The Problem Hostname on server [geeklab_new] does not match hostname recorded in /var/log/messages file. [root@geeklab_new]# /bin/hostname geeklab_new [root@geeklab_new]# tail -5 /var/log/messages Mar 2 23:42:01 geeklab_old rsyslogd-2177: imuxsock lost 928 messages from pid 20559 due to rate-limiting Mar 2 23:42:01 geeklab_old puppet-agent[20559]: (/Stage[main]/Main/File[/etc/mcollective/facts.yaml]) Filebucketed /etc/mcollective/facts.yaml to puppet with sum 74964a9f330a61507c47deca4a39fcb3 Mar 2 23:42:03 geeklab_old puppet-agent[20559]: (/Stage[main]/Core_mcollective_config::Config/Service[mcollective]) […]
Archives for May 2021
Hostname change not reflecting in sar report for CentOS/RHEL
The Problem After changing the hostname from geeklab_old to geeklab_new, the sar report still shows the old hostname. # sar -f /var/log/sa/sa09 Linux 5.4.17-2102.200.13.el8uek.x86_64 (geeklab_old) 04/09/2021 _x86_64_ (4 CPU) … The hostname change is reflected in /var/log/messages: Apr 9 14:32:33 geeklab_old systemd[1]: Starting Hostname Service… Apr 9 14:32:33 geeklab_old dbus-daemon[1117]: [system] Successfully activated service ‘org.freedesktop.geeklab_old’ […]
How to enable Debug Option For CIFS Module in CentOS/RHEL 7 and 8
Question: How to configure CIFS debug option in Linux servers to provide additional debug information in the client system logs? 1. Take backup of existing debug or to check the default value: # cp /sys/kernel/debug/dynamic_debug/control /root/backup # cat /proc/fs/cifs/cifsFYI # cat /proc/fs/cifs/traceSMB 2. Enable debug chosen options: # echo ‘module cifs +p’ > /sys/kernel/debug/dynamic_debug/control # […]
How to Create/Format/Extend Virtual Data Optimizer(VDO) Volumes using Cockpit Web Console in CentOS/RHEL 8
This post describes the Virtual Data Optimizer (VDO) configuration using the Cockpit web console. Create VDO volumes 1. Log in to the OL 8 cockpit web console. 2. Click Storage. 3. Click the + icon in the VDO Devices box. 4. In the Name field, enter a name of a VDO volume without spaces. 5. […]
How to Debug systemd boot process in CentOS/RHEL 7 and 8
Question: How to debug/find, changes or failing commands during boot process? During boot process, when seeing grub boot menu press “e” for edit the grub, then scroll down until you see boot entry: echo “Loading Linux… linux16 /vmlinuz-XXX root=XXXro crashkernel=auto rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet LANG=en_US.UTF-8 On the line with “linux” remove the following entries if […]
“not enough to start the array” – error while staring mdadm RAID array
The Problem After replacing issue disk on software RAID, mdadm Fails to Start the RAID Array with Error – “not enough to start the array” and Software Raid State is showing “active, FAILED, Not Started” “mdadm –detail /dev/md0” showing only 4 disks are active and 8 removed disks. # mdadm –detail /dev/md0 State : active, […]
How to Enable IPv6 in CentOS/RHEL 8
By default, IPv6 is enabled on CentOS/RHEL 8 systems. However, in certain situations, some users may find it desirable to disable IPv6 support. This post outlines steps to enable ipv6 on a CentOS/RHEL 8 system. 1. Edit /etc/default/grub and delete the entry ipv6.disable=1 from the GRUB_CMDLINE_LINUX, as shown below: # vi /etc/default/grub GRUB_CMDLINE_LINUX=”rd.lvm.lv=rhel/swap crashkernel=auto rd.lvm.lv=rhel/root” […]
How to Disable IPv6 in CentOS/RHEL 8
By default, IPv6 is enabled on CentOS/RHEL 8 systems. However, in certain situations, some users may find it desirable to disable IPv6 support. This post outlines steps to disable ipv6 on a CentOS/RHEL 8 system. For systems Using NetworkManager For all systems that run NetworkManager, IPv6 must be disabled on each interface with the option […]
“Logical volume vg/lv contains a filesystem in use” – while removing LVM filesystem
The Problem How to remove an LVM volume which returns “filesystem in use” error. # lvchange -an /dev/mapper/vg-lv Logical volume vg/lv contains a filesystem in use The Solution Step 1: Try to identify if this particular LVM is mounted in your server. # mount -a | grep /path-to-LV-volume If mounted, unmount it. Step 2: Check […]