Basic Linux Operations
Showing the kernel version and hostname
Verify the kernel module list
Showing the list of packets installed
Information about the mounted file systems
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
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
Showing Memory information
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 255.255.255.0
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=192.168.65.129 -> Shows the actual IP used by this interface
NETMASK=255.255.255.0 -> 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:
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:
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
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
Search for all objects of Active Directory
ldapsearch -h <ldap_server_IP> -b ′dc=example,dc=com′ -x -D “email@example.com” -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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