A system administrator manages configuration, upkeep and reliable operations of computer operations. Sysadmin handles servers, has to manage system performance and security without exceeding the budget to meet users need.

A system administrator only deals with terminal interface and hence it is very important to learn and become master in commands to operate from terminal.

Uptime

The uptime command tells us how long a system has been running.

folaukaveinga@Folaus-MacBook-Pro-3 sidecar-api-partner % uptime
18:34  up 19:47, 4 users, load averages: 3.05 2.49 2.30

From the left, it shows,

• currrent system time
• duration for which system has been running (system is running since 18 minutes)
• number of users logged in (2 users are logged in)
• system load average CPU load for past 1, 5 and 15 minutes.

WGET

wget is used to download files onto the current directory.

wget {url}

folaukaveinga@Folaus-MacBook-Pro-3 Downloads % wget google.com  
--2020-11-09 21:31:28--  http://google.com/
Resolving google.com (google.com)... 2607:f8b0:400f:805::200e, 172.217.11.238
Connecting to google.com (google.com)|2607:f8b0:400f:805::200e|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://www.google.com/ [following]
--2020-11-09 21:31:28--  http://www.google.com/
Resolving www.google.com (www.google.com)... 172.217.2.4, 2607:f8b0:400f:800::2004
Connecting to www.google.com (www.google.com)|172.217.2.4|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: ‘index.html.1’

index.html.1                                          [ <=>                                                                                                        ]  12.62K  --.-KB/s    in 0s      

2020-11-09 21:31:30 (88.6 MB/s) - ‘index.html.1’ saved [12918]

wget -o {filename} {url}

 To save file with a different name option O can be used.

wget -o google.html google.com

Download a whole website for local use

wget --mirror -p --convert-links -P {path} {url}

// example. 
wget --mirror -p --convert-links -P ./yourtimer https://yourtimer.io

–mirror – it enables the options suitable for mirroring

-p – download all files which are necessary to display html page

–convert-links – after downloading, convert links into documents for local viewing

-P ./ local dir ? save whole website in the specified local directory.

wget –tries={number} {url}

By default, wget command tries 20 times to downlod a file. This problem generally come when a large file is getting downloaded and internet connection is weak.

Here, you can set number of attempts which wget should make to download a file.

wget -O yourtimer.html --tries=10 https://yourtimer.io

SFTP

SFTP to a server with ssh key.

sftp -o IdentityFile={ssh-private-key} user@host

folaukaveinga@Folaus-MacBook-Pro-3 ~ % sftp -o IdentityFile=~/.ssh/testa/server_ssh_key ubuntu@qa.testa.com 
Connected to qa.testa.com.
sftp> ls
testa.sql
sftp>

// use quit or ! to exit

sftp upload

PUT {filename}

sftp> PUT test.txt

// upload multiple tiles
sftp> MPUT *.txt

sftp download

GET -p  {remoteFile} {localFilename}

sftp> GET -p bin-deploy.sh bin.sh

// download multiple files
sftp> MGET -p *.txt