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  • 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........
  • hwloc-nox set CPU affinity in Linux


    sudo apt-get install  hwloc-nox Reading package lists... Done Building dependency tree       Reading state information... Done The following NEW packages will be installed:   hwloc-nox 0 upgraded, 1 newly installed, 0 to remove and 530 not upgraded. Need to get 151 kB of archives. After this operation, 453 kB of additional disk space will be used. Get:1 http://archive.ubuntu.com/ubunt........
  • VMWare ESXi 6.7 SSH/PowerShell CLI Commands


    [root@localhost:~] BootModuleConfig.sh          echo                         host-ind                     nfcd                   ........
  • Debian Mint Ubuntu compiling xmr-stak


    sudo apt-get install libcurl4-openssl-dev git build-essential autotools-dev autoconf libcurl3 sudo apt-get install libcurl4-gnutls-dev git clone https://github.com/wolf9466/cpuminer-multi sudo apt-get install cmake  libpthread-* libmicrohttpd-dev libssl-dev libhwloc-dev git clone https://github.com/fireice-uk/xmr-stak-cpu.git make install cd bin chmod +x xmr-stak-cpu ./xmr-stak -O xmr........
  • migration/4 migration 4 is using too much CPU


    top - 13:02:52 up 603 days, 19:19,  2 users,  load average: 5.01, 4.15, 3.44 Tasks: 604 total,   5 running, 599 sleeping,   0 stopped,   0 zombie Cpu(s): 17.7%us, 36.1%sy,  0.0%ni, 42.0%id,  4.1%wa,  0.0%hi,  0.2%si,  0.0%st Mem:  16278908k total,  4269684k used, 12009224k free,   119672k buffers Swap:        8k total,    ........
  • postfix errors fatal: no SASL authentication mechanisms /usr/libexec/postfix/smtpd: bad command startup -- throttling solution


    Jul  3 22:12:17mailserver postfix/smtpd[6195]: fatal: no SASL authentication mechanisms Jul  3 22:12:18mailserver postfix/master[4881]: warning: process /usr/libexec/postfix/smtpd pid 6195 exit status 1 Jul  3 22:12:18mailserver postfix/master[4881]: warning: /usr/libexec/postfix/smtpd: bad command startup -- throttling This only ever happens in my experience when the authentication method is actually Dovecot.  Usually the problem........
  • MySQL Cannot Update/Write to any database table solution


    This happened on Centos for no apparent reason with no obvious issue in the logs.  Data could be read fine but not written (possibly due to some corruption or out of memory issue in the OpenVZ container is the best guess).   All mysql update and insert queries failed freezing without any error log on any database and table. Tried to restart: service mysqld restart Timeout error occurred trying to stop MySQL........
  • Centos 6.6/6.9 KVM VM Kernel Panic On Boot - Kernel panic - not syncing: Attempted to kill init!


    I am not sure why this is happening neither the hostnode or VM changed.  All I did was reboot the hostnode and startup the Centos VM again, also note it happened with the original kernel on the VM and also the latest 6.9 kernel as of this writing as shown below. Host Node: Centos 6.9 Kernel: 2.6.32-696.6.3.el6.x86_64  Kernel: 2.6.32-042stab123.9 Same result in any kernel above........
  • OpenVZ error : Container start failed (try to check kernel messages, e.g. "dmesg | tail") Locked by: pid 166638, cmdline vzctl start 888171


    This container won't start after exhausting its memory.  There are no relevant or helpful messages in dmesg or vzctl.log as well.  Standard troubleshooting such as disabling PPP etc has not helped.   2017-07-06T23:33:29-0400 vzctl : CT 888171 : Locked by: pid 166029, cmdline vzctl start 888171 2017-07-06T23:33:29-0400 vzctl : CT 888171 : Container already locked 2017-07-06T23:33:29-0400 vzctl : CT 888171 : Container was stopped 2017-07........
  • cudaminer freezes Linux Mint taints kernel


    When running cudaminer once it tries to initialize the card the entire screen freezes.  The computer itself is still running but the Xorg is done for, you cannot even switch to another console window and must reboot (even an mdm or Xorg restart does not help). At first cudaminer will give you these errors: stratrum_recv_line failed ...retry after 15 seconds GPU #0: Geforce 210 with compute ca........
  • How to Properly Secure SSL/TLS Apache Settings against Heartbleed Poodle (TLS) Poodle (SSLv3) FREAK BEAST CRIME


    Many users still are not aware but simply patching OpenSSL does not secure you against many known and easy to exploit attacks that will render your encryption useless by an attacker. Use the following setings in /etc/httpd/conf.d/ssl.conf   SSLCipherSuite "EECDH+ECDSA+AESGCM EECDH+aRSA+AESGCM EECDH+ECDSA+SHA384 EECDH+ECDSA+SHA256 EECDH+aRSA+SHA384 EECDH+aRSA+SHA256 EECDH EDH+aRSA !CAMELLIA !SEED !3DES !RC4 !aNULL !eNULL !LOW !MD5 !EXP !PSK !........
  • MySQLD Server shutdown remotely unexpectedly


    170110  5:35:23 [Note] /usr/libexec/mysqld: Normal shutdown 170110  5:35:23 [Note] Event Scheduler: Purging the queue. 0 events 170110  5:35:23  InnoDB: Starting shutdown... 170110  5:35:24  InnoDB: Shutdown completed; log sequence number 0 12765401 170110  5:35:24 [Note] /usr/libexec/mysqld: Shutdown complete 170110 05:35:24 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended........
  • bind/named rndc: connect failed: 127.0.0.1#953: connection refused (solution)


    service named status rndc: connect failed: 127.0.0.1#953: connection refused named (pid  10557) is running... Check /var/log/messages: Jan  4 17:06:22 storagebox named[10753]: none:0: open: /etc/rndc.key: permission denied Jan  4 17:06:22 storagebox named[10753]: couldn't add command channel 127.0.0.1#953: permission denied Jan  4 17:06:22 storagebox named[10753]: non........
  • Linux Mint/Ubuntu/Debian Dual NICs networks problem when enabling and disabling one device


    The Scenario You have dual NICs and you disable NIC1 which uses 192.168.1.1 as its gateway.  With NIC2 you enable it/connect it to another network which also has the gateway 192.168.1.1 Everything will work fine at this point. When switching back to NIC1 even with NIC2 disabled and even unplugged, the OS basically can't pick up the new/updated ARP entry of the old device for 192.168.1.1 and perhaps thinks it is a security risk or spoof of some sorts and blocks i........
  • Centos cannot login by console or ssh session closed immediately


    In my case I could login with the initial install but I rsync'd everything over while preserving ownership and permissions to another RAID partition and booted from that.was fine before. The problem is that you are kicked out the second you login and the problem was SELINUX for some reason (perhaps it noticed something strange when it was moved to the new partition) login: pam_unix(login:session): session opened for user root by LOGIN(uid=0) login: ROOT LOG........
  • ssh session and port forward or reverse port matching or assocation howto


    Use netstat with the -anpe option.  The e option shows the inodes and I do not know if it will always work or if it was by fluke but I was dealing with dozens of SSH sessions and needed to know which session was related to which forward (the PIDs of the SSH and SSHD did not match etc...) Notice the "59560675" and "59560762" those are almost identical, if you find two sets that are nearly identical except for the last 3 digits they may match (in my ca........
  • Dell CS24,FS12 NV5 and NV7 1U Server Information & Parts


      Motherboard: Gigabyte GA-3CESL: http://b2b.gigabyte.com/products/product-page.aspx?pid=2658#dl Dell Part Numbers for the motherboard:  R1232 R1232L R2232S SERVER MOTHERBOARD GENUINE 408P9 CN-0408P9 GA-3CESL Manual Download here RAM Slots: 16 (8 controlled by each CPU) RAM Type: DDR2 ECC 5300P........
  • Vbox/Virtualbox devices grayed out for non-root user solution


    <p>It is a permissions issue that is hard to fix.</p> <p><strong>All but one USB device is greyed out.</strong></p> <p>I am already a member of &quot;vboxusers&quot;</p> <ul> <li>I have already enabled and disabled USB support for the guest.</li> <li>I have already reinstalled the latest VBOx guest editions</li> <li>If running as root it all works fine</li> <li>Changing........
  • Linux Centos 6 Weird Kernel Panic


    Kernel panic - not syncing: Attempted to kill init! Pid: 1, comm: init Not tained: 3.2.51-3.el6.x86_64 #1 Call Trace:  panic+0x8c/0x1a2 forget_original_parent+0x34d/0x360 exit_notify+0x12/0x140 do_exit+0x1d8/0x400 do_group_exit_+0x50/0xc0 sys_exit_group+0x12/0x20 system_call_fastpath+0x16/0x1b panic occurred, switching back to text console........
  • Asterisk iptables block bruteforce attacks howto with fail2ban


    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........
  • Linux find what processes are swapping


    Here is a handy script that will check all processes and report what is swapping #!/bin/bash for pid in `ps x|awk '{print $1}'`; do result=`cat /proc/$pid/status|grep VmSwap|awk '{print $2}'|grep -v ^"0"` if [ ! -z "$result" ]; then  programresult=`ps x|grep $pid|grep -v grep`  if [ $? == 0 ]; then      program=`echo $programresult|awk '{print $5}'|grep -v ^grep`........
  • Openvz OOM Centos Issue Memory Config Settings Solution


    Linux box13. 2.6.32-042stab076.5 #1 SMP Mon Mar 18 20:41:34 MSK 2013 x86_64 x86_64 x86_64 GNU/Linux even setting privvmpages to a specific setting DOES not affect "free -m" in containers. This is probably a kernel issue  23:36:29 up 159 days,  7:12,  4 users,  load average: 0.42, 0.44, 0.33 [root@box13 ~]# free -m              total  &n........
  • pxe-32 tftp open timeout


    pxe-32 tftp open timeout   The solution was to enable tftp in xinetd with "chkconfig tftp on". See the troubleshooting below:   chkconfig --list NetworkManager     0:off    1:off    2:off    3:off    4:off    5:off    6:off acpid              0:off&n........
  • Starting MySQL. ERROR! Manager of pid-file quit without updating file. - Solution/How To Fix


    service mysql start Starting MySQL. ERROR! Manager of pid-file quit without updating file. Solution killall -9 mysqld_safe killall -9 mysqld service mysql start Starting MySQL SUCCESS!........
  • Kernel panic - not syncing: Attempted to kill init! Pid: 1,comm: init Tained: G I------------- 2.6.32-358.el6.x86_64 #1 Call Trace: [] ? panic+0xa0/0x16f [] ? do_exit+0x862/0x870 [] ? fput+0x25/0


    Kernel panic - not syncing: Attempted to kill init! Pid: 1,comm: init Tained: G        I-------------    2.6.32-358.el6.x86_64 #1 Call Trace:  [<fffffff8150cfc8>] ? panic+0xa0/0x16f  [<fffffff81073ae2>] ? do_exit+0x862/0x870  [<fffffff81182885>] ? fput+0x25/0x30  [<fffffff81073b48>] ? do_group_exit+0x58/0xd0  [<fffffff81073bd7>] ? sys_exit_........
  • Error code: sec_error_unknown_issuer Solution Valid SSL Certificate Throwing Error in Firefox


    So you've just purchased your SSL cert, renewed it and installed it or maybe you've had it installed and working fine all the time with all other browsers but you've upgraded to a recent version of Firefox and suddenly get the warning "Error code: sec_error_unknown_issuer" error. This is terrible since if you bought an SSL cert, you are most likely using it for trust purposes for your business and obviously that message will scare away most potential customers.........
  • Linux Out of Memory OOM Object Killer Solution "Out of memory: kill process 1955 (sshd) score 81 or a child"


    I had a system running a 128MB live CD image with 2.8 gigs of available RAM and the OOM kernel killer went crazy when using dd for more than 8 minutes and kept killing everything.  I've read that this is due to a low-memory issue and paging in the kernel and 32-bit systems with lots of RAM. I even enabled swapspace on my LiveCD and the issue happened 25 minutes into dd rather than 8 minutes, so what gives? Also no swap space was ever used! cat /proc/s........
  • Openvz YUM Error Solution to "[Errno -1] Metadata file does not match checksum Trying other mirror."


    It's weird because I have a nearly identical box and setup and I can update the ovzkernel-PAE* just fine but on this box it doesn't work. I only get this error with the openvz.repo and not others such as Centos-Base.repo With my other server it works normally: ================ Setting up Update Process Resolving Dependencies --> Running transaction check ---> Package ovzkernel-PAE.i686 0:2.6.18-238.12.1.el5.0........
  • Kernel/make compilation time and how to improve compile times/compile the Linux kernel faster without hardware upgrades


    I thought only a faster CPU and SSD would 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........
  • Virtualbox Guest Hang/Freeze Ghost Zombie VM Machine Problem/Solution


    Virtualbox hang problem A VM just froze and wouldn't close so I had to force it, but the VBox GUI thinks it's running even when I close it. I manually killed the related process by doing ps aux|grep VirtualBox and found the PID 6191 I killed it with "kill -kill 6191" but it remains open and as "defunct" so I can't restart it because the GUI freezes when I click on it because it thinks it is running still........
  • Apache High CPU Usage Enable Mod_Status Guide Solution - Find Cause of High CPU Usage Script/Domain


    mod_status is a great way to track down the source of high CPU usage and to find what vhost/script is the cause of it. It gives you a live view of bandwith usage, CPU usage, and memory usage broken down by domain/vhost and script/URI. Enable mod_status vi /etc/httpd/conf/httpd.conf ExtendedStatus On <Location /server-status> SetHandler server-status Order Deny,Allow Deny from all All........
  • monit example tutorial how to enable status checking and manipulation


    You need to enable the httpd daemon with monit to actually view the status and control, it's not only for the web interface since the httpd is the ONLY way of controlling monit and viewing the status. monit monitor all will also reinstate disabled services if they've timed out too much.  Just restarting the service will do nothing to re-monitor a service that monit has stopped monitoring due to too many failures. *Also note that /etc/monit.conf i........
  • Enable SPAMASSASSIN on Postfix in 5 minutes


    Centos 5 Postfix and SPAMASSASSIN Tutorial yum install spamassassin chkconfig spamassassin on vi /etc/mail/spamassassin/local.cf ############## #required_hits 5 #report_safe 0 #rewrite_header Subject [SPAM] #5 is the least restrictive (means only the most obvious SPAM is caught. 0 is obviously the most restrictive/sensitive and would have lots of false positives require........
  • sshfs cannot unmount error: device is busy. (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1))


    umount: /home/diret/mount: device is busy.         (In some cases useful info about processes that use          the device is found by lsof(8) or fuser(1)) I tried everything (fusermount -u) to unmount it but the only thing that worked was actually doing this: ps aux|grep sshfs Then I identified the sshfs connection and did: kill -kill pid........
  • Ubuntu 9.04 Crash


    CPU/Kernel/MB/RAID problem? Jan  5 12:45:05 testbox kernel: [653298.890004] BUG: soft lockup - CPU#0 stuck for 61s! [hal-acl-tool:4168] Jan  5 12:45:05 testbox kernel: [653298.890005] Modules linked in: vmnet vmci vmmon binfmt_misc drbd video output input_polldev ocfs2_stackglue ocfs2_dlmfs ocfs2_dlm ocfs2_nodemanager configfs k8temp hwmon_vid lp snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi........
  • ERROR! MySQL manager or server PID file could not be found! ERROR! Manager of pid-file quit without updating file.


    I found the cause of this issue was from all the diskspace being used but clearing it was not enough.  I guess the tables became inconsistent when space ran out and myisamchk is what fixed the rest.   service mysqld restart ERROR! MySQL manager or server PID file could not be found! ....................................................................................... ERROR! Manager of pid-file quit without updating file. se........
  • WD EARS/Green 2TB Cannot Disable Power Saving/Head Parking with hdparm


    hdparm -B 255 /dev/sdb /dev/sdb:  setting Advanced Power Management level to disabled  HDIO_DRIVE_CMD failed: Input/output error   The one thing you can do though is to set hdparm spindown time lower (it doesn't seem to work that well).  -S   set standby (spindown) timeout   hdparm -S 251 /dev/sda /dev/sda:  setti........
  • EOL for Kubuntu/Ubuntu 8.04 - W: Failed to fetch http://ca.archive.ubuntu.com/ubuntu/dists/intrepid/universe/source/Sources.gz 404 Not Found [IP: 91.189.92.171 80]


    I couldn't figure out why I couldn't install a simple package.  This is what's annoying about cutting edge Debian distros, yes we know you support each license on average for 1-2 years but why take down the supporting binary packages and basically disable the older versions? sudo apt-get install update Reading package lists... Done Building dependency tree       Reading state information... Done E: Couldn't find p........
  • Nautilus/GNOME File Manager handy list of extensions


    nautilus-gksu - privilege granting extension for nautilus using gksu nautilus-sendto - integrates Evolution and Pidgin into the Nautilus file manager nautilus-share - Nautilus extension to share folder using Samba nautilus-actions - nautilus extension to configure programs to launch nautilus-bzr - Bazaar (bzr) integration for nautilus nautilus-cd-burner - CD Burning front-end for Nautilus nautilus-clamscan - Antivirus scanning for Nautilus n........
  • After installation Directadmin does not work directadmin dead but pid file exists on OpenVZ VPS when browsing http://ip.ip.ip.ip:2222


    After installation Directadmin does not work on OpenVZ VPS when browsing http://ip.ip.ip.ip:2222 service directadmin status directadmin dead but pid file exists tail /var/log/directadmin/error.log Check the value of your ethernet_dev=eth0 setting in your /usr/local/directadmin/conf/directadmin.conf file and the output of /sbin/ifconfig<br> 2010:07:10-12:44:01: ioctl can't find........
  • Realtek r8169 1gbit/1000mbit NIC/Ethernet Goes Down/Halts on Large File Transfer/Heavy Network Usage


    This is obviously a bug in the r8169 kernel module and it seems to affect a lot of people.  I upgraded to the latest kernel and hope this won't happen anymore, as it is a very serious error.  This is especially serious for those who are running servers with this chipset, who can afford for the NIC to randomly go off-line for no apparent reason?   [655548.189113] type=1505 audit(1277067560.902:5): operation="profile_load" name="/usr/bin/freshclam&q........
  • Use rcconf to edit startup/init.d/init scripts on Debian/Ubuntu based distributions


    I've never understood how to enable and disable services for different run levels in Debian based distros, it's just weird, annoying and doesn't make sense.  I much prefer chkconfig from RHEL. Just install the package called 'rcconf' and be done with it.  rcconf makes things easy for you. apt-get install rcconf Reading package lists... Done Building dependency tree        Reading state information... Done........
  • rsync halted froze Out of memory: kill process 7559 (rsync) score 635 or a child Killed process 7559 (rsync)


    Out of memory: kill process 7559 (rsync) score 635 or a child Killed process 7559 (rsync) I was surprised to see this in my dmesg when my rsync backup suddenly stalled/stopped. This system has 3 gigs of RAM and lots of free memory so I don't understand what is happening.   rsync invoked oom-killer: gfp_mask=0x200d2, order=0, oomkilladj=0 Pid: 7600, comm: rsync Not tainted 2.6.24.2 #83  [<c014990e>] oom_kill_pr........
  • XMPP Chat Protocol using Jabber - Guide Tutorial Setup Linux Chat Server


    In Debian based distros: apt-get install jabber Reading package lists... Done Building dependency tree       Reading state information... Done The following packages were automatically installed and are no longer required:   fakeroot dkms Use 'apt-get autoremove' to remove them. The following extra packages will be installed:   jabber-common The following NEW packag........
  • heartbeat is stopped for some reason


    heartbeat is stopped for some reason Anyway hnode2 was active and the services are running fine but I see heartbeat has been stopped somehow. Here is the last log I see of heartbeat: [quote:23c84415f5] Sep 9 17:15:32 hnode2 heartbeat: [16738]: info: MSG stats: 9/1762471 ms age 0 [pid16738/MST_CONTROL] Sep 9 17:15:32 hnode2 heartbeat: [16738]: info: cl_malloc stats: 716/51784021 152624/74519 [pid16738/MST_CONTROL] Sep 9 17:15:32........
  • PHP cannot access /usr/bin/openssl


    PHP cannot access /usr/bin/opensslI have verified the username that runs the process is able to access /usr/bin/openssl and it does exist but the PHP script is saying it doesn't exist: [code:1:1fd0f3abbe] if (!file_exists($OPENSSL)) { //echo "ERROR: OPENSSL $OPENSSL not foundn"; }[/code:1:1fd0f3abbe] I don't get itI can clearly see the contents of /usr/bin by using the PHP system fu........
  • Javascript Get a specified element using getElementById()


    Javascript Get a specified element using getElementById()Great, it produces the value for whatever "id" is passed to the function. http://www.java2s.com/Code/JavaScript/Development/GetaspecifiedelementusinggetElementById.htm [code:1:1287ede953] <html> <head> <script type="text/javascript"> function getElement(){ var x=document.getElementById("myHead........
  • How to Track Down/Find Cause of Linux high disk iowait/wa


    top - 09:34:12 up 2 days, 20:57,  2 users,  load average: 1.83, 1.99, 2.03 Tasks:  59 total,   2 running,  57 sleeping,   0 stopped,   0 zombie Cpu(s):  0.3%us,  0.0%sy,  0.0%ni,  0.0%id, 99.7%wa,  0.0%hi,  0.0%si,  0.0%st That 99.7% wa is iowait, it means the server is waiting for a process to complete an IO operation or in plain English, there is a delay in........
  • OCFS2 crash


    When trying to even cd or ls the mounted OCFS2 partition it crashes.  I think this is a combination of VMWare Server's problem and the way I mounted and symlinked to it. More than anything this shows the problem and lack of forsight with VMWare, but also that OCFS2 is easily crashed if you do strange things. Output of /var/log/messages for OCFS2   Apr 10 15:57:45 localhost kernel: [84331.691258] Modules linked in: vmnet vmci vmmon ocfs2_stac........
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