error: Failed to create domain from /etc/libvirt/qemu/

We had a issue in one of the virtualizor node

Where the server on rebooting the KVM VM were not starting

With error message being

error: Failed to create domain from /etc/libvirt/qemu/
error: Cannot get interface MTU on ‘viifbr0’: No such device

ON checking around found the issue with virtnetwork

Below command fixed the issue

service virtnetwork start

~]# service virtnetwork start
Bringing up viifbr0 – OK
Waiting for 10 seconds…1…2…3…4…5…6…7…8…9…10
Internet connectivity check successful viifbr0 – OK

Open port in Centos 7

Below are the commands which are to be used in centos 7 to open port 80

[root@onlinesupport ~]# firewall-cmd --permanent --zone=public --add-port=80/tcp success

[root@onlinesupport]# firewall-cmd --reload


Mysql Upgrade Process

While upgrading mysql in server make sure you make a backup of existing mysql

using commmand mysqldump --all-databases > all_databases.sql

Once you have complete backup , You can proceed with with upgrade of mysql.

How to add multiple ips in centos 7

In centos 7 by default ifconfig command will not work.
You need to install it using this command yum install net-tools
1.  Create a file in /opt/1.sh
2.  create ip list in an excel sheet,
Example:
ip addr add 198.xxx.xx.xx dev enp6s0f0 label   enp6s0f0:1
ip addr add 198.xxx.xx.xx dev enp6s0f0 label   enp6s0f0:2
ip addr add 198.xxx.xx.xx dev enp6s0f0 label enp6s0f0:3
ip addr add 198.xxx.xx.xx dev enp6s0f0 label enp6s0f0:4
3. Add ips in /opt/1.sh file
4. Execute sh 1.sh for the ips to display in ifconfig
5. For the ips to reflect in ifconfig even after server is rebooted add this command sh /opt/1.sh in /etc/rc.d/init.d/network file and it should be added above exit $rc

/tmp is 100% due to Mysql

Was having an issue where /tmp was getting 100% full every few minutes

on investigation i see the files of 3Gb over there in /tmp

#sql_436_0.MAD

ddvps20 tmp]# ls -al
total 3779332
drwxrwxrwt 12 root root 4096 Sep 21 10:24 .
dr-xr-xr-x 21 root root 4096 Sep 21 09:17 ..
drwxrwxrwt 2 root root 4096 Sep 21 09:17 .font-unix
drwxr-xr-x 2 cpanelsolr cpanelsolr 4096 Sep 21 10:22 hsperfdata_cpanelsolr
drwxr-xr-x 2 root root 4096 Sep 21 10:21 hsperfdata_root
drwxrwxrwt 2 root root 4096 Sep 21 09:17 .ICE-unix
drwx—— 2 root root 16384 Sep 21 09:56 lost+found
lrwxrwxrwx 1 root root 30 Sep 21 10:23 mysql.sock -> ../../var/lib/mysql/mysql.sock
-rw——- 1 cpdigita cpdigita 4096 Sep 21 10:11 .spamassassin1694OHMO4Dtmp
-rw——- 1 cpdigita cpdigita 0 Sep 21 10:17 .spamassassin1694voSq6Ctmp
-rw——- 1 cpdigita cpdigita 0 Sep 21 10:11 .spamassassin1694y0CJyjtmp
-rw——- 1 cpdigita cpdigita 0 Sep 21 10:04 .spamassassin18453ZHMaRtmp
-rw——- 1 cpdigita cpdigita 0 Sep 21 10:06 .spamassassin1845bypIDCtmp
-rw——- 1 cpdigita cpdigita 0 Sep 21 10:03 .spamassassin1845pCtlHqtmp
-rw-rw—- 1 mysql mysql 3866185728 Sep 21 10:07 #sql_436_0.MAD
-rw-rw—- 1 mysql mysql 8192 Sep 21 10:00 #sql_436_0.MAI
-rw——- 1 cpanelsolr cpanelsolr 165 Sep 21 10:22 start_2180387910403356223.properties
drwx—— 3 root root 4096 Sep 21 09:17 systemd-private-1d4af49159364e018772426d7df23a9d-named.service-8XVCsj
drwx—— 3 root root 4096 Sep 21 09:17 systemd-private-1d4af49159364e018772426d7df23a9d-named.service-FyUDBs
drwxrwxrwt 2 root root 4096 Sep 21 09:17 .Test-unix
drwxrwxrwt 2 root root 4096 Sep 21 09:17 .X11-unix
drwxrwxrwt 2 root root 4096 Sep 21 09:17 .XIM-unix

So mysql was going down due to /tmp being full

So as a work around found a better solution

To change the /tmp file to something else for mysql

vi /etc/my.cnf
tmpdir=/mysqltmp

Save the file with :wq

2. Create the /mysqltmp directory

Code:
mkdir /mysqltmp
chmod 1777 /mysqltmp



3. Restart MySQL and check that the tmpdir is now /mysqltmp
Code:
/etc/init.d/mysql restart
mysqladmin var | grep tmpdir
You should see the following return:

Code:
# mysqladmin var | grep tmpdir
| slave_load_tmpdir                       | /mysqltmp
| tmpdir                                  | /mysqltmp

Redirecting HTTP to HTTPS

Redirecting HTTP to HTTPS

RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://www.yourdomain.com/$1 [R,L]

Redirect Only a Specific Domain

RewriteEngine On
RewriteCond %{HTTP_HOST} ^yourdomain\.com [NC]
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://www.yourdomain.com/$1 [R,L]
Redirecting to HTTPS on a specific folder, add the following:

[ERROR] Can’t init tc log Mariadb

2018-03-30 2:06:19 139671858284288 [Note] InnoDB: Dumping buffer pool(s) not yet started
2018-03-30 2:06:19 139672598403328 [Note] Plugin ‘FEEDBACK’ is disabled.
2018-03-30 2:06:19 139672598403328 [Note] Recovering after a crash using tc.log
2018-03-30 2:06:19 139672598403328 [ERROR] Can’t init tc log
2018-03-30 2:06:19 139672598403328 [ERROR] Aborting

Was getting above error in mysql errorlog

The solution to this issue was just to go ahead and delete tc.log

rm -rf /var/lib/mysql/tc.log

Went ahead and restart mysql.. Mysql was online

root@server lib]# rm -rf /var/lib/mysql/tc.log
[root@server lib]# /etc/init.d/mysql restart
MySQL server PID file could not be found! [FAILED]
Starting MySQL.180330 02:07:40 mysqld_safe Logging to ‘/var/lib/mysql/server.cpanel.com.err’.
180330 02:07:40 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
[ OK ]
[root@server lib]#