Linux (Page 3)

rrdtool dump filename.rrd rrdtool info filename.rrd   rrdtool graph /dev/null -s 3600 DEF:ierr=filename.rrd:ds1:AVERAGE VDEF:ioct_a=ierr,AVERAGE PRINT:ierr:%lf this command will get the avg value of ds1 (ds1 is the dataset – you can see it in rrdtool info )  , assign it to variable ierr  and print out #3600 => one hourRead More →

Create a service: sudo vi /etc/systemd/system/rc-local.service Add your code there: [Unit] Description=/etc/rc.local Compatibility ConditionPathExists=/etc/rc.local [Service] Type=forking ExecStart=/etc/rc.local start TimeoutSec=0 StandardOutput=tty RemainAfterExit=yes SysVStartPriority=99 [Install] WantedBy=multi-user.target Create and make sure /etc/rc.local is executable and add this code inside it: sudo chmod +x /etc/rc.local #!/bin/sh -e # # rc.local # # This script is executed at the end of each multiuser runlevel. # Make sure that the script will “exit 0” on success or any other # value on error. # # In order to enable or disable this script just change the execution # bits. # # By default this script does nothing. exit 0 Enable the service: sudoRead More →

minicom -s  (this is to configure the terminal) to exit minicom Press Ctrl – A , select Z , select XRead More →

When you tried to stop Nagios to monitor some services from web interfaces – you see the message below: Sorry, but Nagios is currently not checking for external commands, so your command will not be committed! This is because we haven’t enable this feature in our configuration, it’s easy to fix. Open your nagios config file , /etc/nagios3/nagios.cfg Look for this line: check_external_commands=0   change it to check_external_commands=1   and reload nagios /etc/init.d/nagios3 restart You might receive this error: Error: Could not stat() command file ‘/var/lib/nagios3/rw/nagios.cmd’!.  The fix is # /etc/init.d/nagios3 stop Stopping nagios3 monitoring daemon: nagios3Waiting for nagios3 daemon to die… . # dpkg-statoverride –updateRead More →

it’s because the new line difference between Unix and windows , the easiest fix it run this command dos2unix filename  Read More →

I just found out that i could not access my wordpress today, i checked the server, everything looked good. i restarted the server, it’s still slow, there is no error. I decided to do a debug using the following command: cd /www/myswebsite.com/httpdocs/ strace php index.php I see my script stopped at sendmmsg(6, {{{msg_name(0)=NULL, msg_iov(1)=[{“-\265\1\0\0\1\0\0\0\0\0\0\24tech-banker-service”…, 42}], msg_controllen=0, msg_flags=MSG_DONTROUTE|MSG_DONTWAIT|MSG_FIN|MSG_SYN|MSG_ERRQUEUE|MSG_NOSIGNAL|MSG_FASTOPEN|0x6a80010}, 42}, {{msg_name(0)=NULL, msg_iov(1)=[{“\207E\1\0\0\1\0\0\0\0\0\0\24tech-banker-service”…, 42}], msg_controllen=0, msg_flags=MSG_OOB|MSG_DONTROUTE|MSG_CTRUNC|0x10}, 42}}, 2, MSG_NOSIGNAL) = 2 poll([{fd=6, events=POLLIN}], 1, 5000) = 1 ([{fd=6, revents=POLLIN}]) ioctl(6, FIONREAD, [58]) = 0 recvfrom(6, “-\265\201\200\0\1\0\1\0\0\0\0\24tech-banker-service”…, 2048, 0, {sa_family=AF_INET, sin_port=htons(53), sin_addr=inet_addr(“213.133.99.99”)}, [16]) = 58 poll([{fd=6, events=POLLIN}], 1, 4999) = 1 ([{fd=6, revents=POLLIN}]) ioctl(6, FIONREAD, [135]) = 0 recvfrom(6,Read More →

The folder /etc/cron.d/ is used to store all cronjobs, the cronjob is saved on the file , the format is: minute hour day month dayofweek username command_to_run. There might some problems – the syntax is not correct , and the result is that the whole file will be ignore.  I don’t know how to check the syntax , but i can watch to the syslog to see if there is any error. After we edit the file in crontab , the system will reload the cronjob, if there is any error it will throw an error in syslog. So i setup this before editing theRead More →

smartctl is a nice tool to check your hard disk health – it will let you know how many hours your disk have been running , the hard disk serial number, temperature … by default smartctl is not installed by default, it’s in smartmontools package. To make it ready to use, you must install smartmontools apt-get install smartmontools After you install smartmontools you can run this command to check your hard disk health: smartctl –xall /dev/sda Here is a sample: smartctl 6.5 2016-01-24 r4214 [x86_64-linux-4.4.0-28-generic] (local build) Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org === START OF INFORMATION SECTION === Model Family: Toshiba 3.5″Read More →

Check this out: https://www.cloudflare.com/technical-resources/#mod_cloudflare Option 1: Installation from Packages Download the appropriate package to your web server and install it using your operating system’s ‘rpm’ or ‘dkpg’ commands. For RedHat / CentOS / CloudLinux: # yum install glibc.i686 # rpm -i mod_cloudflare-elX.latest.rpm For Debian / Ubuntu: # dpkg -i mod_cloudflare-XXXXX.latest.deb RHEL/CentOS/CloudLinux RHEL/CentOS/CloudLinux 7 (64-bit) RHEL/CentOS/CloudLinux 6 (64-bit) Debian Debian 8 (64-bit) Debian 7 (64-bit) Ubuntu Ubuntu 16.04 (64-bit) Ubuntu 15.10 (64-bit) Ubuntu 15.04 (64-bit)Ubuntu 14.04 (64-bit) Ubuntu 12.04 (64-bit)Read More →