Category Archives: UNIX & Linux

Debian /boot old kernel images

Posted on 29. July 2017 by #!/bin/blog

So I was looking at yet another failed apt-get upgrade because /boot was full. After my initial whining on Twitter, I immediately received a hint towards /etc/apt/apt.conf.d/01autoremove-kernels, which gets generated from /etc/kernel/postinst.d/apt-auto-removal after the installation of new kernel images. The … Continue reading →

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How expiration dates in the shadow file really work

Posted on 7. July 2017 by #!/bin/blog

tl;dr: Accounts expire as soon as UTC reaches the expiration date. In today‘s installment of my classic shame-inducing series “UNIX basics for UNIX professionals”, I want to talk about account (and password) expiration in /etc/shadow on Linux. The expiration time … Continue reading →

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SSH firewall bypass roundup

Posted on 5. January 2016 by #!/bin/blog

So my SSH workflow has reached a turning point, where I’m going to clean up my ~/.ssh/config. Some entries had been used to leverage corporate firewall and proxy setups for accessing external SSH servers from internal networks. These are being … Continue reading →

Posted in UNIX & Linux | Tagged | 2 Comments

CentOS 7 on MD-RAID 1

Posted on 25. October 2014 by #!/bin/blog

Figuring this out took me quite a bit of time. In the end, I approached the starter of this hilariously useless CentOS mailing list thread, who assured me that indeed he had found a way to configure MD-RAID in the … Continue reading →

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What does the slash in crontab(5) actually do?

Posted on 17. October 2014 by #!/bin/blog

That’s a bit of a stupid question. Of course you know what the slash in crontab(5) does, everyone knows what it does. I sure know what it does, because I’ve been a UNIX and Linux guy for almost 20 years. … Continue reading →

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OpenSSH connection multiplexing

Posted on 24. April 2009 by #!/bin/blog

The Challenge I was in touch with a developer the other day who used SSH to programmatically connect to a remote machine where he would start some kind of processing job. Unfortunately, he was in trouble when he wanted to … Continue reading →

Posted in Security, UNIX & Linux | Tagged , , | 3 Comments

Using the SSH agent from daemon processes

Posted on 31. December 2008 by #!/bin/blog

One of my more recent installations, the BackupPC server I wrote about earlier, needs full access as the user root to his clients in order to retrieve the backups. Here’s how I implemented authentication on this machine. BackupPC runs as … Continue reading →

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Swap im Reality Check

Posted on 4. May 2008 by #!/bin/blog

Swap unter Linux scheint so eine Sache zu sein, um die sich reichlich Mythen und Legenden ranken. Deshalb schreibe ich heute mal auf, was ich so von der Sache halte. Wie wir alle wissen, wird der Swap-Bereich zusammen mit dem … Continue reading →

Posted in UNIX & Linux | 8 Comments