Linux – RFC 3092

Teams on Windows grey Overlay Foo

Posted on March 4, 2022 - March 4, 2022 by peter

After being forced to work with Windows for a while I finally was able to switch back to Linux. And one of the first things I needed for work was MS Teams. So I updated the already installed version and when I first had to do a screen share I had a flashback, why I switched to use Teams in a VM, rather than the native Linux version: a grey overlay.

It’s nice to have the red frame, so that I know which screen I am sharing, but the grey overlay makes things very hard to read. Especially when you share a dark themed window. But see for yourself. This is what I got:

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OpenVPN in Ubuntu 18.04 Foo within OpenVZ Container (Strato)

Posted on March 21, 2019 - March 21, 2019 by peter

It has been a while since my last blog post, but there was no real foo happening to me during that time. But this issue really gave me some heartburn.

Let’s start with the general setup. We have a Linux VM in an OpenVZ environment. The hoster is Strato in Germany, but I don’t think that really matters. There are some known issues with the TUN device not being accessible within the VM, but Strato did their homework and I could see the module:

# lsmod | grep tun
tun                     4242  -2
vznetstat               4242  -2 tun,ip_vznetstat,ip6_vznetstat

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OpenVPN 2.4 CRL Expired Foo

Posted on December 21, 2017 - December 15, 2018 by peter

I chose a nice Friday evening and a good Scotch to upgrade an older Ubuntu LTS to the latest and greatest. And all went well, until I wanted to connect one of the clients via VPN. All I saw was this nasty little line in the log files of the server
... VERIFY ERROR: depth=0, error=CRL has expired: ...

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Send Email from the Command Line using an External SMTP Server

Posted on June 14, 2017 - December 15, 2018 by peter

Sending email in Linux is pretty straight forward, once an email server is set up. Just use mutt or mail and all is good. But sometimes you actually want to test if SMTP is working correctly. And not only on your box, but on a remote box. That is of course easy using a MUA like Thunderbird or Sylpheed, but that is not always feasible on a remote server in a remote network.

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MySQL max_connections limited to 214 on Ubuntu Foo

Posted on June 13, 2017 - December 15, 2018 by peter

After moving a server to a new machine with Ubuntu 16.10 I received some strange Postfix SMTP errors. Which turned out to be a connection issue to the MySQL server:
postfix/cleanup[30475]: warning: connect to mysql server 127.0.0.1: Too many connections

Oops, did I forgot to up max_connections during the migration:

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Check SSL Connection Foo

Posted on July 6, 2016 - December 15, 2018 by peter

It was that time of the year, when I had to renew some SSL certificates. Renewing and updating them in the server is a nice and easy process. But checking, whether the server is delivering the correct certificate and, that I updated and popluated the intermediate certificates correctly, is a different story.

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Nagios Enabling External Command on Debian based Distributions

Posted on December 4, 2015 - December 15, 2018 by peter

While debugging my check disk problem after the 15.10 upgrade, I saw that I forgot to enable external commands. That is handy, when you want to re-schedule a check to see, if your changes took effect. Again, something that is easily activated. So if you see something like this, then you might want to make some changes:

Error: Could not stat() command file ‘/var/lib/nagios3/rw/nagios.cmd’!

The external command file may be missing, Nagios may not be running, and/or Nagios may not be checking external commands. An error occurred while attempting to commit your command for processing. Continue reading “Nagios Enabling External Command on Debian based Distributions” →

Nagios check_disk Foo on Ubuntu 15.10

Posted on December 4, 2015 - December 15, 2018 by peter

Another day another foo, this time done to the check_disk plugin for Nagios on Ubuntu. After updating to 15.10 my disk space check all of a sudden failed with this one here:

DISK CRITICAL - /sys/kernel/debug/tracing is not accessible: Permission denied

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Automatic Ubuntu Kernel Clean Up Foo (Update)

Posted on June 27, 2014 - July 26, 2014 by peter

Cleaning up old kernel images on a Ubuntu machine is a quite annoying task. If you forget it and you have a separate /boot partition, then you will sooner or later run out of disk space. And then of course all your updates will fail.

Doing the clean up manually is, as mentioned, more than annoying and very tedious. But other smart people have spent some time and created a nice little one-liner that will get rid of old kernel versions. This command line will of course make sure that the currently running kernel is not removed. So it is very important to reboot after a kernel upgrade before you run this script!

And without further ado I present….
dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/$.*$-$[^0-9]\+$/\1/")"'/d;s/^[^ ]* [^ ]* $[^ ]*$.*/\1/;/[0-9]/!d' | xargs apt-get -y purge

Update:
Not a big deal but a sudo snuck into the xargs call. It is now removed and shouldn’t cause any trouble anymore.

Too Many Open Files Foo With Chrome On Ubuntu 13.10

Posted on May 19, 2014 by peter

The last Chrome update and one of the last Thunderbird updates caused some strange crashes of either on of them on my Ubuntu 13.10. All is fine, it runs great and all of a sudden *boom*, browser window gone, or email client gone.

Luckily .xsession-errors exists and there I could find some entries like this:
[3827:4038:0518/230904:ERROR:shared_memory_posix.cc(226)] Creating shared memory in /dev/shm/.com.google.Chrome.12UDei failed: Too many open files

Not good. But there is help. For MyEclipse I had the same issue in the past. But it didn’t seem necessary anymore since 13.10. But I also haven’t used it in a while. Anywhoo, here is what has to be done. And before I forget it, all these changes have to be done as root.

First check the setting for file-max with the following command
cat /proc/sys/fs/file-max

In my case this value seems fine, as it is well beyond the 200,000 that they recommend.
peter@majestix:~$ cat /proc/sys/fs/file-max 1627431

If that is below 200,000 you can set by adding the following line to /etc/sysctl.conf
fs.file-max=200000

The next is the ulimit setting for open files. You can check it with the following command
ulimit -n

This one was set to 1024 in my case and that can be a little bit low. At MyEclipse they recommend setting it to 65535 and that’s what I did. Just add the following lines to /etc/security/limits.conf
* hard nofile 65535 * soft nofile 65535

Afterwards restart your machine and all should be fine. If you only have to change the sysctl.conf setting then you can activate that change with the following command
service procps start