We may drop the file system caches on Linux to free up memory for applications. Kernels 2.6.16 and newer provide a mechanism via the /proc/ to make the kernel drop the page cache and/or inode and dentry caches on command. We can use this mechanism to free up the memory. However, this is a non-destructive…
We introduced how to create a LVM group with two hard disk partitions, which the LVM group can be used for [[setting-up-lvm-backed-xen-domu|installing LVM backed Xen DomUs]]. The LVM volume can have large capacity from several hard disks. However, we may use all the disk space after some time and we may need to extend the…
Different Linux distros have different method to set the hostname. On Fedora Linux, it is quite simple. On newer Fedora releases At least from Fedora 19 (sorry, no sure the exact earliest version): You need to edit the file /etc/hostname which just contains the hostname. On older Fedora releases Sorry, I do not know the…
NFS is widely deployed and used even after more than twenty year. NFS is easy to set up and easy to use. This introduces how to set up the NFS server and clients. We use the Fedora system as the example. The tutorial here is for RHEL/CentOS/Fedora and derived Linux OSes. Set up an NFS…
The latest tools for upgrading Fedora is FedUp, please check How to upgrade Fedora 19 to Fedora 20 through the network. Please consider PreUpgrade for upgrading Fedora. This is the recommended method. This post makes a list of actions should be done to upgrade Fedora using yum. Please note that this is for experienced users…
Setting up Ubuntu 10.10 DomU on top of Fedora Xen Dom0 is introduced in this post. The process of setting up Ubuntu 10.10 DomU is the same as Setting Up Stable Xen DomU with Fedora: Unmodified Fedora 12 on top of Xenified Fedora 12 Dom0 with Xen 4.0 This post only show the difference which…
Update: this only works on older Linux kernels (e.g. Fedora 12). For newer kernels, please see How to disabling IPv6 on Linux IPv6 is enabled by default on most Linux distros. However, IPv4 is still the mostly used network and IPv6 is not used in many environment. This post introduces how to disable IPv6 support on…
It is common to connect servers with only internal IPs from several clusters. VPN is a common technique for this. With iptables, we can implement many functions of VPN with possibly higher performance. The slides here give a brief introduction to how to set up a VPN-like network between 2 clusters which connect to each…
The is a simple introduction to paravirt_ops in Linux kernel for Xen, VMware, etc. We make this introduction from the view of code. We use the function raw_local_irq_disable() and raw_local_irq_enable() functions in Linux kernel to introduce paravirt_ops for Xen and Xenified kernel. Please download the introduction to paravirt_ops pdf file: introduction-to-pv-ops-v3.pdf
LVM’s snapshot feature enables us to duplicate an LVM backed Xen DomU in seconds rather than minutes. We no longer need to copy the entire file system image like backing up file backed Xen DomU. We just need to make a snapshot of the current Xen DomU in seconds. When there are changes to the…
LVM’s snapshot feature enables us to duplicate an LVM backed Xen DomU in seconds inside of the same volume group. When we want to duplicate LVM backed Xen DomU from a remote server, we need to make use of LVM’s snapshot function and tools like scp and dd. Backing up the DomU is only part…
Solutions to Linux cluster construction and management such as unified account management, NFS home directory, network configurations are summarised in this post. The post is keeping updating while new solutions is added to this site. ===Account and storage management=== [[unified-linux-login-and-home-directory-using-openldap-and-nfsautomount|Unified Linux Login and Home Directory Using OpenLDAP and NFS/automount]] [[backup-linux-home-directory-using-rsync|Backup Linux Home Directory Using rsync]]…
This is the latest stable and recommended stable Xen Dom0 solution on Fedora 12. No serious bug found till now and we will fix the bugs by ourselves if some appears. It also works on Fedora 14 as well. It should not be hard to use this solution on other versions of Fedora or other…
Here is a list of problem that may occur during installing and configuring Xen Dom0 in Fedora. It is found originally in Fedora systems, but the tips in this post should also be helpful for installing Xen Dom0 on other platforms. BIOS configuration If xen stops at: “I/O virtualization disabled.” We may need to enable…
The Xen solutions including installing and configuring Dom0 and DomU are summarized here. LVM volumes as backing for DomU’s file system is an appealing solution to Xen VBD. LVM volumes can dynamically grow/shrink and snapshot. These features make it simple and fast to duplicate DomU and adding storage to DomU. LVM backed DomU is recommended….
We may need to install some old packages such as the kernel in our Linux box. Let’s use installing a older version of Linux kernel in Fedora as the example to introduce how to install old packages from the repository using yum. By now, suppose we have install kernel-2.6.32.16-143 in the Linux box and we…
There is various network configuration information in Linux and lots tools can be used to find out those configuration information. Finding out these network information in Fedora Linux as the example will be introduced. IP address, MAC address and netmask ifconfig will print out all the network interfaces and their information including the IP address…
How to set date, time and timezone on Linux/Unix box will be introduced in this post. Unix time, or POSIX time which is a system for describing points in time is the number of seconds elapsed since midnight UTC on the morning of January 1, 1970, not counting leap seconds. The number of seconds elapsed…
MAC stands for Media Access Control which is a six byte number, usually expressed as a twelve digit hexadecimal number. IPs in LAN are translated to MAC address by the ARP (Address Resolution Protocol) protocol. For some reasons such as keeping the true MAC address from being logged, accessing to the network which bounds IPs…
We may not want to update some packages such the kernel on a stable server while updating the system. If we run “dnf update” or “yum update”, we may get suggested by dnf/yum to install all the packages with updates. In this post, how to make dnf/yum not update certain packages such the kernel when…