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16.7 System Information
16.7.1 System Activity Information: sar
To use sar, sadc (system activity data collector) needs to be running. Check its status
or start it with rcsysstat {start|status}.
sar can generate extensive reports on almost all important system activities, among
them CPU, memory, IRQ usage, IO, or networking. With its many options, it is too
complex to explain further here. Refer to the man page for extensive documentation
with examples.
16.7.2 Memory Usage: free
The utility free examines RAM usage. Details of both free and used memory and
swap areas are shown:
tester@linux:~> free
Mem:
-/+ buffers/cache:
Swap:
The options -b,-k,-m,-g show output in bytes, KB, MB, or GB, respectively. The
parameter -d delay ensures that the display is refreshed every delay seconds. For
example, free -d 1.5 produces an update every 1.5 seconds.
16.7.3 User Accessing Files: fuser
It can be useful to determine what processes or users are currently accessing certain
files. Suppose, for example, you want to unmount a file system mounted at /mnt.
umount returns "device is busy." The command fuser can then be used to determine
what processes are accessing the device:
tester@linux:~> fuser -v /mnt/*
324
Installation and Administration
total
used
515584
501704
94072
658656
0
free
shared
13880
0
421512
658656
buffers
cached
73040
334592
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Troubleshooting
