Logging into my system via my personal laptop, which is running the Mac OS X operating system, was actually more eventful than expected.
Since I know that OS X ships with a preinstalled version of OpenSSH, I went straight to my terminal and fired the command:
$ uname -a
Darwin Theodors-MacBook-Air.local 14.0.0 Darwin Kernel Version 14.0.0: Fri Sep 19 00:26:44 PDT 2014; root:xnu-2782.1.97~2/RELEASE_X86_64 x86_64
$ ssh vararut@meno.lsbu.ac.uk
ssh: connect to host meno.lsbu.ac.uk port 22: Operation timed out
$Well, now that's not a promising start. First idea: are ports blocked?
$ ssh $arcturus
Welcome to Ubuntu 12.04.4 LTS (GNU/Linux 3.2.0-60-virtual i686)
* Documentation: https://help.ubuntu.com/
Last login: Wed Dec 10 03:02:44 2014 from 136.148.10.8
$Looks like they are not, as SSHing through port 22 on one of my own GNU/Linux boxes works unhitched.
Note: my password was not requested for the login as I have set this machine up with my public RSA key.
$ uname -a
Linux blog.vararu.org 3.2.0-60-virtual #91-Ubuntu SMP Wed Feb 19 04:35:08 UTC 2014 i686 i686 i386 GNU/Linux
$ ssh vararut@meno.lsbu.ac.uk
Warning : Unauthorised Access Prohibited
vararut@meno.lsbu.ac.uk\'s password:Interesting! My GNU/Linux box can get through just fine, and proceeds to the SSH password prompt. Investigating further, and running the ssh command in verbose mode via ssh -v, reveals that my OS X machine is choking before it can even form a connection:
$ ssh -v vararut@meno.lsbu.ac.uk
OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 103: Applying options for *
debug1: Connecting to meno.lsbu.ac.uk [136.148.76.159] port 22.
debug1: connect to address 136.148.76.159 port 22: Operation timed out
ssh: connect to host meno.lsbu.ac.uk port 22: Operation timed out
$I've tried other avenues of investigation to figure out what the root cause is, but after coming up empty-handed I decided to skip to the exercise itself, since my GNU/Linux box can connect just fine:
$ ssh vararut@meno.lsbu.ac.uk
Warning : Unauthorised Access Prohibited
vararut@meno.lsbu.ac.uk\'s password:
Last login: Wed Dec 10 03:07:37 2014 from 188.226.201.122
### SNIPPED ###
Disk quotas for user vararut (uid 171224):
Filesystem blocks quota limit grace files quota limit grace
/dev/sdb1 136 50000 60000 18 2000 2500
[vararut@meno ~]$ uname -a
Linux meno.lsbu.ac.uk 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:19 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
[vararut@meno ~]$We're in! Logging out is simple:
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~Then, compare this list and its descriptions to the general connection categories and methods of logging on and logging off. These general categories are: - a. Local Area Network (LAN) Connection - b. Internet Connection - c. Stand-Alone Connection
Turns out, my eventual login method is actually rather convoluted. It involves using an Internet Connection to first connect to my Amsterdam-based GNU/Linux blog server, followed by another SSH tunnel back here in London to where I assume the LSBU Meno servers are located. All in all, thanks to the magic of broadband, the end result is actually superbly usable and stable, despite the unnecessary roundtrip.
If your method of connection is completely different from anything shown in lecture notes, try to give a descriptive name to your method.
I shall dub my method as such: "Mac OS X is a miserable pile of faux POSIX compliance so I just used Ubuntu".
Onward to the next task.
Pretty straightforward, let's go!
[vararut@meno ~]$ ls
[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$ xy
-bash: xy: command not found
[vararut@meno ~]$ cd ..
[vararut@meno va]$ pwd
/users/std/stud/v/va
[vararut@meno va]$ cd
[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$ cd /usr/local
[vararut@meno local]$ ls
bin etc include lib64 man sbin src
cams2 games lib libexec mysql-3.23.32 share tomcat
[vararut@meno local]$ cd
[vararut@meno ~]$Explanations as follows:
lslists the contents of our home folder, which is empty.pwdprints our working directory, which is ourMenohome folder:/users/std/stud/v/va/vararutxyis not a valid command, so the shell rejects it and prints out an error message.cd ..takes us up a folder in the directory hierarchy.pwdprints that we're not in the sharedvafolder, which contains what I assume are the home folders of other students whose surnames start withva.cdwith no command arguments will take us back to our home folder.pwdconfirms that we're back home.cd /usr/localtakes us to the/usr/localfolder.lsshows us the contents of/usr/local, which includes some binary executables, games, and various other software and documentation.cdhome sweet home again!
Let's create the two files!
[vararut@meno ~]$ cat > 1st
Lorem ipsum
[vararut@meno ~]$ cat 1st
Lorem ipsum
[vararut@meno ~]$ cat > 2nd
Dolor sit
[vararut@meno ~]$ cat 2nd
Dolor sit
[vararut@meno ~]$And now, let's create the directory structures! Figure 1:
[vararut@meno ~]$ mkdir old temp new
[vararut@meno ~]$ mkdir temp/junk
[vararut@meno ~]$ mv 1st old/
[vararut@meno ~]$ mv 2nd new/
[vararut@meno ~]$ tree
.
|-- new
| `-- 2nd
|-- old
| `-- 1st
`-- temp
`-- junk
4 directories, 2 files
[vararut@meno ~]$Resetting the directory structure as before:
[vararut@meno ~]$ mv old/1st .
[vararut@meno ~]$ mv new/2nd .
[vararut@meno ~]$ rm -rf old temp new
[vararut@meno ~]$ tree
.
|-- 1st
`-- 2nd
0 directories, 2 files
[vararut@meno ~]$Constructing Figure 2:
[vararut@meno ~]$ mkdir -p major minor aug/7th
[vararut@meno ~]$ mv 1st major/
[vararut@meno ~]$ mv 2nd aug/7th/
[vararut@meno ~]$ tree
.
|-- aug
| `-- 7th
| `-- 2nd
|-- major
| `-- 1st
`-- minor
4 directories, 2 files
[vararut@meno ~]$Reset, and then proceed to constructing Figure 3:
[vararut@meno ~]$ mkdir -p big small medium/tall
[vararut@meno ~]$ cp 1st big/1stcopy
[vararut@meno ~]$ mv 1st small/
[vararut@meno ~]$ mv 2nd medium/tall/
[vararut@meno ~]$ tree
.
|-- big
| `-- 1stcopy
|-- medium
| `-- tall
| `-- 2nd
`-- small
`-- 1st
4 directories, 3 files
[vararut@meno ~]$And finally, Figure 4:
[vararut@meno ~]$ mkdir -p time/now space/then arch/nice
[vararut@meno ~]$ cp 1st time/now/1stcopy
[vararut@meno ~]$ mv 1st space/then/
[vararut@meno ~]$ mv 2nd arch/nice/
[vararut@meno ~]$ tree
.
|-- arch
| `-- nice
| `-- 2nd
|-- space
| `-- then
| `-- 1st
`-- time
`-- now
`-- 1stcopy
6 directories, 3 files
[vararut@meno ~]$Here is the table with my own personalised descriptions of all of the methods:
| Command | Description |
|---|---|
cat |
Concatenate files or input streams. Often used to show the contents of files. |
more |
Page and search through long files and outputs with ease. "Show me more". |
cp |
Copy files and directories. |
mv |
Rename (move) files and directories. |
rm |
Remove files and directories. |
ls |
List and sort files and directories. |
mkdir |
Make a directory. |
pwd |
Show the path to the current working directory. |
cd |
Change the current directory. |
rmdir |
Remove a directory. Must be empty. |
###Task 6
Since I was already familiarised with these commands, as well as some of their particularities (such as the -p option for mkdir to recursively create subdirectories that occur in the specified path), I don't think I would change anything, but I am always open to learning new tricks!
Off we go!
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~Logging into my system right away.
➜ ~ ssh vararut@meno.lsbu.ac.uk
Warning : Unauthorised Access Prohibited
vararut@meno.lsbu.ac.uk's password:
Last login: Wed Dec 10 21:23:21 2014 from 188.226.201.122
[vararut@meno ~]$[vararut@meno ~]$ who
richj3 pts/9 2014-12-10 20:30 (cpc2-slam6-2-0-cust66.2-4.cable.virginm.net)
santamaa pts/10 2014-12-10 19:54 (host86-132-102-246.range86-132.btcentralplus.com)
coxr2 pts/11 2014-12-10 22:18 (5ec1bde7.skybroadband.com)
sekyewaj pts/12 2014-12-10 21:53 (90.198.211.30)
vararut pts/15 2014-12-10 22:17 (188.226.201.122)
[vararut@meno ~]$Looks like there are 5 users logged in, and the longest active user is santamaa who logged in at 2014-12-10 19:54. I assume there are no users logged in via telnet, since trying to do so on the default port times out:
➜ ~ telnet meno.lsbu.ac.uk
Trying 136.148.76.159...
telnet: Unable to connect to remote host: Connection timed out
➜ ~Use the
datecommand to display the current time. Show your session.
[vararut@meno ~]$ date
Wed Dec 10 22:50:27 GMT 2014
[vararut@meno ~]$[vararut@meno ~]$ history | grep "cal"
224 cd /usr/local
294 cal 4
295 cal 52
296 cal 1752
297 cal 1952
298 cal 2004
299 cal 2013
300 history | grep "cal"
[vararut@meno ~]$Does the command work fine both leap and non-leap years? How could you tell?
I honestly didn't bother inspecting the output when I used the commands, since I already know that cal is rock solid, but scrolling up to look at the output for cal 2014 does reveal that February has 29 days as expected.
1752 has 366 days and this is unsurprising, as it is divisible by 4 and as such a leap year. Google presents 10 results on the main page, as is standard, with a proeminent entry for the Wikipedia Article on this subject, http://en.wikipedia.org/wiki/Gregorian_calendar. It states that its namesake is after its inventor:
It is named for Pope Gregory XIII, who introduced it in 1582.
Use the
pwdcommand to display the name of your home directory. Show your session.
[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$[vararut@meno ~]$ uname
Linux
[vararut@meno ~]$ uname -n
meno.lsbu.ac.uk
[vararut@meno ~]$ uname -p
x86_64
[vararut@meno ~]$The operating system is GNU/Linux, which consists of the GNU core utils running on top of the Linux kernel. This is evident by running uname -o, which will return the operating system name:
[vararut@meno ~]$ uname -o
GNU/Linux
[vararut@meno ~]$Richard Stallman is always keen to remind us of the fact that Linux is just the kernel, rather than the full operating system: http://en.wikipedia.org/wiki/GNU/Linux_naming_controversy.
The nodename is meno.lsbu.ac.uk, and the processor type is x86_64.
Which operating system does the operating system run on?
Err, this question seems phrased incorrectly. The operating system runs on 16-bit minicomputers.
Who owns the rights of RSTS?
Apparently DEC sold their rights to Mentec at one point.
How old is RSTS?
The first version was released in 1970, so 34 years old.
What does RSTS stand for?
"Resource Sharing Timesharing System".
When was RSTS operating system written?
Where was RSTS written?
Digital Equipment Corporation headquarters in Maynard, Massachusetts, United States.
| OS | Google.com Hits |
|---|---|
| UNIX | 174,000,000 |
| Linux | 454,000,000 |
| FreeBSD | 23,900,000 |
| NetBSD | 818,000 |
| Solaris | 78,100,000 |
| Windows 8 | 756,000,000 |
| Windows 7 | 786,000,000 |
| Windows XP | 238,000,000 |
| Windows 2000 | 145,000,000 |
| Windows NT | 53,100,000 |
| Windows 98 | 96,400,000 |
| Windows 95 | 91,900,000 |
| Windows 3.1 | 25,300,000 |
| Mac OS | 213,000,000 |
The most popular are, ordered by hits: Windows 7, Windows 8 and Linux. Windows aggregates a total of 2,482,800,000 results.
What is the name of world’s first time-sharing operating system?
CTSS, apparently.
| Acronym | Expansion |
|---|---|
| BOS | Either IBM's Basic Operating System or Motorola's Business Operating System |
| BOSS | Bharat Operating System Solutions |
| DOS | Disk Operating System |
| JOSS | JOHNNIAC Open-Shop System |
| MOS | Mobile Operating System |
| POS | PERQ Operating System |
| TSOS | Time Sharing Operating System |
EDSAC, 6 May 1949, the University of Cambridge Mathematical Laboratory in England.
When did the first version of UNIX come out and what was its name?
The first version was called UNICS and it came out in 1970.
Who were the authors of UNIX?
It was written by Ken Thompson and Dennis Ritchie (RIP).
Where (organization) was UNIX designed and written?
AT&T Bell Labs.
When (year) was UNIX rewritten in C?
When did BSD UNIX come out?
When did FreeBSD come out?
Who said this and when: "...the number of UNIX installations has grown to 10, with more expected..."
Dennis Ritchie and Ken Thompson, June 1972.
When was TCP/IP implemented in the UNIX kernel and in which UNIX flavor?
In BSD Unix, starting with version 4.1c.
When did Solaris 9.0E come out?
Who created the B language and when?
Ken Thompson with Dennis Ritchie, circa 1969.
Who created the C language and when?
Dennis Ritchie, circa 1969.
Off we go!
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~| Command | Short Description | Example Use |
|---|---|---|
touch |
Create an empty file, or update an existing one. | touch test.txt |
cp |
Copy files and directories. | cp -rv ~/Desktop/*.jpg ~/Pictures/ |
mv |
Rename/move files and directories. | mv .bashrc .bash_profile |
rm |
Remove files and directories. | rm -rf / |
mkdir |
Make directories and subdirectories. | mkdir -p ho/ho/ho/merry/christmas |
rmdir |
Remove empty directories. | rmdir -p ho/ho/ho/merry/christmas |
ls |
List files. | ls ~/Pictures/*.jpg |
lpr |
Print files. | lpr thesis.txt |
cd |
Change directory. | cd /bin/ |
pwd |
Print working directory. | pwd |
| Command | Short Description |
|---|---|
open |
Opens a file or device. |
read |
Read from the standard input and store in a shell variable. |
write |
Write to a file descriptor. |
close |
Close a file descriptor. |
pipe |
Create a pipe inode. |
socket |
Create a network communication endpoint. |
mkfifo |
Create a named pipe. |
system |
Execute a shell command. |
printf |
Format and print data. |
[vararut@meno ~]$ cat /etc/motd
################################################################################
Unauthorised access is prohibited
NOTE: meno now supports https. To develope a https site create a .private_html directory and then run wwwset to set the correct permissions viz
$ cd
$ mkdir .private_html
$ wwwset
By putting content into .private_html you make now view it at https://mypages.lsbu.ac.uk/~username
Non-https personal web pages are still available on this server using the URL
http://mypages.lsbu.ac.uk/~username
STUDENT personal web pages are only visible on-campus. If you are developing a web site and wish to view it from off campus you will need to connect to the VPN first. Details can be found at
http://www.lsbu.ac.uk/ict/services/vpn.shtml
Please note that web pages should be located in your .public_html folder and any PHP scripts you develop should be located in your .public_html/cgi-bin folder
###############################################################################
[vararut@meno ~]$[vararut@meno ~]$ echo $PATH
/usr/lib64/qt-3.3/bin:/usr/kerberos/bin:/usr/local/bin:/bin:/usr/bin:/usr/lib/oracle/11.2/client64/bin:/users/std/stud/v/va/vararut/bin:.
[vararut@meno ~]$ echo $path
[vararut@meno ~]$ echo $LINES
25
[vararut@meno ~]$ echo $HOME
/users/std/stud/v/va/vararut
[vararut@meno ~]$ echo $home
[vararut@meno ~]$[vararut@meno ~]$ echo $LINES
25
[vararut@meno ~]$ export LINES=15
[vararut@meno ~]$ echo $LINES
15
[vararut@meno ~]$ man ls
[vararut@meno ~]$ echo $LINES
25
[vararut@meno ~]$Running man ls changes the value of LINES back to 25. So, still 25.
What does the abbreviation pwd stand for?
pwd stands for print working directory.
What does the output of the pwd command represent with respect to the location of the root directory in the Linux file system hierarchy?
It represents a location string starting from the filesystem root, /.
What does the abbreviation
cdstand for?
Change directory.
What does the result of the
cd ..command represent with respect to the location of the previous directory location in the Linux file system hierarchy?
cd .. takes you up one directory in the filesystem hierarchy.
Which directory in the Linux file system does the
cd /command take you to?
The root.
Which directory in the Linux file system does the
cdcommand take you to?
Your home folder.
Is it obvious what the
touchcommand is designed to do?
Intuitive, but not exactly obvious.
Type
man touchand press the Enter key. What does the MAN page fortouchsay about the purpose of this command?
"Change file timestamps".
What are the permissions assigned to users and groups for
file1?
Read/Write for the owner (me), Read for my group, Read for global. rw-r--r--.
What are the new
file1permissions for users and groups?
Everyone can read, write and execute. rwxrwxrwx.
Are these permissions reasonable for
file1?
777 is generally never reasonable, and a crutch used in cases where proper permissions are misunderstood.
Why is it not possible for you to create the xyz directory in the
/usr/bindirectory?
[vararut@meno ~]$ cd /usr/bin
[vararut@meno bin]$ mkdir xyz
mkdir: cannot create directory xyz': Permission denied
[vararut@meno bin]$Permission denied.
Which character in the listing displayed after typing
ls -lindicates that xyz is a directory?
The d at the start.
Why was it not possible to delete the subfiles directory?
rmdir will not work on non-empty directories, to prevent accidental misuse.
How does the output of the
lscommand differ from that of thels -lcommand?
-l switches to a long listing format, with more information.
A file listing for which directory is displayed after typing
ls /?
The root directory.
[vararut@meno ~]$ ls /
bin etc lib64 misc opt save srv tom usr
boot home lost+found mnt proc sbin sys user var
dev lib media net root selinux tmp users
[vararut@meno ~]$Which files in your home directory are listed after typing
ls A*.txt? What do these files have in common?
They all start with the prefix A and end in .txt.
Explain the error messages that are displayed after typing the
lsandmvcommands.
ls will return that there is no such file or directory.
mv will return permission denied for each affected file.
Which account could perform the
mvcommand without getting the error message?
The root user.
Procedurally, how does copying a file differ from moving a file?
cp creates a new inode while moving a file just switches a pointer. Moving/renaming is atomic, while copying takes time.
What additional feature does the
rm -icommand offer over the rm command?
It makes the rm command interactive, prompting for user confirmation.
What output is produced for the command
cat mlist?
[vararut@meno ~]$ ls
file1 mlist xyz
[vararut@meno ~]$ ls > mlist
[vararut@meno ~]$ echo "This is the last line of the file" >> mlist
[vararut@meno ~]$ cat mlist
file1
mlist
xyz
This is the last line of the file
[vararut@meno ~]$This is because the ls > mlist redirection will overwrite the file, and then the echo >> mlist redirection will append the last line.
Assume the previous paragraph is stored in a file called
textfile3.rtf. What would be the output for the followinggrepcommand?grep -c "Data" textfile3.rtf
[vararut@meno ~]$ echo "For example, the command grep "ACK" ftpSummaryLarge.rtf displays only those lines in the ftpSummaryLarge.rtf file that contain the key word ACK. Grep can also be used to determine how many lines in a given file contain a specific keyword. For example, one may wish to know the number of packets exchanged during a data transfer between two computers that meets a specific condition, such as the number of packets that contain application data. Issuing a command such as grep -c "Data" tftpSummaryLarge.rtf, would instantly reduce a potentially large file into a single value that represents the number of data packets transferred." > textfile3.rtf
[vararut@meno ~]$ grep -c "Data" textfile3.rtf
1
[vararut@meno ~]$[vararut@meno ~]$ mkdir -p temp personal/funstuff personal/taxes professional/societies/ieee professional/societies/acm professional/courses/general professional/courses/major/cs475 professional/courses/major/cs381/programs professional/courses/major/cs381/labs professional/courses/major/cs381/notes professional/courses/major/cs213
[vararut@meno ~]$ tree
.
|-- personal
| |-- funstuff
| `-- taxes
|-- professional
| |-- courses
| | |-- general
| | `-- major
| | |-- cs213
| | |-- cs381
| | | |-- labs
| | | |-- notes
| | | `-- programs
| | `-- cs475
| `-- societies
| |-- acm
| `-- ieee
`-- temp
17 directories, 0 files
[vararut@meno ~]$[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$Path to home directory:
[vararut@meno courses]$ cd
[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$Path to acm directory:
[vararut@meno ~]$ cd professional/societies/acm/
[vararut@meno acm]$ pwd
/users/std/stud/v/va/vararut/professional/societies/acm
[vararut@meno acm]$Two relative pathnames:
[vararut@meno courses]$ pwd
/users/std/stud/v/va/vararut/professional/courses
[vararut@meno courses]$ ls ../societies/acm/
[vararut@meno courses]$ ls ~/professional/societies/acm/
[vararut@meno courses]$[vararut@meno ~]$ cd /usr
[vararut@meno usr]$ ll
total 344
drwxr-xr-x 2 root root 69632 Sep 28 15:40 bin
drwxr-xr-x 2 root root 4096 Oct 10 2006 etc
drwxr-xr-x 2 root root 4096 Oct 10 2006 games
drwxr-xr-x 129 root root 12288 Aug 13 2010 include
drwxr-xr-x 5 root root 4096 Dec 10 2010 java
drwxr-xr-x 6 root root 4096 Sep 11 2007 kerberos
drwxr-xr-x 79 root root 65536 Nov 3 2011 lib
drwxr-xr-x 90 root root 69632 Nov 7 2011 lib64
drwxr-xr-x 10 root root 4096 Mar 4 2008 libexec
drwxr-xr-x 16 root root 4096 Dec 10 2010 local
drwxr-xr-x 2 root root 20480 Jul 11 12:46 sbin
drwxr-xr-x 208 root root 4096 Aug 13 2010 share
drwxr-xr-x 4 root root 4096 Mar 4 2008 src
drwx--x--x 3 tftp bin 4096 Sep 16 2008 tftpdir
lrwxrwxrwx 1 root root 10 Mar 4 2008 tmp -> ../var/tmp
drwxr-xr-x 2 root root 4096 Jun 21 2010 users
drwxr-xr-x 3 root root 4096 Mar 4 2008 X11R6
[vararut@meno usr]$ ls | wc -l
17
[vararut@meno usr]$There are 17, through ls | wc -l. They are all directories, except for tmp which is a symlink.
[vararut@meno ~]$ pwd
/users/std/stud/v/va/vararut
[vararut@meno ~]$ ls /usr/bin/ | wc -l
2328
[vararut@meno ~]$[vararut@meno ~]$ cat /etc/motd
################################################################################
Unauthorised access is prohibited
NOTE: meno now supports https. To develope a https site create a .private_html directory and then run wwwset to set the correct permissions viz
$ cd
$ mkdir .private_html
$ wwwset
By putting content into .private_html you make now view it at https://mypages.lsbu.ac.uk/~username
Non-https personal web pages are still available on this server using the URL
http://mypages.lsbu.ac.uk/~username
STUDENT personal web pages are only visible on-campus. If you are developing a web site and wish to view it from off campus you will need to connect to the VPN first. Details can be found at
http://www.lsbu.ac.uk/ict/services/vpn.shtml
Please note that web pages should be located in your .public_html folder and any PHP scripts you develop should be located in your .public_html/cgi-bin folder
###############################################################################
[vararut@meno ~]$[vararut@meno ~]$ cat /etc/passwd | grep vararut
vararut:x:171224:219:Theodor Vararu, Student,:/users/std/stud/v/va/vararut:/bin/bash
[vararut@meno ~]$| User name | User ID | Group ID | Personal Information | Home Directory | Login Shell |
|---|---|---|---|---|---|
vararut |
171224 | 219 | Theodor Vararu, Student | /users/std/stud/v/va/vararut |
/bin/bash |
[vararut@meno ~]$ cd /boot/
[vararut@meno boot]$ ll
total 7897
-rw-r--r-- 1 root root 61583 Oct 10 2007 config-2.6.18-53.el5
drwxr-xr-x 2 root root 1024 Apr 8 2011 grub
-rw------- 1 root root 2547073 Jul 11 12:46 initrd-2.6.18-53.el5.img
-rw-r--r-- 1 root root 2334422 Mar 4 2008 initrd-2.6.18-53.el5kdump.img
drwx------ 2 root root 12288 Mar 4 2008 lost+found
-rw-r--r-- 1 root root 88644 Oct 10 2007 symvers-2.6.18-53.el5.gz
-rw-r--r-- 1 root root 1150812 Oct 10 2007 System.map-2.6.18-53.el5
-rw-r--r-- 1 root root 1844028 Oct 10 2007 vmlinuz-2.6.18-53.el5
[vararut@meno boot]$vmlinuz-2.6.18-53.el5.
There are no .profile or .login files in the home directory for this particular user configuration. Rather, there is a .bash_profile file in the home directory:
[vararut@meno ~]$ cat .bash_profile | head -n 5
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
[vararut@meno ~]$[vararut@meno ~]$ ls -lah
total 84K
drwx--x--x 4 vararut ustud 4.0K Dec 11 01:35 .
drwxr-xr-x 186 root root 4.0K Nov 25 20:03 ..
-rw------- 1 vararut ustud 3.5K Dec 11 00:01 .bash_history
-rw-r--r-- 1 vararut ustud 24 Aug 22 12:03 .bash_logout
-rw-r--r-- 1 vararut ustud 178 Aug 22 12:03 .bash_profile
-rw-r--r-- 1 vararut ustud 124 Aug 22 12:03 .bashrc
-rw-r--r-- 1 vararut ustud 515 Aug 22 12:03 .emacs
drwxr-xr-x 3 vararut ustud 4.0K Aug 22 12:03 .kde
-rw------- 1 vararut ustud 65 Dec 11 01:35 .lesshst
drwxrws--T+ 3 root www 4.0K Aug 22 12:03 .public_html
-rw------- 1 vararut ustud 8 Sep 25 15:13 .sh_history
-rw------- 1 vararut ustud 3.6K Sep 25 14:20 .viminfo
-rw-r--r-- 1 vararut ustud 22K Sep 25 14:14 .zcompdump
-rw-r--r-- 1 vararut ustud 658 Sep 25 14:21 .zshrc
-rw-r--r-- 1 vararut ustud 658 Sep 25 14:18 .zshrc-old
[vararut@meno ~]$[vararut@meno ~]$ ls -il
total 12
232512 drwxr-xr-x 4 vararut ustud 4096 Dec 11 01:43 personal
232515 drwxr-xr-x 4 vararut ustud 4096 Dec 11 01:43 professional
232510 drwxr-xr-x 2 vararut ustud 4096 Dec 11 01:43 temp
[vararut@meno ~]$ ls -ila /
total 218
2 drwxr-xr-x 29 root root 4096 Dec 11 01:05 .
[vararut@meno ~]$[vararut@meno ~]$ ls -ilah /boot/vmlinuz-2.6.18-53.el5
15 -rw-r--r-- 1 root root 1.8M Oct 10 2007 /boot/vmlinuz-2.6.18-53.el5
[vararut@meno ~]$ more /boot/vmlinuz-2.6.18-53.el5
******** /boot/vmlinuz-2.6.18-53.el5: Not a text file ********
[vararut@meno ~]$[vararut@meno labs]$ ls -ilah lab1
232528 -rw-r--r-- 1 vararut ustud 0 Dec 11 01:47 lab1
[vararut@meno labs]$[vararut@meno ~]$ ls /usr/include/sys/t*.h
/usr/include/sys/termios.h /usr/include/sys/timex.h
/usr/include/sys/timeb.h /usr/include/sys/ttychars.h
/usr/include/sys/time.h /usr/include/sys/ttydefaults.h
/usr/include/sys/times.h /usr/include/sys/types.h
[vararut@meno ~]$Off we go!
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~[vararut@meno ~]$ rm -rf temp/*
[vararut@meno ~]$ ll temp/
total 0
[vararut@meno ~]$[vararut@meno ~]$ cd temp/
[vararut@meno temp]$ mkdir d1 d2 d3
[vararut@meno temp]$ cp ../smallFile d1/
[vararut@meno temp]$ ls -ilah d1/
total 12K
232364 drwxr-xr-x 2 vararut ustud 4.0K Dec 11 11:29 .
232510 drwxr-xr-x 5 vararut ustud 4.0K Dec 11 11:29 ..
232532 -rw-r--r-- 1 vararut ustud 150 Dec 11 11:29 smallFile
[vararut@meno temp]$[vararut@meno d2]$ ln ../d1/smallFile smallFile.hard
[vararut@meno d2]$ ls -ilah
total 12K
232529 drwxr-xr-x 2 vararut ustud 4.0K Dec 11 11:34 .
232510 drwxr-xr-x 5 vararut ustud 4.0K Dec 11 11:29 ..
232532 -rw-r--r-- 2 vararut ustud 150 Dec 11 11:29 smallFile.hard
[vararut@meno d2]$ ls -ilah ../d1/
total 12K
232364 drwxr-xr-x 2 vararut ustud 4.0K Dec 11 11:29 .
232510 drwxr-xr-x 5 vararut ustud 4.0K Dec 11 11:29 ..
232532 -rw-r--r-- 2 vararut ustud 150 Dec 11 11:29 smallFile
[vararut@meno d2]$They are hard links to the same file because they have the same inode.
[vararut@meno ~]$ cat temp/d2/smallFile.hard
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno ~]$ ls -l smallFile
-rw-r--r-- 1 vararut ustud 150 Dec 11 11:20 smallFile
[vararut@meno ~]$ chmod 244 smallFile
[vararut@meno ~]$ ls -l smallFile
--w-r--r-- 1 vararut ustud 150 Dec 11 11:20 smallFile
[vararut@meno ~]$ cat smallFile
cat: smallFile: Permission denied
[vararut@meno ~]$ cat temp/d2/smallFile.hard
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno ~]$ ls -l temp/d2/smallFile.hard
-rw-r--r-- 2 vararut ustud 150 Dec 11 11:29 temp/d2/smallFile.hard
[vararut@meno ~]$ chmod 644 smallFile
[vararut@meno ~]$ ls -l smallFile
-rw-r--r-- 1 vararut ustud 150 Dec 11 11:20 smallFile
[vararut@meno ~]$ cat smallFile
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno ~]$ cp smallFile smallFile.bak
[vararut@meno ~]$ rm smallFile
[vararut@meno ~]$ cat temp/d2/smallFile.hard
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno ~]$It makes sense, since while ~/smallFile no longer has read permissions, a hard link pointing to the same inode can have a completely independent set of permissions.
The file can still be displayed upon deleting one of its hard links. A file is considered completely deleted from the filesystem only when its number of hard links reaches 0.
[vararut@meno d2]$ ln smallFile.hard ../d1/smallFile
[vararut@meno d2]$ ln -s ../d1/smallFile smallFile.soft
[vararut@meno d2]$ ls -ilah
total 12K
232529 drwxr-xr-x 2 vararut ustud 4.0K Dec 11 11:59 .
232510 drwxr-xr-x 5 vararut ustud 4.0K Dec 11 11:29 ..
232532 -rw-r--r-- 2 vararut ustud 150 Dec 11 11:29 smallFile.hard
232528 lrwxrwxrwx 1 vararut ustud 15 Dec 11 11:59 smallFile.soft -> ../d1/smallFile
[vararut@meno d2]$They are different files because they point to different inodes. The size of the symlink is only 15 bytes.
[vararut@meno d2]$ cat smallFile.soft
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno d2]$ chmod 244 ../d1/smallFile
[vararut@meno d2]$ cat smallFile.soft
cat: smallFile.soft: Permission denied
[vararut@meno d2]$ chmod 644 ../d1/smallFile
[vararut@meno d2]$ cat smallFile.soft
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno d2]$ cat smallFile.soft
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno d2]$ rm ../d1/smallFile
[vararut@meno d2]$ cat smallFile.soft
cat: smallFile.soft: No such file or directory
[vararut@meno d2]$ ls
smallFile.hard smallFile.soft
[vararut@meno d2]$It makes sense, because a symbolic link is just a pointer to a specific address in the filesystem. If the other end dissapears, the filesystem reacts accordingly.
Off we go!
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~[vararut@meno ~]$ ps -e -o uid,pid,ppid,pri,ni,cmd | grep inet
0 15315 1 24 0 xinetd -stayalive -pidfile /var/run/xinetd.pid
171224 16604 26685 21 0 grep inet
[vararut@meno ~]$ ps -e -o uid,pid,ppid,pri,ni,cmd | grep sched
171224 16612 26685 21 0 grep sched
[vararut@meno ~]$ ps -e -o uid,pid,ppid,pri,ni,cmd | grep cron
0 2727 1 24 0 crond
171224 16615 26685 21 0 grep cron
[vararut@meno ~]$ ps -e -o uid,pid,ppid,pri,ni,cmd | grep inetd
0 15315 1 24 0 xinetd -stayalive -pidfile /var/run/xinetd.pid
171224 16623 26685 21 0 grep inetd
[vararut@meno ~]$The parent for all of them is root.
| Process | PPID | Priority |
|---|---|---|
init |
1 | 24 |
crond |
1 | 24 |
xinetd |
1 | 24 |
grep -v grep used to eliminate extra entries.
[vararut@meno ~]$ ps aux | grep httpd | grep -cv grep
9
[vararut@meno ~]$ ps -e -o pid,cmd | grep httpd | grep -v grep
2577 /usr/sbin/httpd
2578 /usr/sbin/httpd
2579 /usr/sbin/httpd
2580 /usr/sbin/httpd
2581 /usr/sbin/httpd
2582 /usr/sbin/httpd
2583 /usr/sbin/httpd
2589 /usr/sbin/httpd
22710 /usr/sbin/httpd
[vararut@meno ~]$[vararut@meno ~]$ ps aux | grep -w "/bin/.*sh" | grep -v grep
root 2554 0.0 0.0 65900 1252 ? S Aug21 0:00 /bin/sh /usr/bin/mysqld_safe --defaults-file=/etc/my.cnf --pid-file=/var/run/mysqld/mysqld.pid --log-error=/var/log/mysqld.log
root 2605 0.0 0.0 65900 1300 ? S Aug21 28:42 /bin/bash /usr/local/cams2/bin/cams_watcher.sh
[vararut@meno ~]$top - 15:22:55 up 112 days, 2:41, 5 users, load average: 0.02, 0.03, 0.00
Tasks: 129 total, 1 running, 122 sleeping, 6 stopped, 0 zombie
Cpu(s): 0.3%us, 0.5%sy, 0.0%ni, 99.0%id, 0.0%wa, 0.2%hi, 0.0%si, 0.0%st
Mem: 3735588k total, 3688652k used, 46936k free, 1467928k buffers
Swap: 2040212k total, 104k used, 2040108k free, 1028888k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
19748 vararut 15 0 12716 1072 792 R 1 0.0 0:00.65 top
2584 mysql 15 0 675m 106m 4372 S 0 2.9 39:55.50 mysqld
2605 root 18 0 65900 1300 1040 S 0 0.0 28:42.98 cams_watcher.sh
26684 vararut 15 0 97.9m 2172 1244 S 0 0.1 0:01.16 sshd
1 root 15 0 10312 684 568 S 0 0.0 0:20.31 init
2 root RT 0 0 0 0 S 0 0.0 33:51.07 migration/0
3 root 34 19 0 0 0 S 0 0.0 0:02.19 ksoftirqd/0
4 root RT 0 0 0 0 S 0 0.0 0:01.10 watchdog/0
5 root RT 0 0 0 0 S 0 0.0 20:24.08 migration/1
6 root 34 19 0 0 0 S 0 0.0 0:02.94 ksoftirqd/1
7 root RT 0 0 0 0 S 0 0.0 0:01.36 watchdog/1
8 root 10 -5 0 0 0 S 0 0.0 76:07.80 events/0
9 root 10 -5 0 0 0 S 0 0.0 3:14.90 events/1
10 root 10 -5 0 0 0 S 0 0.0 0:00.00 khelper
41 root 16 -5 0 0 0 S 0 0.0 0:00.00 kthread
46 root 10 -5 0 0 0 S 0 0.0 0:07.14 kblockd/0
47 root 10 -5 0 0 0 S 0 0.0 0:04.43 kblockd/1
48 root 14 -5 0 0 0 S 0 0.0 0:00.00 kacpidtop refreshes once every 3 seconds. 1 running process, 122 sleeping.
[vararut@meno ~]$ sleep 3600 && echo "Time for Lunch\!" &
[1] 19956
[vararut@meno ~]$[vararut@meno ~]$ find ~ -name "foobar" 1>find.out 2>/dev/null & sort -nrk4 smallFile 1>sort.out 2>/dev/null &
[1] 22999
[2] 22300
[vararut@meno ~]$ ll
total 20
-rw-r--r-- 1 vararut ustud 0 Dec 11 21:03 find.out
drwxr-xr-x 4 vararut ustud 4096 Dec 11 11:18 personal
drwxr-xr-x 4 vararut ustud 4096 Dec 11 11:18 professional
-rw-r--r-- 1 vararut ustud 150 Dec 11 11:47 smallFile
-rw-r--r-- 1 vararut ustud 150 Dec 11 21:03 sort.out
drwxr-xr-x 5 vararut ustud 4096 Dec 11 11:29 temp
[vararut@meno ~]$ cat find.out
[vararut@meno ~]$ cat sort.out
James Davis ECE 3.71 davis@jd.work.org 111.222.1111
John Doe ECE 3.54 doe@jd.home.org 111.222.3333
Al Davis CS 2.63 davis@a.lakers.org 111.222.2222
[vararut@meno ~]$[vararut@meno ~]$ kill 12345
-bash: kill: (12345) - No such process
[vararut@meno ~]$ kill %2
-bash: kill: %2: no such job
[vararut@meno ~]$[vararut@meno ~]$ date & uname -a & who & ps &
[1] 23108
[2] 23109
[3] 23110
[4] 23111
Thu Dec 11 21:10:00 GMT 2014
Linux meno.lsbu.ac.uk 2.6.18-53.el5 #1 SMP Wed Oct 10 16:34:19 EDT 2007 x86_64 x86_64 x86_64 GNU/Linux
-bash: echo: write error: Interrupted system call
[1] Done date
[vararut@meno ~]$ sagayarl pts/11 2014-12-11 13:15 (0543f9f8.skybroadband.com)
richj3 pts/12 2014-12-11 20:36 (cpc2-slam6-2-0-cust66.2-4.cable.virginm.net)
gharibr pts/15 2014-12-11 15:34 (bus-2402603.lsbu.ac.uk)
sekyewaj pts/17 2014-12-11 10:06 (90.198.211.30)
vararut pts/18 2014-12-11 20:57 (188.226.201.122)
PID TTY TIME CMD
22440 pts/18 00:00:00 bash
23111 pts/18 00:00:00 ps
[2] Done uname -a
[3]- Done who
[4]+ Done ps
[vararut@meno ~]$[vararut@meno ~]$ find / -inum 123456 1>find.out 2>/dev/null &
[1] 23194
[vararut@meno ~]$ kill %%
[1]+ Terminated find / -inum 123456 > find.out 2> /dev/null
[vararut@meno ~]$ find ~ -inum 123456 1>find.out 2>/dev/null &
[1] 23200
[vararut@meno ~]$[vararut@meno ~]$ pstree
init─┬─acpid
├─atd
├─auditd─┬─python
│ └─{auditd}
├─cams_watcher.sh───sleep
├─crond
├─dbus-daemon
├─events/0
├─events/1
├─13*[free]
├─gdm-binary───gdm-binary─┬─Xorg
│ └─gdmgreeter
├─generate
├─gpm
├─hald───hald-runner─┬─hald-addon-acpi
│ ├─hald-addon-keyb
│ └─hald-addon-stor
├─hcid
├─httpd───8*[httpd]
├─irqbalance
├─jsvc───jsvc───18*[{jsvc}]
├─khelper
├─klogd
├─krfcommd
├─ksoftirqd/0
├─ksoftirqd/1
├─kthread─┬─aio/0
│ ├─aio/1
│ ├─ata/0
│ ├─ata/1
│ ├─ata_aux
│ ├─cqueue/0
│ ├─cqueue/1
│ ├─kacpid
│ ├─kauditd
│ ├─kblockd/0
│ ├─kblockd/1
│ ├─khubd
│ ├─5*[kjournald]
│ ├─kmpathd/0
│ ├─kmpathd/1
│ ├─kpsmoused
│ ├─kseriod
│ ├─kswapd0
│ ├─2*[pdflush]
│ ├─scsi_eh_0
│ └─vmmemctl
├─ls
├─migration/0
├─migration/1
├─6*[mingetty]
├─mysqld_safe───mysqld───17*[{mysqld}]
├─ntpd
├─portmap
├─sdpd
├─2*[sendmail]
├─sshd─┬─sshd───sshd───bash───4*[generate]
│ ├─sshd───sshd───bash
│ ├─sshd───sshd───bash───mysql
│ ├─sshd───sshd───bash─┬─more
│ │ ├─rusers
│ │ └─4*[telnet]
│ └─sshd───sshd───bash───pstree
├─syslogd
├─udevd
├─vmtoolsd
├─watchdog/0
├─watchdog/1
├─xfs
├─xinetd
└─yum-updatesd
[vararut@meno ~]$[vararut@meno ~]$ ps -o pid,ppid,pgid,sid,comm
PID PPID PGID SID COMMAND
22440 22438 22440 22440 bash
23397 22440 23397 22440 ps
[vararut@meno ~]$[vararut@meno ~]$ ps -o pid,ppid,pgid,sid,comm &
[1] 23428
[vararut@meno ~]$ PID PPID PGID SID COMMAND
22440 22438 22440 22440 bash
23428 22440 23428 22440 ps
[1]+ Done ps -o pid,ppid,pgid,sid,comm
[vararut@meno ~]$Off we go!
[vararut@meno ~]$ exit
logout
Connection to meno.lsbu.ac.uk closed.
➜ ~Good examples of multithreading:
-
Strategy games that can run the rendering logic independently from the AI pathing algorithms. E.g. Starcraft 2.
-
Video rendering applications, as each frame can be rendered individually. E.g. Final Cut Pro.
Single-threaded applications:
-
Node.js uses a single-threaded event loop and handles I/O with asynchronous callbacks.
-
Applications that perform simple calculations on small sample sizes. E.g. a tax calculator.
The hello.sh command does not work since the current directory is not part of the shell $PATH. As such, the shell is not taking it into consideration when considering valid program names. To get the example to work, ./hello.sh should do the trick.
[vararut@meno ~]$ vi hashcheck.pl
[vararut@meno ~]$ perl hashcheck.pl
This is a hash character: #
This is a print statement...
[vararut@meno ~]$