Common Linux commands (1)-Basics

View user IDs and group IDs

 
[Amonest @ centos-server ~] $IDUID=500(Amonest) gid =500(Amonest)Groups=500(Amonest ),10(Wheel) Context = unconfined_u: unconfined_r: unconfined_t: s0-s0: c0.c1023
 

 

View the users currently logged on to the system

 
[Amonest @ centos-server ~] $WhoAmonest PTS/0 2012-07-13 17:59(C60601199.xxxx.com)
 

 

View the machine's Ken time on the start date

[Amonest @ centos-server ~] $Who-Bsystem boot2012-07-13 16:49
 

 

View machine running time

 
[Amonest @ centos-server ~] $Uptime18:15:04Up1:25,1User, load average:0.00,0.00,0.00
 

 

View machine running time and login user

[Amonest @ centos-server ~] $W18:16:10Up1:27,1User, load average:0.00,0.00,0.00User tty from login @ idle jcpu pcpu whatamonest PTS/0C60601199.xxxxx.17:59 0. 00 s0. 07 s0. 00 sW
 

 

View system hard disk space information

[Amonest @ centos-server/etc] $DF - Ahfilesystem size used avail use % Mounted on /Dev/sda2 18g 6 . 3G 11g 39 %/ Proc  0   0   0 -/ Procsysfs  0   0   0 -/ Sysdevpts  0  0   0 -/Dev/ Ptstmpfs 499 m  0 499 m 0 %/Dev/ SHM /Dev/sda1 485 m 31 m 429 m 7 %/ Bootnone  0   0   0 -/Proc/sys/fs/binfmt_misc

 

View System Process Information

[Amonest @ centos-server/etc] $ PS -Efuid PID ppid C stime tty time cmdroot  1   0   0   16 : 49 ? 00 : 00 : 01 /Sbin/ Initroot  2   0   0   16 : 49 ?00 : 00 : 00  [Kthreadd] root  3   2   0   16 : 49 ? 00 : 00 : 00 [Migration/ 0  ] Root  4   2  0   16 : 49 ? 00 : 00 : 00 [Ksoftirqd/ 0  ] Root  5   2   0   16 : 49 ? 00 : 00 :00 [Migration/ 0  ] Root  6   2   0   16 : 49 ? 00 : 00 : 00 [Watchdog/ 0  ] Root  7   2   0  16 : 49 ? 00 : 00 : 00 [Events/ 0 ]

 

Display process tree

[Amonest @ centos-server ~] $ Pstree-Ainit Certificate-auditd │ audio-{auditd} audio-avahi-Daemon │ ─ ── avahi-Daemon ‑crond ‑rsyslogd-I/var/run/syslogd. PID-C4│ ── {Rsyslogd} ── sshd │ ── bash │ ── pstree-A transaction-udevd-D ├ ── udevd-D └ ── udevd-D
 

 

Search for a keyword in man page (only in command names)

[Amonest @ centos-server ~] $Man-F avahiavahi-Daemon (8)-The avahi mdns/DNS-SD daemonavahi-Daemon. conf [avahi-daemon] (5)-Avahi-Daemon ConfigurationFileAvahi. hosts [avahi] (5)-Avahi-daemon static Host NameFileAvahi. Service [avahi] (5)-Avahi-daemon static ServiceFile
 

 

Search for a keyword in man page (search for the keyword in command name and command description)

[Amonest @ centos-server ~] $ Man - K printarch ( 1 )-Print machine hardware name (same Uname - M) base64 (  1 )-Base64 encode/ Decode data and print to standard outputblkid (  8 )-Command-line utility Locate / Print block device attributes  Cat ( 1 )- Concatenate files and print on the standard outputconsoletype (  1 )-Print type of the console connected to standard input  Date ( 1 )-Print or set the system Date And Time 

 

Check whether a package has been installed:

[Amonest @ centos-server ~] $ Rpm-Qa |Grep-ISSHOpenSSH-Server-5. 3p1-70. El6.x86 _ 64libssh2-1.2.2-7. El6_1.1. X86_64openssh-5. 3p1-70. El6.x86 _ 64 OpenSSH-Askpass-5. 3p1-70. El6.x86 _ 64 OpenSSH-Clients-5. 3p1-70. El6.x86 _ 64
 

 

Query the configuration file of a package:

 [amonest @ centos-server ~] $ Rpm-QC openssh- server /etc/PAM. d/ SSH - keycat /etc/PAM. d/ sshd /etc/ SSH / sshd_config /etc/sysconfig/sshd