RHCSA Exam EX200 Cheat Sheet Part 3


SMBclient

To list Windows share

smbclient -U wtse -W smgtec -L x.x.x.x

To access windows share

smbclient -U wtse -W smgtec //x.x.x.x/share

To mount windows share

mount -t cifs -o user=wtse //x.x.x.x/share /mountpoint

Processes

To display a snapshot of info

pstree -p (/w PID) -a (/w command line)>/pre>
To display processes
ps -U (/w particular user) u (/w detail with the current account) aux (all users)

To view processes in realtime

top (-p2644)

nice value -20 to 19, -20 is the highest priority, zero is default

To set nice value

nice -n -10 service vsftpd start
ps -eo pid,nice,comm | grep vsftpd

Set the nice value on a current process

renice -n -5 2644 <--PID

To stop a process

kill PID = kill -s 15 PID (15 = clear shut down)

To kill a hang process

kill -9 PID

grep the http process owned by root user

pgrep -u root httpd

Use kill to reload the config file

kill -s 1 PID

To setup a cron job

crontab -e
mm hh dd MM DOW command

cron job is saved under /var/spool/cron

all daily job is stored in /etc/cron.daily

To setup atd job (runs once only)

at -f script now+2minutes (runs the script 2 mins from now)
at -f script 12pm tomorrow

To view atd job

atq or /var/spool/at

To remove atd job

atrm #

Syslogs

Syslogs config

/etc/rsyslog.conf

Kernel

dmesg to list the HW info
lspci -k to list PCI info
lsusb -t to view USB bus and device
dmidecode -t display every HW CPU/MEM/BIOS by default
lsmod	    to list loaded modules	
modinfo modulename	to list the detail of a specific module
modprobe -r -v modulename	to remove a module
modprobe modulename to load a module

To list the module in a kernel

ls /lib/modules/$(uname -r)/kernel

Boot Process

To protect grub menu
grub-md5-crypt to generate a md5 key
edit grub.conf before title
add password –md5″md5 key”

rcS.conf --> rc.sysinit --> inittab
runlevel	0	halt
1	single user mode
2	basic multi user mode (text mode, no nfs)
5	multi user GUI
6	reboot

To switch runlevel

telinit x

boot to single user mode during grub, enter 1 follow the parameter
passwd to change root password

prompt for a password in runlevel 1 by modify /etc/sysconfig/init
sulogin

Shedule a reboot

shutdown -r +5 (reboot in 5 mins)

To cancel a reboot

shutdown -c

Send notification

shutdown -h 23:00 "system will be down"

Shutdown immediately

shutdown -h now
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About the Author

Alfred Tong
Author and owner of this blog. A Networking enthusiast, full time networking and systems Engineer. Generally curious about all things IT.Certifications: GIAC GSEC, CCNP-S, CCNP, CCSP, CCDP, CCNA, RHCE, JNCIA - FWV