KActivityManager blocking unmounting

While un-mounting a partition to safely remove the external hard drive, I got an error about the device being busy. Both Dolphin and the command line said the same thing.

umount /run/media/myuser/New\ Volume/
umount: /run/media/myuser/New Volume: target is busy.

It seems kactivitymanagerd was using it.


[root@clown myuser]# fuser -vm /run/media/myuser/New\ Volume/
                    USER        PID ACCESS COMMAND
/run/media/myuser/New Volume:
                     myuser     612 ..c.. kactivitymanage


I tried to stop the daemon but I got the following error.

root@clown myuser]# /usr/bin/kactivitymanagerd
QStandardPaths: wrong ownership on runtime directory /run/user/1000, 1000 instead of 0


After some discussion on Freenode, I got to know that when graphical apps are run with escalated priviledges, similar error is found. I guessed I was getting the error because I was trying to stop the daemon as root user. I tried changing back to my regular user and stopping the daemon. It worked  and I was able to unmount the drive after that.

/usr/bin/kactivitymanagerd stop
Service stopped
Cleaning up...

Increasing the maximum number of file descriptors allowed per user on Cent OS 6

For some applications like elasticsearch, the maximum number of file descriptors needs to quite high. The way of modifying the value varies from distro to distro. In Cent OS6, the following did not work.

1. Using sysctl as root
sysctl -w fs.file-max=100000

2. Using ulimit as root

After the above approaches, when you check the value using the following, the value will show up.

cat /proc/sys/fs/file-max

However, setting the values as root, does not change the values for other regular users. To set it specifically for any user, change the value in /etc/security/limits.conf file. Setting only the soft or hard limit will not be sufficient. Therefore, the following lines should be added.

<user> soft nofile <value>

<user> hard nofile <value>

After the modifications, it is required to logout and log back into the system.

HTML5 video in YouTube

After Firefox blacklisting all versions of Flash, YouTube started annoying me by asking to enable the plugin for the same. So, I decided to try HTML5 video. So, I requested for it. However, I was only getting 360p videos. After reading a bit about it, I found that I had to enable the following options in about:config page of Firefox.

media.mediasource.enabled
media.mediasource.mp4.enabled
media.mediasource.webm.enabled
media.fragmented-mp4.exposed
media.fragmented-mp4.ffmpeg.enabled

Also, to get H.264 codec, I had to install gst-libav package. That solved the issue and I can get all resolution options after that.

Heroku suports only Ubuntu

Heroku supports Ubuntu nicely but seems to ignore other distributions. Their reference points to an OS-specific choice page.

points to toolbelt.heroku.com

That page provides a script and a command that uses the script to install heroku toolbet for Ubuntu.

Ubuntu option

However, even for standalone option, the script does not change.

Standalone option

deadlock completed

Now standalone essentially is the category of other linux and BSD distributions. So, having an apt-get script for them is like saying "We hardly care about you". They could have provided a source link there. In fact given that another link on the same page links to their source hosted at Github. And interestingly their Github page asks to first install heroku toolbelt redirecting back to the same page.

Finding the file or device pointed to by a file descriptor

I had been noticing that Firefox starts off with around 400mb and reaches around 1.4 gb as I keep using it throughout the day. Also, CPU utilization clocked at 25% on my i7. So, I thought of trying to mess around in the hope of finding something interesting. I found the pid using the following.

ps aux | grep firefox

I ran an strace to try and see what was keeping it so busy.

strace -p <pid_of_firefox_process>

This is what I got.

poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
getrusage(RUSAGE_SELF, {ru_utime={17387, 398261}, ru_stime={821, 999917}, ...}) = 0
getrusage(RUSAGE_SELF, {ru_utime={17387, 438261}, ru_stime={821, 999917}, ...}) = 0
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
write(18, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])
read(17, "\372", 1) = 1
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 0) = 0 (Timeout)
recvmsg(4, 0x7fff427b9fb0, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=5, events=POLLIN}, {fd=4, events=POLLIN}, {fd=17, events=POLLIN}, {fd=19, events=POLLIN}], 4, 4294967295) = 1 ([{fd=17, revents=POLLIN}])

Now, I wanted to know the files pointed to by file descriptors 4, 5, 17, 19. To look those use, I read that I can use /proc filesystem. So, I just tried simply looking it up there.

ls -l /proc/<pid_of_firefox_process>/fd

The files turned out to be as follows:

• 4 - a socket
• 5 - anon_inode:[eventfd]
• 17 - a pipe
• 19 - another socket

Any suggestions are welcome. I will keep looking into the issue.

Compiling in Emacs

I use Emacs for development in C. I was trying out some algorithms and I had used some functions from math.h. I had included the header of course. However, when I wanted to compile I knew I would have to use the -lm flag to include math.h in the compilation. I use M-x compile for compilation. It usually asks me to enter the name of the executable to be built. In that same line, I added the CFLAGS=-lm part to the end of that line and the compilation worked fine. So instead of

make -k application

my compilation command looked like the following.

make -k application CFLAGS=-lm

Speeding up RubyMine on linux

I use RubyMine for development on Ruby on Rails platform. A lot of my friends and colleagues using it often have the opinion that it is a resource hog and slows down the system. I have also observed a little slowness. Of late, the effect increased and crossed my tolerable limit. So, I decided to dig in and find out what was happening. Using top, I could see that for some reason a process jbd2 was being triggerred every 2 seconds. Reading about it, I found out that it was the process updating access time. I am using ext4 filesystem and I had not specified the noatime option in fstab for the partition. So, access times for files were being updated in real time. I do not need that at all. Access times are updated even for page cache hits, which is of no use to me. So, I turned it off by changing the mount options for the partition.

Now, it was time to look into RubyMine in particular. I was using 64-bit version of it and it is well known that the 64-bit version has deteriorated performance initially because the default heap size is set at the same value as the 32-bit version. I had already taken care of it by changing the heap size from 512 mb to 1536 mb. To do this, you can edit bin/rubymine64.vmoptions and edit it to reflect the following.

-Xmx1536m

Another important property that I had not set was the ReservedCodeCacheSize. It was also having the same value as the 32-bit version, i.e. 64mb. Changing it as follows, improved performance.

-XX:ReservedCodeCacheSize=256m

This ensured a good deal of code could be cached in memory making RubyMine's operations faster.

Combining multiple PDF documents into one

A number of times I have faced the requirement of combining multiple PDF files into a single file. Doing that is fairly simple actually. It can be done using a number of tools. Two ways of doing it using tools very common on linux systems are as follows.

• Using Imagemagick

A lot many systems have imagemagick installed.  Using it is so simple that I use it as my default tool for this purpose.

convert file1.pdf /path/to/file2.pdf /destination/path/store.pdf

It takes a lot of options. For PDFs containing images, it is better to specify a quality parameter.

convert -quality 100 mine1.pdf mine2.pdf merged.pdf

• Using Ghostscript

Ghostscript is also very commonly found package in linux systems. Its usage is a little more obscure. However, it is very fast. I use it when I need to get PDF files of reduced size.

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input1.pdf input2.pdf

The above however reduces image quality badly. To get decent image quality with a little larger PDFs, we can use the following.

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input1.pdf input2.pdf

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -dPDFSETTINGS=/prepress -sOutputFile=output.pdf input1.pdf input2.pdf

Counting words on the command line

Recently, I have been writing a number of essays with various word limits. So, I have been finding myself in need of doing frequent word counts. Getting a word count for a file is easy using the wc utility.

wc -w /path/to/file

However, sometimes I just write a piece in a browser text box, which don't have word count. So, I want to get a word count from the console rather than saving it to a file and working with it. It turned out to be quite easy actually. I just had to cat the entire text and pipe that to wc.

cat << EOF | wc -w
>Your text here
>
>More here.
>EOF

Spellcheck in Emacs

Recently I am using Emacs for writing a few essays. While writing, I started missing spellcheck feature of Microsoft Word. The fact that feature is also provided my many browser based tools, like in GMail has made me used to it. So, I did a quick lookup to find the shortcut for triggering spellcheck in the current Emacs buffer. The answer was to simply use M-x ispell. Trying that I got the following error in the Messages buffer below the main buffer.

No word lists can be found for the language "en_US"

The shortcut mentioned above uses aspell which I knew is installed on my system. So, looking for aspell errors, I figured I needed to install the package aspell-en to get it fixed. On Arch linux, it can be done using the following.

pacman -S aspell-en

Gem installation fails due to packaged gems

Rake 0.9.6 comes bundled with ruby 2. However, I needed to build ruby-debug-ide 0.4.17.beta16 against rake 0.8.7. I tried uninstalling rake 0.9.6 but there is no way to do it. Using the following command does not list 0.9.6 as an option.

gem uninstall rake

So, now I had to find a way to tell the gem utility to use rake 0.8.7 instead of 0.9.6. A little reading showed that setting the RAKE environment variable could do this.

RAKE=/usr/lib/ruby/gems/2.0.0/gems/rake-0.8.7/bin/rake gem install ruby-debug-ide -v 0.4.17.beta16 --pre

The above  did not work for some reason. After that I tried the following and it worked.

RAKE=`bundle exec rake` gem install ruby-debug-ide -v 0.4.17.beta16 --pre

Checking memory usage for a set of processes

Recently, I had to monitor memory usage of a set of processes. I used pmap to help me out. The following script gave memory usage of each PID I was interested in.

for foo in `ps aux | grep <my_process_identifier> | awk -F ' ' '{print $2}'`
do
echo $foo
pmap $foo | tail -n 1
done

Remove X-Powered-By header in Nginx server

It is often desired to remove the 'X-Powered-By' from the HTTP headers. When using Nginx, it can be using a simple setting. The setting has to be in http section and it takes the following form.

<module_name>_hide_header X-Powered-By;

For example, if it is a FastCGI server the configuration setting will be as follows:

fastcgi_hide_header X-Powered-By;

If you are using Nginx as a load balancer, the configuration setting will be as follows:

proxy_hide_header X-Powered-By;

Unfortunately this configuration setting is not available yet in Passenger because Passenger is a thord party module and they have not implemented it yet.

Retrieving crontab after accidental removal

Yesterday at my workplace someone accidentally deleted all entries in crontab. We started looking for ways of restoring it as fast as possible. The tedious way of finding all processes on that machine would be our last option and it would also miss out frequency optimization done on the machine for various crons set on it.

Based on the usual Unix practice of backing up every file while saving an edit, we wanted to find out if the same happens with crontab too. To do that we needed to find out where crontab file was stored. A look at the manual page using the following command was enough to tell us that the file was stored at /var/spool/cron/.

man 8 cron

Looking in the folder, we could see the empty crontab file but no backup file was found. At this point, we did not have much hope of retrieving. Just to try our luck we tried looking at /tmp folder and fortune did favour us. We found the following file which had the previous contrab entries.

/tmp/crontab.XXXX6r0pD6

Change repeat rate in awesome WM

I had noticed that when you keep a button pressed in KDE it takes less time to repeat that character than when I do the same in Awesome. To get my desired behaviour, I had to set something called the auto-repeat rate option. A quick look at the manual page [1] tells us that we can turn it off either completely r for specific buttons. We can also the delay of auto-repeat and the rate of repetition, if XFree86-Misc extension of X server is implemented. Now, I had to find the delay and repetition rate values that I felt comfortable with. So, I found out the values in my KDE environment [2]. When I tried the values in Awesome, I was back in my comfort zone with the keyboard. The last step was to set the values every time Awesome started [3] and my system was all set.

[1] To see the options, try man xset, search for the option r or the string "autorepeat".

[2] The values can be found using the following command.

xset q | grep rate

[3] In the rc.lua file, just add the following line. You might want to customize the values for yourself.

os.execute("xset r rate 220 30")

Cleaning up MySQL binary logs

While analyzing disk usage, I found that /var/lib/mysql was running into gigabytes. I use MySQL for local testing. So, there is no way I can generate that much data. When I checked the folder out, there were many logs files which were eating up the space. Following the docs, clearing them was rather easy. All I had to do was run the following command on MySQL console.

purge binary logs before '2013-06-28 00:00:00';

Only one catch here: this will work only when log_bin option in my.cnf is not commented out.

Rails not detecting iconv

Whenever I started rails console or server, I was getting the following line about iconv.

no iconv, you might want to look into it.

I tried installing iconv package followed by the gem. Yet, I was unable to get rid of the message. I was not bothered much about the message till I started using rubyzip gem for creating some archives as it requires iconv gem. The solution is quite simple actually. Just add iconv to the Gemfile and rubyzip works fine. Also, the error line disappears. Of course, this is just a by-pass to get things working. I might go for an analysis some time later. Suggestions for that are welcome.

Directory size listing

A lot of times when freeing up disk space [Well yes in today's world also people like me need to do it.], instead of opening my file manager and finding the size of the folders by checking the properties section in the right-click drop-down, I wanted to look at a list view where I can sort by folder size. Now, KDE's Dolphin file manager shows number of items within a folder but not the size and I anyways prefer the command line so I wanted a command line tool that lists size of directories. The amount of space left on the partitions can be easily found by the following command:

df -h

I also found a command for directory size.

du

However, its default behaviour is to show the size of files recursively. So, I do not get the size of the folders in the directory I am interested in. Instead, I get the size of files within those folders and recursively so forth. I needed to set the depth of search into the folders. I found a parameter with a similar name. The following command works just as I need.

du --max-depth=1 -h

Uninstalling python packages

Continuing my system cleanup, I decided to get rid of all unnecessary python packages.

pip2 list | awk -F ' ' '{print $1}' | grep -vE "django-paypal|boto|mercurial|MySQL-python|nltk" | xargs pip2 uninstall -y

The -y flag indicates confirmation of uninstallation.

Uninstalling all gems

Some time back I was trying out jruby. I had installed multiple gems for it. Today, while cleaning up my system I was trying to get rid of it because it does not have much use to me. However, uninstalling the gems one by one is a pain. So, I wrote the following line to uninstall all gems.

jruby -S gem list | awk -F ' ' '{print $1}' | xargs jruby -S gem uninstall

P.S. : To understand how to construct such one liners please look at my previous post.