Howtos Archives - Page 24 of 24

Installing vim editor.

Posted on July 29, 2012July 29, 2012 by David Saliba

To install vim

[root@testarossa-00-0c-29-47-8f-35 ~]# yum whatprovides vim-enhanced
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.crazynetwork.it
 * epel: fr2.rpmfind.net
 * extras: mirror.crazynetwork.it
 * updates: mirror.crazynetwork.it
2:vim-enhanced-7.0.109-7.el5.i386 : A version of the VIM editor which includes
                                  : recent enhancements.
Repo        : base
Matched from:

[root@testarossa-00-0c-29-47-8f-35 ~]# yum install vim-enhanced-7.0.109-7.el5.i386 
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.crazynetwork.it
 * epel: ftp.uni-koeln.de
 * extras: mirror.crazynetwork.it
 * updates: mirror.crazynetwork.it
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package vim-enhanced.i386 2:7.0.109-7.el5 set to be updated
--> Processing Dependency: vim-common = 2:7.0.109-7.el5 for package: vim-enhanced
--> Running transaction check
---> Package vim-common.i386 2:7.0.109-7.el5 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package              Arch         Version                   Repository    Size
================================================================================
Installing:
 vim-enhanced         i386         2:7.0.109-7.el5           base         1.2 M
Installing for dependencies:
 vim-common           i386         2:7.0.109-7.el5           base         6.4 M

Transaction Summary
================================================================================
Install       2 Package(s)
Upgrade       0 Package(s)

Total download size: 7.7 M
Is this ok [y/N]: y
Downloading Packages:
(1/2): vim-enhanced-7.0.109-7.el5.i386.rpm               | 1.2 MB     00:03     
(2/2): vim-common-7.0.109-7.el5.i386.rpm                 | 6.4 MB     00:18     
--------------------------------------------------------------------------------
Total                                           344 kB/s | 7.7 MB     00:22     
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing     : vim-common                                               1/2 
  Installing     : vim-enhanced                                             2/2 

Installed:
  vim-enhanced.i386 2:7.0.109-7.el5                                             

Dependency Installed:
  vim-common.i386 2:7.0.109-7.el5                                               

Complete!
[root@testarossa-00-0c-29-47-8f-35 ~]#

VIM cheat sheet

Posted on July 29, 2012July 29, 2012 by David Saliba

< The list of Vim commands >

Working with files
Vim command	Action
:e filename	Open a new file. You can use the Tab key for automatic file name completion, just like at the shell command prompt.
:w filename	Save changes to a file. If you don’t specify a file name, Vim saves as the file name you were editing. For saving the file under a different name, specify the file name.
:q	Quit Vim. If you have unsaved changes, Vim refuses to exit.
:q!	Exit Vim without saving changes.
:wq	Write the file and exit.
: x	Almost the same as :wq, write the file and exit if you’ve made changes to the file. If you haven’t made any changes to the file, Vim exits without writing the file.
Moving around in the file
These Vim commands and keys work both in command mode and visual mode.
Vim command	Action
j or Up Arrow	Move the cursor up one line.
k or Down Arrow	Down one line.
h or Left Arrow	Left one character.
l or Right Arrow	Right one character.
e	To the end of a word.
E	To the end of a whitespace-delimited word.
b	To the beginning of a word.
B	To the beginning of a whitespace-delimited word.
0	To the beginning of a line.
^	To the first non-whitespace character of a line.
$	To the end of a line.
H	To the first line of the screen.
M	To the middle line of the screen.
L	To the the last line of the screen.
:n	Jump to line number n. For example, to jump to line 42, you’d type :42
Inserting and overwriting text
Vim command	Action
i	Insert before cursor.
I	Insert to the start of the current line.
a	Append after cursor.
A	Append to the end of the current line.
o	Open a new line below and insert.
O	Open a new line above and insert.
C	Change the rest of the current line.
r	Overwrite one character. After overwriting the single character, go back to command mode.
R	Enter insert mode but replace characters rather than inserting.
The ESC key	Exit insert/overwrite mode and go back to command mode.
Deleting text
Vim command	Action
x	Delete characters under the cursor.
X	Delete characters before the cursor.
dd or :d	Delete the current line.
Entering visual mode
Vim command	Action
v	Start highlighting characters. Use the normal movement keys and commands to select text for highlighting.
V	Start highlighting lines.
The ESC key	Exit visual mode and return to command mode.
Editing blocks of text
Note: the Vim commands marked with (V) work in visual mode, when you’ve selected some text. The other commands work in the command mode, when you haven’t selected any text.
Vim command	Action
~	Change the case of characters. This works both in visual and command mode. In visual mode, change the case of highlighted characters. In command mode, change the case of the character uder cursor.
> (V)	Shift right (indent).
< (V)	Shift left (de-indent).
c (V)	Change the highlighted text.
y (V)	Yank the highlighted text. In Windows terms, “copy the selected text to clipboard.”
d (V)	Delete the highlighted text. In Windows terms, “cut the selected text to clipboard.”
yy or :y or Y	Yank the current line. You don’t need to highlight it first.
dd or :d	Delete the current line. Again, you don’t need to highlight it first.
p	Put the text you yanked or deleted. In Windows terms, “paste the contents of the clipboard”. Put characters after the cursor. Put lines below the current line.
P	Put characters before the cursor. Put lines above the current line.
Undo and redo
Vim command	Action
u	Undo the last action.
U	Undo all the latest changes that were made to the current line.
Ctrl + r	Redo.
Search
Vim command	Action
/pattern	Search the file for pattern.
n	Scan for next search match in the same direction.
N	Scan for next search match but opposite direction.
Replace
Vim command	Action
:rs/foo/bar/a	Substitute foo with bar. r determines the range and a determines the arguments.
The range (r) can be
nothing	Work on current line only.
number	Work on the line whose number you give.
%	The whole file.
Arguments (a) can be
g	Replace all occurrences in the line. Without this, Vim replaces only the first occurrences in each line.
i	Ignore case for the search pattern.
I	Don’t ignore case.
c	Confirm each substitution. You can type y to substitute this match, n to skip this match, a to substitute this and all the remaining matches (“Yes to all”), and q to quit substitution.
Examples
:452s/foo/bar/	Replace the first occurrence of the word foo with bar on line number 452.
:s/foo/bar/g	Replace every occurrence of the word foo with bar on current line.
:%s/foo/bar/g	Replace every occurrence of the word foo with bar in the whole file.
:%s/foo/bar/gi	The same as above, but ignore the case of the pattern you want to substitute. This replaces foo, FOO, Foo, and so on.
:%s/foo/bar/gc	Confirm every substitution.
:%s/foo/bar/c	For each line on the file, replace the first occurrence of foo with bar and confirm every substitution.

Original Post : Here at tuXfiles.org

List interfaces and IPs neatly

Posted on July 29, 2012 by David Saliba

The following command gives a neat list of the Devices and their IPs / details without all the gruesome details.

ifconfig | egrep  "Link|inet"

A sample result would be:

[root@testarossa-00-0c-29-47-8f-35 vm]# ifconfig | egrep "Link|inet"
eth0 Link encap:Ethernet HWaddr 00:0C:29:47:8F:2B 
 inet addr:192.168.47.135 Bcast:192.168.47.255 Mask:255.255.255.0
eth1 Link encap:Ethernet HWaddr 00:0C:29:47:8F:35 
 inet addr:192.168.1.71 Bcast:192.168.1.255 Mask:255.255.255.0
lo Link encap:Local Loopback 
 inet addr:127.0.0.1 Mask:255.0.0.0
peth1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF 
vif0.1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF 
vif4.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF 
virbr0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF 
 inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
xenbr1 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF 
[root@testarossa-00-0c-29-47-8f-35 vm]#

Slash notation lookup table

Posted on July 28, 2012July 28, 2012 by David Saliba

Total-addresses: how many unique addresses can be represented. To determine how many are available to be assigned to devices you need to subtract 2 from the provided number to allow for the ‘network’ and ‘broadcast’ address. A further one of these may need to be assigned to a router.

Net bits	Subnet mask	Total-addresses
/20	255.255.240.0	4096
/21	255.255.248.0	2048
/22	255.255.252.0	1024
/23	255.255.254.0	512
/24	255.255.255.0	256
/25	255.255.255.128	128
/26	255.255.255.192	64
/27	255.255.255.224	32
/28	255.255.255.240	16
/29	255.255.255.248	8
/30	255.255.255.252	4

eg: 192.168.1.0/25 would include all address between 192.168.1.0 and 192.168.1.127.

eg: 192.168.1.128/25 would include all address between 192.168.1.128 and 192.168.1.255

Virtual Loopback Filesystem: Building A Linux Filesystem From An Ordinary File

Posted on July 21, 2012July 25, 2012 by David Saliba

Unix / Linux has a great inbuilt simplicity to it where you can create file systems on any block set . Now .. a file is a block set so technically and truly at it’s core a file system can be built on a file and mounted :

I need a 100MB partition for some tests :

Using ofcourse Google as my calculator {pfsssst !!! obviously .. DUH}. I tried 100MB / 512 bytes and got

(100 megabytes) / (512 bytes) = 204 800

[root@localhost admin]# dd if=/dev/zero of=disk-image count=204800
204800+0 records in
204800+0 records out
104857600 bytes (105 MB) copied, 41.8633 s, 2.5 MB/s
[root@localhost admin]#

This command leaves me with a 105MB file in which to create my etx3 fs like so :

[root@localhost admin]# ls -al disk-image 
-rw-r--r--. 1 root root 104857600 Jul 13 18:17 disk-image
[root@localhost admin]#

Once this file is created I will use the mkfs to format over the disk-image file:

[root@localhost admin]# /sbin/mkfs -t ext3 -q disk-image
disk-image is not a block special device.
Proceed anyway? (y,n) y
[root@localhost admin]#

Thus a filesystem now resides on my file named disk-image.

We can now use a loopback device to mount the disk-image anywhere we need it:

[root@localhost admin]# mkdir /mnt/test1
[root@localhost admin]# mount
/dev/sda2 on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
/dev/sda1 on /boot type ext4 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
[root@localhost admin]# mount disk-image /mnt/test1/
mount: /home/admin/disk-image is not a block device (maybe try `-o loop'?)
[root@localhost admin]# mount -o loop disk-image /mnt/test1/
[root@localhost admin]# cd /mnt/test1/
[root@localhost test1]# ls
lost+found
[root@localhost test1]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2              18G  2.7G   14G  16% /
tmpfs                 504M  768K  503M   1% /dev/shm
/dev/sda1             291M   50M  226M  19% /boot
/home/admin/disk-image
                       97M  5.6M   87M   7% /mnt/test1

[root@localhost test1]# touch file1
[root@localhost test1]# mkdir -p top1/bottom1
[root@localhost test1]# tree
.
+-- file1
+-- lost+found
+-- top1
    +-- bottom1

3 directories, 1 file
[root@localhost test1]#

Thus a new file system is now running inside the file.

Backing up that file or moving it to another system would entail now quiescing any applications/scripts working with the file, unmounting the loopback fs system, doing your thing then replace all the cards on the deck 🙂

How do I enable the Extra Packages for Enterprise Linux (EPEL) repository on Amazon AMI?

Posted on July 9, 2012July 10, 2012 by David Saliba

EPEL (Extra Packages for Enterprise Linux) is a repository of (as the name implies) A collection of packages not directly released with the given linux distribution release cycle. By default these packages are not available but all the wiring in the amazon AMI instance is already done all one needs to do is enable it. To do so check the two following ways.

Modify /etc/yum.repos.d/epel.repo.

Under the section marked [epel], change enabled=0 to enabled=1.

To temporarily enable the EPEL 6 repository, use the yum enablerpo option :

--enablerepo=epel.

Example

yum search iperf  --enablerepo=epel

This will return :

That’s it short and sweet 😛

Tar a folder or entire system through ssh

Posted on July 8, 2012April 25, 2016 by David Saliba

We all had the problem of needing to backup a folder or an entire system from a machine before decommissioning or as a postfix backup solution only to find tarring aint gonna work cause you have very little space left. Also there are folders you want to avoid tarring since they contain logs or system virtual folders that you want to skip.

So you need to get a tar from a machine have very little space left and you need to pull all the files in a compressed fashion; the following command calls a backup as root through ssh using tar on the source machine and skips the folders you do not want :

ssh root@pollux "tar zcvf - --exclude=/proc/* --exclude=/dev/* --exclude=/sys/* --exclude=/var/logs/* /" > /root/backup/pollux.fullandfinal.$(date '+%Y-%m-%d-%k-%M').tar.gz

The result of the above command is a backup of the / compressed at source piped through console through ssh back to your local / backup repo machine in .tar.gz format leaving out the rubbish thanks to the :

- --exclude=/proc/* --exclude=/dev/* --exclude=/sys/* --exclude=/var/logs/*

section. Note the “– —” the first – indicates extended parameters and –except leaves out any match to the path.

There you go one command to back them all.

(this could be easily bash-ed and cron-ed to produce a decent makeshift backup tool.

To check out the contents of the tar file you can use

tar -tvzf <archive.tar.gz>

This will show you the contents and leave a fail exit code in a bash script.

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