Posts Tagged “linux”

Fix tmux eating Ctrl+Tab/Ctrl+Shift+Tab

I have no idea why this happens, but on one of my machines, tmux swallows Ctrl+Tab and Ctrl+Shift+Tab. I have other machines, running the same tmux version and config, where this doesn’t happen. The only significant difference I’m aware of is that I access the other machines via SSH, but I’ve tried ssh localhost and […]

Running a script after updating a TLS certificate with certbot

This proved to be blessedly simple. As per the documentation, any executable in /etc/letsencrypt/renewal-hooks/deploy will be run after a certificate was successfully renewed (may need to be owned by root). This worked first time: #!/bin/bash   cp -L /etc/letsencrypt/live/<domain>/{fullchain,privkey}.pem /etc/exim4/ chown Debian-exim:Debian-exim /etc/exim4/{fullchain,privkey}.pem systemctl restart exim4#!/bin/bash cp -L /etc/letsencrypt/live/<domain>/{fullchain,privkey}.pem /etc/exim4/ chown Debian-exim:Debian-exim /etc/exim4/{fullchain,privkey}.pem systemctl restart […]

Setting IO scheduler for use with ZFS

If you’re using rotational hard drives, Linux’s default IO scheduler can interact very badly with ZFS’s IO scheduler, greatly reducing performance. This is further exaggerated if you have any SMR devices due to their pathological worst-case performance characteristics. I’ve found that switching to “none” (this was called “noop” historically) can improve performance by a full […]

Fixing emails from Nextcloud via Debian’s default exim setup

At some point, my Nextcloud quietly stopped being able to send email. This is currently Nextcloud 27.1.3, running in docker on Debian 11.8, but it might have been broken for some time. When setting up exim on Debian, debconf asks you a few questions and generates a default config. My setup has no other deviations […]

Automating Debian security updates

Thanks to ‘foom’ on LWN, comes a neat recipe for automatically installing critical updates on a Debian system with minimal risk: It’s explained in some detail, but in brief it uses (optionally) a separate sources.list into which you can put only critical sources, and makes dpkg/apt choose the default responses to any questions. Fortunately […]

Using physical disks with VMWare server

For some reason (product differentiation? simple oversight?) VMWare Server 2 ((Downloadable from has no option to create a VM using a physical disk. Fortunately, that doesn’t mean that it can’t use them; you just need to import a predefined VM and tell it to use that. It’s possible to create a VM in the […]

Stop amavisd-new wrapping long lines in syslog

Update: Newer versions of amavisd-new (certainly 2.6.4-3) have a variable called $logline_maxlen which does exactly what it says on the tin. The rest of this post is therefore of only historic interest. I administer a mail server that uses the popular amavisd-new to perform virus scanning, and spam filtering using SpamAssassin. That server uses Logcheck […]