Guide to Unix/Commands/System Information

uptime uptime tells you how long the computer has been running since its last reboot or power-off. Example: $ uptime 22:27:49 up 10:14, 2 users, load average: 0.03, 0.32, 0.28 Links: uptime, freebsd.org 21.7 uptime in GNU Coreutils manual, gnu.org uname uname displays the system information such as hardware platform,system name and processor, Operating System type. Example: $ uname -a Linux DarkBox 2.4.27-1-k6 #1 Wed Apr 14 19:00:29 UTC 2004 i586 GNU/Linux Links: uname, opengroup.org uname, freebsd.org 21.4 uname in GNU Coreutils manual, gnu.org dmesg dmesg display the messages from the kernel, since boot. Example: $ dmesg Tips: While a UNIX system is booting, usually a lot of messages flash on the console screen in rapid succession; to view those messages after the system is booted, use the following command: $ dmesg | less Using a command option, dmesg can filter the kernel messages, based on priority. The '-n 1' arguments will display only the panic messages: $ dmesg -n 1 Links: dmesg, freebsd.org dmesg, manpages.ubuntu.com free free display used and free memory Example: $ free total used free shared buffers cached Mem: 123260 119540 3720 0 8752 58096 -/+ buffers/cache: 52692 70568 Swap: 369452 63212 306240 Display in human readable form using MegaByte block sizes: $ free -m total used free shared buffers cached Mem: 120 116 3 0 8 56 -/+ buffers/cache: 51 68 Swap: 360 61 299 Tips: Display system memory usage every 5 seconds, use Ctl+c to exit: $ free -m -s 5 total used free shared buffers cached Mem: 120 116 3 0 8 56 -/+ buffers/cache: 51 68 Swap: 360 61 299 total used free shared buffers cached Mem: 120 116 3 0 8 55 -/+ buffers/cache: 52 68 Swap: 360 61 299 Links: free, manpages.ubuntu.com vmstat vmstat displays a compact summary of overall system activity (processes, memory, and cpu information). Example: $ vmstat procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 2 0 63108 4484 7432 56480 8 11 93 45 1110 622 41 11 48 0 Tips: Print out vmstat summaries every two seconds, for five iterations. $ vmstat -n 2 5 procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 1 0 63100 5172 7440 55892 8 10 90 44 1110 622 41 10 49 0 2 0 63100 5168 7440 55892 0 0 0 0 1120 559 32 3 65 0 1 0 63100 5160 7440 55892 0 0 0 0 1111 499 8 6 86 0 1 0 63100 5160 7440 55892 0 0 0 0 1113 505 12 3 85 0 1 0 63100 5168 7440 55892 0 0 0 0 1121 532 20 3 77 0 Links: vmstat, freebsd.org vmstat, manpages.ubuntu.com top top displays system process in real time Example: $ top Tasks: 50 total, 2 running, 45 sleeping, 2 stopped, 1 zombie Cpu(s): 40.9% user, 10.5% system, 0.0% nice, 48.7% idle Mem: 123260k total, 119508k used, 3752k free, 7420k buffers Swap: 369452k total, 63036k used, 306416k free, 57212k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 5340 arky 15 0 968 968 780 R 13.8 0.8 0:00.22 top 1408 root 6 -10 23712 6692 3252 S 1.5 5.4 3:39.58 [XFree86] 1 root 8 0 500 472 448 S 0.0 0.4 0:00.31 init [2] 2 root 9 0 0 0 0 S 0.0 0.0 0:01.60 [keventd] 3 root 19 19 0 0 0 S 0.0 0.0 0:00.02 [ksoftirqd_CPU0] 4 root 9 0 0 0 0 S 0.0 0.0 0:07.03 [kswapd] 5 root 9 0 0 0 0 S 0.0 0.0 0:00.00 [bdflush] 6 root 9 0 0 0 0 S 0.0 0.0 0:00.44 [kupdated] 154 root 9 0 0 0 0 S 0.0 0.0 0:00.00 [khubd] 562 root 9 0 604 588 508 S 0.0 0.5 0:05.09 /sbin/syslogd 565 root 9 0 1152 492 448 S 0.0 0.4 0:01.24 /sbin/klogd -c 3 ......... Links: top, freebsd.org top, manpages.ubuntu.com df df reports the amount of free disk space available on each partition. $ df Filesystem 1K-blocks Used Available Use% Mounted on /dev/md0 5763508 207380 5263352 4% / /dev/md1 78819376 13722288 61093296 19% /home /dev/md4 23070564 4309572 17589056 20% /usr /dev/md2 5763508 1757404 3713328 33% /var /dev/md3 2877756 334740 2396832 13% /tmp To report the number of free i-nodes $ df -i Filesystem Inodes IUsed IFree IUse% Mounted on /dev/hda3 321952 32558 289394 11% / /dev/hda2 67320 67 67253 1% /boot /dev/mapper/vg00-home 372352 34227 338125 10% /home /dev/mapper/vg00-tmp 242784 11649 231135 5% /tmp /dev/mapper/vg00-usr 1821568 208669 1612899 12% /usr /dev/mapper/vg00-var 1282560 75704 1206856 6% /var Reports disk usage in human readable format with block-sizes in Kilo,Mega,Gigabytes. This option is specific for Wikipedia:GNU version of df. $ df -h Filesystem Size Used Avail Use% Mounted on /dev/hda1 2.3G 2.1G 133M 95% / tmpfs 61M 8.0K 61M 1% /dev/shm /dev/hda2 2.0G 1.8G 113M 94% /usr In some of Unix systems (SYS V family i.e. HP-UX) df displays the information in a different way: $ df /home (/dev/vg01/lvol2 ): 262478 blocks 2647709 i-nodes /tmp (/dev/vg00/lvol5 ): 952696 blocks 125941 i-nodes /usr (/dev/vg00/lvol6 ): 132842 blocks 17633 i-nodes /var (/dev/vg00/lvol7 ): 131704 blocks 17288 i-nodes /stand (/dev/vg00/lvol1 ): 47548 blocks 13390 i-nodes / (/dev/vg00/lvol3 ): 160772 blocks 21215 i-nodes In such cases try to use bdf command. Links: df, opengroup.org df man page, man.cat-v.org 14.1 df in GNU Coreutils manual, gnu.org hostname hostname displays and set system host name Example: Display the host name: $ hostname Darkstar Display the IP address of the system: $ hostname -i 61.95.196.52 Set the host name of the system to 'DarkHorse': $ hostname DarkHorse DarkHorse Links: hostname, freebsd.org 21.5 hostname in GNU Coreutils manual, gnu.org