System Reports

Many utilities report on one thing or another. The who, finger, ls, ps, and other utilities generate simple end-user reports. In some cases, these reports can help with system administration. This section describes utilities that generate more in-depth reports that can usually provide more assistance with system administration tasks. Linux has many other report utilities, including (from the sysstat package) sar (system activity report), iostat (input/output and CPU statistics), and mpstat (processor statistics); (from the net-tools package) netstat (network report); and (from the nfs-utils package) nfsstat (NFS statistics).

vmstat: Reports Virtual Memory Statistics

The vmstat utility (procps package) generates virtual memory information along with (limited) disk and CPU activity data. The following example shows virtual memory statistics in 3-second intervals for seven iterations (from the arguments 3 7). The first line covers the time since the system was last booted; the rest of the lines cover the period since the previous line.

$ vmstat 3 7 procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----  r  b   swpd   free   buff  cache   si   so    bi    bo   in     cs us sy id wa  0  2      0 684328  33924 219916    0    0   430   105 1052    134  2  4 86  8  0  2      0 654632  34160 248840    0    0  4897  7683 1142    237  0  5  0 95  0  3      0 623528  34224 279080    0    0  5056  8237 1094    178  0  4  0 95  0  2      0 603176  34576 298936    0    0  3416   141 1161    255  0  4  0 96  0  2      0 575912  34792 325616    0    0  4516  7267 1147    231  0  4  0 96  1  2      0 549032  35164 351464    0    0  4429    77 1120    210  0  4  0 96  0  2      0 523432  35448 376376    0    0  4173  6577 1135    234  0  4  0 95

The following list explains the column heads displayed by vmstat.

procs r b	Process information Number of waiting, runnable processes Number of blocked processes (in uninterruptable sleep)
memory swpd free buff cache	Memory information in kilobytes Used virtual memory Idle memory Memory used as buffers Memory used as cache
swap si so	System paging activity in kilobytes per second Memory swapped in from disk Memory swapped out to disk
io bi bo	System I/O activity in blocks per second Blocks received from a block device Blocks sent to a block device
system in cs	Values are per second Interrupts (including the clock) Context switches
cpu us sy id wa	Percentage of total CPU time spent in each of these states User (nonkernel) System (kernel) Idle Waiting for I/O

top: Lists Processes Using the Most Resources

The top utility is a useful supplement to ps. At its simplest, top displays system information at the top and the most CPU-intensive processes below the system information. The top utility updates itself periodically; type q to quit. Although you can use command line options, the interactive commands are often more helpful. Refer to Table 16-2 and to the top man page for more information.

$ top top - 21:30:26 up 18 min,  2 users,  load average: 0.95, 0.30, 0.14 Tasks:  63 total,   4 running,  58 sleeping,   1 stopped,    0 zombie Cpu(s): 30.9% us, 22.9% sy, 0.0% ni,  0.0% id, 45.2% wa, 1.0% hi, 0.0%si Mem:   1036820k total,  1032276k used,     4544k free,    40908k buffers Swap:  2048276k total,        0k used,   2048276k free,   846744k cached   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM     TIME+  COMMAND  1285 root      25   0  9272 6892 1312 R 29.3  0.7    0:00.88 bzip2  1276 root      18   0  3048  860 1372 R  3.7  0.1    0:05.25 cp     7 root      15   0     0    0    0 S  0.7  0.0    0:00.27 pdflush     6 root      15   0     0    0    0 S  0.3  0.0    0:00.11 pdflush     8 root      15   0     0    0    0 S  0.3  0.0    0:00.06 kswapd0   300 root      15   0     0    0    0 S  0.3  0.0    0:00.24 kjournald  1064 mgs2      16   0  8144 2276 6808 S  0.3  0.2    0:00.69 sshd  1224 root      16   0  4964 1360 3944 S  0.3  0.1    0:00.03 bash  1275 mgs2      16   0  2840  936 1784 R  0.3  0.1    0:00.15 top  1284 root      15   0  2736  668 1416 S  0.3  0.1    0:00.01 tar     1 root      16   0  2624  520 1312 S  0.0  0.1    0:06.51 init

Table 16-2. top:interactive commands

Command	Function
A	Sorts processes by age (newest first).
h or ?	Displays a Help screen.
k	Prompts for a PID number and type of signal and sends the process that signal. Defaults to signal 15 (SIGTERM); specify 9 (SIGKILL) only when 15 does not work.
M	Sorts processes by memory usage.
P	Sorts processes by CPU usage (default).
q	Quits.
s	Prompts for time between updates in seconds. Use 0 for continuous updates.
SPACE	Updates the display immediately.
T	Sorts tasks by time.
W	Writes a startup file named ~/.toprc so that next time you start top, it uses the same parameters it is currently using.