Some command for Back Track

File Command

ls directory listing
ls -al formatted listing with hidden files
cd dir Change directory to dir
cd Change to home
pwd show current directory
mkdir dir create a directory dir
rm file delete file
rm -r dir -delete directory dir
rm -f file force remove file
rm -rf dir force remove directory dir*
cp file1 file2 copy file1 to file2
cp -r dir1 dir2 copy dir1 to dir2 ; create dir2 if it doesnt exit
mv file1 file2 rename or move file1 to file2 ;if file2 is an existing directory , move file1 into directory file2
ln -s file link create symbolic link link to file
touch file create or update file
cat > file places standard input into file
more file output the contents of file
head file output the first 10 lines of file
tail file out put the last 10 lines of file
tail -f file output the contents of file as it grows, starting with the last 10 lines

Installation

Install form source

./ configure
make
make install
dpkg -i pkg.deb install a package (debian)
rpm -Uvh pkg.rpm install a package (RPM)

Network

Ping host ping host and output results
whois domain get whois information for domain
dig domain get DNS information for domain
dig -x host reverse lookup host
wget file download file
wget -c file continue a stopped download

Shortcuts

Ctrl+C halts the current command
Ctrl+Z stops the current command resume with fg in the foreground or bg in the background
Ctrl+D log out of current session, similar to exit
Ctrl+W erases one word in the current line
Ctrl+U erases the whole line
Ctrl+R type to bring up a recent command ..repeats the last command
exit log out of current session

Compression

tar cf file.tar files created a tar named file.tar containing files
tar xf file.tar -extract the files from file.tar
tar czf file.tar.gz files create a tar with Gzip compression
tar xzf file.tar.gz extract a tar using Gzip
tar cjf file.tar.bz2 create a tar wiht Bzip2 compression
tar xjf file.tar.bz2- extract a tar using Bzip2
gzip file compresses file and rename it to file.gz
gzip -d file.gz decompress file.gz back to file

Searching

grep pattern file search for a pattern in file
grep -r pattern dir search recursively for pattern in dir
command | grep pattern search for pattern in the output command
locate file find all instances of file

SSH

ssh user@host connect to host as user
ssh -p port user@host connect to host on port on port as user
ssh -copy -id user@host- add your key to host for user to enable a keyed or passwordless login

File Permissions

chmod octal file change the premission of file to octal , which can be found separately for user,gruop and world by adding :

4 read (r)
2 write (w)
1 execute (x)

Examples;

chmod 777 read, write ,execute for all

chmod 755 rwx for owner , rx for group and world For more option see man chmod .

Process Management

ps display your currently active processes
top display all running processes
kill pid kill process id pid
killall proc kill all processes and named proc*
bg lists stopped for background jobs: resume a stopped job in the background
fg -brings the most recent job to foreground
fg n brings job n to the foreground

System Info

date show the current date and time
cal - show this month calendar
uptime show current uptime
w display who is online
whoami who you are logged in as
finger user display information about the user
uname -a show kernel information
cat / proc/ cpuinfo cpu information
cat / proc/ meminfo memory information
man command show the manual for command
df show disk usage
du show directory space usage
free show memory and swap usage
whois app show possible location of app
which app show which app will be run by defult