firewalld is the default method in Red Hat Enterprise Linux 7 for managing host-level firewalls. Started from the firewalld. service systemd service, firewalld manages the Linux kernel netfilter subsystem using the low-level iptables, ip6tables, and ebtables commands. Default Configuration of firewalld Zones Zone name Default configuration trusted Allow all incoming traffic. home Reject incoming traffic […]
Archives for February 2018
How to restore files under user’s home directory to default in Linux
The Problem If accidentally the context or file permission of files under user’s home directory had been changed, permission errors or unexpected application behavior might be encountered after this user login system. For instance, if the file permission of /home/user1/.bash_profile is wrong, login user1 will get prompt “/home/user1/.bash_profile: Permission denied”: login as: user1 user1@geeklab’s password: […]
Understanding iscsiadm Utility in CentOS / RHEL
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage devices. iSCSI uses IP networks to encapsulate SCSI commands, allowing data to be transferred over long distances. iSCSI provides shared storage among a number of client systems. Storage devices are attached to servers (targets). Client systems (initiators) access the remote storage devices […]
How to troubleshoot iSCSI issues in CentOS / RHEL 6,7
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage devices. iSCSI uses IP networks to encapsulate SCSI commands, allowing data to be transferred over long distances. iSCSI provides shared storage among a number of client systems. Storage devices are attached to servers (targets). Client systems (initiators) access the remote storage devices […]
CentOS / RHEL 6,7 : How to delete an iSCSI Target on the initiator (iSCSI client)
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage devices. iSCSI uses IP networks to encapsulate SCSI commands, allowing data to be transferred over long distances. iSCSI provides shared storage among a number of client systems. Storage devices are attached to servers (targets). Client systems (initiators) access the remote storage devices […]
How to configure iSCSI Initiator (client) in CentOS / RHEL 7
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage devices. iSCSI uses IP networks to encapsulate SCSI commands, allowing data to be transferred over long distances. iSCSI provides shared storage among a number of client systems. Storage devices are attached to servers (targets). Client systems (initiators) access the remote storage devices […]
How to configure iSCSI target using targetcli in CentOS / RHEL 7
Internet Small Computer System Interface (iSCSI) is an IP-based standard for connecting storage devices. iSCSI uses IP networks to encapsulate SCSI commands, allowing data to be transferred over long distances. iSCSI provides shared storage among a number of client systems. Storage devices are attached to servers (targets). Client systems (initiators) access the remote storage devices […]
How to configure iSCSI Initiator (client) in CentOS / RHEL 6
iSCSI is a protocol that allows clients (called initiators) to send SCSI commands (CDBs) to SCSI storage devices (targets) on remote servers. It is a popular Storage Area Network(SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts (such as database and web servers) with the illusion of locally-attached disks. […]
CentOS / RHEL 5 : How to Boot into Rescue Mode
It is possible to boot Linux in rescue mode using the installation media and bypassing the disk. During the rescue session, you can choose a network. Once the system is up, you will have access to the disk. Follow the below steps to boot in rescue mode: Note: In rescue mode, HDD/NIC will be recognized […]
How to backup Linux OS using “dd” Command
“dd” command can be really handy when it comes to taking an Operating System backup to clone the disk the OS is installed on. Here are few examples of using dd command for taking OS backup. NOTE: The target drive must be either of identical size to the drive being cloned or larger. The dd […]