Linux directory structure
/ "Root" "Slash"
/bin Binaries files or executable files
/etc Configuration files
/home User home directory, separate user data (pics etc)
/home/shannan User Shannan home directory
/root Home directory for root account.
/opt Third-party software (google earth gets installed)
/tmp Temporary space (OS cleans these directory at boot time)
/usr User related programs lives
/usr/bin
/usr/lib
/usr/sbin
/var Variable data (logs files). Things that change often
/var/log
/cdrom Mount point for CD-ROM
/media
/boot Files needed to boot OS
/lib System libraries
/lost+found Used by the filesystem keep recovered files after check has been performed
/mnt Used for mounting external file systems
/proc Info about running processes
/sbin System Administration binaries
/selinux Display info about SELINUX
/srv Contains data which is served by the systems
/srv/www Webserver files
/srv/ftp FTP files
Shell
$ typical user prompt
# root user prompt
Root user can do all things
Normal user account can do subset of things
Basic Linux Commands
commands are case sensitive
ls, cd, pwd, cat, echo, man, exit, clear
man ls --> space, enter, g, G
Environmental Variables
Storage location with name/value
Name typically uppercase
Print value $VAR_NAME
Locate command "which ls"
Directories
. current dir
.. parent dir
cd - previous dir
./ execute command in the current dir
/opt/command/cat executes cat file in the dir
Creating/Removing directories
mkdir [-p] directory - Create dir
rmdir [-p] directory - Remove dir
rm -rf directory - Recursively remove all
ls -l
permissions links user groups size modified-date name
- file
d dir
l symbolic link
r read
w write
x execute
three sets of permissions user, group, other
chmod
chmod ugao (user group all other) +(add) -(remove) =(set) x(execute) file
find command
find path expression
find / -iname dchq (ignore case)
find / -iname *dchq (ignore case)
tail -50 filename (print last 50 lines)
tail -50f filename (print last 50 lines and follows the file)
vi has modes (command, insert, line)
command (h j k l)
insert (i)
line (:no) :$ last line
shift + 6 is beginning of line
shift + $ is end of line
TAR
c create
x extract
z compression
f file
t list
v verbose
tar cf bkp.tar abc
tar tf bkp.tar (prints files)
tar xf bkp.tar (extracts file)
tar zcf bkp.tar.gz or bkp.tgz
gzip
gunzip
gzcat
du -h
IO Redirection
Output redirection
ls -lrt > files.txt
ls -lrt >> files.txt (appends)
ls -lrt 1> files.txt (0 is standard input, 1 output, 2 error)
lss -lrt 2> files.txt (standard error)
lss -lrt 2> /dev/null (standard error)
ls -lrt 1> files.txt 2>&1 (standard error is also going to files.txt)
input redirection
sort < files.txt
grep (search file contents)
grep abc file.txt
grep -i abc file.txt (ignore case)
Cron
crontab -l
crontab file
su (switch user)
sudo (super user do) execute command as other user
Packages & Package Managers
package is collection of files for an application
Package Managers - installs, updates, remove packages
RPM (RHEL, CentOS, Oracle Linux, Fedora, Scientific Linux) Redhat Package Manager
yum search
yum install yum install -y
yum info
yum remove
rpm -ql (list)
rpm -ivh (install)
rpm -e (remove)
DEB Distro
apt (Advance packaging tool)
dpkg
apt-get install -y
apt-get remove -y
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