Linux Commands

Basic Linux Operations


Showing the kernel version and hostname

uname -a


Verify the kernel module list




Showing the list of packets installed

rpm -qa|more



Information about the mounted file systems




Disk Usage

fdisk -l /dev/sda



Showing the status of the Volume Group




Showing the disks and partitions included in the Volume Group




Showing the logical volumes




Showing the Default Gateway

netstat -rn (look for the IP that has FLAG UG)



Showing the NIC status

ethtool eth0



Changing NIC configuration

ethtool -s eth0 speed 1000 duplex full autoneg off



Showing the Iptables rules

iptables -L -n

iptables -t nat -vnL



Verify the processes that are listening in a specific port

lsof –iTCP –n –P



Verify the IP tunnel configuration




Showing the MACs associated to a bridge

brctl showmacs br0



Showing the routing table




Showing CPU configuration

more /proc/cpuinfo



Showing Memory information

more /proc/meminfo



Verify and change of the IP address

To verify what is the actual IP, first execute “ifconfig –a”, if the output is too long use this command instead “ifconfig –a|more” and look for the “eth0” interface.

To change your Linux IP temporarily: Use the following command, the IP will be changed until next reboot.

ifconfig eth0 [New IP] NETMASK

where eth0 is the interface whose IP you want to change.


Permanently changing your Linux IP: For this change, you have to edit /etc/sysconfig/network-scripts/ifcfg-eth0 (if you want to change the IP of a different interface then look for the proper file, for example ifcfg-eth1 for eth1 and so on). Change the following parameters:

DEVICE=eth0 -> Indicates the interface you are changing

BOOTPROTO=none -> Shows if the IP is dynamic (via DHCP) or static

ONBOOT=yes -> Shows if the interface is active after the system starts

HWADDR=00:0c:29:4f:3a:c7 -> Shows the NIC MAC address

IPADDR= -> Shows the actual IP used by this interface

NETMASK= -> Shows the network mask



Creating a new file

Go to the path where you want to create your new file or write the complete path as shown below:

vi new.txt

vi /etc/new.txt


An empty file will be opened, you can start adding lines to your new file or you just can close it by typing:



The file will be created in the path indicated when you executed the “vi” command.



Rename a file

Go to the path of the file or specify it as shown below:

mv oldfile.txt newfile.txt

mv /etc/oldfile.txt /etc/newfile.txt


Be carefull to change the appropiate extension or the file may end up without extension.



Deleting a file

Go to the path or specify it as shown below:

rm file.txt

rm /etc/file.txt


If you get a confirmation prompt just type “y”. If you want to force the operation just add “-f”.

rm -f file.txt


If you want to delete a folder with all its contents type:

rm -rf folder

rmdir –ignore-fail-on-non-empty folder



Creating a folder

mkdir folder




Showing the CPU and Memory Use


This will give you a list ordered by the highes CPU usage, to change it to memory usage type “m” and then “q” to return to CPU.



Finding a process

ps -fea|grep process



Showing network connections


To show the port number instead of the port name (show 25 instead of smtp) use:

[root@tmcent01 ~]# netstat -n



Showing files and folders

ls          Shows the names of files and folders

ls -lha   Shows all files and folders in a detailed list with sizes of  KB,MB,GB,etc…

ls -lct     Shows and sorts the list by modification time





LDAP Commands


Search for all objects of Active Directory

ldapsearch -h <ldap_server_IP> -b ′dc=example,dc=com′ -x -D “” -W ′(objectClass=*)′



Search for all objects of OpenLDAP

ldapsearch -h <ldap_server_IP> -b ′dc=example,dc=com′ -x -D “cn=Manger,dc=example,dc=com” -W ′(objectClass=*)′


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