CentOS/RHEL 6

CentOS/RHEL usually uses rsyslogd rate-limit mechanism. Below is an example of message logged in /var/log/messages due to rsyslog rate-limiting. Feb 9 10:22:32 localhost rsyslogd: imuxsock lost 432 messages from pid 9832 due to rate-limiting Feb 9 10:22:45 localhost rsyslogd: imuxsock begins to drop messages from pid 9832 due to rate-limiting The rate limitation prevents logging from using excessive levels of system resources and to flood the /var/log/message with unnecessary messages. To … [Read more...] about How To Disable Or Extend System Logging Rate-limit on CentOS/RHEL 6

The Setup This configuration uses below OS, Storage and Server Hardware - OS release - "RHEL 7.1" Kernel - 3.8.13-55.1.6.el7.x86_64 Hardware: HP ProLiant BL460c Gen8 Ethernet Interfaces with FCoE capability - 04:00.0 Ethernet controller: Broadcom Corporation BCM57840 NetXtreme II 10/20-Gigabit Ethernet (rev 11) 04:00.1 Ethernet controller: Broadcom Corporation BCM57840 NetXtreme II 10/20-Gigabit Ethernet (rev 11) 04:00.2 Ethernet controller: Broadcom Corporation BCM57840 NetXtreme … [Read more...] about How to Configure a Fiber-Channel Over Ethernet (FCoE) Interface in CentOS/RHEL

1. Check the attributes of the FC remote port(s) using the below command: # udevadm info --attribute-walk --path=/sys/class/fc_remote_ports/rport-x:y-z 2. Then create udev rules that match all viable rports by matching the 'role' mentioned in the attributes returned in the above command. For example, create /etc/udev/rules.d/99-tmo.rules and include the below contents. ACTION!="add|change", GOTO="tmo_end" KERNELS=="rport-?*", SUBSYSTEM=="XXXX", ATTR{roles}=="XXXX", … [Read more...] about How to Set “dev_loss_tmo” Value Persistently Using Udev Rule

The Problem While executing: # yum update The following error occurs: One of the configured repositories failed (Unknown), and yum doesn't have enough cached data to continue. At this point the only safe thing yum can do is fail. There are a few ways to work "fix" this: 1. Contact the upstream for the repository and get them to fix the problem. 2. Reconfigure the baseurl/etc. for the repository, to point to a working upstream. This is most often useful if you are using a … [Read more...] about “Could not resolve proxy: https; Unknown error” – error with ‘yum update’

This post will guide the user on how to reinstall a corrupted library via yum. In general, the command below will find which package the corrupted library belongs to: # yum provides \*/[so_file] In this example, we used this error message "/bin/login: error while loading shared libraries: /lib64/libcrypt.so.1: file too short" to identify the corrupted library and the find the package it originally came from: # yum provides \*/libcrypt.so.1 ... glibc-2.17-260.0.17.el7_6.6.x86_64 : The … [Read more...] about How to Reinstall Corrupted Library with yum

The Task Create an LVM snapshot of the root filesystem. Revert Snapshot Changes To An Earlier State. The Solution 1. Before proceeding make sure LVM Volume Group (VG) has enough space for the snapshot. # vgs VG #PV #LV #SN Attr VSize VFree ol 2 2 0 wz--n- 12.00g 1.01g 2. In this example we are creating a root snapshot of 512M. Here "snap" is the snapshot name of a root volume. # lvcreate -L 512M -s -n snap /dev/ol/root Logical volume "snap" created. 3. … [Read more...] about How to Create An LVM Snapshot Of The Root Filesystem And Restore To An Earlier State

Below we demonstrate three common methods for transforming the iptables rules into the firewalld controls. Our example shows the transformation of one iptables rule output by the iptables-save command: LOG_TEST_NEW - [0:0] -A LOG_TEST_NEW -m limit --limit 2/min -j LOG --log-prefix "New Connection" The example rule logs up to two log entries per minute. The log entry is labeled with the string "New Connection." Using The firewalld GUI (Applications -> Sundry -> Firewall) 1. Create a Rule … [Read more...] about How to Migrate CentOS/RHEL 6 iptables Rules to CentOS/RHEL 7 firewalld

The purpose of this post is to explain the steps to disable NUMA on servers which use the EFI boot loader. GRUB 2 is the default EFI-mode boot loader, so the steps are based on GRUB2. 1. Take a backup of /etc/default/grub configuration file. # cp -p /etc/default/grub /etc/default/grub_backup 2. Edit /etc/default/grub file and replace numa=on to numa=off. # vi /etc/default/grub .. GRUB_CMDLINE_LINUX_DEFAULT="root=LABEL=DBSYS bootarea=dbsys bootfrom=BOOT ro loglevel=7 panic=60 debug … [Read more...] about How to disable NUMA on EFI Boot Loaders using GRUB2 (CentOS/RHEL 6)

In CentOS/RHEL 8, the default iptables network packet filtering framework been replaced with the nftables framework. As the designated successor to iptables, ip6tables, arptables, and ebtables, the nftables framework includes packet classification facilities and several improvements, which provide added convenience and improved performance over the previously used packet-filtering tools. In this post we will discuss on how to migrate existing iptables rules to nftables in CentOS/RHEL … [Read more...] about How To Migrate Existing Iptables rules to Nftables In CentOS/RHEL 8