All users should be logged out of server except root. Fsck the filesystem. Reduce the non-root LVM by entering following command on root shell; lvresize --resizefs --size lvresize --resizefs --size -200G /dev/VolGroup00/LogVoL-USER After non-root LVM filesystem is reduced, increase the root-LVM filesystem using; lvresize --resizefs --size +500M /dev/VolGroup00/LogVol-ROOT Mount the filesystem.
Author: Albert
How to convert LVM thin to LVM thick
There is no way to convert LVM thin to LVM thick. You can only transfer data from LVM thin to LVM thick. LVM thick is standard LVM.
Effect of restarting sshd daemon on current ssh sessions
After editing ssh configuration file /etc/ssh/sshd_config, there is no effect on current ssh connections. However, it is necessary to reload sshd after configuring /etc/ssh/sshd_config
How to boot server with older kernel and set it as default in CentOS and AlmaLinux
Identify the Linux Kernel installed on your server by executing following command in shell on file /boot/grub/grub.conf; grep '^[[:space:]]*kernel' /boot/grub/grub.conf To boot from old kernel which is 0 in /boot/grub/grub.conf, change the default value of old kernel to 1 in /boot/grub/grub.conf.
How to disable transparent huge pages [THP] in CentOS 8
On CentOS 8, In file editor open /etc/default/grub file, and add “transparent_hugepage=never” kernel parameter on the GRUB_CMDLINE_LINUX in options as shown below; GRUB_CMDLINE_LINUX="options transparent_hugepage=never" On command line execute grub2-mkconfig to build /boot/grub2/grub.cfg grub2-mkconfig -o /boot/grub2/grub.cfg [System with BIOS]grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg [System with UEFI] Reboot Server to apply changes. If THP is still not disabled, stop …
How to measure maximum available network speed of your Linux server?
You can use iperf that use client and server scenario to test network speed between two Linux based servers. The tool iperf is available in EPEL free repository else you can download from https://iperf.fr/iperf-download.php The following iperf command will send a buffer size enough to test network speed for 120 seconds iperf3 -i 5 -t …
Why do Linux Kernel log “martian source” in log file /var/log/messages?
Mention of martian source in file /var/log/messages indicates a packet received on the active network interface eth0 whose source or destination IP address is not correct. An example of this scenario is source network IP address is already configured on the current system throwing martian source in log files. All this indicates a configuration error …
How to configure a SSH tunnel?
On the client machine perform the following step: [root@host]# ssh -N -L :: user@remote-machine-ip From a new console/terminal execute the telnet command as follows: [root@host]# telnet localhost This kb is relevant to the following; Encrypt the traffic by SSH tunneling the connection to remote host. Encrypt unencrypted network traffic