Core dump

More than once I have hit myself on the foot by running

git --init

Sometimes while copying big files, I'd like to know how much longer the copy will take. Rsync to the rescue:

Yesterday, I did something dumb. Really dumb. Arch Linux made a fundamental change in the file system, so manual intervention was needed during update. No big deal. I had followed such instruction multiple times. The instructions said:

# pacman -Syu --ignore filesystem,bash # pacman -S bash # pacman -Su

Now, unlike 90% of humanity, I don't use bash; rather I use zsh  as my shell. As an idiot, I thought that the --ignore bash line corresponded to the shell. So, instead of following the instructions as I should have, I did something stupid. I changed bash to zsh:

# pacman -Syu --ignore filesystem,zsh # pacman -S zsh # pacman -Su

After the upgrade, I rebooted and was greeted by the following prompt:

grub>

Brilliant. After a bit of fiddling around with the grub commands, I figured that this was because I still used grub-legacy instead of grub. So, the update had overwritten my /boot/grub/menu.lst file as /boot/grub/menu.lst.pacsave. After reading the help for all available commands, I found out that I could simply use

grub> configfile /grub/menu.lst.pacsave

to boot. Not so fast. Once I tried this, I got an error message that the hard disk could not be found and I was dumped to a recovery terminal. After googling around for a day, I finally figured out the right solution:

Boot using a recovery CD/USB

Chroot into your existing installation:

mount /dev/sda3 /mnt mkdir /mnt/boot mount /dev/sda1 /mnt/boot mount -t proc /proc /mnt/proc mount -t sysfs /sys /mnt/sys mount -o bind /dev /mnt/dev mount -o bind /dev/pts /mnt/dev/pts chroot /mnt bash

Recreate the linux image:

mkinitcpio -p linux

Rename menu.lst.pacsave to menu.lst

mv /boot/grub/menu.lst.pacsave /boot/grub/menu.lst

Phew, I had been postponing upgrading to systemd for a while. Finally upgraded. Took most part of the day, and figure out how the boot-loader works, the raw commands to set up a static ip, and how to set up the default nameserver. I wish the install procedure was simpler.

Well, we all know that you can use

cd -

but did you know that in ZSH you can use

cd -3

to change to the third last directory! Of course, if you press a tab after

cd -<TAB>

I wanted to use msmtp as a sendmail alternative with cron. First I tried to set

CRONARGS=-m/usr/bin/msmtp

in /etc/conf.d/crond but it did not work. The cron.logfile said

(CRON) INFO (Syslog will be used instead of sendmail.): No such file or directory

ZSH allows you to switch to a parallel directory by substituting any part of the current working directory with something else. For example, consider the following directory structure:

mkdir -p {first,second}/common cd first/common

At this stage, you can do

cd first second

I wanted to diff two directories to see what files are different between the two. Out of curiosity, I ran

diff -r dir1 dir2

Often I log in as one user, then do

su otheruser

However, getting X11 applications to work after that is a pain. There are various solutions floating around the Internet, messing with .Xauthority file, and what not. The simplest solution is to just log in using

sux otheruser