Vargolino – Page 2

Using LDAP to authenticate with a svnserve server

I had this already set up in another server but we had to set up a new svn server even though we already switch most of our stuff to git…

So, after setting the the svnserve daemon, we need to set up LDAP authentication.

We are using debian servers so I needed to install sasl2-bin in order to have the saslauthd daemon.

apt-get install sasl2-bin

After that, we need to set the daemon to start automatically, editing the file: /etc/defaults/saslauthd and changing two lines:

#...
START=no
#...
#...
MECHANISMS="pam"
#...

#...
START=yes
#...
#...
MECHANISMS="ldap"
#...

Then the saslauthd daemon needs to know how to reach the LDAP server, we configure this in the file /etc/saslauthd.conf, it is simple as:

ldap_servers: ldap://server.address.example.com
ldap_port: 389
ldap_version: 3
ldap_password_attr: userPassword
ldap_auth_method: bind
ldap_filter: (uid=%u)
ldap_search_base: ou=Users,dc=example,dc=com

The daemon will look for an entry with the uid=USERNAME in the base ou=Users,dc=example,dc=com and will check the password against the attribute userPassword.

You can test if it is working using the testsaslauthd app, like this:

user@svn:/svn# testsaslauthd -u username -p secret
0: OK "Success."

user@svn:/svn# testsaslauthd -u username -p wrongSecret
0: NO "authentication failed"

We can then start the daemon running service saslauthd start.

Now, we need to change the svnserve.conf so it will actually request the authentication to sasl. So, make sure that the [sasl] section of the file looks like this:

[sasl]
use-sasl = true
#...

And we need to register the svn app into the sasl. Apps are registered by creating a file in /usr/lib/sasl2/appname.conf. svnserve uses the name svn internally, we need to create the file as: /usr/lib/sasl2/svn.conf, with the following contents:

pwcheck_method: saslauthd
mech_list: PLAIN LOGIN

We are now all set up. We only need to restart the svnserve daemon and voilà, it’s done!

Setting up a UTF-8 environment in linux

Based on this post.

Check if the locales package is installed (dpkg -l locales). Then run:

dpkg-reconfigure locales

and choose the desired locales (en_US.UTF-8, for me).

Then, to be sure, export the variables (~/.bashrc)

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8
export LANGUAGE=en_US.UTF-8

You should start tmux or screen with the parameters, to be sure:

$ tmux -u
$ screen -U

Cycling throught windows in Windows 8

This Lifehacker post is about a really useful Windows 7 hack, that works fine on Windows 8 and Windows 10.

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced

New DWORD (32-bit), name it LastActiveClick, value 1.

Restart explorer.

Fearing that the link may break someday, here is a copy of the full content:

Windows 7’s taskbar is undoubtedly a great addition to Windows, but if you’ve got more than one application window open, you’ve got to either click twice or patiently hover to navigate to an open window. Reader Richard details how he fixed this:

I’ve been frustrated as of late with the Windows 7 taskbar (which led me to try hot-dogging it on the left-hand side as detailedhere—by the way GREAT and useful tips in the 331 comments!). The fundamental problem was that you needed two clicks to navigate to your document if you have two instances of a program running. Or you’re stuck with hovering for what feels like an eternity.

At Windows 7 Forums I finally found a nice step in the right direction. Full post is here, but summarized below. In short, this hack causes an application’s last active window to activate when you click the taskbar icon, and the next window in the second click, etc. The hover preview still works if you hover to begin with, but if you want the preview after you’ve clicked on an app’s icon in the taskbar, you can Ctrl+Click to bring it back. The current default settings are the exact opposite (that is, Ctrl+Click cycles through the last active windows of an application).

Launch regedit.exe (Win+R, then paste regedit.exe)
Navigate in the left tree control to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
Go to Edit->New->DWORD (32-bit) Value
Name the value LastActiveClick
Hit enter to assign the value and change it to 1
Restart Explorer and you’re good to go.

To restart Explorer without rebooting, open the Task Manager (Ctrl+Shift+Esc) and end the Explorer.exe process. Then create a new task (under “File”) and paste “explorer.exe”.

Thanks Richard!

Edited on 2016/01/21. Wow, my last post is 3 year old but still useful (to me, at least).

Resizing a tmpfs partition without losing the files

Took me just a few seconds of Googleing, but it seems worth taking a note here.

To resize a tmpfs filesystem without losing the files. Assuming that /tmp is being mounted in a tmpfs.

You can do it so it lasts until next reboot with:

mount /tmp -o size=3000M,remount

Or you can do it so it lasts forever :

Modify /etc/fstab line to look something like this:

none                   /tmp                tmpfs   size=3g        0 0

Remount the filesystem
```
# mount -o remount /tmp
```
Check if it all went OK
```
# df -h
```

Note: Increasing too much can cause the system to hang if the amount cannot be allocated.

References (hope at leat one of these links still work):

http://lxr.linux.no/linux/Documentation/filesystems/tmpfs.txt
http://www.xenotime.net/linux/doc/swap-mini-howto.txt
http://wiki.linuxquestions.org/wiki/Tmpfs#ixzz13amAsYk1
http://ihazem.wordpress.com/2011/03/08/increase-size-of-tmpfs-file-system/
http://www.biosplus.com/2012/02/increasing-size-tmpfs-losing-files/

Good Console solution for Windows

After coming across this stackoverflow post: http://stackoverflow.com/questions/913912/bash-shell-for-windows

I discovered Console: http://sourceforge.net/projects/console

And I can use it with the Git shell, setting the shell to:

"C:\Program Files (x86)\Git\bin\sh.exe" --login -i

Just amazing!

Update 2017/05/04: The original project is no longer active, but this fork seems to be: https://github.com/cbucher/console

Visualizing thread context switch and schedule timeline in Linux

Recently I needed to see when my threads were executing and in which processor, and

it took me a couple of days to get this done. Here is the best solution I’ve found.
First of all, we need the kernel to be compiled with some debug features enabled

http://www.mjmwired.net/kernel/Documentation/trace/ftrace.txt
https://www.kernel.org/doc/Documentation/trace/ftrace.txt

We’ll need to mount the debugfs

mount -t debugfs nodev /sys/kernel/debug

There is a front-end to the ftrace which is the trace-cmd command. It will enable the debugging features, start the tracing, and disable afterwards, and it can be really simple to use:

# trace-cmd start -e "sched:sched_switch" ./program_to_trace

After that you can use the KernelShark app to read the trace.dat file. Or you can convert it to VCD using:

# trace-cmd report > trace.txt
# sched_switch2vcd trace.txt trace.vcd

The sched_switch2vcd app is available here: https://github.com/rsvargas/sched_switch2vcd . I like to use gtkwave to visualize the data.

Update in 2015/07/08:

“Xlib: PuTTY X11 proxy: wrong authentication protocol attempted” solution!

After wasting a couple hours I’ve found someone who had the solution, which I found through this guy’s blog.

In my case, what I had was a chroot jail inside a server (which I also had full control), here are the steps:

Connect to the server

Execute:

# xauth list
devserver/unix:10  MIT-MAGIC-COOKIE-1  f44098e4ee6687e163c152a72c7dacbd

and copy the auth data;

Enter the chroot jail, and execute

# xauth add devserver/unix:10  MIT-MAGIC-COOKIE-1  f44098e4ee6687e163c152a72c7dacbd

And thats it, It should be working now.