Posts filed under Linux

Increase Ubuntu VM Disk Space

I ran into a very familiar problem (for me anyway) on an Ubuntu 18 virtual machine today. It started with, what I thought was, a Cisco ISE issue. Cisco ISE reports that I wanted to write to a repository ended up as empty files (0 bytes). Initial thought was that I ran into an Cisco ISE bug related to repositories, but it turned out that my Ubuntu server had run out of disk space;

Err:2 bionic-updates InRelease
  Error writing to output file - write (28: No space left on device) [IP: 80]

A quick df -h revealed that my Ubuntu server had only 4GB (out of the 100GB I assigned in VMWare).

willem@ubuntu:~$ df -h
Filesystem                         Size  Used Avail Use% Mounted on
udev                               967M     0  967M   0% /dev
tmpfs                              200M  1.1M  199M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv  3.9G  3.9G    0M 100% /
tmpfs                              997M     0  997M   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              997M     0  997M   0% /sys/fs/cgroup
/dev/loop0                          90M   90M     0 100% /snap/core/7713
/dev/loop1                          90M   90M     0 100% /snap/core/7917
/dev/sda2                          976M  222M  688M  25% /boot
tmpfs                              200M     0  200M   0% /run/user/1000

So, now I had to add the unassigned 96GB to the Ubuntu filesystem. Thankfully, askubuntu to the rescue.

root@ubuntu:~# lvm
lvm> lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv
  Size of logical volume ubuntu-vg/ubuntu-lv changed from 4.00 GiB (1024 extents) to <99.00 GiB (25343 extents).
  Logical volume ubuntu-vg/ubuntu-lv successfully resized.
lvm> exit
root@ubuntu:~# resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 13
The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 25951232 (4k) blocks long.

root@ubuntu:~# df -h
Filesystem                         Size  Used Avail Use% Mounted on
udev                               967M     0  967M   0% /dev
tmpfs                              200M  1.1M  199M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   98G  3.4G   91G   4% /
tmpfs                              997M     0  997M   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              997M     0  997M   0% /sys/fs/cgroup
/dev/loop0                          90M   90M     0 100% /snap/core/7713
/dev/loop1                          90M   90M     0 100% /snap/core/7917
/dev/sda2                          976M  222M  688M  25% /boot
tmpfs                              200M     0  200M   0% /run/user/1000
Posted on October 16, 2019 and filed under Linux, Tips'n Tricks.

Add Routes To Ubuntu Server

Routes (non-default ones) can be added to the platform by using the interfaces configurations file.

Just add the following to the interface configuration:

up route add -net <destination_network> netmask <netmask> gw <gateway_address>


$ cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto ens160
iface ens160 inet static
        # dns-* options are implemented by the resolvconf package, if installed
        up route add -net netmask gw
Posted on September 15, 2017 and filed under Linux, Tips'n Tricks.

Capture Network Traffic With Wireshark Under Ubuntu

When you install Wireshark on Ubuntu Linux you need to be root to be able to capture traffic. The standard user doesn't have enough privileges to do this. 

A workaround for this is to add the user to a wireshark group and give the group special permissions. Afterwards, you're able to cpature traffic in Ubuntu with Wireshark, without needing root access. 

The complete list of commands: 

sudo groupadd wireshark

sudo usermod -a -G wireshark <YOUR-USER-NAME>

sudo chgrp wireshark /usr/bin/dumpcap

sudo chmod 750 /usr/bin/dumpcap

sudo setcap cap_net_raw,cap_net_admin=eip /usr/bin/dumpcap

sudo getcap /usr/bin/dumpcap

Just reboot, or log out and back in, and you're finished. 


Posted on August 14, 2013 and filed under Linux, Tips'n Tricks.

Courier IMAPd and warnings

After installing an ISPConfig deployment, everything seemed to work properly, but every now-and-then I got this weird error that there was something wrong with the mail server configuration. The Apple showed a exclamation mark with the following message:

The server returned the error: The attempt to read data from the server server.domain.ext failed.

Some research showed that the Apple mail clients tend to open several connections for IMAP, and the default setting of the Courier IMAPd server is to allow (only) 4 connections from the same IP address.

Modifying the Courier config file (/usr/lib/courier-imap/etc/imapd) and allowing e.g. 20 connections from 1 IP address solved this problem.

#  Maximum number of connections to accept from the same IP address


#  Maximum number of connections to accept from the same IP address


 If your company / household holds several imap mail clients you may need to increase the counter even more (65536 is the maximum amount of connections for ANY IP address).

If you have SSL enabled on the Courier IMAPd server you also need to add the MAXPERIP variable to the imap-ssl config file (/usr/lib/courier-imap/etc/imapd-ssl).

Finally, you need to restart the Courier IMAPd services (/etc/init.d/courier-imap restart)

Posted on January 23, 2012 and filed under Apple, Linux, Tips'n Tricks.

Changing SSL Certificates in a ISPConfig v3 Configuration

When you install a Perfect Server based on Centos and ISPConfig v3.x, the system / 'installer' creates for the components self-signed certificates. All these certificates will generate different warnings in your browser, mail clients etc. So time to eliminate those warnings.

First I needed to find out where all those certificates are located, and what there formats are. In my case, there are three services that use SSL/TLS in some form;

  1. Postfix SMTP service
  2. Courier IMAP service
  3. http / Apache2 webservice

Checking the configuration files will reveal their locations.

Posted on January 7, 2012 and filed under Linux, Operating Systems, Security, Software, Tips'n Tricks.

Getting ISPConfig to Work on Centos

This is not a manual describing the installation (pre-requisites) of ISPConfig software on a Centos platform. An excellent manual can be found online. It's just that I ran into a problem when I tried to connect an e-mail client to the (IMAP) mailserver (controled by ISPConfig). All the appropriate ports / listeners were up and running, so it had to be a configuration issue.

Googling around didn't solve my problem. My collegue, Xander (@xmoments /, cam eto the rescue with the solution;

yum install cyrus-sasl-plain-2.1.23-13.el6.x86_64

Software that handles cleartext passwords between mail processes. After the installation, the mail went flying across the Interwebs.

Posted on January 5, 2012 and filed under Linux, Software, Tips'n Tricks.

Configuring Syslog-ng on Ubuntu

Syslog-ng is a replacement for the default syslog daemons you get with most Linux distributions. The advantage of syslog-ng is that the configuration is easier to understand, and it gives the sys-admin numerous advantages. Especially in complex environments.

Let's say we have a RADIUS environment which is able to send authentication and accounting information through syslog to external devices. And let's assume that a relevant part of this syslog information is needed by a department within a large cooperation.

Installing syslog-ng (on Ubuntu) is done by the following command:

# sudo apt-get install syslog-ng

Through the use of syslog-ng we can store, and/or forward syslog information based on the following (but not limited to):

  • source IP address
  • destination IP address
  • syslog level
  • content in the original syslog message by using regular expressions.

All this can be configured in the /etc/syslog-ng/syslog-ng.conf file.

Posted on August 26, 2011 and filed under Linux, Tips'n Tricks.

Wireshark on Ubuntu 10.10

Last week, I acquired a small netbook @ work for testing purposes (HP Mini 5103). You don't want to know how handy a second laptop is when you're testing authentication environments.

For flexibility purposes I installed a dual-boot with Microsoft Windows 7 Enterprise and Ubuntu Linux v10.10 from a USB Flashdrive (1, 2), erasing all the preinstalled HP/McAfee crap. This all worked like a charm, up to the installtion of Wireshark in Ubuntu. Starting the sniffer application resulted in an empty list of network adapters. No network adapters mean no capturing capabilities.

This was probably related to the lack of rights while starting the application. Running it from the terminal with sudo resulted in some weird error regarding a display-thingy (which is still the main reason why Linux isn't penetrating the desktop market).

While searching the Interwebs, I found the following solution. Which, after some alterations to the commands, the following worked for me;

In a terminal session, execute these commands:

sudo addgroup –quiet –system wireshark (this command simply didn't work in my case)
sudo chown root:wireshark /usr/bin/dumpcap
sudo setcap cap_net_raw,cap_net_admin=eip /usr/bin/dumpcap

usermod -a -G wireshark <my user name>

Reconfigure the Wireshark Common package and answer ‘Yes’ to the question ‘Should non-superusers be able to capture packets?

sudo dpkg-reconfigure wireshark-common (I needed to add the sudo part on this command)

After rebooting the laptop, Wireshark started normally with all the network interfaces available for capturing traffic.

UPDATE: I did a reinstall of the OS, and this time Wireshark started 'properly' from the Terminal application by typing (without the quotes) 'sudo wireshark'.

Posted on March 6, 2011 and filed under Linux, Software, Tips'n Tricks.