To change PHP version for a web site hosted in Virtualmin, click on the Virtualmin tab. Select the domain from drop down that you need to change PHP version for.
Virtualmin > YourDomain > Server Configuration > PHP Versions
On this page, select PHP version from drop down.
See Virtualmin
On a CentOS server, when sending mail from PHP scripts, mail failed to work. On checking postfix log file (/var/log/maillog), i see following error.
Aug 11 01:41:53 forums postfix/sendmail[44463]: fatal: open /etc/postfix/main.cf: Permission denied
To fix this, disable selinux
setenforce 0
To permanantly disable SELinux, run
sed -i 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config
To protect files on Linux by accidently overwritten by > operator, you can use
set -o noclobber
Now if you try to overwrite a file with >, you will get error
root@ok:~# echo "Hello" > 1.txt -bash: 1.txt: cannot overwrite existing file root@ok:~#
If you really need to overwrite, use >! operator.
echo "Hello" >! FILE_NAME
Example
root@ok:~# echo "Hello" > 1.txt -bash: 1.txt: cannot overwrite existing file root@ok:~# echo "Hello" >! 1.txt root@ok:~#
Instead of running the command “set -o noclobber” everytime, you can add it to .bashrc file.
To extract Audio from Video using ffmpeg, run
ffmpeg -i VIDEO_FILE.mp4 audio.mp3
On web servers, you may need to get email alert when someone logs in to your server using SSH. To do this edit file
vi ~/.bashrcAdd
echo "ALERT - Bash shell access by user \"`whoami`\" to server $HOSTNAME on `date` " | mail -s "Alert: Shell access detected from user \"`whoami`\" from IP_Address: `who | cut -d"(" -f2 | cut -d")" -f1`" [email protected]In above, replace [email protected] with your actual email address. You need a mail server installed on your server for this to work.
If you want to log to a file, add
echo 'ALERT - Root Shell Access (' `hostname` ') on:' `date` `who` >> /var/log/user-loginsSee SSH
By default VNC Console on a KVM virtual Machine only listens to localhost. So you need to do SSH tunnel to access VNC console.
To make VNC available on all interfaces on Host machine, you need to edit file
vi /etc/libvirt/qemu.conf
You need to uncomment the line vnc_listen = “0.0.0.0”.
# VNC is configured to listen on 127.0.0.1 by default. # To make it listen on all public interfaces, uncomment # this next option. # # NB, strong recommendation to enable TLS + x509 certificate # verification when allowing public access # vnc_listen = "0.0.0.0"
Once this is done, you need to shutdown and start the virtual machine. Just reboot won’t work.
root@PAR-199235:~# virsh vncdisplay kali-linux 127.0.0.1:0 root@PAR-199235:~# virsh shutdown kali-linux Domain kali-linux is being shutdown root@PAR-199235:~# virsh list --all Id Name State ----------------------------- - kali-linux shut off root@PAR-199235:~# virsh start kali-linux Domain kali-linux started root@PAR-199235:~# virsh vncdisplay kali-linux :0 root@PAR-199235:~#
See Linux KVM
This script will check disk usage on / partition and email you if disk usage is above 80%
We can use df / command to find current disk usage
df /
As you can see, the result have 2 lines. We don’t need first line. To ignore first line, we can use
df / | grep -v 'Filesystem'
From the result, we only need the Use% part. In this case 66%, to find this, you can use awk command, that split the line, then prient specified part. In our case, we need 5th part.
df / | grep -v 'Filesystem' | awk '{print $5}'
To use disk usage % in our script for calculation, we need it converted to number. That is remove %. This can be done with sed command
df / | grep -v 'Filesystem' | awk '{print $5}' | sed 's/%//g'
Now we have disk usage as a number. We can use it in our script.
vi disk-usage-checker
Add following content to it
#!/bin/bash
CURRENT_USAGE=$(df / | grep -v 'Filesystem' | awk '{print $5}' | sed 's/%//g')
ALERT_ON=80
if [ "$CURRENT_USAGE" -gt "$ALERT_ON" ] ; then
mail -s 'Disk Usage Warning' YOUR_EMAIL_HERE << EOF
Disk almost full on / partition. Current Useage: $CURRENT_USAGE%
EOF
fi
In above script, replace YOUR_EMAIL_HERE with your email address.
You can run the script daily using cronjob. If disk usage ever go above 80%, you will get email alert.
See bash
To install Linux KVM hypervisor on CentOS 8, run
dnf install qemu-kvm
Install libvirtd
dnf install libvirt-daemon libvirt-daemon-kvm libvirt-client
Enable libvirtd to start on boot
systemctl enable libvirtd
Start libvirtd
systemctl start libvirtd
To see status, run
systemctl status libvirtd
Install virt-install
dnf install virt-install
Now you have Linux KVM installed. You can use virt-install or Virt Manager to create virtual machine.
I have a movie cut with hjspit.
-rw-r--r-- 1 root root 110100480 Apr 17 10:42 MSFT_1.avi.001
-rw-r--r-- 1 root root 110100480 Apr 17 10:45 MSFT_1.avi.002
-rw-r--r-- 1 root root 110100480 Apr 17 10:45 MSFT_1.avi.003
-rw-r--r-- 1 root root 110100480 Apr 17 10:47 MSFT_1.avi.004
-rw-r--r-- 1 root root 110100480 Apr 17 10:47 MSFT_1.avi.005
-rw-r--r-- 1 root root 110100480 Apr 17 10:49 MSFT_1.avi.006
-rw-r--r-- 1 root root 110100480 Apr 17 10:49 MSFT_1.avi.007
-rw-r--r-- 1 root root 110100480 Apr 17 10:51 MSFT_1.avi.008
-rw-r--r-- 1 root root 62759034 Apr 17 10:51 MSFT_1.avi.009To join them on Linux, run
cat MSFT_1.avi.00? > MSFT_1.aviBack to cat
When you run a docker image, it create a container and run it. After docker container stop, container stays, so you can use it again if required.
Some times, you need to delete docker container after it is run. This is useful if your docker container is just a command line executable. In my case, docker container have ffmpeg in it, i don’t want container left over after i executed ffmpeg command.
To auto delete container after execution, use –rm option.
docker run --rm DOCKER_IMAGE
Example
docker run --rm --name ffmpeg jrottenberg/ffmpeg:3.2-ubuntu -format
One of my internet provider only provide IPv4 connection. When i run apt install command, it failed with error as it try to connect using IPv6.
boby@sok-01:~$ sudo apt install php7.3-curl Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: php7.3-curl 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 29.6 kB of archives. After this operation, 123 kB of additional disk space will be used. Err:1 http://ppa.launchpad.net/ondrej/php/ubuntu bionic/main amd64 php7.3-curl amd64 7.3.13-1+ubuntu18.04.1+deb.sury.org+1 Could not connect to ppa.launchpad.net:80 (2001:67c:1560:8008::15). - connect (101: Network is unreachable) Could not connect to ppa.launchpad.net:80 (91.189.95.83), connection timed out E: Failed to fetch http://ppa.launchpad.net/ondrej/php/ubuntu/pool/main/p/php7.3/php7.3-curl_7.3.13-1+ubuntu18.04.1+deb.sury.org+1_amd64.deb Could not connect to ppa.launchpad.net:80 (2001:67c:1560:8008::15). - connect (101: Network is unreachable) Could not connect to ppa.launchpad.net:80 (91.189.95.83), connection timed out E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? boby@sok-01:~$
To force apt to use IPv4 only, edit
sudo vi /etc/apt/apt.conf.d/99-force-ipv4
Add
Acquire::ForceIPv4 "true";
If you want to force IPv6, add
Acquire::ForceIPv6 "true";
On rebooting the CentOS 7 server, changes made to resolv.conf is lost. This is because one of the network interface is configured to use DNS server.
[root@server ~]# grep DNS /etc/sysconfig/network-scripts/ifcfg-*
/etc/sysconfig/network-scripts/ifcfg-eno1:DNS1="127.0.0.1"
[root@server ~]# To fix, edit
vi /etc/sysconfig/network-scripts/ifcfg-eno1Remove the line
DNS1="127.0.0.1"Now NetworkManager will not modify /etc/resolv.conf file on boot.
Or you can set valid DNS servers in network config file like
[root@server ~]# cat /etc/sysconfig/network-scripts/ifcfg-eno1 | grep DNS
DNS1="1.1.1.1"
DNS2="8.8.8.8"
[root@server ~]# If your network configuration use DHCP, set set PEERDNS=no.
BOOTPROTO=dhcp
PEERDNS=noAnother solution is to make file immutable with
chattr +i /etc/resolv.confRelated Posts