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Linux is very important to me, so here's my way of sharing that with you. I've gathered a list of commands that are useful for anyone trying to get the most out of a Unix or Linux box.

<h2>What does the command dos2unix do?</h2>
“DOS/MAC to UNIX text file format converter … [a] program that converts plain text files in DOS/MAC format to UNIX format.”

<h2>What does the command unix2dos do?</h2>
“UNIX to DOS text file format converter … [a] program that converts text files in UNIX format to DOS format.”

<h2>Some commands are useful for system administrators when running scripts and programs. What are the following pair of commands useful for?</h2>
<b>at and cron</b>
- <b>at</b> let’s you “Queue, examine or delete jobs for later execution … at … read[s] commands from standard input or a specified file which are to be executed at a later time.” Times are accepted in the form HH:MM.
- <b>cron</b> is a daemon that’s used to “... execute scheduled commands”. Crontab files are loaded into memory and cron checks if it should be run in the current minute.

<b>bg and fg</b>
- <b>bg</b> is a BASH_BUILTIN command. It “[resumes] each suspended job ‘jobspec’ in the background”.
- <b>fg</b> is a BASH_BUILTIN command. It “[resumes] jobspec in the foreground, and make it in the current job …”

<b>jobs and nice</b>
- <b>jobs</b> is a BASH_BUILTIN command. It allows for different ways to list running processes, their IDs, when they undergo changes and their general status.
- <b>nice</b> allows the user to “... run a program with modified scheduling priority.” It “run[s] COMMAND with an adjusted niceness, which affects process scheduling. With no COMMAND, print the current niceness.” Niceness is measured from -20 to 19.

<b>watch and dmesg</b>
- <b>watch</b> lets you “... execute a program periodically…” and displays the output of the periodically executed program. The program “... is run every 2 seconds …” by default.
- <b>dmesg</b> “print[s] or control[s] the kernel ring buffer”. Effectively, it lets “users … print out their bootup messages …”.

<h2>What is a daemon (in terms of Unix/Linux jargon)?</h2>
A daemon is a program/process that runs in the background. It lurks invisibly while listening for service requests to respond/act accordingly.

<h2>What are 5 commonly used daemons? How are they usually named?</h2>
<i>I used https://en.wikipedia.org/wiki/List_of_Unix_daemons as my source for these daemons and their descriptions, on top of checking corresponding man pages.</i>

One can often identify a daemon if the program name ends with a ‘d’.
- <b>crond</b>: “Time-based job scheduler …” that “run[s] jobs in the background.”
- <b>inetd</b>: “Listens for network connection requests…” that “...launch a background daemon to handle the request…” that are also known as “...super servers...”
- <b>ftpd</b>: A daemon that listens for “FTP requests from a remote system.”
- <b>sshd</b>: A daemon that listens for SSH requests from remote systems.
- <b>syncd</b>: A daemon that “... keeps the file systems synchronized with system memory.”

<h2>Now some examples: What would be the result of the following commands?</h2>
<b>chmod 775 masterfile</b>
Changes permissions of file with name ‘masterfile’ to read, write and execute for owner and owner group. But only read and write for others.

<b>chmod go+rx myfile</b>
Changes permissions of file with name ‘myfile’ to add read and execute permissions for the owner group and others.

<b>who > textfile</b>
Writes output of who command into file with name ‘textfile’, while overwriting the current content of ‘textfile’. <b>who</b> outputs current logged in users, the time when they logged in and the address they connected from.

<b>ln Masterfile file</b>
Makes link named ‘file’ to a file named ‘Masterfile’. Commands that use ‘file’ will act as if they used ‘Masterfile’.

<b>ps - f</b>
“Full format listing…” of ps command. When I ran it in my shell it gave two processes, their UID, PID, PPID, C, STIME, TTY, TIME and CMD.

<i>Quoted text was taken directly from the man pages</i>

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