System – Kea IPv4 DHCP server (ver 2.2.0) running on Debian 12, serving addresses on second network interface (PCIe card).
On reboot the server starts, but warns that it could not open the socket on the prescribed interface, and so is not serving any addresses. Running
systemctl status kea-dhcp4-server.service
The error is
kea-dhcp4[582]: WARN DHCPSRV_OPEN_SOCKET_FAIL failed to open socket: the interface enp3s0 is not running
kea-dhcp4[582]: INFO DHCP4_OPEN_SOCKETS_FAILED maximum number of open service sockets attempts: 0, has been exhausted without success
Restarting the service afterwards works normally. This is a known problem. There are various suggestions to fix the ordering, but the simplest (albeit slightly inelegant) way to get it to work is to tell it to retry a bunch of times with the service-sockets-max-retries and service-sockets-retry-wait-time options. So the start of the configuration looks like this:
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Scenario: You have a new HP Color LaserJet Pro MFP 4302. It has been powered up and assigned (manually or by DHCP) an IP address which already has a DNS address associated with it. After finding the label with the initial admin password you try and access the Embedded Web Server (EWS) via your web browser. You use the DNS address for this.
What you get after a couple of seconds is a HTTP 403 error.
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Had a server that decided to drop a disk (or disk went faulty) in a md RAID5 array. On reboot the array didn’t want to start. Output of mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed May 22 18:17:58 2013
Raid Level : raid5
Used Dev Size : -1
Raid Devices : 3
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Sun Jan 3 06:50:05 2021
State : active, degraded, Not Started
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name : nebula:0 (local to host nebula)
UUID : 962b8ff0:00d88161:5a030e1f:236466af
Events : 31168
Number Major Minor RaidDevice State
4 8 16 0 active sync /dev/sdb
1 0 0 1 removed
3 8 48 2 active sync /dev/sdd
Try to start array with mdadm --run /dev/md0
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After a system crash I ran svnadmin verify on some of the relevant repositories to check things were ok – this was done as root. Afterwards normal network access (via Apache) was broken with
Internal error: Berkeley DB error for filesystem
appearing in the logs. The fix was to chown -R www-data:www-data on the broken repositories. It looks like running svnadmin verify as root changes permissions on SVN repositories somewhere (at least Berkeley DB ones).
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Suppose you have a linux network setup with automounter maps that come from the network (via nis, sssd, LDAP etc.) and you want to block some of them acting on a particular system. In our case we have an automount map that acts on /opt and mounts various software packages from network shares. The problem with this is that you can’t then install your own stuff locally to /opt, which is what a lot of Debian/Ubuntu packages expect to be able to do.
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