escaping Characters:
\: is used for escaping
- Backslash Escape Situation:
| Escape Sequence | Meaning |
|---|---|
\a | Bell (an alert that causes the computer to beep) |
\b | Backspace |
\n | Newline; on Unix-like systems, this produces a line feed |
\r | Carriage return |
\t | tab |
┌──(shreyas㉿kali)-[~] └─$ sleep 10; echo -e "Time's up\a" Time's up -
clear: Clear the terminal screen -
history: Display or manipulate the history list -
Cursor Movement:
| Key | Action |
|---|---|
CTRL-A | Move the cursor to the beginning of line |
CTRL-E | Move cursor to the end of the line |
CTRL-F | Move cursor forward one character; same as the right arrow key |
CTRL-B | Move cursor backward one character; same as the left arrow key |
ALT-F | Move cursor one word forward |
ALT-B | Move cursor backward one word |
CTRL-L | Clear screen and move the cursor to the top left corner. Same as clear command |
- Modifying Text
| Key | Action |
|---|---|
CTRL-D | Delete the character at the cursor location |
CTRL-T | Transpose the character at the cursor location |
ALT-T | Transpose the word at the cursor location with the one preceding it. |
ALT-L | Convert the characters from the cursor location to the end of the word to lowercase. |
ALT-U | Convert the characters from the cursor location to the end of the word to uppercase. |
- History Expansion
| Sequence | Action |
|---|---|
!! | Repeat the last command. It is probably easier to press the up arrow and ENTER |
!number | Repeat history list item number. |
!string | Repeat last history list item starting with string |
!?string | Repeat last history list item containing string |
-
id: Display user identity -
chmod: Change a file’s mode -
umask: Set the default file permissions -
su: Run a shell as another user -
sudo: Execute a command as another user -
chown: Change a file’s owner -
chgrp: Change a file’s group ownership -
passwd: Change a user’s password -
Permission attribute Examples:
| File Attributes | Meaning |
|---|---|
-rwx------ | A regular file that is readable, writable, and executable by the file’s owner. No one else has any access. |
-rw------- | A regular file that is readable and writable by the file’s owner. No one else has any access. |
-rw-r--r-- | A regular file that is readable and writable by the file’s owner. Members of the file’s owner group may read the file. The file is world-readable. |
-rwxr-xr-x | A regular file that is readable, writable, and executable by the file’s owner. The file may be read and executed by everybody else. |
-rw-rw---- | A regular file that is readable and writable by the file’s owner and members of the file’s group owner only. |
lrwxrwxrwx | A symbolic link. All symbolic links have “dummy” permissions. The real permissions are kept with the actual file pointed to by the symbolic link. |
drwxrwx--- | A directory. The owner and the members of the owner group may enter the directory and create, rename, and remove files within the directory. |
drwxr-x--- | A directory. The owner may enter the directory and create, rename, and delete files within the directory. Members of the owner group may enter the directory but cannot create, delete, or rename files. |
chmod: Change File Mode- 6(rw-)
- 7(rwx)
- 5(r-x)
- 4(r--)
- 0(---)
| Symbol | Meaning |
|---|---|
u | Short for "user" but means the file or directory owner. |
g | Group owner |
o | Short for "others" but means world |
a | Short for "all". This is a combination of u, g, and o. |
- If no character is specified, “all” will be assumed. The operation may be a + indicating that a permission is to be added, a - indicating that a permission is to be taken away, or a = indicating that only the specified permissions are to be applied and that all others are to be removed.
| Notation | Meaning |
|---|---|
u+x | Add execute permission for the owner. |
u-x | Remove execute permission from the owner. |
+x | Add execute permission for the owner, group, and world. This is equivalent to a+x. |
o-rw | Remove the read and write permissions from anyone besides the owner and group owner. |
go=rw | Set the group owner and anyone besides the owner to have read and write permissions. If either the group owner or the world previously had execute permission, it is removed. |
u+x,go=rx | Add execute permission for the owner and set the permissions for the group and others to read and execute. Multiple specifications may be separated by commas. |
ps: Report a snapshot of current processestop: Display tasksjobs: List active jobsbg: Place a job in the backgroundfg: Place a job in the foregroundkill: Send a signal to a processkillall: Kill process by nameshutdown: Shut down or reboot the system
ping: Checks if a network is reachable,pingcommand sends a special network packet called anICMP ECHO_REQUESTto a specified host. Most network devices receiving this packet will reply to it, allowing the network connection to be verified.
┌──(shreyas㉿kali)-[~] └─$ ping youtube.com PING youtube.com (142.250.204.46) 56(84) bytes of data. 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=1 ttl=128 time=149 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=2 ttl=128 time=151 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=3 ttl=128 time=188 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=4 ttl=128 time=140 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=5 ttl=128 time=139 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=6 ttl=128 time=120 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=7 ttl=128 time=131 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=8 ttl=128 time=148 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=9 ttl=128 time=137 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=10 ttl=128 time=132 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=11 ttl=128 time=144 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=12 ttl=128 time=128 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=13 ttl=128 time=128 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=14 ttl=128 time=141 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=15 ttl=128 time=135 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=16 ttl=128 time=130 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=17 ttl=128 time=133 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=18 ttl=128 time=142 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=19 ttl=128 time=134 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=20 ttl=128 time=137 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=21 ttl=128 time=139 ms ^C64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=22 ttl=128 time=140 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=23 ttl=128 time=121 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=24 ttl=128 time=146 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=25 ttl=128 time=136 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=26 ttl=128 time=165 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=27 ttl=128 time=176 ms 64 bytes from hkg07s38-in-f14.1e100.net (142.250.204.46): icmp_seq=28 ttl=128 time=132 ms ^C --- youtube.com ping statistics --- 28 packets transmitted, 28 received, 0% packet loss, time 27045ms rtt min/avg/max/mdev = 120.372/140.817/187.758/14.526 ms traceroute: lists all the “hops” network traffic takes to get from the local system to a specified host.
┌──(shreyas㉿kali)-[~] └─$ traceroute google.com traceroute to google.com (142.250.204.110), 30 hops max, 60 byte packets 1 192.168.29.2 (192.168.29.2) 0.227 ms 0.099 ms 0.175 ms 2 * * * 3 * * * 4 * * * 5 * * * 6 * * * 7 * * * 8 * * * 9 * * * 10 * * * 11 * * * 12 * * * 13 * * * ip a: It replaces the earlier and now deprecatedifconfigprogram.
┌──(shreyas㉿kali)-[~] └─$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:0c:29:c5:88:a0 brd ff:ff:ff:ff:ff:ff inet 192.168.x.x/24 brd 192.168.x.x scope global dynamic noprefixroute eth0 valid_lft 1630sec preferred_lft 1630sec inet6 fe80::20c:29ff:x:x/64 scope link noprefixroute valid_lft forever preferred_lft forever netstat: The netstat program is used to examine various network settings and statistics.-roption will display the kernel’s network routing tableie: we can examine the network interfaces in our system
┌──(shreyas㉿kali)-[~] └─$ netstat -ie Kernel Interface table eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.x.x netmask 255.255.255.0 broadcast 192.168.29.255 inet6 fe80::20c:29ff:x:x prefixlen 64 scopeid 0x20<link> ether 00:0c:29:c5:88:a0 txqueuelen 1000 (Ethernet) RX packets 102 bytes 11285 (11.0 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 207 bytes 17053 (16.6 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen 1000 (Local Loopback) RX packets 8 bytes 400 (400.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 8 bytes 400 (400.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ┌──(shreyas㉿kali)-[~] └─$ netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface default 192.168.29.2 0.0.0.0 UG 0 0 0 eth0 192.168.29.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 Transporting Files over a Network
ftp:ftpis used to communicate with FTP servers, machines that contain files that can be uploaded and downloaded over a network.FTP(in its original form) is not secure because it sends account names and passwords in cleartext.
[me@linuxbox ~]$ ftp fileserver Connected to fileserver.localdomain. 220 (vsFTPd 2.0.1) Name (fileserver:me): anonymous 331 Please specify the password. Password: 230 Login successful. Remote system type is UNIX. Using binary mode to transfer files. ftp> cd pub/cd_images/ubuntu-18.04 250 Directory successfully changed. ftp> ls 200 PORT command successful. Consider using PASV. 150 Here comes the directory listing. -rw-rw-r-- 1 500 500 733079552 Apr 25 03:53 ubuntu-18.04-desktop-amd64.iso 226 Directory send OK. ftp> lcd Desktop Local directory now /home/me/Desktop ftp> get ubuntu-18.04-desktop-amd64.iso local: ubuntu-18.04-desktop-amd64.iso remote: ubuntu-18.04-desktop-amd64.iso 200 PORT command successful. Consider using PASV. 150 Opening BINARY mode data connection for ubuntu-18.04-desktop-amd64.iso (733079552 bytes). 226 File send OK. 733079552 bytes received in 68.56 secs (10441.5 kB/s) ftp> bye | Command | Meaning |
|---|---|
ftp fileserver | Invoke the ftp program and have it connect the FTP server fileserver |
anonymous | Login name. After the login prompt, a password prompt will appear. Some servers will accept a blank password; others will require a password in the form of an email address. In that case, try something like user@example. |
cd | change directory |
ls | list directory |
lcd Desktop | Change the directory on the local system to ~/Desktop. In the example, the ftp program was invoked when the working directory was ~. This command changes the working directory to ~/Desktop. |
get | transfer file from remote server to local system |
bye | Log off the remote server and end the ftp program session. The commands quit and exit may also be used. |
lftpis a Better ftp
wget: It is useful for downloading content from both web and FTP sites. Single files, multiple files, and even entire sites can be downloaded.
[me@linuxbox ~]$ wget http://linuxcommand.org/index.php --11:02:51-- http://linuxcommand.org/index.php => `index.php' Resolving linuxcommand.org... 66.35.250.210 Connecting to linuxcommand.org|66.35.250.210|:80... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] [ <=> ] 3,120 --.--K/s 11:02:51 (161.75 MB/s) - `index.php' saved [3120] ssh: SSH solves the two basic problems of secure communication with a remote host.- It authenticates that the remote host is who it says it is (thus preventing so-called man-in-the-middle attacks).
- It encrypts all of the communications between the local and remote hosts.
ssh remote-sys: To connect to a remote host named remote-sysssh username@remote-sys: login with specific usernamessh remote-sys <command>: to execute just a single command
[me@linuxbox ~]$ ssh remote-sys The authenticity of host 'remote-sys (192.168.1.4)' can't be established. RSA key fingerprint is 41:ed:7a:df:23:19:bf:3c:a5:17:bc:61:b3:7f:d9:bb. Are you sure you want to continue connecting (yes/no)? scp- (secure copy). copy files from local host to remote host
[me@linuxbox ~]$ scp remote-sys:document.txt . me@remote-sys's password: document.txt 100% 5581 5.5KB/s 00:00 [me@linuxbox ~]$ sftp: SSH file-copying program
[me@linuxbox ~]$ sftp remote-sys Connecting to remote-sys... me@remote-sys's password: sftp> ls ubuntu-8.04-desktop-i386.iso sftp> lcd Desktop sftp> get ubuntu-8.04-desktop-i386.iso Fetching /home/me/ubuntu-8.04-desktop-i386.iso to ubuntu-8.04-desktop-i386.iso /home/me/ubuntu-8.04-desktop-i386.iso 100% 699MB 7.4MB/s 01:35 sftp> bye locate: Find files by namefind: Search for files in a directory hierarchyxargs: Build and execute command lines from standard inputtouch: Change file timesstat: Display file or file system status
find: find files the hard wayfind ~: to produce a listing of our home directoryfind ~ | wc -l: to count the number of files.find ~ -type d | wc -l:-type dlimit the search to directoriesfind ~ -type f | wc -l:-type flimit the search to regular filesfind ~ -type f -name "*.JPG" -size +1M | wc -l: all the regular files that match the wildcard pattern *.JPG and are larger than one megabyte
| File type | Description |
|---|---|
b | Block special device file |
c | Character special device file |
d | Directory |
f | Regular file |
l | Symbolic link |
- find size units
| Character | Unit |
|---|---|
b | 512-byte blocks. This is default if no unit is specified. |
c | Bytes |
w | 2-byte words |
k | Kilobytes (units of 1,024 bytes) |
M | Megabytes (units of 1,048,576 bytes) |
c | Gigabytes (units of 1,073,741,824 bytes) |
- More about
findoptions: Find cheatsheet
xargs- It accepts input from standard input and converts it into an argument list for a specified command
find ~ -type f -name 'foo*' -print | xargs ls -l -rwxr-xr-x 1 me me 224 2007-10-29 18:44 /home/me/bin/foo -rw-r--r-- 1 me me 0 2016-09-19 12:53 /home/me/foo.txt Remaining:
- archiving and backup
- regular expressions
- text processing
- compiling programs
- that's enough for now i guess