htop komutu

Giriş

Açıklaması şöyle

htop is a process viewer similar to top but it allows you to scroll both vertically and horizontally, and even interact with a mouse pointer. You can use the F-keys to perform tasks such as search, filter, or kill a process.

Şeklen şöyle. Altta F tuşlarına ait açıklamalar görülebilir

Symbolic Links veya Softlink

Giriş

Özet olarak şöyle yaparız

#Create symbolic link
ln -sf /var/name.txt /etc/name.txt

#Remove symbolic link
unlink /etc/name.txt

#or remove the actual file
rm /etc/name.txt

Symbolic Link Yaratma

ln komutu kullanılır. Söz dizimi şöyle. İlk parametre gerçek dosya ismi, ikinci parametre softlinkfile ismidir.

ln -s <target> <link-name>

softlink (bir diğer ismiyle symbolic link) oluşturur. Symbolic link için eskiden fast ve slow gerçekleştirimleri vardı.  Açıklaması şöyle. Fast gerçekleştirim biraz daha optimize bir şekilde symbolic link'i depoluyor.

As for the "slow" / "fast" symbolic links, they are now a bit of history. Most filesystems have space in their inode tables of their directories. If the file is small enough to fit into the inode table itself, the file isn't created with its own block number, but rather a flag is set in the inode table and the contents of the file is stored in the inode entry directly. This only works for very small files, and symlinks are one of those kinds of files.

ln komutu ile bu özellikleri kontrol etmenin imkanı yok. Gerçekleştirim tamamen dosya sistemine bağlı. Açıklaması şöyle

There’s no way to tell ln to create “fast” or “slow” symlinks, the file system determines how it stores symlinks.

Örnek
Şöyle yaparız.

$ ln -s "hello world" README.txt
$ ls -l
total 0
lrwxr-xr-x  1 kk  wheel  11 Sep 15 11:39 README.txt -> hello world

Örnek
Şöyle yaparız. sourcefile silinirse softlinkfile işe yaramaz.

ln -s sourcefile softlinkfile

Örnek

Şöyle yaparız

ln -s original_file my_symlink
cat my_symlink > original_file

Bu komut aslında şununla aynıdır

cat original_file > original_file

Açıklaması şöyle

In any shell command > some_file will first open and truncate (zero) some_file and then execute command, writing the result to some_file.

So if you cat x > x then the shell will open and truncate x, then cat x will open and read the truncated file writing all of it's zero bytes.

Örnek
Eğer link-name verimezse target'ın en son kısmı kabul edilir. Eğer target /path/dir ise dir kabul edilir. Aşağıdaki örnekte root'a soft link yartılmaya çalışılıyor ve link-name belirtilmiyor. Bu durumda ./ yaratılamadı hatası alıyoruz.

~$ ln -s /
ln: failed to create symbolic link './': File exists

Sanal Konsol (Virtual Console) Nedir

Giriş

3 çeşit Sanal Konsol var gibi düşünülebilir. Bunlar şöyle

tty0

tty1-7

ttyS1

tty0 Nedir

Açıklaması şöyle

tty0 is special. Rather than a real tty, this is internally aliased by the kernel to the current active virtual console. It can be treated as a normal tty device, except that it won't work until one of the other tty%d devices has been initialized and assigned as console.

tty1-7 Nedir

Açıklaması şöyle

tty%d (numeric suffix, with no letter between, starting from 1) are all "virtual consoles" which have no specific designated purpose. These can be text terminals, or a graphical server can be launched on top of the text terminal. These might be dynamically allocated. Some distros will start their first graphical interface on a specific one of these, but which one has changed several times and subsequent ones will be dynamically assigned.

Ubuntu'da Ctrl + Alt + F1...F6 tuşları ile Virtual Console'a geçiş yaparız. GUI Console'a ile Ctrl + Alt + F7 ile geçeriz. Açıklaması şöyle. 

usually the first six virtual consoles provide a text terminal with a login prompt to a Unix shell. The graphical X Window System starts in the seventh virtual console.

Açıklaması şöyle.

As far as "the OS" (ie the kernel) is concerned, you have 7 tty consoles and any number of SSH connections (aka "login sessions") - it just so happens that ubuntu ships with scripts to auto-start the GUI on the tty7 session, but to the kernel it's just another application.

ttyS Nedir

Açıklaması şöyle

ttyS%d are hardware serial ports. The devices are likely preallocated and may not necessarily correspond to existing serial hardware. But if you do have directly connected serial ports, they typically are assigned sequentially starting from ttyS0