talkingpumpkin

Prometheus-alertmanager and graphana (especially graphana!) seem a bit too involved for monitoring my homelab (prometheus itself is fine: it does collect a lot of statistics I don't care about, but it doesn't require configuration so it doesn't bother me).

Do you know of simpler alternatives?

My goals are relatively simple:

1. get a notification when any systemd service fails
2. get a notification if there is not much space left on a disk
3. get a notification if one of the above can't be determined (eg. server down, config error, ...)

Seeing graphs with basic system metrics (eg. cpu/ram usage) would be nice, but it's not super-important.

I am a dev so writing a script that checks for whatever I need is way simpler than learning/writing/testing yaml configuration (in fact, I was about to write a script to send heartbeats to something like Uptime Kuma or Tianji before I thought of asking you for a nicer solution).

I'm not much hoepful, but... just in case :)

I would like to be able to start a second session in a window of my current one (I mean a second session where I log in as a different user, similar to what happens with the various ctrl+alt+Fx, but starting a graphical session rather than a console one).

Do you know of some software that lets me do it?

Can I somehow run a KVM using my host disk as a the disk for the guest VM (and without breaking stuff)?

I have two subnets and am experiencing some pretty weird (to me) behaviour - could you help me understand what's going on?

Scenario 1

PC:                        192.168.11.101/24
Server: 192.168.10.102/24, 192.168.11.102/24

From my PC I can connect to .11.102, but not to .10.102:

ping -c 10 192.168.11.102 # works fine
ping -c 10 192.168.10.102 # 100% packet loss

Scenario 2

Now, if I disable .11.102 on the server (ip link set <dev> down) so that it only has an ip on the .10 subnet, the previously failing ping works fine.

PC:                        192.168.11.101/24
Server: 192.168.10.102/24

From my PC:

ping -c 10 192.168.10.102 # now works fine

This is baffling to me... any idea why it might be?

Here's some additional information:

• The two subnets are on different vlans (.10/24 is untagged and .11/24 is tagged 11).

• The PC and Server are connected to the same managed switch, which however does nothing "strange" (it just leaves tags as they are on all ports).

• The router is connected to the aformentioned switch and set to forward packets between the two subnets (I'm pretty sure how I've configured it so, plus IIUC the second scenario ping wouldn't work without forwarding).

• The router also has the same vlan setup, and I can ping both .10.1 and .11.1 with no issue in both scenarios 1 and 2.

• In case it may matter, machine 1 has the following routes, setup by networkmanager from dhcp:

default via 192.168.11.1 dev eth1 proto dhcp              src 192.168.11.101 metric 410
192.168.11.0/24          dev eth1 proto kernel scope link src 192.168.11.101 metric 410

• In case it may matter, Machine 2 uses systemd-networkd and the routes generated from DHCP are slightly different (after dropping the .11.102 address for scenario 2, of course the relevant routes disappear):

default via 192.168.10.1 dev eth0 proto dhcp              src 192.168.10.102 metric 100
192.168.10.0/24          dev eth0 proto kernel scope link src 192.168.10.102 metric 100
192.168.10.1             dev eth0 proto dhcp   scope link src 192.168.10.102 metric 100
default via 192.168.11.1 dev eth1 proto dhcp              src 192.168.11.102 metric 101
192.168.11.0/24          dev eth1 proto kernel scope link src 192.168.11.102 metric 101
192.168.11.1             dev eth1 proto dhcp   scope link src 192.168.11.102 metric 101

solution

(please do comment if something here is wrong or needs clarifications - hopefully someone will find this discussion in the future and find it useful)

In scenario 1, packets from the PC to the server are routed through .11.1.

Since the server also has an .11/24 address, packets from the server to the PC (including replies) are not routed and instead just sent directly over ethernet.

Since the PC does not expect replies from a different machine that the one it contacted, they are discarded on arrival.

The solution to this (if one still thinks the whole thing is a good idea), is to route traffic originating from the server and directed to .11/24 via the router.

This could be accomplished with ip route del 192.168.11.0/24, which would however break connectivity with .11/24 adresses (similar reason as above: incoming traffic would not be routed but replies would)...

The more general solution (which, IDK, may still have drawbacks?) is to setup a secondary routing table:

echo 50 mytable >> /etc/iproute2/rt_tables # this defines the routing table
                                           # (see "ip rule" and "ip route show table <table>")
ip rule add from 192.168.10/24 iif lo table mytable priority 1 # "iff lo" selects only 
                                                               # packets originating
                                                               # from the machine itself
ip route add default via 192.168.10.1 dev eth0 table mytable # "dev eth0" is the interface
                                                             # with the .10/24 address,
                                                             # and might be superfluous

Now, in my mind, that should break connectivity with .10/24 addresses just like ip route del above, but in practice it does not seem to (if I remember I'll come back and explain why after studying some more)

I want to have a local mirror/proxy for some repos I'm using.

The idea is having something I can point my reads to so that I'm free to migrate my upstream repositories whenever I want and also so that my stuff doesn't stop working if some of the jankiest third-party repos I use disappears.

I know the various forjego/gitea/gitlab/... (well, at least some of them - I didn't check the specifics) have pull mirroring, but I'm looking for something simpler... ideally something with a single config file where I list what to mirror and how often to update and which then allows anonymous read access over the network.

Does anything come to mind?