Notes about open source software, computers, other stuff.
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.
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):
Simply stop nmbd, delete them, restart nmbd and you’re happy.
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…
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.
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 |
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 |
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
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.
Ubuntu Linux uses the LightDM greeter (the login screen you see after booting). Since I’m using an LDAP server to store my user accounts and LightDM by default only shows local users I needed to tell LightDM to give me an ‘other user’ option where I can enter a user name and password (I first checked to see if my LDAP connection work by logging in with an LDAP user from the console (tty1).
LightDM is configured in /etc/lightdm/lightdm.conf, but also provides command line tools to set the options. To show the ‘other user’ use:
sudo /usr/lib/lightdm/lightdm-set-defaults --show-manual-login true |
This will disable the user list. It adds the line
greeter-show-manual-login=true |
to the lightdm.conf file.
If you only want to see the “Other” entry run:
sudo /usr/lib/lightdm/lightdm-set-defaults --hide-users true |
And lastly you can turn off guest:
sudo /usr/lib/lightdm/lightdm-set-defaults --allow-guest false |
Thanks to mfish at askubuntu.com!
I use Emacs‘ org-mode a lot for writing notes, todo lists, presentations and writing short reports. Recently I started writing a larger report which I normally would have done in LaTeX. This time, since the notes related to the project were already in org format, I decided to write the whole report in org-mode. The one thing I needed for that was using BibTeX bibliographies (and RefTeX) from org-mode. A quick web search revealed that that can easily be done by adding the following to your .emacs file:
;; Configure RefTeX for use with org-mode. At the end of your ;; org-mode file you need to insert your style and bib file: ;; \bibliographystyle{plain} ;; \bibliography{ProbePosition} ;; See http://www.mfasold.net/blog/2009/02/using-emacs-org-mode-to-draft-papers/ (defun org-mode-reftex-setup () (load-library "reftex") (and (buffer-file-name) (file-exists-p (buffer-file-name)) (reftex-parse-all)) (define-key org-mode-map (kbd "C-c )") 'reftex-citation) ) (add-hook 'org-mode-hook 'org-mode-reftex-setup) |
After that, RefTeX works, but exporting the org document to PDF (via LaTeX) didn’t include the bibliography entries. A quick look at the error log showed that bibtex hadn’t been run, so the question was: how to tell org-mode to do that too when exporting. The answer is to tell org-mode to use the latexmk Perl script (on Debian/Ubuntu it is easily installed from the package repositories) when exporting to PDF. I added the following lines to my .emacs file:
;; Use latexmk for PDF export (setq org-latex-to-pdf-process (list "latexmk -pdf -bibtex %f")) |
One of the XFS filesystems at work almost ran out of space recently, so I extended the Logical Volume it was on, followed by xfs_growfs. This worked fine, df -h showed enough free space for the upcoming data. In the XFS FAQ I read that by default all inodes are placed in the first 1 TB of disk, which could lead to problem. Therefore, I added the inode64 option to the mount options and ran
mount -o remount
on the partition.
While reviewing my log messages this morning I noticed a lot of
No space left on device
messages for that filesystem. Having this inode64 option in mind I wondered what went wrong. Although df -h and df -i showed enough free space and free inodes, respectively, I still couldn’t create a file. Again the XFS FAQ had an entry for that, but it puzzled me, because I was already using the inode64 option. Since the filesystem wasn’t in use I decided to completely unmount it and then mount it again. That worked. Apparently -o remount is not enough to enable the inode64 option.
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