Month: January 2017

Linux for DBA: Basic “vi” Editor Tutorial

 

UNIX/Linux “vi” is a very powerful text editor, unfortunately at the beginning the utilization can be difficult. To help our memory, I wrote this post.

This is NOT an exhaustive guide, but a concentrate of the most useful commands and options.

 

vi Operation Modes:

Command mode: allows to execute administrative tasks (run command, move cursor, serch/replace string, save, etc.). This is the default mode when started.
When Insert mode is active press ESC to revert to Command mode.

Insert mode:  enables to write into the file. To switch to Insert mode you simply type i.

 

To open a file in edit mode:

# vi filename

 

Basic Moving commands

Enable Command mode (pressing ESC twice)
j  -- Cursor down one line
k  -- Cursor up one line
h  -- Cursor left one line
l  -- Cursor right one line
Multiple lines/columns move ex.: 5h -- Cursor 5 move left

$   -- Cursor at the end of the line.
0   -- Cursor at the beginning of the line. Same than |
b   -- Cursor at the next word.
w   -- Cursor at the next word.
G   -- Cursor at the end of the file.
1G  -- Cursor at the beginning of the line.
:,4 -- Cursor at the 4th line.

 

Basic Editing commands

Enable Insert mode (pressing i)

a  -- Insert text after the cursor location. 
A  -- Insert text at the end of the line. 
i  -- Insert text before the cursor location. 
I  -- Insert text at the beginning of the line. 
o  -- Insert a new line below the cursor location. 
O  -- Insert a new line above the cursor location.
dd -- Delete the current line.
x  -- Delete the character under the cursor location.
cw -- Change the word under the cursor location.
r  -- Replace the character under the cursor location.
R  -- Replace multiple characters starting from the cursor location. ESC to stop the replacement.
yy -- Copy the current line.
yw -- Copy the current word.
p  -- Paste the copied text before the current cursor location
P  -- Paste the copied text after the current cursor location

 

Basic Search and  Replace options

Enable Command mode (pressing ESC twice)

:set ic -- Ingnore case when searching.
:set nu -- Disply line number on the left side.
:%s/<search_string>/<replacement_string>/g -- Global search and replace

 

Exiting from vi

:q  -- Exit without Saving
:q! -- Force Exit without Saving
:w  -- Save the file
:wq -- Save & Exit

 

 

Linux for DBA: Red Hat 7 removed and deprecated few commands

 

Linux Red Hat 7 and derived distributions have removed and deprecated few commands. Among them netstat and lsof,  which are popular between DBAs.

This post shows how to obtain the network information in compliance with the new OS commands.

 

NETSTAT

netstat – is now considered obsolete, and it has been replaced by ss:

root@oel7qa01:~$ ss -t
State       Recv-Q Send-Q       Local Address:Port           Peer Address:Port 
ESTAB       0      0            192.168.1.117:54360          192.0.78.23:https 
ESTAB       0      0            192.168.1.117:48538          198.252.206.25:https 
ESTAB       0      0            192.168.1.117:42744          162.125.18.133:https 
ESTAB       0      0            127.0.0.1:38106              127.0.0.1:52828 
ESTAB       0      0            192.168.1.117:54008          192.0.78.23:https 
CLOSE-WAIT  1      0            192.168.1.117:60054          51.2xx.195.xx:https 
ESTAB       0      0            192.168.1.117:47904          198.2xx.202.xx:https 
CLOSE-WAIT  32     0            192.168.1.117:56724          108.1xx.172.xxx:https 
CLOSE-WAIT  32     0            192.168.1.117:47050          54.xx.201.xxx:https 
ESTAB       0      0            127.0.0.1:52828              127.0.0.1:38106 
CLOSE-WAIT  32     0            192.168.1.117:44728          108.1xx.xxx.6x:https 
ESTAB       0      0            192.168.1.117:41848          195.xxx.2xx.xxx:https 
ESTAB       0      0            192.168.7.50:41268           192.168.7.60:ssh 
ESTAB       0      0            2a02:1203:ecb0:7b80:58d9:f6e5:90d9:f266:53060 2a00:1450:400e:800::2003:https 
ESTAB       0      0            2a02:1203:ecb0:7b80:58d9:f6e5:90d9:f266:37978 2a00:1450:400a:804::200e:https 
ESTAB       0      0            2a02:1203:ecb0:7b80:58d9:f6e5:90d9:f266:51682 2a00:1450:400a:804::2003:https

 

The netstat -r information is now provided by the command ip route:

--Until Red Hat 6
[root@oel7node00 ~]# netstat -r
Kernel IP routing table
Destination     Gateway     Genmask        Flags  MSS Window irtt Iface
default         gateway     0.0.0.0        UG       0 0         0 enp0s8
default         gateway     0.0.0.0        UG       0 0         0 enp0s3
10.0.2.0        0.0.0.0     255.255.255.0  U        0 0         0 enp0s3
172.31.100.0    0.0.0.0     255.255.255.0  U        0 0         0 enp0s9
192.168.7.0     0.0.0.0     255.255.255.0  U        0 0         0 enp0s8
192.168.200.0   0.0.0.0     255.255.255.0  U        0 0         0 enp0s10


--As of Red Hat 7
[root@oel7node00 ~]# ip route
default via 192.168.7.50 dev enp0s8 proto static metric 100 
default via 10.0.2.2 dev enp0s3 proto static metric 101 
10.0.2.0/24 dev enp0s3 proto kernel scope link src 10.0.2.15 metric 100 
172.31.100.0/24 dev enp0s9 proto kernel scope link src 172.31.100.10 metric 100 
192.168.7.0/24 dev enp0s8 proto kernel scope link src 192.168.7.60 metric 100 
192.168.200.0/24 dev enp0s10 proto kernel scope link src 192.168.200.10 metric 100

 

The netstat -i information is now provided by the command ip route:

--Until Red Hat 6
[root@oel7node00 ~]# netstat -i
Kernel Interface table
Iface     MTU    RX-OK RX-ERR RX-DRP RX-OVR   TX-OK TX-ERR TX-DRP TX-OVR Flg
enp0s3   1500       66      0      0 0           72      0      0      0 BMRU
enp0s8   1500     1201      0      0 0          687      0      0      0 BMRU
enp0s9   1500        2      0      0 0            2      0      0      0 BMRU
enp0s10  1500        2      0      0 0            7      0      0      0 BMRU
lo      65536        0      0      0 0            0      0      0      0 LRU


--As of Red Hat 7
[root@oel7node00 ~]# ip -s link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT 
 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
 RX: bytes packets errors dropped overrun mcast 
 0         0       0      0       0       0 
 TX: bytes packets errors dropped carrier collsns 
 0         0       0      0       0       0 
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
 link/ether 08:00:27:4c:63:1b brd ff:ff:ff:ff:ff:ff
 RX: bytes packets errors dropped overrun mcast 
 5860      66      0      0       0       0 
 TX: bytes packets errors dropped carrier collsns 
 5662      72      0      0       0       0 
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
 link/ether 08:00:27:2b:ca:66 brd ff:ff:ff:ff:ff:ff
 RX: bytes packets errors dropped overrun mcast 
 131645    1237    0      0       0       0 
 TX: bytes packets errors dropped carrier collsns 
 223396    704     0      0       0       0 
4: enp0s9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
 link/ether 08:00:27:cc:fb:2e brd ff:ff:ff:ff:ff:ff
 RX: bytes packets errors dropped overrun mcast 
 120        2      0      0       0       0 
 TX: bytes packets errors dropped carrier collsns 
 120       2       0      0       0       0 
5: enp0s10: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
 link/ether 08:00:27:6f:7e:47 brd ff:ff:ff:ff:ff:ff
 RX: bytes packets errors dropped overrun mcast 
 120       2       0      0       0       0 
 TX: bytes packets errors dropped carrier collsns 
 558       7       0      0       0       0

 

The netstat -g information is now provided by the command ip maddr:

--Until Red Hat 6
[root@oel7node00 ~]# netstat -g
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 all-systems.mcast.net
enp0s3 1 all-systems.mcast.net
enp0s8 1 all-systems.mcast.net
enp0s9 1 all-systems.mcast.net
enp0s10 1 all-systems.mcast.net
lo 1 ff02::1
lo 1 ff01::1
enp0s3 1 ff02::1
enp0s3 1 ff01::1
enp0s8 1 ff02::1
enp0s8 1 ff01::1
enp0s9 1 ff02::1
enp0s9 1 ff01::1
enp0s10 1 ff02::1
enp0s10 1 ff01::1


--As of Red Hat 7
[root@oel7node00 ~]# ip maddr
1: lo
 inet 224.0.0.1
 inet6 ff02::1
 inet6 ff01::1
2: enp0s3
 link 01:00:5e:00:00:01
 inet 224.0.0.1
 inet6 ff02::1
 inet6 ff01::1
3: enp0s8
 link 01:00:5e:00:00:01
 inet 224.0.0.1
 inet6 ff02::1
 inet6 ff01::1
4: enp0s9
 link 01:00:5e:00:00:01
 inet 224.0.0.1
 inet6 ff02::1
 inet6 ff01::1
5: enp0s10
 link 01:00:5e:00:00:01
 inet 224.0.0.1
 inet6 ff02::1
 inet6 ff01::1

 

 

LSOF

lsof is no longer included on the OS minimal installation, but not considered as obsolete or deprecated, therefore simply use yun to intall the missing package:

[root@oel7node00 ~]# which lsof
/usr/bin/which: no lsof in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)

[root@oel7node00 ~]# yum install lsof
Loaded plugins: ulninfo
Resolving Dependencies
--> Running transaction check
---> Package lsof.x86_64 0:4.87-4.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

=========================================================================================================================================================
 Package Arch Version Repository Size
=========================================================================================================================================================
Installing:
 lsof x86_64 4.87-4.el7 ol7_latest 330 k

Transaction Summary
=========================================================================================================================================================
Install 1 Package

Total download size: 330 k
Installed size: 927 k
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
lsof-4.87-4.el7.x86_64.rpm | 330 kB 00:00:00 
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
 Installing : lsof-4.87-4.el7.x86_64 1/1 
 Verifying : lsof-4.87-4.el7.x86_64 1/1

Installed:
 lsof.x86_64 0:4.87-4.el7

Complete!