Contents
Tripwire
1.Install
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# dnf -y install tripwire Installed: tripwire-2.4.3.7-16.el9.x86_64 Complete! |
2.Passphrase setting
Set site passphrase and local passphrase
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# tripwire-setup-keyfiles |
------------------------------------------------
The Tripwire site and local passphrases are used to sign a variety of
files, such as the configuration, policy, and database files.
Passphrases should be at least 8 characters in length and contain both
letters and numbers.
See the Tripwire manual for more information.
------------------------------------------------
Creating key files…
(When selecting a passphrase, keep in mind that good passphrases typically
have upper and lower case letters, digits and punctuation marks, and are
at least 8 characters in length.)
Enter the site keyfile passphrase: [site pass]
Verify the site keyfile passphrase: [site pass]
Generating key (this may take several minutes)…Key generation complete.
(When selecting a passphrase, keep in mind that good passphrases typically
have upper and lower case letters, digits and punctuation marks, and are
at least 8 characters in length.)
Enter the local keyfile passphrase: [local pass]
Verify the local keyfile passphrase: [local pass]
Generating key (this may take several minutes)…Key generation complete.
------------------------------------------------
Signing configuration file…
Please enter your site passphrase: [site pass]
Wrote configuration file: /etc/tripwire/tw.cfg
A clear-text version of the Tripwire configuration file:
/etc/tripwire/twcfg.txt
has been preserved for your inspection. It is recommended that you
move this file to a secure location and/or encrypt it in place (using a
tool such as GPG, for example) after you have examined it.
------------------------------------------------
Signing policy file…
Please enter your site passphrase: [site pass]
Wrote policy file: /etc/tripwire/tw.pol
A clear-text version of the Tripwire policy file:
/etc/tripwire/twpol.txt
has been preserved for your inspection. This implements a minimal
policy, intended only to test essential Tripwire functionality. You
should edit the policy file to describe your system, and then use
twadmin to generate a new signed copy of the Tripwire policy.
Once you have a satisfactory Tripwire policy file, you should move the
clear-text version to a secure location and/or encrypt it in place
(using a tool such as GPG, for example).
Now run "tripwire --init" to enter Database Initialization Mode. This
reads the policy file, generates a database based on its contents, and
then cryptographically signs the resulting database. Options can be
entered on the command line to specify which policy, configuration, and
key files are used to create the database. The filename for the
database can be specified as well. If no options are specified, the
default values from the current configuration file are used.
3.Tripwire Configuration
①Configuration File Edit
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# vi /etc/tripwire/twcfg.txt ●Line 9 : change LOOSEDIRECTORYCHECKING =true ●Line 12 : change Level 4 provides the most detailed report of the five levels from "0" to "4". #REPORTLEVEL =3 REPORTLEVEL =4 |
②Create a Tripwire configuration file (cryptographically signed version)
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# twadmin -m F -c /etc/tripwire/tw.cfg -S /etc/tripwire/site.key /etc/tripwire/twcfg.txt Please enter your site passphrase: ←site pass Wrote configuration file: /etc/tripwire/tw.cfg |
③Delete Tripwire configuration file (text version)
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# rm -f /etc/tripwire/twcfg.txt |
④Policy File Settings
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# cd /etc/tripwire/ # vi twpolmake.pl |
Contents of twpolmake.pl
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#!/usr/bin/perl # $POLFILE=$ARGV[0]; open(POL,"$POLFILE") or die "open error: $POLFILE" ; my($myhost,$thost) ; my($sharp,$tpath,$cond) ; my($INRULE) = 0 ; while (<POL>) { chomp; if (($thost) = /^HOSTNAME\s*=\s*(.*)\s*;/) { $myhost = `hostname` ; chomp($myhost) ; if ($thost ne $myhost) { $_="HOSTNAME=\"$myhost\";" ; } } elsif ( /^{/ ) { $INRULE=1 ; } elsif ( /^}/ ) { $INRULE=0 ; } elsif ($INRULE == 1 and ($sharp,$tpath,$cond) = /^(\s*\#?\s*)(\/\S+)\b(\s+->\s+.+)$/) { $ret = ($sharp =~ s/\#//g) ; if ($tpath eq '/sbin/e2fsadm' ) { $cond =~ s/;\s+(tune2fs.*)$/; \#$1/ ; } if (! -s $tpath) { $_ = "$sharp#$tpath$cond" if ($ret == 0) ; } else { $_ = "$sharp$tpath$cond" ; } } print "$_\n" ; } close(POL) ; |
⑤Policy File Optimizations
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# perl /etc/tripwire/twpolmake.pl /etc/tripwire/twpol.txt > /etc/tripwire/twpol.txt.new |
⑥Create policy file (cryptographically signed version) based on optimized policy file
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# twadmin -m P -c /etc/tripwire/tw.cfg -p /etc/tripwire/tw.pol -S /etc/tripwire/site.key /etc/tripwire/twpol.txt.new Please enter your site passphrase: ←site pass Wrote policy file: /etc/tripwire/tw.pol |
⑦Create database and check operation
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# tripwire -m i -s -c /etc/tripwire/tw.cfg Please enter your local passphrase: ←local pass |
Create test files
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# echo test > /root/test.txt |
Check Tripwire operation
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# tripwire -m c -s -c /etc/tripwire/tw.cfg |
If it displays as shown below, it's OK.
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Open Source Tripwire(R) 2.4.3.7 Integrity Check Report Report generated by: root Report created on: Sat 03 Jan 2026 10:24:42 AM JST Database last updated on: Never =============================================================================== Report Summary: =============================================================================== Host name: Lepard Host IP address: 192.168.11.83 Host ID: None Policy file used: /etc/tripwire/tw.pol Configuration file used: /etc/tripwire/tw.cfg Database file used: /var/lib/tripwire/Lepard.twd Command line used: tripwire -m c -s -c /etc/tripwire/tw.cfg =============================================================================== Rule Summary: =============================================================================== ------------------------------------------------------------------------------- Section: Unix File System ------------------------------------------------------------------------------- Rule Name Severity Level Added Removed Modified --------- -------------- ----- ------- -------- User binaries 66 0 0 0 Tripwire Binaries 100 0 0 0 Libraries 66 0 0 0 Operating System Utilities 100 0 0 0 File System and Disk Administraton Programs 100 0 0 0 Kernel Administration Programs 100 0 0 0 Networking Programs 100 0 0 0 System Administration Programs 100 0 0 0 Hardware and Device Control Programs 100 0 0 0 System Information Programs 100 0 0 0 (/sbin/runlevel) Application Information Programs 100 0 0 0 (/sbin/rtmon) Critical Utility Sym-Links 100 0 0 0 Shell Binaries 100 0 0 0 Critical system boot files 100 0 0 0 * Tripwire Data Files 100 1 0 0 System boot changes 100 0 0 0 OS executables and libraries 100 0 0 0 Security Control 100 0 0 0 Login Scripts 100 0 0 0 Critical configuration files 100 0 0 0 * Root config files 100 1 0 0 Invariant Directories 66 0 0 0 Temporary directories 33 0 0 0 Critical devices 100 0 0 0 (/proc/kcore) Total objects scanned: 57353 Total violations found: 2 =============================================================================== Object Summary: =============================================================================== ------------------------------------------------------------------------------- # Section: Unix File System ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- Rule Name: Tripwire Data Files (/var/lib/tripwire) Severity Level: 100 ------------------------------------------------------------------------------- Added: "/var/lib/tripwire/Lepard.twd" ------------------------------------------------------------------------------- Rule Name: Root config files (/root) Severity Level: 100 ------------------------------------------------------------------------------- Added: "/root/test.txt" =============================================================================== Error Report: =============================================================================== No Errors ------------------------------------------------------------------------------- *** End of report *** Open Source Tripwire 2.4 Portions copyright 2000-2018 Tripwire, Inc. Tripwire is a registered trademark of Tripwire, Inc. This software comes with ABSOLUTELY NO WARRANTY; for details use --version. This is free software which may be redistributed or modified only under certain conditions; see COPYING for details. All rights reserved. |
Delete test files
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# rm -f /root/test.txt |
⑧Create a script for reporting results via email
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# cd /var/www/system # vi tripwire.sh |
#!/bin/bash
PATH=/usr/sbin:/usr/bin:/bin:/usr/local/tripwire/sbin
#Passphrase Setup
LOCALPASS=xxxxx # local pass
SITEPASS=xxxxx # site pass
#Specify notification email address
MAIL="[your mail address] "
cd /etc/tripwire
#Tripwire Check Execution
tripwire -m c -s -c tw.cfg|mail -s "Tripwire(R) Integrity Check Report in `hostname`" $MAIL
#Policy File Update
twadmin -m p -c tw.cfg -p tw.pol -S site.key > twpol.txt
perl twpolmake.pl twpol.txt > twpol.txt.new
twadmin -m P -c tw.cfg -p tw.pol -S site.key -Q $SITEPASS twpol.txt.new > /dev/null
rm -f twpol.txt* *.bak
#Database Update
rm -f /usr/local/tripwire/lib/tripwire/*.twd*
tripwire -m i -s -c tw.cfg -P $LOCALPASS
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# chmod 700 tripwire.sh Add to cron # crontab -e 0 3 * * * /var/www/system/tripwire.sh |
Confirmation that the results of the tripwire execution are notified to the specified e-mail address
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# /var/www/system/tripwire.sh |
Chkrootkit
Install the rootkit detection tool chkrootkit to check whether a rootkit has been installed on the Linux server.
Since chkrootkit performs checks using the following command, it becomes ineffective if the command itself has been tampered with by a rootkit. Therefore, it is advisable to install it during the initial stages after Linux installation.
【Commands used by chkrootkit】
awk, cut, echo, egrep, find, head, id, ls, netstat, ps, strings, sed, uname
Note that chkrootkit can only detect known rootkits and cannot detect new rootkits.
①Download and install chkrootkit
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# cd /usr/local/src # wget https://launchpad.net/chkrootkit/main/0.55/+download/chkrootkit-0.55.tar.gz # tar xvf chkrootkit-0.55.tar.gz |
➁Create /root/bin directory and move chkrootkit command to that directory
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# mkdir -p /root/bin # mv chkrootkit-0.55/chkrootkit /root/bin |
➂Check chkrootkit.
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# chkrootkit | grep INFECTED If nothing is displayed, there is no problem. |
④Create chkrootkit periodic execution script and change permissions
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# vi /etc/cron.daily/chkrootkit |
Scheduled Script Contents
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#!/bin/bash PATH=/usr/bin:/bin:/root/bin LOG=/tmp/$(basename ${0}) # Run chkrootkit chkrootkit > $LOG 2>&1 # log output cat $LOG | logger -t $(basename ${0}) # SMTPS bindshell false positive response if [ ! -z "$(grep 465 $LOG)" ] && \ [ -z $(/usr/sbin/lsof -i:465|grep bindshell) ]; then sed -i '/465/d' $LOG fi # Support for Suckit false positives when updating upstart package if [ ! -z "$(grep Suckit $LOG)" ] && \ [ -z "$(rpm -V `rpm -qf /sbin/init`)" ]; then sed -i '/Suckit/d' $LOG fi # Send mail to root only when rootkit is detected [ ! -z "$(grep INFECTED $LOG)" ] && \ grep INFECTED $LOG | mail -s "chkrootkit report in `hostname`" root |
Add execution permission to chkrootkit execution script
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# chmod 700 /etc/cron.daily/chkrootkit |
⑤Backup commands used by chkrootkit
If the commands used by chkrootkit are tampered with, rootkit will not be detected.
Back up these commands.
If necessary, run chkrootkit with the backed up command
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# cd /root # mkdir /root/chkrootkit_cmd # cp `which --skip-alias awk cut echo egrep find head id ls netstat ps strings sed ssh uname` chkrootkit_cmd/ # ls -l /root/chkrootkit_cmd/ total 2628 -rwxr-xr-x 1 root root 714968 Dec 28 14:09 awk -rwxr-xr-x 1 root root 48760 Dec 28 14:09 cut -rwxr-xr-x 1 root root 36136 Dec 28 14:09 echo -rwxr-xr-x 1 root root 32 Dec 28 14:09 egrep -rwxr-xr-x 1 root root 291800 Dec 28 14:09 find -rwxr-xr-x 1 root root 44656 Dec 28 14:09 head -rwxr-xr-x 1 root root 40472 Dec 28 14:09 id -rwxr-xr-x 1 root root 140752 Dec 28 14:09 ls -rwxr-xr-x 1 root root 160608 Dec 28 14:09 netstat -rwxr-xr-x 1 root root 144536 Dec 28 14:09 ps -rwxr-xr-x 1 root root 116736 Dec 28 14:09 sed -rwxr-xr-x 1 root root 863632 Dec 28 14:09 ssh -rwxr-xr-x 1 root root 32504 Dec 28 14:09 strings -rwxr-xr-x 1 root root 32232 Dec 28 14:09 uname |
⑥Run chkrootkit on the copied command
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# chkrootkit -p /root/chkrootkit_cmd | grep INFECTED |
If nothing is displayed, no problem.
⑦Compresses backed up commands
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# tar zcvf chkrootkit_cmd.tar.gz chkrootkit_cmd chkrootkit_cmd/ chkrootkit_cmd/awk chkrootkit_cmd/cut chkrootkit_cmd/echo chkrootkit_cmd/egrep chkrootkit_cmd/find chkrootkit_cmd/head chkrootkit_cmd/id chkrootkit_cmd/ls chkrootkit_cmd/netstat chkrootkit_cmd/ps chkrootkit_cmd/strings chkrootkit_cmd/sed chkrootkit_cmd/ssh chkrootkit_cmd/uname |
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# ls -l total 1804 -rw-------. 1 root root 1200 Dec 30 18:48 anaconda-ks.cfg -rw------- 1 root root 407 Jan 2 16:46 appid_stats.log drwxr-xr-x 2 root root 24 Jan 3 10:30 bin drwxr-xr-x 2 root root 172 Jan 3 10:32 chkrootkit_cmd -rw-r--r-- 1 root root 1227992 Jan 3 10:39 chkrootkit_cmd.tar.gz drwxr-xr-x 9 root root 4096 Jan 2 16:22 libdaq drwxr-xr-x 4 5001 2010 134 Jun 10 2023 odp -rw-r--r-- 1 root root 599862 Jun 17 2023 OpenAppId-33380.tgz drwx------ 3 root root 21 Jan 1 10:38 snap drwxr-xr-x 10 root root 4096 Jan 2 16:25 snort3 |
⑧Send chkrootkit use command (compressed version) to root by e-mail
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# echo|mail -a chkrootkit_cmd.tar.gz -s chkrootkit_cmd.tar.gz root |
⑨Download and save chkrootkit_cmd.tar.gz file to Windows
⑩Delete commands on the backed up server
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# rm -f chkrootkit_cmd.tar.gz |
Logwatch
①Install
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# dnf -y install logwatch |
②Edit configuration file
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# cat /usr/share/logwatch/default.conf/logwatch.conf >> /etc/logwatch/conf/logwatch.conf # vi /etc/logwatch/conf/logwatch.conf Line 51 : Comment #MailTo = root Line 52 : Add MailTo = [mail address] Per Line 84 : Set the level of detail for log notifications #Detail = Low Detail = High |
③Output Logwatch reports
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# logwatch --output stdout |
It will appear as follows
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################### Logwatch 7.5.5 (01/22/21) #################### Processing Initiated: Sat Jan 3 10:41:56 2026 Date Range Processed: yesterday ( 2026-Jan-02 ) Period is day. Detail Level of Output: 10 Type of Output/Format: stdout / text Logfiles for Host: Lepard ################################################################## --------------------- Clamav Begin ------------------------ Daemon check list: Database status OK: 59 Time(s) ---------------------- Clamav End ------------------------- --------------------- Clamav-milter Begin ------------------------ --------------------------------- --------------------------------- --------------------- Disk Space Begin ------------------------ Filesystem Size Used Avail Use% Mounted on /dev/mapper/rl-root 17G 8.5G 8.6G 50% / /dev/nvme0n1p1 960M 395M 566M 42% /boot ---------------------- Disk Space End ------------------------- --------------------- lm_sensors output Begin ------------------------ No sensors found! Make sure you loaded all the kernel drivers you need. Try sensors-detect to find out which these are. ---------------------- lm_sensors output End ------------------------- ###################### Logwatch End ######################### |
④Test to see if the report arrives at the address you set. Check if you receive a log report email like the one above.
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# /etc/cron.daily/0logwatch |
DNS Update
Whenever the internet connection is lost or the router reboots, causing the global IP address to change, you must access the dynamic DNS service to notify it of the IP address change.
Create a dedicated Python file and schedule it for regular execution via Cron.
This time, it's about DNS settings on Valudomain.
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# cd /var/www/system # vi ddnsset.py |
Contents of ddnset.py
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#setddns.py import requests import ipaddress from datetime import datetime from pathlib import Path # SETTING DATA MY_DOMAIN = "example.jp" ←Self-hosted domain MY_PASS = "xxxxxxxxxx" ←Password MY_HOSTNAME = "xxxx" ←Hostname OUT_FILE = Path("/tmp/ipadress") ←IP Address Log File def time_msg(): now = datetime.now() return now.strftime("%Y/%m/%d %H:%M:%S") def is_valid_ip(ip_str): try: ipaddress.ip_address(ip_str) return True except ValueError: return False def main(): # Check Global IP Address url_get_ip = "https://dyn.value-domain.com/cgi-bin/dyn.fcg?ip" try: response = requests.get(url_get_ip, timeout=10) response.raise_for_status() current_ip = response.text.strip() except requests.RequestException as e: print(f"{time_msg()} Failed to get IP: {e}") return # IP check mssg = time_msg() if not current_ip: print(f"{mssg} invalid IP NULL") return if not is_valid_ip(current_ip): print(f"{mssg} invalid IP={current_ip}") return # Read previous IP previous_ip = "" if OUT_FILE.exists(): with open(OUT_FILE, "r") as f: previous_ip = f.read().strip() if current_ip == previous_ip: print(f"{time_msg()} no change IP={current_ip}") return else: print(f"change IP from {previous_ip} to {current_ip}") # Update DDNS mssg = time_msg() print(f"{mssg} access to value-domain") url_set_ddns = ( f"https://dyn.value-domain.com/cgi-bin/dyn.fcg?" f"d={MY_DOMAIN}&p={MY_PASS}&h={MY_HOSTNAME}" ) try: response = requests.get(url_set_ddns, timeout=10) response.raise_for_status() # Convert line breaks to spaces and consolidate consecutive spaces into a single space. result = ' '.join(response.text.strip().split()) except requests.RequestException as e: print(f"{time_msg()} Failed to update DDNS: {e}") return mssg = time_msg() print(f"{mssg} {MY_HOSTNAME}.{MY_DOMAIN} {result} IP={current_ip}") # Only save the IP address if the DDNS update is successful. if "status=0" in result: with open(OUT_FILE, "w") as f: f.write(current_ip) print(f"{mssg} Successfully saved new IP: {current_ip}") else: print(f"{mssg} DDNS update failed, IP not saved") if __name__ == "__main__": main() |
IP Address Log File Creation
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# touch /tmp/ipadress |
Run periodically
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# crontab -e * 00 * * * /usr/bin/python3 /var/www/system/ddnsset.py >> /var/log/ddns_updater.log 2>&1 |
Introduce disk usage check script
1.Script Creation
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# cd /var/www/system # vi disk_capacity_check.sh |
Contents of disk_capacity_check.sh
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#!/bin/bash #Designation of e-mail address to be notified MAIL="<your mailaddress>" DVAL=`/bin/df / | /usr/bin/tail -1 | /bin/sed 's/^.* \([0-9]*\)%.*$/\1/'` if [ $DVAL -gt 80 ]; then echo "Disk usage alert: $DVAL %" | mail -s "Disk Space Alert in `hostname`" $MAIL fi |
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# chmod 700 disk_capacity_check.sh |
2. Execution Confirmation
①Check current usage rates
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# df -h |
It appears as follows
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Filesystem Size Used Avail Use% Mounted on devtmpfs 4.0M 0 4.0M 0% /dev tmpfs 1.8G 0 1.8G 0% /dev/shm tmpfs 725M 12M 714M 2% /run /dev/mapper/almalinux-root 17G 8.6G 8.4G 51% / /dev/loop3 128K 128K 0 100% /var/lib/snapd/snap/hello-world/29 /dev/loop2 67M 67M 0 100% /var/lib/snapd/snap/core24/1243 /dev/loop4 51M 51M 0 100% /var/lib/snapd/snap/snapd/25577 /dev/loop0 105M 105M 0 100% /var/lib/snapd/snap/core/17272 /dev/loop1 72M 72M 0 100% /var/lib/snapd/snap/certbot/5234 /dev/nvme0n1p1 960M 395M 566M 42% /boot tmpfs 363M 8.0K 363M 1% /run/user/1000 |
②Create a dummy file to achieve at least 80% utilization(In the example, a file named dummyfile with a size of about 6GB)
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# dd if=/dev/zero of=dummyfile bs=1M count=6000 |
③check again
Verify that it is at least 80% by performing the following:
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# df -h |
④Run check scripts
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# /var/www/system/disk_capacity_check.sh |
You will receive an email to the email address you have set up, stating something like "Disk usage alert: 86 %".
⑤Delete "dummyfile"
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# rm dummyfile |
⑥Periodic Execution Setting
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# crontab -e Add the following 30 2 * * * /var/www/system/disk_capacity_check.sh |
