Display Past Date and Time

Following are various ways to display a past date and time: 

 

$ date --date='3 seconds ago' 

Thu Jan  1 08:27:00 PST 2009 

 

$ date --date="1 day ago" 

Wed Dec 31 08:27:13 PST 2008 

 

$ date --date="1 days ago" 

Wed Dec 31 08:27:18 PST 2008 

 

$ date --date="1 month ago" 

Mon Dec  1 08:27:23 PST 2008 

 

$ date --date="1 year ago" 

Tue Jan  1 08:27:28 PST 2008 

 

$ date --date="yesterday" 

Wed Dec 31 08:27:34 PST 2008 

 

$ date --date="10 months 2 day ago" 

Thu Feb 28 08:27:41 PST 2008 

Display Current Date and Time in a Specific Format

Following are different ways of displaying the current date and time in 

various formats: 

$ date 

Thu Jan  1 08:19:23 PST 2009 

 

$ date --date="now" 

Thu Jan  1 08:20:05 PST 2009 

 

$ date --date="today" 

Thu Jan  1 08:20:12 PST 2009 

 

$ date --date='1970-01-01 00:00:01 UTC +5 hours' +%s 

18001 

 

$ date '+Current Date: %m/%d/%y%nCurrent Time:%H:%M:%S' 

Current Date: 01/01/09 

Current Time:08:21:41 

 

$ date +"%d-%m-%Y" 

01-01-2009 

 

$ date +"%d/%m/%Y" 

01/01/2009 

 

$ date +"%A,%B %d %Y" 

Thursday,January 01 2009 

 

Following are the different format options you can pass to the date 

command: 

o    %D   date (mm/dd/yy) 

o    %d   day of month (01..31) 

o    %m   month (01..12) 

o    %y   last two digits of year (00..99) 

o    %a   locale’s abbreviated weekday name (Sun..Sat) 

o    %A   locale’s full weekday name, variable length 

(Sunday..Saturday) 

o    %b   locale’s abbreviated month name (Jan..Dec) 

o    %B   locale’s full month name, variable length 

(January..December) 

o    %H   hour (00..23) 

o    %I   hour (01..12) 

o    %Y   year (1970…) 

 

Set Hardware Date and Time

Before setting the hardware date and time, make sure the OS date and time 

is set appropriately as shown in the set-system-date-and-time

 

Set the hardware date and time based on the system date as shown below: 

 

# hwclock –systohc 

 

# hwclock --systohc –utc 

 

Use hwclock without any parameter, to view the current hardware date and 

time: 

 

# hwclock 

 

Check the clock file to verify whether the system is set for UTC: 

 

# cat /etc/sysconfig/clock 

 

ZONE="America/Los_Angeles" 

UTC=false 

ARC=false 

Set System Date and Time

To change the system date use:  

 

# date {mmddhhmiyyyy.ss} 

 

o    mm – Month 

o    dd – Date 

o    hh – 24 hour format 

o    mi – Minutes 

o    yyyy – Year 

o    ss – seconds 

 

For example, to set system date to Jan 31st 2008, 10:19 p.m, 53 seconds 

 

# date 013122192009.53 

 

You can also change system date using set argument as shown below. 

 

# date 013122192009.53 

 

# date +%Y%m%d -s "20090131" 

 

# date -s "01/31/2009 22:19:53"  

 

# date -s "31 JAN 2009 22:19:53" 

 

# date set="31 JAN 2009 22:19:53" 

 

To set the time only: 

 

# date +%T -s "22:19:53" 

 

# date +%T%p -s "10:19:53PM" 

Use “shopt -s cdspell” to automatically correct mistyped directory names on cd

Use shopt -s cdspell to correct the typos in the cd command automatically as 

shown below. If you are not good at typing and make lot of mistakes, this will 

be very helpful. 

 

# cd /etc/mall 

-bash: cd: /etc/mall: No such file or directory 

 

# shopt -s cdspell 

 

# cd /etc/mall 

 

# pwd 

/etc/mail 

 

[Note: By mistake, when I typed mall instead of mail, 

          cd corrected it automatically] 

Use dirs, pushd and popd to manipulate directory stack

You can use directory stack to push directories into it and later pop directory 

from the stack. Following three commands are used in this example. 

o    dirs: Display the directory stack 

o    pushd: Push directory into the stack 

o    popd: Pop directory from the stack and cd to it 

Dirs will always print the current directory followed by the content of the 

stack. Even when the directory stack is empty, dirs command will still print 

only the current directory as shown below. 

# popd 

-bash: popd: directory stack empty 

 

# dirs 

~ 

 

# pwd 

/home/ramesh 

How to use pushd and popd? Let us first create some temporary directories 

and push them to the directory stack as shown below. 

 

 

# mkdir /tmp/dir1 

# mkdir /tmp/dir2 

# mkdir /tmp/dir3 

# mkdir /tmp/dir4 

 

# cd /tmp/dir1 

# pushd . 

 

# cd /tmp/dir2 

# pushd . 

 

# cd /tmp/dir3 

# pushd . 

 

# cd /tmp/dir4 

# pushd . 

# dirs 

/tmp/dir4 /tmp/dir4 /tmp/dir3 /tmp/dir2 /tmp/dir1 

 

[Note: The first directory (/tmp/dir4) of the dir 

command output is always the current directory and not 

the content from the stack.] 

 

# dirs 

/tmp/dir4 /tmp/dir4 /tmp/dir3 /tmp/dir2 /tmp/dir1 

 

[Note: The first directory (/tmp/dir4) of the dir 

command output is always the current directory and not 

the content from the stack.] 

 

At this stage, the directory stack contains the following directories: 

 

/tmp/dir4 

/tmp/dir3 

/tmp/dir2 

/tmp/dir1 

 

The last directory that was pushed to the stack will be at the top. When you 

perform popd, it will cd to the top directory entry in the stack and remove it 

from the stack. As shown above, the last directory that was pushed into the 

stack is /tmp/dir4. So, when we do a popd, it will cd to the /tmp/dir4 and 

remove it from the directory stack as shown below. 

 

# popd 

# pwd 

/tmp/dir4 

 

[Note: After the above popd, directory Stack Contains: 

/tmp/dir3 

/tmp/dir2 

/tmp/dir1] 

 

# popd 

# pwd 

/tmp/dir3 

 

[Note: After the above popd, directory Stack Contains: 

/tmp/dir2 

/tmp/dir1] 

 

# popd 

# pwd 

/tmp/dir2 

 

[Note: After the above popd, directory Stack Contains: 

/tmp/dir1] 

 

# popd 

# pwd 

/tmp/dir1 

 

[Note: After the above popd, directory Stack is empty!] 

 

# popd 

-bash: popd: directory stack empty 

Perform mkdir and cd using a single command

Sometimes when you create a new directory, you may cd to the new directory 

immediately to perform some work as shown below. 

# mkdir -p /tmp/subdir1/subdir2/subdir3 

 

# cd /tmp/subdir1/subdir2/subdir3 

 

# pwd 

/tmp/subdir1/subdir2/subdir3 

Wouldn’t it be nice to combine both mkdir and cd in a single command? Add 

the following to the .bash_profile and re-login. 

$ vi .bash_profile 

 

function mkdircd () { mkdir -p "$@" && eval cd "\"\$$#\""; } 

Now, perform both mkdir and cd at the same time using a single command as 

shown below: 

# mkdircd /tmp/subdir1/subdir2/subdir3 

 

[Note: This creates the directory and cd to it automatically] 

 

# pwd 

/tmp/subdir1/subdir2/subdir3 

OK CU next time 

Use cd alias to navigate up the directory effectively

When you are navigating up a very long directory structure, you may be using 

cd ..\..\ with multiple ..\’s depending on how many directories you want to go 

up as shown below. 

# mkdir -p 

/tmp/very/long/directory/structure/that/is/too/deep 

 

# cd /tmp/very/long/directory/structure/that/is/too/deep 

 

# pwd 

/tmp/very/long/directory/structure/that/is/too/deep 

 

# cd ../../../../ 

 

# pwd 

/tmp/very/long/directory/structure 

Instead of executing cd ../../../.. to navigate four levels up, use one of the 

following three alias methods: 

 

Method 1: Navigate up the directory using “..n” 

In the example below, ..4 is used to go up 4 directory level, ..3 to go up 3 

directory level, ..2 to go up 2 directory level. Add the following alias to your 

~/.bash_profile and re-login. 

alias ..="cd .." 

alias ..2="cd ../.." 

alias ..3="cd ../../.." 

alias ..4="cd ../../../.." 

alias ..5="cd ../../../../.." 

 

# cd 

/tmp/very/long/directory/structure/that/is/too/deep 

 

# ..4 

[Note: use ..4 to go up 4 directory level] 

 

# pwd 

/tmp/very/long/directory/structure/

Method 2: Navigate up the directory using only dots 

In the example below, ….. (five dots) is used to go up 4 directory level.  

Typing 5 dots to go up 4 directory structure is really easy to remember, as 

when you type the first two dots, you are thinking “going up one directory”, 

after that every additional dot, is to go one level up. So, use …. (four dots) to 

go up 3 directory level and .. (two dots) to go up 1 directory level. Add the 

following alias to your ~/.bash_profile and re-login for the ….. (five dots) to 

work properly. 

alias ..="cd .." 

alias ...="cd ../.." 

alias ....="cd ../../.." 

alias .....="cd ../../../.." 

alias ......="cd ../../../../.." 

 

# cd /tmp/very/long/directory/structure/that/is/too/deep 

 

# ..... 

[Note: use ..... (five dots) to go up 4 directory level] 

 

# pwd 

/tmp/very/long/directory/structure/ 

Method 3: Navigate up the directory using cd followed by consecutive dots 

In the example below, cd….. (cd followed by five dots) is used to go up 4 

directory level. Making it 5 dots to go up 4 directory structure is really easy to 

remember, as when you type the first two dots, you are thinking “going up 

one directory”, after that every additional dot, is to go one level up. So, use 

cd…. (cd followed by four dots) to go up 3 directory level and cd… (cd 

followed by three dots) to go up 2 directory level. Add the following alias to 

your ~/.bash_profile and re-login for the above cd….. (five dots) to work 

properly. 

alias cd..="cd .." 

alias cd...="cd ../.." 

alias cd....="cd ../../.." 

alias cd.....="cd ../../../.." 

alias cd......="cd ../../../../.." 

 

# cd /tmp/very/long/directory/structure/that/is/too/deep 

 

# cd..... 

[Note: use cd..... to go up 4 directory level] 

 

# pwd 

/tmp/very/long/directory/structure 

Method 5: Navigate up the directory using cd followed by number 

In the example below, cd4 (cd followed by number 4) is used to go up 4 

directory level.  

 

alias cd1="cd .." 

alias cd2="cd ../.." 

alias cd3="cd ../../.." 

alias cd4="cd ../../../.." 

alias cd5="cd ../../../../.." 

CU next tutorial 

Use CDPATH to define the base directory for cd command

If you are frequently performing cd to subdirectories of a specific parent 

directory, you can set the CDPATH to the parent directory and perform cd to 

the subdirectories without giving the parent directory path as explained 

below. 

 

[ramesh@dev-db ~]# pwd 

/home/ramesh 

 

[ramesh@dev-db ~]# cd mail 

-bash: cd: mail: No such file or directory 

 

[Note: This is looking for mail directory under current 

directory] 

 

[ramesh@dev-db ~]# export CDPATH=/etc 

[ramesh@dev-db ~]# cd mail 

/etc/mail 

 

[Note: This is looking for mail under /etc and not 

under current directory] 

 

[ramesh@dev-db /etc/mail]# pwd 

/etc/mail 

 

To make this change permanent, add export CDPATH=/etc to your 

~/.bash_profile 

Similar to the PATH variable, you can add more than one directory entry in 

the CDPATH variable, separating them with : , as shown below. 

 

export CDPATH=.:~:/etc:/var 

 

This hack can be very helpful under the following situations: 

o    Oracle DBAs frequently working under $ORACLE_HOME, can set 

the CDPATH variable to the oracle home 

o    Unix sysadmins frequently working under /etc, can set the 

CDPATH variable to /etc 

o    Developers frequently working under project directory 

/home/projects, can set the CDPATH variable to /home/projects 

o    End-users frequently accessing the subdirectories under their 

home directory, can set the CDPATH variable to ~ (home 

directory)  

Linux Kernel 2.6.37 Released

Another year has passed and thus another new kernel release by Linus. As expected, Linus finally released the final Linux Kernel 2.6.37 as of today after having several RC release before Christmas and eventually it didn't make it as Christmas gift for everyone, so let's just consider this as a new year gift. Fair enough.

At this moment, the link on Kernel.org hasn't showed up, but you can still download it by clicking on this link. More information about what has been included in this release in human-friendly language can be seen inKernelNewbies (give some tim to update the page as the kernel has just been released).

Now, time to look for patches for NVidia and VMWare if i wanted to compile this kernel 

open port in microtik

Mikrotik on setting the default to open five ports to access the server, to see the open ports can use the command: 

/ip service pr
It will look something like this 

 

01	[admin@MikroTik] > /ip service pr

02	Flags: X - disabled, I - invalid

03	#   NAME               PORT  ADDRESS

04	0   telnet             23    0.0.0.0/0

05	1   ftp                21    0.0.0.0/0

06	2   www                80    0.0.0.0/0

07	3   ssh                22    0.0.0.0/0

08	4 X www-ssl            443   0.0.0.0/0

09	5 X api                8728  0.0.0.0/0

10	6   winbox             8291  0.0.0.0/0

suppose we want to close the ports for telnet, the command used is: 

 

 

1	/ip service set telnet disabled=yes

ketik :

 

1	/ip service pr

and shall appear the sign x in the telnet, as in www-ssl and API. 
want to open the port if disabled = no 

 

1	/ip service set telnet disabled=yes

   Cwim