Dirk große Osterhues

In order to let an Ubuntu system access the net via a proxy, edit two files and you're done.

/etc/environment:

http_proxy="http://:/"
https_proxy="http://:/"
ftp_proxy="http://:/"
no_proxy="localhost,127.0.0.1,::1

/etc/apt/apt.conf.d/90_proxy.conf:

Acquire {
  HTTP::proxy "http://:";
  HTTPS::proxy "http://:";
}

This is an update to the article from 2009 regarding quieting down snmpd - this time in recent Ubuntu LTS 18.04. The issue at hand is the intense chattyness of snmpd to syslog.

Due to the complete shift to systemd, files in /etc/default are becoming disregarded. Therefore customisations have to be made to /etc/systemd/system. Two steps are neccessary:

Create a symlink for snmpd in /etc/systemd:

ln -s /lib/systemd/system/snmpd.service /etc/systemd/system

Edit that file and change:

ExecStart=/usr/sbin/snmpd -Lsd -Lf /dev/null -u Debian-snmp -g Debian-snmp -I -smux,mteTrigger,mteTriggerConf -f

to

ExecStart=/usr/sbin/snmpd -LS4d -Lf /dev/null -u Debian-snmp -g Debian-snmp -I -smux,mteTrigger,mteTriggerConf -f

Then run

systemctl daemon-reload && service snmpd restart

Now snmpd should be calmed down.

Lately I ran into some issues using snmp tools, e.g.:

snmpwalk -v2c -c public ${host} test

I received errors like:

Unknown Object Identifier (Sub-id not found: (top) -> test)

This is because MIBs are not installed in Ubuntu by default. To install them use the follwing line:

apt-get install snmp-mibs-downloader

Also comment line 4 of /etc/snmp/snmp.conf so it shows:

# mibs:

Hope that helps someone.

After running virtual machines in KVM for some time, it might come in handy to be able to resize a KVM guest's raw volumes. In order to do so you first have to shutdown your VM:

virsh destroy <guestname>

In order to add an additional 2 gig to your respective machine, you do the following:

qemu-img resize <diskname>.img +2G

Now restart the machine:

virsh start <guestname>

Then use fdisk inside the guest to make use of the new space:

fdisk /dev/vda

There, you delete the respective partition and immediately recreate it - with more space. Now restart the machine in order to let the kernel make note of the changes:

reboot

After a final resize you're able to make use of the sweet new space:

resize2fs /dev/vda1

Voila!

In order to cleanup docker containers from time to time just fire the following:

docker system prune -a