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Web : ImagickException: attempt to perform an operation not allowed by the security policy `PDF’

After updating ImageMagick to version 6.9.10.23+ from an earlier version, the following behavior occur : Thumbnails generation from PDF, XPS, PS, and EPS does not work anymore The following output can be found in the Web server error log :

PHP Fatal error: Uncaught ImagickException: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408 in /path/to//pdfThumb.php:7\nStack trace:\n#0 /path/to/pdfThumb.php(7): Imagick->__construct('../files/9984/C...')\n#1 {main}\n thrown in /path/to/pdfThumb.php on line 7, referer: https://hostname.domain.tld

PHP Fatal error: Uncaught ImagickException: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408 in /path/to//pdfThumb.php:7\nStack trace:\n#0 /path/to/pdfThumb.php(7): Imagick->__construct('../files/9984/C...')\n#1 {main}\n thrown in /path/to/pdfThumb.php on line 7, referer: https://hostname.domain.tld

This is due to the addition of a policy in the newer version that… Read More »

Linux : How to show Apache memory usage and average process size

Here is an easy way to output in a single command the Apache memory usage and average process size :

ps -ylC apache2 | awk '{x += $8;y += 1} END {print "Apache Memory Usage (MB): "x/1024; print "Average Proccess Size (MB): "x/((y-1)*1024)}'

1	ps -ylC apache2 \| awk '{x += $8;y += 1} END {print "Apache Memory Usage (MB): "x/1024; print "Average Proccess Size (MB): "x/((y-1)*1024)}'

This is particularly useful when you need to calculate proper process, max clients, etc. settings.

Windows : MakeMKV can’t find any usable optical drive when connected using RDP

If you are accessing a computer using Remote Desktop (RDP) and try ripping an optical media (DVD, BD) using MakeMKV (or any other similar software for that matter), it will fail to access the disk. With MakeMKV, the error message will be as followed : The program can’t find any usable optical drive. This error… Read More »

Linux : sar command return “Cannot open /var/log/sysstat/sa27: No such file or directory”

Attempting to use the SAR (sadc) command to lookup the historical system resources consumption metrics and got the following message? Cannot open /var/log/sysstat/sa27: No such file or directory Please check if data collecting is enabled Most likely data collecting is disabled (it is the default on several systems). You need to enable data collecting and… Read More »

Linux : Issue with mail aliases “database /etc/aliases.db is older than source file /etc/aliases”

If you are experiencing issues with your local mail aliases, make sure there is no syntax error in /etc/aliases file and have a look at the mail log file :

/var/log/mail.log

1	/var/log/mail.log

You most likely will encounter a message like this one :

postfix/local[15083]: warning: database /etc/aliases.db is older than source file /etc/aliases

1	postfix/local[15083]: warning: database /etc/aliases.db is older than source file /etc/aliases

In that case, simply run the command to rebuild the aliases database… Read More »

Linux : phpMyAdmin – Error Incorrect format parameter

Having the following error while importing a MySQL dump? phpMyAdmin – Error Incorrect format parameter Have a look at the “upload_max_filesize” value in your “php.ini” parameters. Most of the time, the dump file you are trying to import exceed that limit. Increase the value as needed.

Windows : Unable to merge cells within a table in Microsoft Excel

If you attempted to merge cells together within a table in Microsoft Excel, you may have faced the grayed out “Merge and Center” button issue. To work around this problem, do the following : 1. Select the cells that you want to merge 2. Right click on the selection 3. In the context menu, click… Read More »

Linux : Mail issues after renaming server hostname

If you changed the hostname/FQDN of a Linux server, you may end up with some issues, especially with mailing if some areas were forgotten with that change. Here is a quick procedure involving all the steps you should be looking for. (The following example is based on a Debian Linux system running Postfix MTA.) 1.… Read More »

Windows : Nmap error dnet: Failed to open device eth0

This symptom occurred all of a sudden with Nmap 7.80 and Windows 10 version 1909 (OS build 18363.836), where nmap tries to query using interface “eth0” : Starting Nmap 7.80 ( https://nmap.org ) at 2020-06-30 11:28 Eastern Daylight Time dnet: Failed to open device eth0 QUITTING! It seems that latest Windows updates is involved in… Read More »

Linux : How to reset OpenVPN user lockout without disconnecting users (or without restarting the openvpnas service)

OpenVPN enforce by default a 15 minutes lockout policy for unsuccessful login attempts. As an avid system administrator and used to end-user struggles, you most likely encountered many times situations where a user tried to log in 20 times and blaming you that it isn’t working (all that because they are entering the wrong password,… Read More »