There are lots of monitoring apps for servers, and they’ve done a lot to help adoption of Linux with sysadmins who aren’t used to the Terminal or who have a real need for graphical representations of data. However, Linux has been a multi-user system since the beginning, and UNIX long before that, so there are built-in tools that go back 40 years to help you monitor who’s logged into your server, who’s using resources, and for what.
You don’t have to be paranoid or even nosy to justify keeping a close watch on a server that’s been made your responsibility. The psacct package contains several commands to gather detailed reports about user status and activity.
Not all commands in the
acct utilities require that you activate accounting, but many do. If you intend to use
acct commands, you should enable accounting with the
$ sudo accton on
By default, accounting records are stored in
/var/account/pacct. This file could feasibly become quite large, so use
logrotate or a similar tool to ensure proper log management.
To deactivate accounting:
$ sudo accton off
ac command prints statistics about connection times. If you need to get an overview of how active users have been on a system, the
--individual-totals option provides that. It generates its report in hours based on logins and logouts recorded in the
The accounting file
wtmp is maintained by
login(1) but neither
login actually creates the file. If
wtmp doesn’t exist, then no report is generated, but you can point
ac to an alternate location using the
--file option. If a
wtmp file doesn’t exist on your system, you can create an empty
wtmp file to enable reporting on your system.
To get a report on login times for individual users:
$ ac --individual-totals seth 20.16 larry 43.60 curly 10.32 moe 35.11
You can also get daily totals:
$ ac --daily-totals Jan 20 total 22.61 Jan 21 total 73.60 Jan 22 total 84.00 Jan 23 total 100.69 Jan 24 total 18.24 Jan 25 total 2.43 Jan 27 total 35.36 Today total 62.13
lastcomm command displays the last commands issued on the system for a given user. If no user is specified, then a report on the current user is generated.
$ sudo lastcomm --strict-match --user curly --tty pts/2 basename curly pts/2 0.00 secs Tue Jan 28 15:41 ps curly pts/2 0.00 secs Tue Jan 28 15:41 bash F curly pts/2 0.00 secs Tue Jan 28 15:41 manpath curly pts/2 0.00 secs Tue Jan 28 15:41 bash F curly pts/2 0.00 secs Tue Jan 28 15:41 tclsh curly pts/2 0.00 secs Tue Jan 28 15:41 bash F curly pts/2 0.00 secs Tue Jan 28 15:41 bash F curly pts/2 0.00 secs Tue Jan 28 15:41 sed curly pts/2 0.00 secs Tue Jan 28 15:41
The commands listed by
lastcomm aren’t necessarily commands a user launched interactively. For instance, simply by logging in, a user spawns nearly 40 items in the output of
lastcomm, so it can be overwhelming. Coupled with
grep, though, it’s an easy way to get a sense of a user’s session history.
sa command summarizes accounting information derived from the
/var/account/pacct file. If you’re auditing the activities of users, then the
--print-users option prints the user name before each command:
$ sudo sa --print-users root 0.00 cpu 579k mem 0 io accton root 0.03 cpu 64064k mem 0 io sudo seth 0.00 cpu 56752k mem 0 io bash * seth 0.00 cpu 54080k mem 0 io sed seth 0.00 cpu 56752k mem 0 io bash * larry 0.00 cpu 56752k mem 0 io bash * curly 0.00 cpu 56752k mem 0 io bash * moe 0.00 cpu 56752k mem 0 io bash * seth 0.00 cpu 54080k mem 0 io ls
Alternatively, you can get just a summary for each user:
$ sudo sa --user-summary 1065 2169.59re 0.97cp 0avio 49373k seth 812 1117.11re 0.83cp 0avio 58163k root 199 1052.42re 0.14cp 0avio 21314k larry 41 0.00re 0.00cp 0avio 19403k curly 1 0.06re 0.00cp 0avio 6706k moe 12 0.00re 0.00cp 0avio 25888k [...]
The columns displayed, in addition to user names, report on CPU (real time and CPU time), I/O operations per command (average and total), and so on. They can be configured using options such as
--sort-tio for total I/O,
--sort-cpu-avmem to sort CPU time by average memory usage, and so on. All sorting filters can be reversed with the
Combined with tools like who, w, and ps, you can get a sense for how users are spending system resources, which commands may be problematic, and what server upgrades could be useful in the future. Because the
acct suite is terminal-based, it can be scripted and utilized by other tools, allowing you to create a customized reporting mechanism.
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