Other useful commands
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Other useful commands. netstat ps tail kill. netstat. Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. Examples: which services are on [[email protected] coursefiles]# netstat --listen

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Other useful commands

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Other useful commands

Other useful commands

  • netstat

  • ps

  • tail

  • kill


Netstat

netstat

Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.

Examples: which services are on

[[email protected] coursefiles]# netstat --listen

Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 *:ssh *:* LISTEN

Active UNIX domain sockets (only servers)

Proto RefCnt Flags Type State I-Node Path

unix 2 [ ACC ] STREAM LISTENING 4280 /var/run/dbus/system_bus_socket

unix 2 [ ACC ] STREAM LISTENING 4299 @/tmp/hald-local/dbus eJfE5o936g


Netstat example

netstat example

[[email protected] man]# netstat -anpt

Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

tcp 0 0 127.0.0.1:47806 127.0.0.1:22 ESTABLISHED 7877/ssh

tcp 0 0 172.24.16.240:56108 193.166.135.6:22 ESTABLISHED 15463/ssh

tcp 0 0 :::22 :::* LISTEN 1254/sshd

tcp 0 0 ::ffff:172.24.16.240:22 ::ffff:193.166.135.10:39625 ESTABLISHED 16288/0

tcp 0 0 ::ffff:172.24.16.240:22 ::ffff:193.166.135.10:38258 ESTABLISHED 16235/1

tcp 0 0 ::ffff:127.0.0.1:22 ::ffff:127.0.0.1:47806 ESTABLISHED 7878/5


Other useful commands

ps

report a snapshot of the current processes.

Example: ps faux

(see all processes in tree like mode, where you can see parent processes etc)


Other useful commands

[[email protected] man]# ps faux

USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND

root 1 0.0 0.3 1740 396 ? S Sep27 0:03 init [3]

root 2 0.0 0.0 0 0 ? SN Sep27 0:00 [ksoftirqd/0]

root 3 0.0 0.0 0 0 ? S< Sep27 0:00 [events/0]

root 4 0.0 0.0 0 0 ? S< Sep27 0:00 [khelper]

root 5 0.0 0.0 0 0 ? S< Sep27 0:00 [kthread]

root 7 0.0 0.0 0 0 ? S< Sep27 0:00 \_ [kblockd/0]

root 69 0.0 0.0 0 0 ? S Sep27 0:01 \_ [pdflush]

root 70 0.0 0.0 0 0 ? S Sep27 0:00 \_ [pdflush]

root 72 0.0 0.0 0 0 ? S< Sep27 0:00 \_ [aio/0]

root 1511 0.0 0.0 0 0 ? S< Sep27 0:00 \_ [kauditd]

root 905 0.0 0.0 0 0 ? S Sep27 0:28 [kjournald]

root 1199 0.0 0.3 1616 484 ? Ss Sep27 0:14 syslogd -m 0

root 1201 0.0 0.3 1564 380 ? Ss Sep27 0:00 klogd -x

root 1212 0.0 0.4 1848 620 ? S Sep27 0:01 /usr/sbin/smartd

root 1254 0.0 0.7 4396 984 ? Ss Sep27 0:00 /usr/sbin/sshd

root 16235 0.0 1.2 7428 1584 ? Ss Nov01 0:05 \_ sshd: [email protected]/1

root 16237 0.0 0.8 4512 1076 pts/1 Ss+ Nov01 0:01 | \_ -bash

root 16288 0.0 1.3 7432 1644 ? Ss Nov01 0:07 \_ sshd: [email protected]/0

root 16290 0.0 0.8 4512 1044 pts/0 Ss Nov01 0:00 | \_ -bash

root 7877 0.0 1.5 4256 1968 pts/0 S+ Nov07 0:04 | \_ ssh [email protected]

root 7878 0.0 1.9 7428 2508 ? Ss Nov07 0:05 \_ sshd: [email protected]/5

root 7880 0.0 1.1 4512 1480 pts/5 Ss Nov07 0:01 \_ -bash

root 24515 0.0 0.6 4452 856 pts/5 R+ 22:28 0:00 \_ ps faux


Other useful commands

tail

tail - output the last part of files

When installing/watching server logs, use option -f which outputs appended

data as the file grows.

Example: tail –f /var/log/messages &

(starts tailing /var/log/messages and puts process in background)


Other useful commands

kill

Kill is used to terminate a process.

The command kill sends the specified signal to the specified process or

process group. If no signal is specified, the TERM signal is sent. The TERM

signal will kill processes which do not catch this signal.

For other processes, it may be necessary to use the KILL (9) signal, since this

signal cannot be caught. You need signal 9 to kill a shell.

Example: Killing normal process. First search process with ps.

[[email protected] man]# ps faux | grep –I dbus

dbus 1282 0.0 0.7 12804 984 ? Ssl Sep27 0:00 dbus-daemon

[[email protected] man]# kill 1282


Other useful commands

Example: Killing shell or other process that doesn’t shutdown normally.

root 16237 0.0 0.8 4512 1076 pts/1 Ss+ Nov01 0:01 | \_ -bash

root 16288 0.0 1.3 7432 1644 ? Ss Nov01 0:07 \_ sshd: [email protected]/0

root 16290 0.0 0.8 4512 1044 pts/0 Ss Nov01 0:00 | \_ -bash

root 7877 0.0 1.5 4256 1968 pts/0 S+ Nov07 0:04 | \_ ssh [email protected]

root 7878 0.0 1.9 7428 2508 ? Ss Nov07 0:05 \_ sshd: [email protected]/5

root 7880 0.0 1.1 4512 1488 pts/5 Ss Nov07 0:01 \_ -bash

root 24519 0.0 0.6 4452 856 pts/5 R+ 22:34 0:00 \_ ps xaufww

root 1269 0.0 0.8 4548 1016 ? Ss Sep27 0:00 crond

root 1290 0.0 14.7 42100 18568 ? Ss Sep27 39:17 hald --retain-privileges

root 1303 0.0 0.2 2148 340 ? S Sep27 21:51 \_ hald-addon-storage

root 1339 0.0 0.4 2408 536 ? Ss Sep27 0:00 login -- root

root 15429 0.0 0.3 4508 444 tty2 Ss Oct31 0:00 \_ -bash

[[email protected] man]# kill -9 16237


Openssh

OpenSSH

  • OpenSSH is a FREE version of the SSH protocol suite of network connectivity tools that increasing numbers of people on the Internet are coming to rely on. Many users of telnet, rlogin, ftp, and other such programs might not realize that their password is transmitted across the Internet unencrypted, but it is. OpenSSH encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other network-level attacks. Additionally, OpenSSH provides a myriad of secure tunneling capabilities, as well as a variety of authentication methods.

  • The OpenSSH suite includes the ssh program which replaces rlogin and telnet, scp which replaces rcp, and sftp which replaces ftp. Also included is sshd which is the server side of the package, and the other basic utilities like ssh-add, ssh-agent, ssh-keysign, ssh-keyscan, ssh-keygen and sftp-server. OpenSSH supports SSH protocol versions 1.3, 1.5, and 2.0.


More information

More information

  • man netstat

  • man ps

  • man kill

  • man tail

  • http://www.openssh.org


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