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Update 02.03.2015: added (modified) Centos / Redhat: A successor to compcache is zram which is fully integrated in the Linux kernel since 2.6.37.1 and uses lzo compression. The idea behind it is to create swap devices made of chunks of the ram and to compress those chunks on the fly to increase the available space used and ideally reduce the need of swapping to slow disks. It uses a small extra amount of the CPU, however, the reduced i/o usage should more than make up for this. This is primarily interesting for a small scaled VPS, Netbooks or low memory devices. Also virtualisation hosts should benefit of compressed memory. Unfortunatly the zram-config script is currently not part of the Debian and Centos distributions. I will run some further tests and update here. In Ubuntu, from 12.04 onwards, the install script is included and it takes only a minute to setup zram. How to […]

I have a new Debain 7 server (VM) and would like to use a raw iSCSI Lun on it presented from my QNAP (and put ZFS on it at the end but thats already covered elsewhere here). Prerequisites: Read and understand some iSCSI best practices (like those ones http://storageblog.typepad.com/storage_blog/2009/03/simple-iscsi-best-practices-top-3.html (I have simply ignored them all here so don’t blame me when you put my construct into production) I have a QNAP NAS under 192.168.1.9 presenting a iSCSI Target and Lun (iSCSI Target) I have a standard Debian 7 Server (VM) on the same network. (iSCSI initiator) On the Debian 7 VM Install the open-iscsi package apt-get install open-iscsi There are 2 things to edit in the /etc/iscsi/iscsid.conf 1) I want my iSCSI to start automatically when I boot my server. Search for node.startup = manual #and change to node.startup = automatic 2) If you use CHAP authentication on the iSCSI device you will need […]

If you just added a new Disk to a Linux Box (for example under VMware) you may want to add that one to a LVM to a new Volume Group. Here are the steps quick and easy with a bit of commenting. You have not yet added the new disk and want to do this hot. Then I refer to this here. How to add a new disk without reboot fdisk -l #to show us the available disks We assume our new disk is /dev/sdb and we will not create a partition on it but use /dev/sdb as it is. This gives us the advantage that if we increase the disksize outside of the OS (for example a vmdk which we just increase or a SAN lun which we just increase in size) we can easily increase the volume under lvm. pvcreate /dev/sdb Writing physical volume data to disk “/dev/sdb” […]

Particularly under VMware you may just add a new disk to linux without the need to reboot the whole thingy. So after adding the new disk as root on the OS: echo “- – -” > /sys/class/scsi_host/host#/scan where host# is the bus address usually 0 example echo “- – -” > /sys/class/scsi_host/host0/scan fdisk -l will show you the new disk as unpartioned while you would expect to see a message in the messages log tail -f /var/log/message and thats it, you now have a new disk which you can partition and add to LVM or whatever you want with it. Related posts: Linux / VMware: Howto Increase a / (Root) LVM partition on a single vmdk without adding another partition Linux: Howto show the Servers IP address at the login console Centos / Debian / LVM: Add a new disk as a LVM volume Linux / RedHat /CentOS / Ubuntu […]

In relation to the outdated post http://www.solaris-cookbook.eu/linux/debian-kanotix-proxmox-install-zfs-native/ Things have become much easier now How to install ZFS native on Debian 7 or Proxmox 3.x 1) become root sudo su – 2) Install ZFS wget http://archive.zfsonlinux.org/debian/pool/main/z/zfsonlinux/zfsonlinux_3%7Ewheezy_all.deb dpkg -i zfsonlinux_3~wheezy_all.deb apt-get update apt-get install debian-zfs kernel upgrade After updating the Kernel you most likely have to do the following steps: make sure you have the headers installed (proxmox example) aptitude install pve-headers-$(uname -r) (it will pick the current running kernel version. If you just updated the kernel you better reboot first.) ln -s /lib/modules/$(uname -r)/build /lib/modules/$(uname -r)/source aptitude reinstall spl-dkms zfs-dkms That should cover you on a kernel update Related posts: Debian / Kanotix / Proxmox: Install ZFS Native Linux: Install Proxmox Virtual Environment on Debian 6.0 Squeeze Distro (Kanopix) ZFS: Fun with ZFS – is compression and deduplication useful for my data and how much memory do I need for zfs dedup? […]

I do it on a regular base but everytime need to go back to my cheat sheet to jumpstart my memory. Whenever I need to reach one system from another without asking me for a password: First login on Server Alpha as the user desired to have the password free ssh and generate a pair of authentication keys. I would advise not to enter a passphrase but I leave that to you: user@Alpha:~> ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/user/.ssh/id_rsa): Created directory ‘/home/user/.ssh’. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/user/.ssh/id_rsa. Your public key has been saved in /home/user/.ssh/id_rsa.pub. The key fingerprint is: xx:xx:xx:xx:xx:xx:xx:xx:… user@Alpha The key’s randomart image is: …..xxxxxx.x.x.x..x.xx.whatever We need to create on the Server Bravo a user’s home subdirectory .ssh. (The directory may already exist, which is […]

Constantly having trouble with the Nvidia drivers install. Quick howto: If there is already any NVdiai driver installed, then run : telinit 1 #to go to single user mode sudo /usr/bin/nvidia-installer –latest If to be installed freshly: sudo su – cd /root wget ftp://download.nvidia.com/XFree86/Linux-x86_64/latest.txt cat latest This tells you the latest version then you can wget ftp://download.nvidia.com/XFree86/Linux-x86_64/304.43/NVIDIA-Linux-x86_64-304.43.run I have no idea why wget ftp://download.nvidia.com/XFree86/Linux-x86_64/`cat latest.txt| awk ‘{print $2}’` doesnt work, I will need to look into this deeper. Then: telinit 1 cd /root apt-get remove nouveau*  ./NVIDIA-Linux-x86_64-304.43.run Reboot afterwards Related posts: Hardware lister lshw Ubuntu: Powersaving Tweak for Netbooks Ubuntu: Howto drastically speed up Firefox Ubuntu: reduce swappiness Ubuntu encrypt the home directory and swap Centos / Debian / LVM: Add a new disk as a LVM volume

Install ZFS Native on Kanotix / Debian Squeeze / Proxmox 2.1 This whole thing below is obsolete. I created a new post with up to date details for Debian 7.0 Wheezy Ok, Ok, I admit, I’m going really crazy now…. as I described here -> Linux: Install Proxmox Virtual Environment on Debian 6.0 Squeeze Distro (Kanopix) I have Proxmov Virtual Environment running on Kanotix Debian. I now spotted that I’m running slowly low of free disk space. I could mount space from my NAS via NFS-CIFS or ISCSI but that’s kind of too easy and for testing purpose the break to success ratio is too low 🙂 . And BTW I love ZFS. so I install it (cause I want to deduplicate and compress). Based on Proxmox http://pve.proxmox.com/wiki/ZFS …This is pretty straight forward and almost too easy too. Kanotix is using Debian and not ubuntu and certainly not the latest ubuntu so we need […]

I constantly get annoyed when I add a new repository and get for example an: GPG error: http://archive.getdeb.net oneiric-getdeb Release: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY A8A515F046D7E7CF If you are good you have anywhere handy the command: wget -q -O- http://archive.getdeb.net/getdeb-archive.key | sudo apt-key add – to add the key for the particular repository. I rarely am that good so I have to run: sudo apt-key adv –keyserver keyserver.ubuntu.com –recv-keys A8A515F046D7E7CF And off I go… Related posts: Ubuntu: Some Usefull Commands Hardware lister lshw Ubunty Unity-2D Unity optimisation RedHat / Ubuntu / Solaris / Linux: Slow SSH logins (5 second delay) Ubuntu / Mint: Install latest Nvidia drivers

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