Slow rsync on ext4 filesystem

On a rather hefty rsync job between two local ext4 filesystems, writing on the target (a mechanical hard drive which should be able to sustain 100 mb/s) would fluctuate strongly (between 0 mb/s and 160 mb/s) and effectively slow down to a few mb/s on average after a few minutes. While I didn't find the … Continue reading Slow rsync on ext4 filesystem →

Ubuntu 20.04 not resolving local network hostnames

An Ubuntu 20.04 laptop installation started not being able to resolve the names of hosts in the same local network. Although the host names were registered with the router, the laptop wouldn't be able to resolve those host names. Surprisingly, neither netbios resolution worked (although nbtscan would find those hosts). The solution is to bypass … Continue reading Ubuntu 20.04 not resolving local network hostnames →

Samba anonymous shares

I'm currently writing up changes to the perfect, cheap NAS [1]. A major change is that I dropped support for user-level windows/samba shares and am using only a few public browsable shares. It turns out that Windows clients always ask the user for a password even though the samba share is anonymous. The reason seems … Continue reading Samba anonymous shares →

Mysql: the definition of table prevents operation … on table

This is a tricky one affecting MySql table updates which have views. Documentation about this error actually explains the cause, but doesn't connect the dots. I have a view V on table T and want to delete some rows from T. That works fine as long as the DELETE statement doesn't involve the view, so … Continue reading Mysql: the definition of table prevents operation … on table →

Ubuntu 20.04 getting wrong IP address

Yesterday (early August 2021) my Ubuntu 20.04 installation started configuring all network interfaces (wifi, ethernet) with IPv4 addresses from the wrong network segment block, namely 192.168.0.x. IPv6 still worked fine. I didn't figure out whether that's due to a change in the router or the OS (I suspect the router, because the situation improved when … Continue reading Ubuntu 20.04 getting wrong IP address →