Linux Examples

clone solaris os to new hard disk

admin — Fri, 13 Apr 2012 07:23:52 +0000

Below steps will show you how to clone solaris OS (root partition) to new hard disk. Note:Here I assume you only have one partition on your disks which are c0t0d0s0(old disk) and c0t1d0s0 1.Power-off your Solaris machine (/sbin/init 5) ,and intert your new hard disk 2.Input "boot -s" to boot to single mode

boot -s

3.Go to below directory

cd /usr/platform/`uname -m`/lib/fs/ufs

4.Install bootblocks to your new disk partition using below command

./installboot ./bootblk /dev/rdsk/c0t1d0s0

5.Mount your new hard disk to /mnt (or other directory)

mount /dev/dsk/c0t1d0s0 /mnt

6.Using command ufsdump and ufsstore to dump clone your solaris OS to your new hard disk

cd /mnt

ufsdump 0bf 126 - / | ufsrestore rf -

7.Replace c0t0d0s0 by c0t1d0s0 ,then done,you just cloned your Solaris root partition to your new hard disk

Fix do_ypcall: clnt_call: RPC: Timed out

admin — Thu, 29 Mar 2012 08:33:07 +0000

Error "Fix do_ypcall: clnt_call: RPC: Timed out" normally means a local problem on your system or site network which cause local NIS client can't communicate with NIS server properly. 1.Check your system log messages to see if there are any network related errors,also you can check if your NIS server is pingable . 2.If no dubious problems been found,just use ps command to check if /usr/sbin/nscd is running,start it if not

/usr/sbin/nscd

3.If step 2 still can't fix the problem,go to your NIS server ,then restart your NIS service

/etc/init.d/ypbind restart

Note:Step 3 resolved my "Fix do_ypcall: clnt_call: RPC: Timed out" error

Enlarge swap space in linux

admin — Mon, 26 Mar 2012 06:58:54 +0000

Swap space is very important in linux,if swap space is exhausted the system will crash,below will show to how to enlarge your swap space using file. The same way you can add swap space if you have new disk installed. 1.Use dd command to create a file to act as swap space.(below example create a 16G file name swapfile under /tmp )

#dd if=/dev/zero of=/tmp/swapfile bs=1024 count=16000000

2.setup the file you created in step 1 as swap area

#/sbin/mkswap /tmp/swapfile

3.Enable the file as new swap space

/sbin/swapon /tmp/swapfile

4.If you want your change still take effect after system reboot ,just put the below line to your /etc/fstab file #echo "/tmp/swapfile swap swap defaults 0 0" >> /etc/fstab 5.You can use below command to make sure if your swap space been enlarged(the last line of output)

#free -m

Fix Acroread high cpu usage in linux

admin — Fri, 23 Mar 2012 02:16:21 +0000

I found there was several acroread process which occupy high cpu on our linux vnc servers.I try to upgrade acroreader to the latest version which didn't work. Now I found the reason is we are accessing internet behind company's proxy server and we don't configure the proxy setting for acroread,this is the root cause why acroread occupy high cpu. Method 1 To fix acroread high cpu usage in linux If you are the only user who using the linux machine,after opening acroread, go to Edit-Preferences-Internet then set your proxy server and port in the right pane Method 2 To fix acroread high cpu usage in linux If many users share the same linux machine,just go to your acrobat installation directory ,find file

i686-linux/Reader9/Reader/GlobalPrefs/reader_prefs

Then add below codes (replace proxy address and port to your own) before the last line

/UnixProxyPreferences [/c << /IsDirectConnection [/i 0] /ProxyName [/s (myproxyserver)] /ProxyPort [/i 1080] >>]

Copy disk drive using dd command in linux

admin — Mon, 12 Mar 2012 03:26:40 +0000

We can use dd command to copy the whole disk or one partition in linux, thus we can backup data or for copy OS purpose. Warning:Please make sure you are using the correct "if=" and "of=" parameters,or this will result in data lost Copy whole disk using dd command Below command will copy disk sda to disk sdb

# dd if=/dev/sda of=/dev/sdb

(Note:disk sdb will be formatted,so please make sure these is no useful data on /dev/sdb) Also you can backup your disk and gzip it to image file

# dd if=/dev/hda | gzip > /path/hdaimage.gz

Copy disk partition using dd command Below examples will copy partition sda2 to partition sdb2 .(Please make sure no useful data on sdb2)

#dd if=/dev/sda2 of=/dev/sdb2 bs=4096 conv=notrunc,noerror

The same as copy whole disk,you also can copy your partition to an image file

# dd if=/dev/hda1 | gzip > /path/hda1image.gz

If you need to know more dd command examples,please refer:linux dd command examples

postfix/qmgr status=deferred (delivery temporarily suspended: transport is unavailable)

admin — Wed, 22 Feb 2012 02:44:46 +0000

I have a crontab job to check something every day and send me the results to me via email,but today no email received,and I found below error messages in mail log files

postfix/qmgr status=deferred (delivery temporarily suspended: transport is unavailable)

Then I just try to restart postfix service ,then I also got below error messages

postfix/local[4470]: fatal: open database /etc/postfix/aliases.db: No such file or directory

So the reason was found ,aliases.db file was missing,also my /etc/postfix/aliase file was missing,then I just did below steps to fix the issue

service postfix stop cp /etc/aliases /etc/postfix/aliases newaliases service postfix start

Hope this can help you ,good luck.

linux chkconfig command example

admin — Tue, 21 Feb 2012 04:46:58 +0000

Linux command chkconfig is used to updates and queries runlevel information for system services. SYNOPSIS

chkconfig --list [name] chkconfig --add name chkconfig --del name chkconfig [--level levels] name <on|off|reset> chkconfig [--level levels] name

EXAMPLES: 1.Example to list all the serviced that chkconfig knows

chkconfig --list

2.Example to list a specified service's status ,below command list the status of service

bash-3.2$ chkconfig --list xinetd[root@server001 ~]# chkconfig --list mysqld mysqld 0:off 1:off 2:off 3:off 4:off 5:off 6:off

3.Example to enable a specified service,below command just enable service mysqld

[root@server001 ~]# chkconfig mysqld on [root@server001 ~]# chkconfig --list mysqld mysqld 0:off 1:off 2:on 3:on 4:on 5:on 6:off [root@server001 ~]#

4.Example to enable a service on at specified levels,below command enable mysqld on level 3 and 5

[root@server001 ~]# chkconfig --list mysqld mysqld 0:off 1:off 2:off 3:off 4:off 5:off 6:off [root@server001 ~]# chkconfig --level 35 mysqld on [root@server001 ~]# chkconfig --list mysqld mysqld 0:off 1:off 2:off 3:on 4:off 5:on 6:off [root@server001 ~]#

5.To delete a service from chkconfig management

chconfig --del service

6.To add a service for management by chkconfig(Make sure your service's script locates under /etc/init.d)

chkconfig --add service

Note:About linux run levels

0: shutdown 1:single mode 2:multiple user mode without network 3.multiple user mode with network 4.Non-used,reserved for future 5.multiple user mode with network and gui mode 6.Reboot

linux ssh automatic login without password prompt

admin — Mon, 20 Feb 2012 05:30:46 +0000

If you need to use ssh to login another host every day,maybe you need to know how to use ssh automatic login to other host without password prompt,here we go 1.On the source host,run below command and hit ENTER 3 times to create rsa keys

user001@client[/home/user001]122% ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/user001/.ssh/id_rsa): Created directory '/home/user001/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/user001/.ssh/id_rsa. Your public key has been saved in /home/user001/.ssh/id_rsa.pub. The key fingerprint is: e1:b8:f0:db:09:02:8d:d6:30:59:66:0c:4e:9d:db:8d user001@client

2.ssh to the server with user user002 and create another .ssh directory under user002's home directory

user001@client[/home/user001]125% ssh user002@server mkdir -p .ssh user001@server's password: user001@client[/home/user001]126%

3.Copy the content of .ssh//id_rsa.pub to /home/user002/.ssh and rename to authorized_keys(if existed,just append)

user001@client[/home/user001]3% cat .ssh/id_rsa.pub | ssh user002@server 'cat >>! .ssh/authorized_keys' user001@server's password: user001@client[/home/user001]4%

4.Done.Now you can ssh automatic login without password prompt Note:If the above steps not working,pls try: 1.Change permission of your .ssh directory to 770 using chmod command "chmod 700 .ssh" 2.Change the parent directory of .ssh to 750 3.Replace authorized_keys with authorized_keys2

regular expression examples

admin — Fri, 17 Feb 2012 08:49:12 +0000

Metacharacter regular expression examples

. (dot)

match any single character except line break characters \r and \n

bash-3.2$ cat file.txt
abc
acc
add
bash-3.2$ sed 's/a.c/relaced/' file.txt
relaced
relaced
add
bash-3.2$

[ ]

A bracket expression. Matches a single character that is contained within the brackets

user1@server1[/home/user1/examples]104% ls [a-c]*
a   b   c
user1@server1[/home/user1/examples]105% ls [0-9]*
1   2   3
user1@server1[/home/user1/examples]106% ls [a-c0-9]*
1   2   3   a   b   c
user1@server1[/home/user1/examples]107%

[^ ]

A bracket expression. Matches a single character that is not contained within the brackets

user1@server1[/home/user1/examples]107% ls
./   ../  1    2    3    a    b    c
user1@server1[/home/user1/examples]108% ls [^0-9]*
a   b   c
user1@server1[/home/user1/examples]109% ls [^a-z]*
1   2   3
user1@sdc-master[/home/user1/examples]110% ls [^0-9a-z]*
ls: No match.
user1@server1[/home/user1/examples]111%

^

Matches at the start of the string the regex pattern is applied to, for examples ^# matches comment lines

user1@server1[/home/user1/examples]120% cat examples.txt
This is the first line

#This is the 3rd line
This is the last line
user1@server1[/home/user1/examples]121% grep -v ^# examples.txt
This is the first line

This is the last line
user1@server1[/home/user1/examples]122%

$

Matches at the end of the string the regex pattern is applied to ,for examples ^$ matches empty lines

user1@server1[/home/user/examples]122% grep -v ^$ examples.txt
This is the first line
#This is the 3rd line
This is the last line
user1@server1[/home/user1/examples]123%

*

Matches previous item zero or more times

{n,m}

Matches the preceding element at least m and not more than n times

bash-3.2$ ls
a  aa  aaa  aaaa  aaaaa  examples.txt
bash-3.2$ ls |grep 'a\{4,5\}'
aaaa
aaaaa
bash-3.2$ ls |grep 'a\{1,5\}'
a
aa
aaa
aaaa
aaaaa
examples.txt
bash-3.2$ ls |grep 'a\{2,5\}'
aa
aaa
aaaa
aaaaa
bash-3.2$

Linux sed command examples

admin — Fri, 17 Feb 2012 06:58:24 +0000

Linux sed command is a powerful stream editor for filtering and transforming text.Below will show you several examples,after which you should can use sed to finish most basic tasks. Below file will be used to do the tests in below examples

bash-3.2$ cat example.txt
This is the first line
This is the second line
#This is the 3rd line

This is the 5th line
bash-3.2$

Use sed command to replace matched text with replacement 1.The simplest replace,below example replace the first "is" to "IS" of every line in file example.txt

bash-3.2$ sed 's/is/IS/' example.txt
ThIS is the first line
ThIS is the second line
#ThIS is the 3rd line

ThIS is the 5th line
bash-3.2$

2.Same as above example,but replace all "is" to "IS"

bash-3.2$ sed 's/is/IS/g' example.txt
ThIS IS the first line
ThIS IS the second line
#ThIS IS the 3rd line

ThIS IS the 5th line
bash-3.2$

3.Example to do replace twice.(-e option is needed )

bash-3.2$ sed -e 's/This/THIS/g' -e 's/the/THE/g' example.txt
THIS is THE first line
THIS is THE second line
#THIS is THE 3rd line

THIS is THE 5th line
bash-3.2$

Use sed command to delete the lines matched 1.Remove comments lines

bash-3.2$ sed '/^#/d' example.txt
This is the first line
This is the second line

This is the 5th line
bash-3.2$

2.Remove empty lines

bash-3.2$ sed '/^$/d' example.txt
This is the first line
This is the second line
#This is the 3rd line
This is the 5th line
bash-3.2$

Use sed command to instert append modify

bash-3.2$ sed -e '/first/a\ THIS IS APPENED' example.txt
This is the first line
THIS IS APPENED
This is the second line
#This is the 3rd line

This is the 5th line
bash-3.2$ sed -e '/first/i\ THIS IS INSERTED' example.txt
THIS IS INSERTED
This is the first line
This is the second line
#This is the 3rd line

This is the 5th line
bash-3.2$ sed -e '/first/c\ THIS IS CHANGED' example.txt
THIS IS CHANGED
This is the second line
#This is the 3rd line

This is the 5th line
bash-3.2$

Use sed command to transfer characters Below example will transfer c to x ,d to y ,e to z

bash-3.2$ sed  'y/cde/xyz/' example.txt
This is thz first linz
This is thz szxony linz
#This is thz 3ry linz

This is thz 5th linz
bash-3.2$