/ - rtt - IT Resource

  • 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........
  • NFS Share Won't Mount Solution - mount: wrong fs type, bad option, bad superblock on 10.10.2.20:/tmp/nfsmount


    nfs mount failed: mount 10.10.2.20:/tmp/nfsmount /mnt/nfs/ mount: wrong fs type, bad option, bad superblock on 10.10.2.20:/tmp/nfsmount,        missing codepage or helper program, or other error        (for several filesystems (e.g. nfs, cifs) you might        need a /sbin/mount.<type> helper program)       ........
  • OpenVPN cannot ping remote IP routing loop issue after connecting


    Sometimes if you have a very basic configuration OpenVPN on the client side for some reason sends all traffic to the OpenVPN server IP through the tun0 which is of course impossible and creates a block or routing loop.  This is because you need to use your normal ISP/LAN gateway to hit the OpenVPN server if it is remote/offsite as is usually the case.  So if you are connected to the OpenVPN through say a tun0 device and your routing is set to connect to the OpenVPN&nbs........
  • Linux Mint Black Screen after boot no graphics solution


    This is not the normal "black screen" issue and I was shocked to eventually find out why.  The normal advice of reconfiguring Xorg didn't work.  Even booting into "Recovery Mode" did not help. Here is the short end of the stick that fixed it: sudo apt-get install mdm mate-desktop-environment Yes you got it right, mdm and the mate-desktop-environment / gnome were somehow uninstalled.  This must be whe........
  • Linux Mint Ubuntu Debian How To Disable Webcam Automatically Onboot To Prevent Spying and Privacy Violations


    It is well known hackers, the NSA, CIA and other groups have created malware to secretly turn on your webcam and microphone on your phone, tv etc.. But fortunately on our computers and laptops we have some options. Most webcams use the "uvcvideo" kernel module / driver.  You can disable this in two ways on boot. I recommend both just as a failsafe.  Disable it on rc.local once your system boots automatically Add the followi........
  • [Wed Sep 20 15:34:44 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Wed Sep 20 15:34:44 2017] [error] Init: Unable to read server certificate from file /www/ssl-certs/server.crt [Wed Sep 20 15:34:44 2017] [error] SSL Library Err


    [Wed Sep 20 15:34:44 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Wed Sep 20 15:34:44 2017] [error] Init: Unable to read server certificate from file /www/ssl-certs/server.crt [Wed Sep 20 15:34:44 2017] [error] SSL Library Error: 218529960 error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag [Wed Sep 20 15:34:44 2017] [error] SSL Library Error: 218595386 error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error........
  • Centos 5 OpenSSL does not support TLS 1.2 Apache Error


    [Thu Jan 26 14:13:31 2017] [notice] caught SIGTERM, shutting down [Thu Jan 26 14:14:00 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Thu Jan 26 14:14:00 2017] [error] Server certificate is expired: 'Server-Cert' [Thu Jan 26 14:14:00 2017] [notice] SSL FIPS mode disabled [Thu Jan 26 14:14:07 2017] [notice] suEXEC mechanism enabled (wrapper: /usr/sbin/suexec) [Thu Jan 26 14:14:07 2017] [error] Server certificate is expired: 'Server-Ce........
  • DRBD Split-brain solution


    Uh oh [17925926.174277] block drbd0: Handshake successful: Agreed network protocol version 96 [17925926.174325] block drbd0: conn( WFConnection -> WFReportParams ) [17925926.174342] block drbd0: Starting asender thread (from drbd0_receiver [1682]) [17925926.174432] block drbd0: data-integrity-alg: <not-used> [17925926.174581] block drbd0: drbd_sync_handshake: [17925926.174586] block drbd0: self 2AAE66AF9252D6DB:2815BF........
  • Ubuntu/Debian OpenVZ Template Problems No Networking and SSH not starting


    It all comes down to a bug essentially where you are running an older kernel that doesn't support the newer Debian templates.  The solution is to update your OpenVZ kernel. Here are some symptoms of the problem/lack of kernel support:   Ubuntu Template 12.04 requires a manual network start: service networking start sshd will not start: /usr/sbin/sshd PRNG is not seeded mknod /dev/random c 1 8........
  • Script runs fine from shell but not from cron job in Linux/Unix Debian/Ubuntu/Mint/Centos


    Usually the cause is inexplicable because some things just don't work correctly even when calling all commands by their full path. Usually adding the following to your crontab file at the top will fix/solve the issue: SHELL=/bin/sh PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin  ........
  • 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........
  • Mount a SMB Samba share in fstab Linux Debian/Ubuntu/Centos


    Add the following to fstab where 192.168.1.125/Media is the samba share and where /home/homeuser/Downloads is where you want to mount. Change user and pass to what is needed (if no pass is required it still works fine with the below). //192.168.1.125/Media /home/homeuser/Downloads cifs        user=guest,pass=bla 0 0 mount: wrong fs type, bad option, bad superblock on //192.168.1.125/Media, &nbs........
  • Howto Convert Xen Image to KVM


    #count=10000 makes an image of 10000MB make sure your image is at least the same as your existing dd if=/dev/zero of=yourimage.img bs=1M count=10000 # losetup -fv newimage.raw # fdisk -cu /dev/loop0 # kpartx -a /dev/loop0 # dd if=<xenimage> of=/dev/mapper/loop0p1 # e2fsck -f /dev/mapper/loop0p1 # resize2fs /dev/mapper/loop0p1 # a lot of guides tell you to edit /etc/fst........
  • kvm centos cannot compile error


    ./configure ./configure: cannot locate gcc 3.x. please install it or specify with --qemu-cc yum -y install gcc make ./configure ./configure: cannot locate gcc 3.x. please install it or specify with --qemu-cc yum -y install compat-gcc-* ./configure Error: Could not find alsa Make sure to have the alsa libs and headers installed. yum -y install alsa-lib-devel ./configure........
  • Migrate Linux Mint OS from one drive to another


    mount -o bind /proc /sda2/proc mount -o bind /dev/ /sda2/dev mount -o bind /sys /sda2/sys chroot /sda2 mint / # mount -o bind /proc /sda2/proc mint / # mount -o bind /dev/ /sda2/dev mint / # mount -o bind /sys /sda2/sys mint / # chroot /sda2 mint / # cd ~ mint ~ # ls Desktop mint ~ # cd / mint / # ls bin   Desktop  dev-temp  home      &nb........
  • How to log all PHP based E-mails for abuse


    Step #1 - Create Wrapper Script vi /usr/local/bin/phpsendmail #!/usr/bin/php <?php //changed by realtechtalk.com to make the log readable /**   This script is a sendmail wrapper for php to log calls of the php mail() function.   Author: Till Brehm, www.ispconfig.org   (Hopefully) secured by David Goodwin <david @ _palepurple_.co.uk> */........
  • kvm cannot boot xen guest using lvm


    This booting error is because the Xen PV guest image uses the Xen kernel, this is not compatible with anything but a host running a Xen kernel. I did a kpartx -av virtual.img and then it created some partitions that showed up in fdisk. I mounted it and did a chroot into it and removed the xen kernel and installed a normal kernel but Xen still shows the same kernel in Grub (only the Xen one). This is strange but it seems like this Xen PV guest has some sort of hidden or........
  • Directadmin Install Segfault Error


    ************************************* *                                   * *   All parts have been installed   * *                        ........
  • LOG: MAIN PANIC failed to expand condition "${if eq {$authenticated_id}{}{0}{${if eq {$sender_address}{$local_part@$domain}{0}{${if match{$received_protocol}{N^e?smtps?a$N}{${perl{checkbx_autowhitelist}{$authenticated_id}}}{${if eq{$received_prot


    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   &........
  • vnstat setup guide/tutorial


    yum -y install vnstat chown nobody.nobody -R /var/lib/vnstat/ #replace venet0 below with your desired interface sudo -u nobody vnstat -u -i venet0 #edit: vi /etc/sysconfig/vnstat #VNSTAT_OPTIONS="-i venet0" # only use the sed below if you are using venet0 instead of eth0 or replace accordingly sed -i 's/eth0/venet0/g' /etc/sysconfig/vnstat   [root@monitor]# yum install vn........
  • 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........
  • 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........
  • Ubuntu/Debian DRBD 8.0 Setup Guide


    I've only used it on Centos, so I thought I'd make a quick Debian guide: Install the DRBD Package apt-get install drbd8-utils Reading package lists... Done Building dependency tree       Reading state information... Done The following packages were automatically installed and are no longer required:   libswfdec-0.8-0 Use 'apt-get autoremove' to remove them. The following........
  • Directadmin License Error The ip of this machine (xx.xx.xx.xx) does not match the ip in the license file.
    Check the value of your ethernet_dev=venet0:0 setting in your /usr/local/directadmin/conf/directadmin.conf file and the output of /sbin/ifco


    2010:09:09-22:22:11: The ip of this machine (xx.xx.xx.xx) does not match the ip in the license file.<br> Check the value of your ethernet_dev=venet0:0 setting in your /usr/local/directadmin/conf/directadmin.conf file and the output of /sbin/ifconfig<br> Solution /usr/local/directadmin/scripts/getLicense.sh........
  • jailkit for chroot ssh account security tutorial and fix for error


    This was done on Centos but I think it's easier on Debian machines, the paths that it is set to use are tailored towards Debian, so there is some fiddling that needs to be done on Centos. This is for chrooting ssh, but jailkit has other uses than just SSH jails but I won't cover them in this writeup. 1. Install jailkit yum install jailkit 2. Setup Jail Home mkdir /home/jail chown root:root /home/ja........
  • 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........
  • OpenVZ backup container to a single file while it's running using "vzdump"


    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........
  • Need identd for port 113 ? Install authd


    Need identd for port 113 ? Install authdyum install authd Happy identing :)Actually it's not that simple. It installs as an "xinetd" service and is disabled and turned off by deafult. To enable it run: [code:1:8c94df8319] chkconfig --level 3 auth on service xinetd restart [/code:1:8c94df8319] This will set identd aka authd to start by default. service xinetd resta........
  • auth/auth_util.c:make_server_info_sam(840) User nobody in passdb, but getpwnam() fails! - SAMBA/SMB Error How To Fix


    auth/auth_util.c:make_server_info_sam(840)   User nobody in passdb, but getpwnam() fails! I never found the solution to this in the web, as usual so I thought I'd post the fix.  In plain English smbd is telling us that the user "nobody" does not exist in /etc/passwd. You can simply add this to your /etc/passwd file like so: nobody:x:65534:65534:nobody:/nonexistent:/sbin/nologin Now SAMBA/smbd should........
  • Latest Articles

  • syntax error, unexpected T_SL in PHP Solution
  • grep regular expression match number range between specific numbers
  • bash how to print out lines of text within a range from the first occurrence
  • bash script how to to check LAN computers for open ports
  • MySQL Using mytop Debug Source of High IO and Slow Performance
  • How To Mathematically Convert and Calculate Binary Value To Decimal Value
  • systemd management using systemctl and journalctl to check systemd logs
  • css how to format code in the code tag
  • css br with extra blank line
  • What is /dev/pts and why do we need it in Linux?
  • Linux What is umask (user mask) for file and directory creation permissions and how to calculate umask and change the defaults
  • Linux Permissions and Groups Real Usecase for Group Access
  • Centos 7 python34 how to install the gi library
  • Centos 7 - Convert Minimal to Graphical GUI GNOME or KDE Desktop
  • AMD Set Fan Speed and Other Powerplay Memory/CPU Timings with a Linux script
  • Ethereum Mining Claymore Nanopool Error
  • genisoimage errors with long filenames and deep directory structures
  • Linux Kernel USB Export Errors
  • How to download gajim 0.16.9 XMPP/Jabber client so you can use OMEMO encryption
  • HP DL385 G7 Linux BIOS Update Flash