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Category: Linux (Page 4 of 9)

Changing the default mode of the Emacs scratch buffer

28 July 2014 / / 0 Comments

After starting Emacs you end up in the *scratch* buffer (assuming you’ve disabled the startup message in your .emacs file). The *scratch* can be used for writing down notes and some Lisp experiments (since it uses the Emacs Lisp major mode by default).

Now, I’m not very much of a Lisp programmer, but I do use Org-mode a lot. Consequently, I found myself changing the buffer’s major mode to org-mode regularly. And Emacs wouldn’t be Emacs if you couldn’t change this to a default. So, thanks to Bozhidar Batsov over at Emacs Redux, I’ve added the following lines to my Emacs configuration file:

;; Set the default mode of the scratch buffer to Org
(setq initial-major-mode 'org-mode)
;; and change the message accordingly
(setq initial-scratch-message "\
# This buffer is for notes you don't want to save. You can use
# org-mode markup (and all Org's goodness) to organise the notes.
# If you want to create a file, visit that file with C-x C-f,
# then enter the text in that file's own buffer.
 
")

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Fixing backlight control with Ubuntu on my ThinkPad T440s

10 May 2014 / / 6 Comments

Some time ago I bought a ThinkPad T440s for work. It’s an amazing machine! Before that I used a ThinkPad X121, which served me very well on my daily commute. This machine was getting a bit old, and given that my new job (more about which in a later post) also requires me to have a better machine with more screen real estate, it was high time to upgrade.

Ubuntu (13.10 and 14.04) runs well on the T440s, only two things didn’t work as expected:

  • The WWAN interface (mobile internet, from Ericsson) seems to connect when I select it in the network manager, but the adaptor seems to disappear almost immediately after that. A few seconds it appears again. [edit 20140514]I just found out that it’s working, probably this was fixed in Ubuntu 14.04[/edit]
  • The screen’s backlight brightness can be reduced/increase using the Fn-F5 and Fn-F6 keys, but only in a weird way: several key presses are needed for one unit of decrease/increase.

This last bug can be fixed by booting with the following kernel argument:

  acpi_backlight=vendor

Simply add this to the GRUB_CMDLINE_LINUX_DEFAULT line in /etc/default/grub:

  GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor quiet splash"

and run sudo update-grub. Reboot and you will be able to change the backlight brightness in finer steps.

I found this solution somewhere on the internet a few weeks ago, wrote it down, but can’t remember anymore what the original URL was. My apologies.

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Fixing colours in git output after upgrading to Ubuntu 14.04

5 May 2014 / / 1 Comment

After upgrading my Ubuntu 13.10 installation to 14.04, I noticed that the output of several git commands (e.g. git diff and git log) didn’t show colours as they used to, but showed ESC[ ANSI codes instead.
A quick internet search lead to this post on unix.stackexchange.com where the LESS environment variable was ‘blamed’. Indeed, I have my LESS variable (re-) defined in my .bashrc and .zshrc files.

The solution was to add -R to the environment variable, which allows raw control characters to be displayed. I now have the environment variable defined as:

LESS='--quiet -X -F -R'

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Using SSH for WordPress updates via the web interface

24 April 2014 / / 0 Comments

Note to self: if you want to be able to upgrade WordPress via the web interface using SSH, you need to have the libssh2-php package installed on Debian/Ubuntu Linux.

Don’t forget to restart Apache after installing the package. Reload the WordPress admin pages and you’ll see the SSH option added.

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Fixing problems after giving your Samba server a new IP address

14 March 2014 / / 1 Comment

While moving my DHCP server to a Raspberry Pi I also changed some of the IPs handed out to my (virtual) servers. This lead to problems when I logged into Windows (which is tied to my Samba domain), Windows complained that my roaming profile wasn’t completely synced and browsing network shares didn’t work, copying from (mounted) network shares didn’t work, etc.

In the Samba log files I noticed some references to the old IP address (192.168.10.23), e.g.:

[2014/03/13 16:22:23,  0] nmbd/nmbd_become_dmb.c:237(become_domain_master_query_success)
  become_domain_master_query_success:
  There is already a domain master browser at IP 192.168.10.23 for workgroup SENW registered on subnet UNICAST_SUBNET.

and

  [2014/03/13 16:20:07,  0] nmbd/nmbd_browsesync.c:248(domain_master_node_status_fail)
  domain_master_node_status_fail:
  Doing a node status request to the domain master browser
  for workgroup SENW at IP 192.168.10.23 failed.
  Cannot sync browser lists.

Even after restarting smbd and nmbd, and checking my smb.conf thoroughly, these kept showing up.

It turns out (thanks a lot Matt Godbolt) that nmbd keeps caches in two files (paths as they are on my Ubuntu 12.04 server):

  • /var/cache/samba/browse.dat
  • /var/lib/samba/wins.dat

Simply stop nmbd, delete them, restart nmbd and you’re happy.

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Slackware on the Raspberry Pi

14 March 2014 / / 1 Comment

I took some time this week to migrate my DNs and DCHP server from an Ubuntu virtual machine to my Raspberry Pi. I wanted to do this because these two servers are so essential to regular network functioning. Before this change whenever my server was down (for whatever reason) any machine connected to the LAN would stop having a working internet connection. Moreover, since I never got the VM to boot correctly on autostart I had to manually start it every time the server came back up again.
Conclusion: not ideal and pissed of family members ;-).

Since I had my Raspberry Pi lying around and, apart from a few toy projects, hadn’t used it for anything, I decided to use it for this task: low power requirements and hardware that was more than up to the task.

The question was which distribution to use. I could have gone for Raspbian (Debian for the Raspberry Pi), which would have blended well with my otherwise Ubuntu-minded network. However, partly for nostalgic reasons, partly make sure I don’t get too tied to one distribution, I decided to try and install Slackware, the distribution I used for my first steps in Linux Land.

I followed most of the steps from the fatdog.eu tutorial (see link below) to get everything running. It’s a very well written, extensive tutorial. Things where I followed my own judgement/experience were the fact that I didn’t use a USB stick to download the Slackware packages on (I used an NFS share on my server) and the package selection. With a relatively simple selection I now have about 2GB of disk usage.

Only one thing left to migrate to the Pi now: my LDAP server. Unfortunately it’s been several years since I configured OpenLDAP (on Ubuntu) and Slackware doesn’t include the OpenLDAP server by default. So this will be something for a rainy day…

Links:

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Fixing the compose key in Emacs on Ubuntu 13.10

7 February 2014 / / 0 Comments

After upgrading to Ubuntu 13.10 some time ago I noticed that my compose key (i.e. the key that you press followed by e.g. c and , to create a ç) didn’t work anymore in Emacs. I found two bug reports on this issue [1, 2], both effectively suggesting the same solution: start Emacs like this

XMODIFIERS=@im=none emacs

So I added the following line to my ~/.zshrc and ~/.bashrc files:

alias emacs='XMODIFIERS=@im=none emacs'

(of course somewhere before I set my EDITOR variable). I also changed the command in the launcher I use (GLX-Dock/Cairo-Dock).
This doesn’t make it a system-wide (or even user-wide) fix, e.g. the Firefox add-on “It’s all text” doesn’t get it, but it covers most of my use cases.

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Puppet commands change when upgrading to v3.0.0

27 December 2013 / / 0 Comments

After upgrading Puppet from versions < v3 to version 3.0.0 or higher, the main commands have changed, keep this in mind when reading my earlier post. From the ChangeLog:

Pre-2.6 Post-2.6
puppetmasterd puppet master
puppetd puppet agent
puppet puppet apply
puppetca puppet cert
ralsh puppet resource
puppetrun puppet kick
puppetqd puppet queue
filebucket puppet filebucket
puppetdoc puppet doc
pi puppet describe

Some examples

To run puppet on a client puppetd --test is changed to:

puppet agent --test

To show a list of clients waiting for signing of their certificates run the following on the master:

puppet cert list

instead of puppet ca -l. To list all certificates, run (on the master):

puppet cert list --all

To completely remove a client’s certificate on the master run:

puppet cert clean client.localdomain

and to sign a client certificate on the master run:

puppet cert sign client.localdomain

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Permantly ban an IP address with fail2ban

12 December 2013 / / 0 Comments

Over the last few days I noticed in my logwatch e-mails that one IP address kept trying to log in to my server, even though it was blocked regularly by fail2ban.

Here’s a post that explains how to simply add a list of IP addresses to block permanently. There’s only one catch: the listing provided there contains an error, the word <name> is missing in the iptables command, probably due to HTML conversion. This is the correct line to be insterted into the actionstart section of /etc/fail2ban/action.d/iptables-multiport.conf:

cat /etc/fail2ban/ip.blacklist | while read IP; do iptables -I fail2ban-<name> 1 -s $IP -j DROP; done

Use the following command to check if the IP address is indeed banned:

$ sudo iptables  -L fail2ban-ssh
Chain fail2ban-ssh (1 references)
target     prot opt source               destination         
DROP       all  --  192.168.20.25        anywhere            
RETURN     all  --  anywhere             anywhere

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Replacing a character in a Bash variable name

4 December 2013 / / 0 Comments

Today I needed to replace a : in a bunch of file names with a -, so I wanted to write a Bash for-loop to do just that. I vaguely remembered that you can do character replacements within variables, but couldn’t remember the details.

This is how it’s done:

for filename in *; do
    mv "$filename" "${filename/:/-}"
done

I put the variables in double quotes, because the file names contained spaces.

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