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sleep 600 then Ctrl+Z or sleep 600 &
|
Start job in background
|
|
fg
|
Move last bg job to foreground
|
|
jobs
|
Show current jobs
|
|
PID-VCZ-RSS-TTY
|
Process ID-Virtual Memory Size-Residence Memory Size-Console Process running on
|
|
ps aux | grep sshd
|
Find SSHD service running on system
|
|
ps -ef | less (PPID)
|
Parent Process ID
|
|
ps -e -o pid,args --forest
|
|
|
PID-VCZ-RSS-TTY
|
Process ID-Virtual Memory Size-Residence Memory Size-Console Process running on
|
|
ps aux | grep sshd
|
Find SSHD service running on system
|
|
ps -ef | less (PPID)
|
Parent Process ID
|
|
ps -e -o pid,args --forest | less
|
Show relation between parent and child processes
|
|
ps aux --sort pmem
|
Sorting process memory
|
|
/etc/cron.d/
|
Main dir to put file for scheduling (used by rpm)
|
|
minute hour dayofmonth month dayofweek username command
|
Crontab syntax
|
|
crontab -e
|
Open crontab for current user
|
|
/10 1-5 /bin/logger
|
Run logger every 10 minute on weekdays
|
|
cat /var/log/cron | grep CRON
|
Verify schedule cron jobs
|
|
Make dir "journal" in /var/log
|
make journal consistently
|
|
vim /etc/systemd/journald.conf
|
change storage=auto to make journalctl consistently
|
|
/usr/lib/systemd
|
Main config dir
|
|
systemctl -t help
|
List available unit types
|
|
ls /usr/lib/systemd/system/*socket
|
List available socket service
|
|
Socket: ListenStream=22
|
Listen on TCP port 22
|
|
Service can be dead and socket can still listening, reducing resource to run service
|
|
|
systemctl show sshd = man systemd.directives
|
List all options can be included in service
|
|
systemctl set-property httpd.service MemoryLimit=500m
|
Modify unit file htttpd
|
|
Target
|
Group of unit file
|
|
systemctl get-default
|
Default targart
|
|
systemctl set-default multi-user.target
|
Set default to multi.user
|
|
When boot systemd.unit=rescue.target
|
|
|
systemctl list-units
|
List all current units
|
|
Within top, press k
|
PID, 15(sigterm)
|
|
kill 14053
|
Kill process 14053
|
|
killall dd
|
Kill all process w/name dd
|
|
kill -9 14321
|
Kill process 14321 w/ signal 9 (kill)
|
|
kill $(pidof dd)
|
Kill all dd process, similar to killall
|
|
kill -l
|
List of kill signal
|
|
tar xvf filename -C /tmp
|
Decompress tar file verbose (v), x (extract) f(file) to /tmp dir
|
|
file filename
|
Find info about compressed file
|
|
gunzip filename
|
Decompress file
|
|
tar czvf etc.tar /etc/
|
Create tarball (c) and compress (z)
|
|
gunzip filename
|
Unzip file
|
|
-p
|
preserver permission while decompress, compress
|
|
ldd /usr/bin/passwd
|
Show all libraries the command need
|
|
rpm -qa | grep httpd
|
List all installed packages (query all) and see if httpd is installed
|
|
rpm -qi httpd
|
Provide info about package
|
|
rpm -ql http
|
Provide list of files installed from package
|
|
rpm -qc httpd
|
List configuration file (c)
|
|
rpm -qd httpd
|
List documentation about package (d)
|
|
rpm -qpi filename
|
Provide info about uninstalled package
|
|
rpm -qp --scripts filename
|
Find which scripts are executed if package is installed
|
|
rpm -qf /etc/nanorc
|
Find out which package the file coming from
|
|
systemctl status rsyslog
|
Check status of Rsyslog
|
|
vim /etc/rsyslog.conf
|
|
|
facility
|
authpriv, kern, mail
|
|
priority
|
.emerg, .crit, .debug
|
|
kern.* /dev/console
|
Log from kern with all priority written to /dev/console
|
|
mail.* -/var/log/maillog
|
Written not in realtime (-)
|
|
.emerg :omusrmsg:
|
Every user will receive emergency messsage on console
|
|
*.crit /var/log/critical
|
Save message with critical priority or higher to /var/log/critical
|
|
logger -p crit Critical Situation
|
Write log with crit priority
|
|
/etc/cron.daily/logrotate
|
|
|
logrotate.conf
|
|
|
Press ESC after boot
|
Stop booting process
|
|
Rescue kernel
|
Boot w/ minimal modules
|
|
Press e
|
Edit
|
|
Take out "rhgb" "quiet"
|
See what's happen upon boot
|
|
Edit /etc/default/grub
|
Permanent boot modifications
|
|
/boot/grub2/grub.cfg
|
Determine everything when system boot
|
|
grub2-mkconfig -o /boot/grub2/grub.cfq
|
Write a new GRUB config
|
|
systemd.unit=rescue.target
|
Start booting at rescue mode
|
|
systemd.unit=emergency.target
|
Boot at minimal
|
|
mount -o remount,rw /
|
Put root file system in read,write mode
|
|
rd.break
|
Break in boot procedure at the end of init params
|
|
chroot /sysroot
|
Set root file system to /sysroot
|
|
echo b > /proc/sysrq-trigger
|
Crash and reset
|
|
touch .autorelabel
|
on CentOS
|
|
getsebool -a
|
List of all current booleans
|
|
setsebool ftpd_anon_write on
|
Switch on to anonymous writing on ftp
|
|
Press f
|
Changing top window and sorting
|
|
Press z
|
Color top window
|
|
Press W
|
Write to config file
|
|
RT
|
Real time process, part of the kernel
|
|
Within top, press r
|
|
|
nice -n 5 dd if/dev/zero of=/dev/null &
|
Run dd command with nice value of 5 and priority of 25
|
|
renice -n 5 14053
|
Change priority of process id 14053
|
|
yum search pacckage
|
Search for package
|
|
yum info package
|
Info about package
|
|
yum provides */filename
|
Provide package info
|
|
yum remove package
|
Remove package
|
|
yum downloader package
|
Download the package to analyse
|
|
yum list
|
Get information about package
|
|
yum install
|
Install from the repo
|
|
yum update
|
Compare packages and update if suitable
|
|
/usr/lib/systemd/system
|
Dir for unit file and timers
|
|
systemctl status atd
|
Check at daemon status
|
|
at 11:00, Ctrl+d to start job
|
start job at 11
|
|
atq
|
Current jobs running w/ at
|
|
atrm jobnumber
|
Remove job
|
|
lsmod | less
|
List modules
|
|
modprobe cdrom
|
Load cdrom module
|
|
modinfo cdrom
|
Info about module
|
|
/etc/modprobe.d
|
|
|
echo options cdrom autoclose=1 > cdrom.conf
|
Create cdrom.conf to automatically apply option
|
|
/proc
|
Interface to modify linux kernel
|
|
echo 1 > /proc/sys/ipv6/conf/all/disable_ipv6
|
Disable ipv6 on runtime
|
|
echo net.ipv6.conf.all.disable_ipv6 = 1 > etc/sysctl.d/ipv6.conf
|
Disable ipv6 persistently
|
|
sysctl -a
|
List all tools
|
|
getenforece
|
Current mode of SELinux
|
|
setenforce Permissive
|
Change to Permissive mode
|
|
cd /etc/sysconfig/selinux
|
Disable or enable SELinux
|
|
man semanage-fcontext
|
man page for setting context
|
|
semanage fcontext -a -t httpd_sys_content_t "/web(/.*)?"
|
Setting SELinux to allow Apache read from /web
|
|
ls -lZd /web
|
|
|
restorecon -Rv /web
|
|
|
semanage port -a -t http_port_t -p tcp 444
|
Allow Apache listen to port 444
|
|
less /var/log/messages
|
Look for sealert
|
|
sealrt -l code
|
Troubleshoot sealert
|
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