CentOS/RHEL 8 now uses iptables as the default packet filtering framework, and is also used by firewalld. But if you try starting iptables, it would fail by default. Follow the steps outlined below to disable firewalld and nftables and enable iptables instead. 1. Install the iptables-services package: # dnf install iptables-services 2. Disable nftables and firewalld: # systemctl disable nftables firewalld Removed /etc/systemd/system/multi-user.target.wants/nftables.service. Removed … [Read more...] about How to disable firewalld and nftables and use iptables instead in CentOS/RHEL 8
How to add an Ethernet connection using nmcli in CentOS/RHEL 7
Question: How to use nmcli to add an Ethernet connection with manual or via DHCP configuration? The NetworkManager command line tool, nmcli, provides those who prefer to use the command line way to configure networking by controlling NetworkManager. It is installed along with NetworkManager. Installing NetworkManager Use nmcli with the object connection and command add. (This can be abbreviated to con add). The first step should be to have the latest version of NetworkManager package, … [Read more...] about How to add an Ethernet connection using nmcli in CentOS/RHEL 7
How to set the order to load certain modules in CentOS/RHEL 7 and 8
If you want to load modules that have dependencies then you can use the modprobe command. It will automatically resolve the dependencies and load the modules. Here are three ways to accomplish loading modules at boot automatically: 1. Using systemd-modules-load.service (Recommended) Use systemd-modules-load.service to load the modules during boot. 1. Add a file in /etc/modules-load.d/[name].conf containing module names. It will read the lines in order and load the modules … [Read more...] about How to set the order to load certain modules in CentOS/RHEL 7 and 8
How to configure initrd / initramfs to including kernel modules in CentOS/RHEL
The method for including kernel modules in the initrd / initramfs varies based on RHEL version. In all examples replace [kernel module] with the module name, not including .ko. For CentOS/RHEL 4 and 5 Three methods can be used to include a kernel module in the initial RAM disk: 1. Use the --withM option when manually building the ram disk with mkinitrd: # mkinitrd --with=[kernel module] /boot/initrd-$(uname -r).img $(uname -r) 2. For storage-related modules put an alias in … [Read more...] about How to configure initrd / initramfs to including kernel modules in CentOS/RHEL
How to configure systemd.path to trigger an event when any changes made to a directory
What is systemd.path systemd.path works similar to auditd in earlier versions with extra features as triggering an event or a run a script when a change is made to file or directory. From the man page of systemd.path: A unit configuration file whose name ends in ".path" encodes information about a path monitored by systemd, for path-based activation. Path files must include a [Path] section, which carries information about the path(s) it monitors. How to configure systemd.path … [Read more...] about How to configure systemd.path to trigger an event when any changes made to a directory
Script to monitor RMAN Backup and Restore Operations
RMAN is designed to complete a backup or restore as quikly and efficiently as possible. But if a job takes longer than expected to complete it can be confusing trying to determine: What precisely is RMAN doing at any particular time? Is RMAN hung or just slow? How far into the backup/restore has it got? How much more work is there to go? Knowing just how much processing has been done so far is often crucial when trying to decide whether or not to wait for job completion. RMAN … [Read more...] about Script to monitor RMAN Backup and Restore Operations
Oracle RMAN Backup Shell Script Example
Pre-requisites 1. Create a catalog database (rmancat) if one does not exist. (With additional UNDO-, USERS- and TEMP-tablespaces) 2. Configure SQL*Net to handle the catalog (rmancat) and the 'target' database connections. 3. Create a user 'RMAN' in the catalog database. SQL> create user rman identified by rman default tablespace USERS quota unlimited on users temporary tablespace TEMP; SQL> grant recovery_catalog_owner to rman; 4. Create the RMAN-catalog in the … [Read more...] about Oracle RMAN Backup Shell Script Example
What are the advantages of using BrowsePoll over client.conf while configuring cups client
Currently, there are two methods to configure the client system to collect all the printers related information from a specific print server. 1. Add following line in /etc/cups/client.conf file : # vi /etc/cups/client.conf ServerName [IP/Hostname of cups server] save and exit. 2. Restart cups service. # service cups restart In this method no local spool is maintained, lpstat -a would fetch the print queues from the cups server specified. When client.conf is used, canceling of the … [Read more...] about What are the advantages of using BrowsePoll over client.conf while configuring cups client
How to Configure a Networked CUPS (IPP) printer in CentOS/RHEL
What is an IPP Printer IPP Printers are printers that are attached to a different Linux system on the same network running CUPS or at least with IPP support configured. The networked IPP printers are found via CUPS browsing as long as the print server and client can send and receive connections on UDP port 631. Configuring CUPS IPP client Listed below are the steps to configure the CUPS IPP client to see all the allowed networked IPP printer: 1. Edit the /etc/hosts file to add the IP … [Read more...] about How to Configure a Networked CUPS (IPP) printer in CentOS/RHEL
How to Configure CUPS Master Print Server and CUPS Client in CentOS/RHEL 6,7
Question: We would like to set up a central CUPS print server and have other Red Hat systems print to printers on that print server. This way we only need to configure the printers in one place. Is it possible to have the printers configured in one location, but also have local queues on the clients? In such a way that queuing jobs is still possible on the clients and jobs get printed when the central server is back online? CUPS Master Print Server 1. Stop CUPS and back up your current CUPS … [Read more...] about How to Configure CUPS Master Print Server and CUPS Client in CentOS/RHEL 6,7