Added common commands

nav/_quickreference/common-commands.md

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+---
+layout: post
+title:  "Common Linux termnal commands"
+description: "Here is a list of commonly used Linux terminal commands"
+categories: quickreference
+order: 51
+---
+
+### Favorite Linux commands
+* `cd [directory]` **Change directory**
+*This command can also be used double dots to go back one level `cd ..` or with dash `cd -` to go back to previous directory. `cd ~` to get to HOME directory and `cd /` to get to root directory.*
+* `mkdir [directory]` **Make directory**
+* `CTRL+l` **Clear screen**
+*`CTRL+r` **Find a previous command**
+*Hit `CTRL+r` and start typing to find a command you have used before*
+* `sudo [command]` **Run command as root**
+* `sudo su` **Change user to `root`**
+* `find -name [name of file]` **Find a file by name**
+* `cat [file name]` **View content of file**
+* `df -h` **shows available and used disk space on the Linux system**
+* `chmod +x [file name]` **Makes file executable**
+* `grep` is used to filter output such as `df -h | grep udev` returns only one row from the `df` command
+* `asw` spits an input into an array. For instance `df -h | grep udev | awk '{print $2}'` returns only the second column.
+
+**grep and awk** sample
+```
+$ df -h
+Filesystem      Size  Used Avail Use% Mounted on
+udev            315M     0  315M   0% /dev
+tmpfs            91M  1.2M   90M   2% /run
+/dev/mmcblk0p2   29G  4.8G   22G  18% /
+tmpfs           454M  8.0K  454M   1% /dev/shm
+tmpfs           5.0M   12K  5.0M   1% /run/lock
+/dev/mmcblk0p1  510M   75M  436M  15% /boot/firmware
+tmpfs            91M   44K   91M   1% /run/user/1000
+
+ $ df | grep udev
+udev              322452       0    322452   0% /dev
+
+$ df | grep udev | awk '{print $2}'
+322452
+```
+
+### Favorite **vi** commands
+*`vi` or `vim` is a commonly used file editor, which can be complex to use, but here are a few commands to get you started.*
+
+* To open a file with `vi`, type `vi [file name]`
+* To edit the content, hit `i`
+* To delete a row, hit `d+d`
+* To leave a mode (such as edit), hit `ESC+ESC`
+* To save your changes, hit `w`
+* To quit `vi`, hit `w` or `wq` to save and quit
+
+### Favorite **less** commands
+*`less` is a great tool for analyzing log files.*
+
+* Open a log file, use `sudo less /var/log/syslog`. Use the `-S` flag to wrap long lines`
+* Use `b` to go backward one window
+* Use `f` to go forward one window
+* Use `G` to go to the end of file
+* Use `g` to go to the beginning of file
+* Use `/` to search forward
+* Use `?` to search backward
+
+### Favorite **systemctl** commands
+`systemd` is a software suite that provides an array of system components for Linux operating systems, such as daemons (services). `systemctl` is the tool you use to interact with `systemd`
+
+* `systemctl start [daemon]` starts a daemon
+* `systemctl stop [daemon]` stops a daemon
+* `systemctl restart [daemon]` re-starts a daemon
+* `systemctl cat [daemon]` view the service file
+* `systemctl daemon-reload` applies changes made to any service file.
+
+### Favorite **journalctl** commands
+`journalctl` is also part of the `systemd` suite and helps you view logfile in real-time.
+
+`journalctl -u [service] -n [number of previous lines] -f`. E.g.
+```
+journalctl -u microservicebus-node -n 100 -f
+``` 
+