atop: T3774: Atop log file rotation fix

The systemd unit for atop service is changed, so the log file name and
location will be always the same. It also adds the logrotate
configuration to conditionally rotate a log file.
Hardcoded values:
- maximum log file size: 10 MB
- maximum count of files: 10
These values can be easily changed within the
`/etc/logrotate.d/vyos-atop`, no additional configuration is required.
Rotation will be done hourly, if necessary, according to
`/etc/cron.hourly/vyos-logrotate-hourly`.

This change has two benefits:
- rotation strategy control can be done via logrotate, and can be
exposed to CLI now;
- the total size of all logs is now controlled more aggressively, so
the chance to get a situation when atop logs took all the space on a
drive is significantly lower. Also, if this will be necessary, rotation
may be done even each minute what reduces risks related to logs size
even more.

1 files changed, 20 insertions, 0 deletions

diff --git a/src/etc/logrotate.d/vyos-atop b/src/etc/logrotate.d/vyos-atop
new file mode 100644
index 000000000..0c8359c7b
--- /dev/null
+++ b/src/etc/logrotate.d/vyos-atop
@@ -0,0 +1,20 @@
+/var/log/atop/atop.log {
+    daily
+    dateext
+    dateformat _%Y-%m-%d_%H-%M-%S
+    maxsize 10M
+    missingok
+    nocompress
+    nocreate
+    nomail
+    rotate 10
+    prerotate
+        # stop the service
+        systemctl stop atop.service
+    endscript
+    postrotate
+        # start atop service again
+        systemctl start atop.service
+    endscript
+}
+