/ - 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........
  • AMD Set Fan Speed and Other Powerplay Memory/CPU Timings with a Linux script


    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........
  • VMWare ESXi 6.7 SSH/PowerShell CLI Commands


    [root@localhost:~] BootModuleConfig.sh          echo                         host-ind                     nfcd                   ........
  • mail command line examples of how to send an email using Linux / Unix and the Bash Shell or Scripting


    A simple way that may work for a lot of people who just need basic output for their scripts or daemons to announce an action is this: echo "body or message" | mail -s "realtechtalk.com" user@domain.com If you want to send a text file as the body just do this instead: mail -s "realtechtalk.com" user@domain.com < /tmp/sometxtfile.txt These a........
  • 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........
  • Debian Linux Mint Ubuntu Disable Automatic apt-get update


    sudo chmod 000 /etc/cron.daily/apt-compat   This is the easiest way to disable the cron without anything more invasive like deleting the file. After that you won't have anymore apt-get's starting. This can be critical for systems without much extra RAM that is not in use.  I've seen systems that have swapped and crashed over apt-get.........
  • Centos How To Update to Glibc 2.14 Plus


    Centos 6 requires GLIBC 2.12 however a lot of new programs you would want to compile may need a newer glibc.  You can't remove the old glibc since the whole OS is based on it but you can install the updated glibc alongside it and do an export pointing to your updated GLIBC. mkdir ~/glibc_install; cd ~/glibc_install wget http://ftp.gnu.org/gnu/glibc/glibc-2.14.tar.gz........
  • phpBB3 slow and internal dummy connection


    Using Apache 2.2 and PHP 5.6 PHPBB3 is very slow to respond.  Actually for some reason it takes so long to even register a log entry in access_log as in several seconds or a few minutes later it shows up in Apache.  All other vhosts and Apache access stops working and freezes until the request to access PHPBB3 slowly completes. It seems to randomly be slow if you stop using it whether for posting or reading the forums.  I've migrated to different machines including........
  • 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........
  • Directadmin compile error solution cc: Internal error: Killed (program cc1)


    cc: Internal error: Killed (program cc1) Please submit a full bug report. See <http://bugzilla.redhat.com/bugzilla> for instructions. make: *** [ext/fileinfo/libmagic/apprentice.lo] Error 1 make: *** Waiting for unfinished jobs.... Stopping crond:                                  ........
  • 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........
  • Country List Names in HTML Select From


    This is useful for developing a lot of applications, I'm putting it here to keep it handy for myself and hopefully others:   <select name='country'><option value=Choose>Choose Country</option><option value=CA>Canada</option><option value=JP>Japan</option><option value=US>United States</option><option value=GB>United Kingdom</option><option value=AF>Afghanistan</option><option value=AL&........
  • 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........
  • 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........
  • Drupal 6.2 Install and how to move install to root/non-subdirectory


    drup 6.2 install $cd drupgoodinst3883/ [ drupgoodinst3883]$ ls CHANGELOG.txt  cron.php  index.php          INSTALL.pgsql.txt  INSTALL.txt  MAINTAINERS.txt  modules   robots.txt  sites   update.php   xmlrpc.php COPYRIGHT.txt  includes  INSTALL.mysql.txt  install.php        LICENSE.txt  misc  &........
  • crontab/cronjob running multiple times at the wrong time


    crontab not working It is running as user Apache I've tried 0 0 * * * (which means midnight 00:00) and it does run at midnight but also 13:25 for some reason? 25 0 * * * with this it runs at 00:25 but again also at 13:25 Solution - Restart the Cron Service (especially if you changed your time/timezone) *Update I had a suspicion that changing the timezone a few weeks ago caused this.  I restarted lhe cron service and the problem h........
  • mdadm Centos 5 automatic resync


    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........
  • mdadm/md-check how to check array integrity without rebuilding


    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........
  • Cygwin and crontab backups via ssh/scp/rsync


    Install the "Editors" and "Net" groups that will give you rsync, ssh, ssh-keygen and cron. The trickiest thing that I keep forgetting about each time is you have to run "cron-config" which adds the cron service to Windows, and without doing that obviously no cron jobs will be run thus making automatic backups impossible. Warning about rsync/cygwin and using the -a archive switch. It's a good thing I caught this because it doesn't work ri........
  • md: data-check of RAID array md3


    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 I never 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'........
  • yum in Centos 5/Xen halts and exits suddenly


    yum exits in the middle The problem is this VPS seems to be an OpenVZ template from HyperVM.  The only way to make it work was to disable i386 packages since this was an x64 kernel.  That shouldn't be necessary but it was the only way to make yum stop quitting after the first package or two.  I couldn't find any issue by checking the logs either. echo y|yum install vim-minimal telnet expect jwhois net-tools slocate iptables elinks gawk L........
  • 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........
  • crontab Reference/How To/Info/Guide


    I can never actually remember the order and the number of parameters so here they are: minute hour day of month month day of week command 0 5 *........
  • 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........
  • Crontab Tutorial - Tips & Shortcuts


    Crontab Tutorial - Tips & Shortcuts*/5 * * * * /command The above is an example of a command that runs every 5 minutes. Normally instead if the "*/5" you'd have to type "5,10,15,20,25,30,35,40,45,50,55" etc... You can use it to run a program every 5 days, 5 months 5 years etc...Crontab run one a day at a certain time[code:1:7a3bd32dfa]0 1 * * * /home/backupguy/databackup.sh[/code:1:7a3bd32dfa]........
  • Backup Shell Script


    Backup Shell Script[quote:aaa4b0b165]#!/bin/sh date=`date -I` mysqldump --all-databases | gzip > /var/backup/backup-$date.sql.gz [/quote:aaa4b0b165] Something like that could be useful as a cronjob to locally or remotely backup your databases........
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