LPIC-1

during studying for LPIC-1 I made some notes; unfortunately in German, so it is quite stupid to write this description in English

• Chapter 101 LPI101_Topic101.txt
• Chapter 102 LPI101_Topic102.txt
• Chapter 103 LPI101_Topic103.txt
• Chapter 104 LPI101_Topic104.txt

Linux commands

dig cheatsheet neverendingsecurity.wordpress.com

LPIC Topic 200: Capacity Planning

sar from the package sysstat shows the processor activity, this gives five measurements every three seconds: sar 3 5

sar also could be used to measure network interfaces and I/O transfer rates, first command measure one time for five seconds: sar -n DEV 5 1

this command measures the I/O rates every 10 seconds three times: sar -b 10 3

to collect data over a longer period, we have to set ENABLED="true" in /etc/default/sysstat and start the service. After ten minutes we can see the collected data with: sar -A

iostatfrom sysstat is similar to sar when running without attributes

• shows CPU usage iostat -c
• shows usage of devices iostat -d
• human readable iostat -h
• extended statistics iostat -x

iotop show I/O like command top. To show the current I/O processes do this:

iotop -o

other commands vmstat netstat ss iptraf

pscommand:

• a – show all processes
• u – start time, path, user
• x – also precesses not bound to a terminal (e.g. init or cron)
• -C – all instances of a process
• -U – user

instead of using ps aux | grep tomcat we could search for java processes with: ps u -C java ps -fC java ps -fC java,apache2

other commands pstree top more modern than top with color an scrolling: htop

show load an uptime with: uptime w

show what file is open at an external drive lsof /media/mydrive

LPIC Topic 201: Linux Kernel

identify current kernel version: uname -r

compile commands make config make oldconfig make menuconfig make dep make clean make bzImage make modules make modules_install

show state of the modules of the running kernel. lsmod basically shows the content of /proc/modules

inspect the modules of a kernel modinfo options of modinfo:

• -a – shows the author
• -d – shows the description
• -l – shows the license
• -p – shows the parameters
• -n – shows the file name of the module

other mod commands

• insmod – insert a module in a running kernel
• rmmod – removes a module
• modprobe – optimized command from insmod and rmmod. modprobe resolves dependencies automatically
• depmode – creates a new modules.dep file where the relations between the modules are stored

At runtime the kernel stores its information in the /proc file system under /proc/sys/kernel/ cd /proc/sys/kernel/ cat osrelease cat ostype cat hostname cat domainname cat modprobe

show which files are open in a mounted drive lsof /media/disk/

udev manges /dev. Configuration at /dev/udev/.
To monitor udev: udevadm monitor

lot of information about a process: cat /proc/9842/environ | tr "\000" "\n" the tr is needed here, to have a line break after every parameter

LPIC Topic 202: System Startup

show differnces in systemd config systemd-delta

create backup of the MBR dd if=/dev/sda of=mbr.backup ibs=512 count=1

update grub after installing new kernerl update-grub2

check file system

fsck -t ext4 -V /dev/sdb1

• -a – automatically repair errors
• -y – automatically answer all questions with "yes"
• -A – automatically check all file systems listed in /etc/fstab

LPIC Topic 203: Filesystem and Devices

parameters of the mount command

• -a – mount all in fstab
• -r – read only
• -w – writeable
• -t – file system type
• -v – verbose
• -o – mount options

remount mount -v -o remount,rw /path

NFS mount mount -t nfs pcname:/path /mnt

SMB mount mount -t smbfs //pcname/share /mnt

Content of /etc/fstab:

1 file system	2 mount point	3 type	4 options	5 dump	6 pass
UUID=9ae73f06-5ee6-45f5-8f55-c4837bc7ca2a	/	ext4	errors=remount-ro	0	1
UUID=d583c4be-8d35-4bb5-bc81-cda80e1606b4	none	swap	sw	0	0
UUID=58236382-9d8f-40a5-ba65-0bc431df69aa	/home	ext4	acl,user_xattr	1	2

column 5 defines, if the file system is saved by dump
column 6 defines, if and when a file system is checked by fsck:

• 0 – not checked
• 1 – checked with priority
• 2 – checked after file systems with "1" are checked

find UUID of your partitions blkid

no fsck when start next time shutdown -hf now

force fsck when start next time shutdown -hF now

LPIC Topic 204: Advanced Storage Device Administration

LVM

• fdisk with LVM (8e)
  
  ↧
• pvcreate
  
  ↧
• vgcreate
  
  ↧
• lvcreate

LPIC Topic 205: Network Configuration

ip command cheatsheet acces.redhat.com (pdf)

ifconfig eth1 192.168.1.111 netmask 255.255.255.0

route add default gw 192.168.1.1
route add -net 192.168.191.0/24 gw 192.168.190.1

route -A inet6

Delete arp entry:
arp -d 192.168.1.1

ip command:
ip route show    # same as route -n command
ip neighbour show    # same as arp command
ip addr show eth0    # same as ifconfig command
ip tunnel show    # capsulated ipv6 packages in ipv4 packages
ip monitor    # live monitoring of arp table

wifi commands iwconfig wlan0 iwconfig wlan0 txpower 30mW iwlist wlan0 frequency iwlist --help
    Usage: iwlist [interface] scanning [essid NNN] [last]
    [interface] frequency
    [interface] channel
    [interface] bitrate
    [interface] rate
    ... iw dev wlan0 link # same as iwconfig wlan0

some network commands:

• add additional IP address to eth0a: ifconfig eth0:1 172.16.111.111
• add route for the net just added to the gateway of that network route add -net 172.16.111.0/16 gw 172.16.111.1
• route with IPv6 route add -A inet6 2001:6f8:1cfe:1::/64 gw 2001:6f8:1cfe:0::4 route -A inet6
• netstat
  • netstat -tulpen – shows all important information
  • netstat -r – shows routing table as route -n
  • netstat -i – shows list of interfaces
  • -t – tcp sockets
  • -u – udp sockets
  • -l – socketes in LISTEN state
  • -p – Show the PID and name of the program to which each socket belongs.
  • -c – continuous display of the connections, cancelling with CTRL+C
  • -n – numerical
  • -e – Display additional information. Use this option twice for maximum detail.
  • -a – shows all connections
  • -c – continuous display of the connections, cancelling with CTRL+C
• ss newer than netstat with similar syntax, e.g. ss -tulpn
• tcpdump dump traffic on a network
  • -i eth0 interface eth0
  • -n numerical
  • -w /tmp/dump.file write to file
  • -F read from a file, not an interface
  • tcpdump tcp port 80 -i eth0 filter the dump on port 80
• show open connections with lsof lsof -i -n -P
• netcat
  • netcat -l -p 4444 – listen on port 4444
  • netcat 192.168.1.199 4444 – connect to port 4444
• add an ip address to an interface without an alias. This address will not be showed in ifconfig only in ip addr show ip address add 172.16.1.123/24 dev eth0 ip address add 2a01:198:5dd::47/64 dev eth0
• add a route wite ip command ip route add 172.16.1.0/24 via 192.168.1.1 ip address add 2001:6f8:1cfe:4f44::/64 via 2001:6f8:1cfe::4
• Port scan with nmap nmap server.tld.com
• Port scan with nmap, avoiding ping if this is disabled nmap server.tld.com -P0
• scan whole network nmap -P0 192.168.0.0/24
• scan whole network on port 80 and 443 nmap -P0 -p 80,443 192.168.0.0/24
• hostname
  • hostname – shows or changes the host name
  • domainname – shows or changes the NIS/YP domain name of a host
  • dnsdomianname – shows the system's DNS domain name of a host
• live traceroute mtr 192.168.0.1
• With /etc/hosts.allow and /etc/hosts.deny we can allow/deny a connection to a machine
  • ALL : ALL in /etc/hosts.deny to deny every connection, if not an allow in the allow file
  • ALL : LOCAL in /etc/hosts.allow to allow every connection in the same domain

LPIC Topic 206: System Maintenance

• install headers with current kernel apt-get install linux-headers-$(uname -r)
• extract a tar.gz tarball tar xvzf mytarball.tar.gz tar xvzf mytarball.tar.gz --directory=/opt/
• create a tar.gz tarball tar cvzf /path/mytarball.tar.gz /myfolder/
• options for tar -x – extract -c – create -z – gzip/gunzip -j – bzip2/bunzip2 -J – xz/unxz -v – verbose -t – table; list all files of the archive, without extracting -f – file: has to be the last one before the file tar cvf /dev/st0 /home – tape archive of /home tar xvf /dev/st0 /home/daniel/important.doc – tape archive restore important.doc
• create gzip without deleting original file: a redirector to the new file is needed, otherwise the output will be printed to the terminal gzip -c bachelorthesis.doc > bachelorthesis.doc.gz
• show content of a gz archive gzip -l bachelorthesis.doc.gz
• gunzip an archive, zcat is the same as gunzip -c gunzip bachelorthesis.doc.gz gzip -d bachelorthesis.doc.gz zcat bachelorthesis.doc.gz
• bzip2 commands bzip2 file bzip2 -c file > file.bz2 bunzip2 file.bz2 bzip2 -d file.bz2 bzcat file.bz2
• xz commands xz file xz -c file > file.bz2 unxz file.bz2 xz -d file.bz2 xzcat file.bz2
• tape devices
  • first rewinding SCSI tape /dev/st0
  • first non rewinding SCSI tape /dev/nst0
  • first rewinding floppy tape /dev/ft0
  • first non rewinding floppy tape /dev/nft0
• dd copy between two disks dd if=/dev/sda of=/dev/sdb
• save mbr with dd dd if=/dev/sda of=mbr.backup ibs=512 count=1
• systemd shutdown command systemctl poweroff