This example is using RTL8821AU chipset from a TP-Link T2U Plus USB adapter and other similar ones should work the same.
Here's how to get this chipset RTL8821AU working in Linux.
Here's how to get RTL8812 and RTL8822 working in Linux.........
sysctl vm.overcommit_memory=1
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo 511 > /proc/sys/net/core/somaxconn
1:M 26 Nov 2023 21:34:33.840 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1:M 26 Nov 2023 21:34:33.840 # Server initialized
1:M 26 Nov 2023 21:34:33.840 # WARNING overcommit_memory is set to 0! Background sa........
You can do a static lease that is tied to the MAC address but what a lot of users prefer is that they come into the office or lab the next day and that their device gets assigned the same IP address (if possible).
As we can see in the dhcpd logs that there is threshold that is defaulted as we'll show later. Whatever the threshold is set at, if the lease is younger than the threshold, it will keep the same lease. In other words, if the device goes to sleep or is powered off........
Virtualbox is a very powerful tool, but for some use cases it is less than optimal.
Say you are in a work, lab or other environment where you are not alone on the physical network and there could be overlap of IPs, but you need all of your VMs to be contactable from your host, VMs need to communicate with each other, and VMs need internet.
NAT Network will give you VM to VM communication and internet, however, it is buggy and unstable. It also doesn't allow host to VM co........
Is your /var/log/journal overweight and bloated? For example a decent install of Debian 11 with most applications and services ends up being about 4.9G with the journal taking a few gigs.
du -hs /var/log/journal/
1.3G /var/log/journal/
By default in a lot of distributions there is no maximum size so it will keep growing. This is especially problematic for embedded distributions and devices, but is also a huge waste of sp........
Bonding is an excellent way to get both increased redundancy and throughput. It is similar to the "Network Teaming" feature in Windows.
There are a few different modes but we will use mode 6, I think it's the best of both worlds, as it is not just a failover, but it provides round robin, so you will get redundancy and load balancing. So if you have a 1G single port, you will have a combined throughput of 4G at this point. Just bear in mind that the true thr........
The Best Docker Tutorial for Beginners
We quickly explain the basic Docker concepts and show you how to do the most common tasks from starting your first container, to making custom images, a Docker Swarm Cluster Tutorial, docker compose and Docker buildfiles.........
In our 2024 VPS Server/Cloud Buyer's Guide, we place the location of your VPS/hosting/server as one of the priorities that is often overlooked.
2024 Update - Datacent........
It really seems limited in that it can mainly give you the things you would see on the physical unit such as load etc..
wget https://downloads.sourceforge.net/project/apcupsd/apcupsd%20-%20Stable/3.14.14/apcupsd-3.14.14.tar.gz?r=https%3A%2F%2Fsourceforge.net%2Fprojects%2Fapcupsd%2Ffiles%2Flatest%2Fdownload&ts=1598115866
tar -zxvf apcupsd-3.14.14.tar.gz
cd apcupsd-3.14.14
[root@somebox apcupsd-3.14.14]#
./conf........
A big problem over ssh and especially sshfs is that your connection will often timeout and disconnect after inactivity.
To fix this you can modify the server but it may not be practical or you may not have access. Why not send keep alives fom your end (client side)?
Just edit /etc/ssh/ssh_config (not to be confused with sshd_config as that is the server side):
Find the line that says "Host *" and change it like this:........
The easiest way to know if your videos are playing with GPU acceleration are to watch the process of xplayer, mpv or whatever you are playing. The CPU usage should be no more than 10% for that process/program if it is using acceleration.
Let's manually play with vdpau to make sure it works before we make it permanent:
First make sure you have libvdpau installed:
sudo apt install vdpau-driver-all
If yo........
Video Links:
How To Setup 2 Phones on a Single CME Router and get the GUI going.
How to use Dialpeers with CME with two routers
How to implement call restrictions using COR / Class of Restriction
Getting started, let's enable ephones and DNs we can add a phone with........
By default at least on Centos 7 nfs only allows 8 connections and starts 8 nfsd daemons.
To fix this edit this file:/etc/sysconfig/nfs
Edit the line "RPCNFSDCOUNT" (uncomment it so it looks like this:
RPCNFSDCOUNT=30
In the example above we are setting 30 nfsd daemons to run (or in other words 30 connections are possible this way).........
The strange thing is that usually the first install or two will work on any new machine but then it suddenly won't. I had this experience on QEMU 2.13 on a different machine. There is something finicky or buggy about the CUCM installer even when choosing the same virtual hardware specs.
qemu-kvm command:
/usr/libexec/qemu-kvm -version
QEMU PC emulator version 0.12.1 (qemu-kvm-0.12.1.2-2.506.el6_10.1), Copyright (c) 2003-2008 Fabrice Bellard
........
Are you tired of coming back to your computer only to find your SSH connections have been broken? Even worse are the ones that hang where it appears to be connected but it is really not.
The one option you have is an SSHclient side modification to send KeepAlive packets, sometimes this can also keep up your WiFi connection and stop it from disconnecting you as well.
To make the keep alive changes for your just yourself (not system wide)........
Do you hate how Centos 7 defaults to allocating most of your valuable space to /home even though it is a production server?
Here is a quick guide on how to take back that space live, while online (of course make sure you have backups just in case something goes wrong!):
First we will reduce our home dir by 100G:
lvreduce -L -100G /dev/mapper/centos-home
WARNING: Reducing active and open logical volume to ........
Cisco's CUCM (Cisco Unified Communication Manager) is a system that combines voice, video, data and mobile products into a single unified management suite. At its core, the CUCMis like a "Super PBX" that controls the flow of all communications through an organization even single or multiple site deployments.
Cisco's CUCMmakes communication more effective and simple through centralized management and unification of communications resources.........
umask are the default permissions that are applied when a file or directory are created. To see this in action simply just "touch filename" or "mkdir somedir" and you'll see what default permissions are applied.
The first thing Ialways tell people you should know is to NEVER change the defaults unless you are making them more restrictive. But they work well and if you change the defaults you could end up creating a file without permission to read........
You can do other things but this particular script is just to set all AMD cards to 80% fan speed (remember this script needs to applied everytime you reboot). You could set it is a cron or just throw it into /etc/rc.local
basepath=/sys/class/drm
for hwmon in `ls -1 /sys/class/drm|grep card[0-99]$`; do
echo card=$hwmon;
hwmonname=`ls $basepath/$hwmon/device/hwmon|grep hwmon[0-99]`
hwmonpath=$basepath/$hwmon/device/hwmon/$hwmonname
echo "ec........
[root@thetor2017 conf]# service httpd restart
Stopping httpd: [ OK ]
Starting httpd: WARNING: MaxClients of 3000 exceeds ServerLimit value of 300 servers,
lowering MaxClients to 300. To increase........
I've read a few guides about this but they didn't work for me.
sudo apt-get install bridge-utils
#don't think the above is enough it won't work still even though you have by default an /etc/qemu-ifup that handles it if you have the right tools and setup
sudo qemu-system-x86_64 -net tap -net nic -enable-kvm -cpu host,vmx=on ~/VirtualBox VMs/vsphere-vcenter/vsphere-vcenter.vdi
W: /etc/qemu-ifup: no bridge for guest interface foun........
#mount the VCSA DVD
mount /dev/sr0 /mnt/cd
#alternatively you could mount the iso directly
mount -o loop vcsa.iso /your/mount/path
#for this purpose we are using the CLI installer on Linux
cd /mnt/cd/vcsa-cli-installer/lin64
#no it's not going to be that easy you can't just run vcsa-deploy like that you need to use a template or configured .json file
./vcsa-deploy
Usage: vcsa-deploy [-h] [--version] [--supported-deploymen........
This happens because Dovecot limits the maximum IMAPconnections per IPto just 10. This may be fine for a single client side IPbut if an entire office or multiple users are behind one IPor a single heavy user is active then you will get bizarre errors in your e-mail clients such as "Password Incorrect" or similar in Thunderbird. It won't be obvious on the client side as to what the problem is and they will probably just think the server is misconfi........
This usually happens when you are using something like an INT and try to insert a larger valuethan the maximum which is larger than "2147483647"
On a practical term I have seen this and been guilty of this error when using scripts like PHPand generating large random numbers:
$hash = mt_rand(5,9999999999999);
Obviously that many 9's are more digits than the maximum of an INT resulting in that error. Change your code accord........
It's fairly simple to start or stop a check but I do wish mdadm's command had this built in. Sometimes it will do a check at the worst time causing the server to crawl to a halt.
Stop check on md126:
echo idle > /sys/block/md126/md/sync_action
Start check on md126:
echo check > /sys/block/md126/md/sync_action
........
MySQL will silently truncate a larger INT than capable.
Check MySQL's own documentation here:
As we can see the maximum size of INT (which is the most commonly used) is 2147483647
A lot of coders make this mistake by using very large values such as 9999999999 but it would actually truncate to 2147483647 which is the maximum size of an INT. This is dangerous beca........
PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib64/php/modules/geoip.so' - /usr/lib64/php/modules/geoip.so: undefined symbol: GeoIP_country_code_by_name_v6 in Unknown on line 0
Remove the GEOIP from PHP:
php71w-pecl-geoip-1.1.1-1.w6.x86_64
PHP Fatal error: PHP Startup: apc_shm_create: shmget(0, 67108864, 914) failed: Invalid argument. It is possible that the........
The Linux Kernel interpretated a very high volume of real traffic as a DDOS attack so it basically ends up blocking your web server.
possible SYN flooding on ctid 42131, port 80. Sending cookies.
Simple fix edit sysctl values for max_syn_backlog
sysctl -w net.ipv4.tcp_max_syn_backlog=5000
To make them permanent edit /etc/sysctl.conf
echo "net.ipv4.tcp_........
add this style="background-size: contain;max-width: 100%; height: auto;" to your img code.
Example: ........
mysqldump or mysql query of a larger file/table
ERROR 2006 (HY000) at line 567: MySQL server has gone away
Add this to /etc/my.cnf
max_allowed_packet=64M
service mysqld restart........
I believe from what I've read that this card's driver doesn't support the features after trying all known troubleshooting methods.
ffmpeg -i uservideoRendered.mp4 -filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload -c:v hevc_nvenc -profile main -preset slow -rc vbr_hq -c:a copy uservideoRendered.mp4-test
ffmpeg -i uservideoRendered.mp4 -filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload........
#if you have nvidia make sure you install the nvidia-cuda-toolkit so hardware acceleration can be used
wget http://ffmpeg.org/releases/ffmpeg-3.3.2.tar.bz2
tar -jxvf ffmpeg-3.3.2.tar.bz2
cd ffmpeg-3.3.2/
./configure --disable-yasm
install prefix /usr/local
source path ........
user@box:~$ sudo tune2fs -l /dev/md99
[sudo] password for user:
tune2fs 1.42.9 (4-Feb-2014)
Filesystem volume name:
Last mounted on: /mnt/md50
Filesystem UUID: 976a8655-2619-4587-878c-dab07f7b7652
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Fi........
I am using a GTX 1060 but replace the download for the driver with the correct/current version for your particular card by visiting: http://www.nvidia.com/Download/index.aspx?lang=en-us
yum install automake curl openssl-devel libcurl-devel gcc gcc-c++
yum -y install kernel-devel-`uname -r`
yum -y install unzip
#the........
This is a VIA made VL805 USB 3.0 Chipset with 4-ports and MOLEX powered. First of all this unit was cheap at about only 9 USD with fast shipping. My biggest concern was if this was a quality unit and would it really give you full USB 3.0 speeds (some people reported with similar cards that for some weird r........
apachectl -l
Compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
It is "prefork.c" so in httpd.conf these settings are what you would use (if you use worker.c it won't have any impact):
StartServers 2
MinSpareServers 5
MaxSpareServers&nb........
The solution is simple but strange, if you copy your /var/lib/mysql directory to another server and think it will work, be sure to check if you have /var/log/mysql and binary log files. If you do, the server will not work and will give you errors like below and crash without the proper log files.
UPDATE user SET password=password("newpass") WHERE user='root';
flush privileges;
ERROR 2013 (HY000): Lost connection to MySQL server durin........
PHP Fatal error: PHP Startup: apc_shm_create: shmget(0, 67108864, 914) failed: Invalid argument. It is possible that the chosen SHM segment size is higher than the operation system allows. Linux has usually a default limit of 32MB per segment. in Unknown on line 0
PHP Fatal error: PHP Startup: apc_shm_attach: shmat failed: in Unknown on line 0
This error is not at all fun because it actually prevents Apache/httpd from starting or working at all. It will........
The only way I've found in mdadm to make 2 drives perform like a proper RAID 1 (eg. the read speed should be 2x that of a single drive) is to use the --layout=f2 (far 2).
mdadm raid10 performance issues.
Be very aware that mdadm seems to default to layout=n2 (which means near). In this scenario it means it is like mdadm RAID 1 performance (you get maximum read speeds of a single drive).
dd if=/dev/md126 of=/dev/null bs=1M cou........
kernel: [10186978.064405] TCP: time wait bucket table overflow (CT3)
Varying opinions are out there but in general it seems like the most common culprit is a lack of privvmpages, with a modern OpenVZ system the best way is to set privvmpages as equal to what your RAM is and this has resolved the messages on another system.
If it's truly a TCP issue you can adjust the following parameters:........
When you start uploading larger images in Wordpress you have to make sure your maximum attachment size is large enough and that the execution time is not too short:
Uploading
Error
HTTP error.
[Thu May 12 16:32:25 2016] [error] [client 10.10.5.2] PHP Fatal error: Maximum execution time of 30 seconds exceeded in /httpdocs/blog/wp-includes/class-wp-image-editor-gd.php on line 182
Solution Edit p........
Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason. Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to? In some cases on a remote system you can't easily reinstall without physical or KVM access.
So in this case you add a second physical or disk or already ha........
1.) My screensaver would take a long time to disable after hitting a key.
2.) Usually errors like below will follow.
3.) Compiz sometimes uses 100% or high CPU
4.) My window controls will disable (eg. the minimize, maximize and close buttons).
It seems like Compiz or appearance/effects disable themselves. Re-enabling Desktop Effects under Appearance temporarily fixes it.
5.) high load in general from things like "Migration" pr........
-------------------------------------
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 to restrictions........
An error occurred during a connection to site.com. SSL received a record that exceeded the maximum permissible length. (Error code: ssl_error_rx_record_too_long)
The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
Please contact the website owners to inform them of this problem.
When the above happens in our experience it is a misconfiguration of........
Have you ever tried to run a command like rm to delete several hundred thousand files? Iam not sure what the limit is but any time it is exceeded you need to use a work around like below (which will delete any number of files).
Solution
find . -maxdepth 1 -name "*.*" -print0 | xargs -0 rm........
I never found a solution to do it live (nothing worked that I found) so it looks like a relogin is required.
Check your maximum file limit
cat /proc/sys/fs/file-max
824460
This is different than your actual's user limit which you'll see below
ulimit -n
1024
Try and set it higher but it won't work
ulimit -n 65000........
yum -y install fail2ban
vi /etc/fail2ban/jail.conf
[asterisk-tcp]
enabled = true
filter = asterisk
action = iptables-multiport[name=asterisk-tcp, port="5060,5061", protocol=tcp]
sendmail-whois[name=Asterisk, dest=you@example.com, sender=fail2ban@example.com]
logpath = /var/log/asterisk/messages
maxret........
The units in echo are kB as in kilobyte.
Setting a high sync speed
echo 120000 >/proc/sys/dev/raid/speed_limit_min
This will increase the speed, note that sometimes a rebuild is slow due to current disk activity/iowait.
If that is not the cause then you may have a hardware issue (controller, cable or a bad drive).
Setting a lower sync speed
echo 1200 >/proc/sys/dev/raid/speed_limit_max........
/scripts/phpextensionmgr install PHPSuHosin
Updating md5sum list
Fetching http://httpupdate.cpanel.net/cpanelsync/easy/targz.yaml (connected:0).......(request attempt 1/12)...Resolving httpupdate.cpanel.net...(resolve attempt 1/65)...
Fetching http://httpupdate.cpanel.net/mirror_addr_list (connected:0).......(request attempt 1/3)......connecting to 74.50.120.123...@74.50.120.123......connected......receiving...100%......request success......Done........
This is usually solved by two variables alone:
max_input_vars=5000
memory_limit=256M
Now you should be able to have unlimited amounts of custom menus in Wordpress.........
The first is a dual CPU AMD Opteron 2373EE (4 cores x 2) and I think it did bad because it has some old 250GB SATAs which can only do about 65MB/s max sequential reads. I think it should have blown away the second (AMD X4 640 Quad Core).
[root@fs12home unixbench-4.1.0-wht-2]# ./Run
make all
make[1]: Entering directory `/root/unixbench-4.1.0-wht-2'
Checking distribution of files
./pgms exists
./src exists........
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........
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........
Another new drive bad from the start:
Jun 2 15:14:18 one-desktop kernel: [15895.386779] ata2.00: exception Emask 0x50 SAct 0x1 SErr 0x280900 action 0x6 frozen
Jun 2 15:14:18 one-desktop kernel: [15895.386782] ata2.00: irq_stat 0x08000000, interface fatal error
Jun 2 15:14:18 one-desktop kernel: [15895.386784] ata2: SError: { UnrecovData HostInt 10B8B BadCRC }
Jun 2 15:14:18 one-desktop kernel: [15895.386788] ata2.00: cmd 60/0........
This is just trying to read 5GB off the drive with dd and the drive initially tested ok but shortly after I wondered why I was seeing 2MB/s read speeds. Notice the "current_pending_sector", anytime I've seen it at anything above 0 even with no other bad fields/attributes, it means the drive is bad.
ata1.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0
ata1.00: irq_stat 0x40000008
ata1.00: failed command: READ FPDMA QUEUED
ata1.00: cmd 60/00:00:........
Client Log
OpenSSH_4.3p2, OpenSSL 0.9.8e-fips-rhel5 01 Jul 2008
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 192.168.1.253 [192.168.1.253] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/id_rsa type 1
debug1: identity file /root/.ssh/id_d........
Here's a proven example of what a bad hard drive can do, it was technically functioning OKin a RAID array but the system became extremely low and the load become high and IOWAIT was even higher and I always thought it was a bad application. The truth is that this failing 1TBHitachi has slowly gotten worse and caused huge slowdowns, (eg. 100% load on Thunderbird waiting for e-mails to load etc..). After swapping it out, tabs change instantly, emails are not lagged, and........
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_12-lv_root
50G 1.2G 46G 3% /
tmpfs 7.8G 0&nb........
ip_conntrack: table full, dropping packet.
A lot of clients I've seen have this issue, it really seems the default level is way too small. Once this connection tracking table becomes full then packets get dropped which is obviously a bad thing.
One thing to be mindful of though is that 350 bytes of memory are used per entry so there is some justification for not keeping it too high. However, if you have multiple servers running or high traffic daemons........
I experienced this with CPanel's Exim after an auto-update (a Google of this error produces lots of complaints with few clear solutions). In this case I'll put the solution at the top.
Run /scripts/buildeximconf to rebuild the Exim config and it should be fine after that.
mail -vs "from test" user@dest.com < .bash_history
LOG: MAIN
cwd=/root 4 args: send-mail -i -v user@dest.com
LOG: MAIN
&........
For years I've always built cheap systems believing that there is little difference in more expensive components when it comes to reliability and quality, I generally believe this still except for Power Supplies.
I've always bought cheap cases with nice sounding 350-550W stock/cheap/crap power supplies and haven't had any issues for the most part until recently.
One such case is an NGEAR case with a 550W Optimax power supply, I always read that these supplies don't produce the........
I'm running Ubuntu 10.10 with Asus NVIDIA GT430
2.6.35-32-generic-pae #65-Ubuntu SMP Tue Jan 24 14:06:16 UTC 2012 i686 GNU/Linux
Nvidia binary driver: 260.19.06
The screen sometimes completely freezes and locks up or everything starts going very slow:
[1903398.100007] NVRM: os_schedule: Attempted to yield the CPU while in atomic or interrupt context
[1903402.373210] NVRM: Xid (0001:00): 53, CMDre 00000000 00000080 00000000 00000005 00........
I like dd, although it only reads it, usually a read test of the entire disk will uncover if your hard drive is bad in some parts. This is a good thing to do at least once a month, a lot of times bizarre program behavior, laginess and crashing/unnmounting problems etc.. are due to a failing disc and SMART won't know it or indicate a problem:
We must also remember there's never a guarantee, I've found that ever since we moved to larger and more platters per drive with 1TB drives........
I had a dying drive that smart thought until it totally disappeared was a good drive, and actually all parameters did look fine but this system was causing my system to lockup and other bad behavior:
=== START OF INFORMATION SECTION ===
Device Model: WDC WD20EARS-00MVWB0
Serial Number: WD-WMAZ20139
Firmware Version: 50.0AB50
User Capacity: 2,000,398,934,016 bytes
Device........
I had one of these shipped and it was not recognized when plugged in, here's what a dead drive looks like (I assume it's teh circuit board which is dead):
ata1: link is slow to respond, please be patient (ready=0)
ata1: softreset failed (device not ready)
ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata1: link online but device misclassified, retrying
ata1: link is slow to respond, please be patient (ready=0)
ata1: softreset f........
I thought only a faster CPUand SSDwould help but I already have a Quad-Core CPU and it wasn't being maxed out. The actual tests were performed on an AMD-V enabled 128MB dual core VMWare container though.
There is a flag that can be passed to make in order to start multiple threads, by specifying 4 threads I was able to reduce the whole kernel compilation time from scratch by about 50%! (65minutes vs 31minutes!). *Yes I did do a make clean before each co........
If you have a webserver and find you have high IO/lagginess MySQL is one of the first things to check. It turns out MySQL was my problem and it was creating a high load on my server, especially for IO.
How to Enable MySQL Slow Query Logging To Find Slow Performance/Queries
vi /etc/my.cnf
Add this anywhere under [mysqld]
#slow queries
log-slow-queries = /var/log/mysql/mysqlslowqueries.log
long_query_time = 1........
This happened during a RAID array check:
SMART says both drives pass the test, but I'm doing a long test on them and hopefully this is not a hardware error.
Apr 3 04:22:01 remote kernel: md: syncing RAID array md2
Apr 3 04:22:01 remote kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Apr 3 04:22:01 remote kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Apr........
high IO wait
424 root 39 19 1900 848 552 D 0.0 0.0 0:00.91 updatedb
root 424 0.0 0.0 1900 848 ? DN Mar11 0:00 /usr/bin/updatedb -f sysfs?rootfs?bdev?proc?cpuset?binfmt_misc?debugfs?sockfs?usbfs?pipefs?anon_inodefs?futexfs?tmpfs?inotifyfs?eventp........
find what MPM Apache is using, it will either be using "worker" or "prefork"
apachectl -l
Compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
In my case it is "prefork"
vi /etc/httpd/conf/httpd.conf
Find the section that looks like this (by default one will normally exist for prefork and for worker, but in my case I only care a........
kernel 2.6.27.54
Fusion MPT base driver 3.04.07
Copyright (c) 1999-2008 LSI Corporation
Fusion MPT SPI Host driver 3.04.07
mptbase: ioc0: Initiating bringup
mptbase: ioc0: WARNING - Unexpected doorbell active!
mptbase: ioc0: ERROR - Doorbell ACK timeout (count=4999), IntStatus=80000001!
mptbase: ioc0: ERROR - Diagnostic reset FAILED! (102h)
mptbase: ioc0: WARNING - NOT READY!
mptbase: ioc0: ERROR - didn't initialize proper........
I think this will be useful to others because I have a server that kept crashing mysteriously during intense disk usage/RAID checks. It would only crash during the weekly RAID integrity check.
ThenI noticed during a reboot that not all CPUs were being brought up, as a result this actually creates much higher temperatures with the output I got from sensors, just booting the system produced higher than normal temperatures.
You can imagine that a full blown RAID check........
Jan 16 04:02:03 centosbox syslogd 1.4.1: restart.
Jan 16 04:07:34 centosbox kernel: INFO: task updatedb:20771 blocked for more than 300 seconds.
Jan 16 04:07:34 centosbox kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jan 16 04:07:34 centosbox kernel: updatedb D F78BE050 6476 20771 20766&n........
This made me nervous but it's clearly a cronjob based on the messages log that happens every Sunday at about 4:22.
I actually can't find any evidence of it in cron.d cron.daily but it is there somewhere obviously.
What I don't get is why doesn't this cronjob do a datacheck like Ubuntu's cronscript does? When you unnecessarily rebuild the array you lose your redundancy during that point which makes your data extremely vulnerable.
*Update I did a grep of &q........
This doesn't seem to be widely known (maybe it's in some documentation that none of us read though)but there's an easy way to check the integrity of any mdadm array:
sudo echo check > /sys/block/md0/md/sync_action
-bash: /sys/block/md0/md/sync_action: Permission denied
sudo will never work, this only works as root since echo is not actually a binary/command. It is built-into bash.
/sys/devices/virtu........
This really made me nervous but notice the mdstat says "check". This is because in Ubuntu there is a scheduled mdadm cronscript that runs everyday on Sunday at 00:57 that checks your entire array. This is a good way because it prevents gradual but unnoticed data corruption which Inever thought of.
As long as the check completes properly you have peace of mind knowing that your data integretiy is assured and that your hard drives are functioning properly (I'........
This server was experiencing loads of up to 80 and maxing out the RAM and kmemsize on a CPanel VPS. There were literally dozens if not hundreds of exim processes. I have no idea why exim has such a design that would allow it to consume this much CPU and RAM. Any normal MTA should not be spawning so many processes, it should be processing them in sequence and if it is going to spawn hundreds of processes in response to a large volume of mail, it's better to have a delayed del........
Here is a RAID 1 partition (500GB Seagate & 2TB WD):
Sequential Reads
File Blk Num Avg Maximum Lat%&nbs........
This is a great way to use your ftp server space, for example on your web hosting account (althoughI believe many hosts don't allow storage like this), but if you have a VPS/Dedicated Server etc.., this would be perfect. Imagine how easy it is to work with an ftp account that you can just mount as a normal partition or directory in Linux, it would be great for backups etc..
Name
curlftpfs - mount a ftp host as a local directory
Synopsis........
www.antec.outervision.com/index.jsp
I found that wattage/power consumption tool to be very useful, especially when you're worried that you're hitting the Power Supply's limit. You'll see very quickly that different CPU's, Graphics, Cards, HDDS use a wide range of energy. That tool can help you choose a build that won't stress or go over the maximum limits of your Power Supply.........
This was unbelievable how much the Xen kernel slows things down, keep in mind both tests were done on the hostnode, one was with the Openvz-Xen hybrid kernel and the other was just OpenVZ. You can see the performance difference is nearly 300% better when not using the Xen kernel.
OpenVZ-Xen Kernel Test Results (I was wondering what was wrong/so slow with my Core i5!)
# # # # # #&n........
This drive is clearly on the way out, the Kernel knows it but I'm surprised that SMART is not concerned. I didn't blame Seagate for their past issues until now. This hard drive has hardly been used and has not even been powered on for a year according to SMART.
Home page is http://smartmontools.sourceforge.net/
=== START OF INFORMATION SECTION ===
Model Family: Seagate Barracuda 7200.11
Device........
I thought there would be an error message or warning from MySQL in the case that the text you submit is greater than the allowed limit based on the field.
So essentially I submitted text that was about 120,000 characters long, whereas the limit of TEXT is just 65,535 characters! I almost lost half of my data/what I typed without knowing it!
I just altered the field type in my database from TEXT to LONGTEXT. I can't see how LONGTEXT wouldn't be long enough for MOST........
Seagate Inventory/Firmware Check
I heard about this issue a long time ago but never looked into it. I figured I wasn't affected since my 500GB drives were running for so long. I've been using Seagate's since 2002 and to this day all of the drives I have are alive from Seagate.
*Update the bad news is that I realize one of my 500GB's is about to die, it's not even a year old, but is also not affected by the recall according to Seagate!
Seagate Inventory/Firm........
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........
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 folder I was trying to archive is about 72GB, but much like rsync at about 17GB it chokes because of the filesize. What's with so many common and essential Linux tools having such limitations? I guess it is likely that the authors never wrote their code with the idea that files would be so large but it's still very annoying. It's important to stay on top of these limitations on production servers because I didn't realize what happened until I checked the file with "........
Proxmox has made this free utility to backup running OpenVZ containers. It's a great program which is actually just a PERL script but gets the job done. This program is not 100% required because all it really does is cp -a from your container's path as far as I know but it is still good to have uniformity to how you backup your containers.
For RPM distros such as Centos/RHEL/Fedora etc.. download and install this:
wget http://www.proxmox.com/cms_proxm........
Here are the results, it is Sempron 3000+ AMD Mobile, 500Gig HDD, 512MB RAM with shared ATI Radeon graphics.
# # # # # # # ##### ###### # # #### # #
# # ## # # # #&nb........
Problems surfing web/servingI noticed sometimes websites wouldn't load at random through a FreeBSD box and other systems on the same link didn't have the issue. I believe it is because of the low default limit of 128 TCP connections that caused the problem. It would also slow down any traffic that requires many connections such as Bittorrent.
The fix is to increase the amount of connections to at least 1024
Edit [b:520b050d3e]/etc/sysctl.conf[/b:520b05........
DVD Burners and Media at an all time lowThis is crazy you can buy a nice Pioneer DVD burner for like $64 CAD now and good media like 50PC Maxell is just $25.97 at Walmart.
I'm liking this. Time to make double archives of important data :)........
Intel's Finnish FetishIntel's Finnish Fetish
By Dave Mock
June 13, 2005
Chipmaker Intel (NASDAQ: INTC) has successfully topped the personal computer market for decades. Breaking into related areas such as communications has been much difficult for the world's largest semiconductor maker. But a new partnership with Nokia (NYSE: NOK) could help to change that.
Intel's forays into cellular-phone and home-entertaiment-device chips have........
NEC ND-3500A is great!I just picked up an NEC 3500A a few weeks ago and I love it.
It is a great all in-one optical drive solution.
It can burn DVD/+R-R at up 16x, read at 16x and rewrite at 4x and CD-R at up to 48x!
Not bad, but the impotant part is that it delivers consistent high quality burns and the drive is as quiet as I could ask it to be.
It's also convenient that it has a lot of hacked firmware for overspeeding of........
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 Iadded 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........
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........
Inever saved any of the logs, but basically no matter what OS (Linux)I used, I could not get my 1000GB hard drive to work (Seagate SATA). The BIOS recognizes the drive and fdisk -l shows the hard drive as it should.
The tricky thing is that different OS's will give you different results, but don't be fooled. You can't use these larger drives for long. Iwas getting all kinds of seek/IOerrors and also messages that the port could not be read.........
This is very disappointing since GlusterFS markets itself as a solution to deploy VPS servers on. On the HNitself I get a Unixbench of about 360.
I'm also using an SSH tunnel to secure the communications, but even before that, things seemed very slow.
# # # # # # # #####&n........
Have you ever seen this dreaded message in your Apache/HTTPD /var/log/httpd/error_log?
[error] server reached MaxClients setting, consider raising the MaxClients setting
The error itself is slightly misleading. Ibelieve this happened to one of my servers, I found Apache was running still, and that you could telnet to port 80 but no respnose would be given.
For some reason my error log initially did not have the above error, but after a restart I saw........
A VPS Server I had just wasn't working right, code that I migrated there just wasn't working. For example, it kept telling me the connection to the database was unsuccessful, halfway through iterating through results it already had.
Then I realized it wasn't my code. Ichecked my /proc/user_beancounters and found this:
cat /proc/user_beancounters
Version: 2.5
uid resource held maxheld barrier limit failcnt........