systemd management using systemctl and journalctl to check systemd logs
systemd is like the service manager for your Centos and other modern Linux distributions (including Debian/Mint/Ubuntu) allows you to enable services, stop them, restart them, check their status and even reboot your system.
The key commands or arguments you will use with systemctl are the following:
Unit Commands:
list-units [PATTERN...] List loaded units
&nbs........
Linux Permissions and Groups Real Usecase for Group Access
I have a directory structure which the primary user needs full access on but wanted a user to access only a specific directory within the main directory (so they could write in there only and nowhere else).
Here's what I did:
[root@compevo8001 dllnow]# ls -alh
drwxrwxr-x 2 someuser software 4.0K Oct 19 2017 ExpireYMD-2017-11-20
drwxrwxr-x 2 someuser software 4.0K Nov 19 2017 ExpireYMD-20........
HP Procurve Switch 2824 CLI Telnet Experience , Guide and Tutorial
telnet 192.168.1.54
-------------------------------------
ProCurve J4903A Switch 2824
Software revision I.10.77
Copyright (C) 1991-2009 Hewlett-Packard Co. All Rights Reserved.
RESTRICTED RIGHTS LEGEND
Use, duplication, or disclosure by the Government is subject........
Dell CS24-NV7 lspci dmidecode info
0000:00:00.0 RAM memory: NVIDIA Corporation MCP55 Memory Controller (rev a2)
0000:00:01.0 ISA bridge: NVIDIA Corporation MCP55 LPC Bridge (rev a3)
0000:00:01.1 SMBus: NVIDIA Corporation MCP55 SMBus (rev a3)
0000:00:02.0 USB controller: NVIDIA Corporation MCP55 USB Controller (rev a1)
0000:00:02.1 USB controller: NVIDIA Corporation MCP55 USB Controller (rev a2)
0000:00:05.0 IDE interface: NVIDIA Corporation MCP55 SATA Controller (rev a3)
0000:00:05.1 I........
Dell FS12-NV7 2U Server Information and Guide
I've got one of these for testing projects from work at home and got more than I bargained for with the time I've spent on it due to the storage handing/Perc 6/i cards.
My particular model came with the following:
2U Rack Mount Server with Rails
2xOpteron 2373 EE (Quad Core, there is a 6-core version that can be found at times)
16GB RAM
2 x 250GB Seagate SATA
2 x Dell Perc 6/i (horrible and a nightmare to work........
Dell Perci 6/i Firmware Upgrade Guide Tutorial
One thing to remember is that you need MegaCli to do the flashing.
You also need the correct file, I tried at least 2 different Perc 6 firmwares from Dell that kept getting rejected as corrupt by MegaCli (they were really the wrong version). I have an external PCI-E Dell 6 Perc/I but I chose images from the 'Integrated" on motherboard version as it was all I could find. They are different, and below is my first time finding success.........
Dell Perc 6/i cannot downgrade
I flashed an LSI Logic firmware to it and it broke the BIOS (cannot do Ctrl+R) for booting purposes but allows other functionality to work normally.
I tried downgrading to a Dell firmware for Perc 6i but it won't work, not even with MegaCli
wget http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN
--2013-08-26 12:53:39-- http://downloads.dell.com/FOLDER00416606M/1/SAS-RAID_Firmware_W83M2_LN32_6.3.1-0003_A14.BIN
Resolvi........
LSI MegaRAID Adventures, Guide and HowTo
LSi Megaraid
At first it was configured as a RAID 0, then I deleted the Virtual Disk Group.
I thought both drives would be shown and detected in Linux as sda and sdb but it actually shows nothing.
To make them work you have to hit Ctrl+R before the system boots (when prompted) and create a Virtual Disk Group. In my case I created each one as RAID 0 (with a single drive only) as I just wanted JBOD but there is no such option or default in these Dell Pe........
WD (Western Digital) Advanced Format Drive Lagged/Slow Speed/Performance/Design Flaw EAD/EARS problem WDC WD20EARS-00S8B1
Let the numbers speak for themselves, from what I read the Load_Cycle_Count which is very high (more than 500,000/half a million times) is the number of head parks. What a stupid "Green" design and design flaw which will probably mean an early life for the drive.
This is almost as silly as Seagate's new reputation for BSY/poor quality disks since the 7200.11 series.
To make it worse this is also when Western Digital introduced "Advanced Format" o........
mdadm won't boot due to fsck error
Nov 29 20:17:58 ubuntu kernel: [ 1157.180789] md: md1 stopped.
Nov 29 20:17:58 ubuntu kernel: [ 1157.180829] md0: unknown partition table
filesystem not responding/reading properly with du or rsync (this needed an fsck).
[ 2571.489217] EXT3-fs error (device md2): ext3_lookup: deleted inode referenced: 35923106
[ 2571.942299] EXT3-fs error (device md2): ext3_lookup: deleted inode referenced: 35923110
[ 2571.9568........
Debian 5.04 RAID 1 mdadm boot problem GRUB error
I successfully created a single RAID 1 partition which includes /boot inside it and my root directory through the Debian installer. It said GRUB installed successfully but when I try booting the OS it seems GRUB can't read anything.
When trying to boot from GRUB
GRUB Loading stage 1.5.
GRUB loading, please wait...
Error 2
I get "Error 2" when trying to boot Debian. I also notice from a LiveCD that........
Convert HDD/Hard Drive Partition(s) into non-RAID into RAID 1 using existing data without data loss and without reformatting.
Before we start I take no responsibility for this, you should have a backup and if you make a mistake during this process you could wipe out all of your data. So backup somewhere else before starting this as a precaution, or make sure it's data you could afford to lose.
The RAID 1 Setup (Hardware Wise)
I've already setup my 2 x 1TB (Seagate) drives with identical partitions, make sure your new hard drive (the empty one) is setup like your curr........
Linux EXT3 16GB-17GB maximum filesize issue solved/how to fix
I have no idea why but mkfs.ext3 defaults to a patheticlly small blocksize of 1024 bytes/1KB (kilobyte). That means the maximum filesize is ONLY 16GB! With 2KB/2048 bytes you get a 256 GB maximum filesize, and with 4KB/4096 bytes you get 2TB!
I finally noticed/paid attention to this after realizing that with rsync and scp that no file larger than 17GB could be transferred. I then realized it must be a file size limit on the partition.
Here is what tune2fs tol........
The New Chips on the Block
The New Chips on the BlockThe New Chips on the Block
By Bruce Gain
Story location: http://www.wired.com/news/infostructure/0,1377,67795,00.html
02:00 AM Jun. 13, 2005 PT
We have embarked upon a new era in x86 PC computing -- so say chip giants AMD and Intel following their launches of dual-core PC processors. So how will dual-core processing change your PC computing experience? Our FAQ should help you decide whether or when you sho........
Unixbench Score with Glusterfs/Openvz & Quad Core Xeon - Updated with GlusterFS 2.0.8 & Optimized Client Config
The results are still not flattering and are nothing close to native performance. Unless GlusterFS has a "DRBD-like" option to delay writes over the network and to only read from the client side, I don't see how performance can ever improve much more.
After doing some client optimizations I added more to the score:
Start Benchmark Run: Sun Nov 29 00:37:44 PST 2009
00:37:44 up 3 min, 1 user, load average: 0.01........
Unixbench Score with Glusterfs/Openvz & Quad Core Xeon - Updated with GlusterFS 2.0.8
You might remember my original GluserFS/OpenVZ benchmark which produced a horrible 29.8
This is the exact same system, but using the latest 2.0.8 (with some small files patch which speeds up performance) you can see it is about 25% faster.
I also haven't tuned my config files at all, but there are some settings that should increase performance on small files which I believe i........