linux commands
File & directory management
nano
Vim
touch
tee
directory level operations
file permissions
644
r read
W write
X execute
changowner chown
Ownership
Owner, group, public
change group
chgrp
User management
users
group
Permission
system accounts
interactive accounts
sudo add user newuser;
m- creates directory for user, if not exist.
M- not creates directory for user
add /change password to user
passwd newuser;
groupadd newgruop;
creates new group.
gpasswd newgruop:
New password
renterpassword
groups; to view all groups
groups groupname
To view users in group
chgrp file/directory ownership to other group.
usermod
add & remove users from gruop
-a adds user to gruop only -G option
-G adds removes users to secondary groups
-g primary group
-d directory users directory
usermod -a -G group user
Disk quota management
backup fstab
backup grub file
edit files
Save
add quota to user, gruop
Remoount & restart
Systemd services
systemd used to manage both services and daemons
systemctl –version
systemd 230
Units are the resources systemd knows how to interpret
12types
-
.service
-
.socket
-
.device
-
.mount
-
.automount
-
.swap
-
.target
-
.path
-
.timer
-
.snapshot
-
.slice
-
.scope
/lib/systemd/system (base unit files)
/etc/systemd/system (modified unit files at runtime)
-t service or sockets
-a loaded units
systemctl -t service
systemctl stop apache2
systemctl –all -t service | grep apache2
Start/stop/reload/restart/enable/disable/status
systemctl status network.service
systemctl is the utility used to control systemd
systemctl status
all status
systemctl status firewalld
Ufw iptables
list-units
systemctl list-units –type=socket
systemctl list-units –type=service
systemctl cat firewalld
Cat to read/write append etc.
cgroups or Control Groups
used assign resources for groups and users by admin
cpu,disk, memory,
Install & enable libcgroup
yum install libcgroup
systemctl enable cgconfig
|
CPU Slices
|
CPUShares
|
Linux process management
Process Management–bg, fg, nohup, ps, pstree, top, kill, killall, free, uptime, nice.
PID= process identification number
Pgrep used to know pid of process.
pgrep systemd
1
jobs − List of the current processes attached to the shell
ctrl+z to. sleep the current process.
ps command
ps axw | grep python
ps= process snapshot
grep : to filter the process name
a= Excludes constraints of only the reporting processes for the current user
X=Shows processes not attached to a tty or shell
W= Formats wide output display of the output
-u= shows all processes by specific user
-c all process by name or PID
-e selects all ptocesses
–sort
to see all processs by user
ps -u www-data
all information about the process nginx
ps -wl -C nginx
top 10 memory consuming process
top,htop
Or
ps aux –sort =-pmem | head -10
pstree
tree like model
killall
killall chrome
kills all the process for all users.
pkill: kill the process by name
pgrep apache2
to know process id
pkill -9 apache2
Kill command
Kill pid
Signals graceful kill
SIGTERM
Firewall setup
firewalld in centos
iptables /, ufw in ubuntu debian Linux distributions
block ports,
block services,
block ipmasq
ICMP (Internet Control Message Protocol)
Block ip addresses
firewalld &ufw uses iptables as a backend.
Remote management of linux sever
ssh client (putty), sftp client (winscp).
whm,capnel,zpanel etc.
Linux Log management
components behind systemd logging are: journald(daemon), jounralctl(analyzes events logged by journald), and journald.conf(config file)
journalctl −k (kernel messages)
journalctl −u (units like services, sockets,sshd,apache2)
logs by type emergency,warn
0-emergency
1 alert
2 critical
3 error
4 warning
5 info
6 debug
journalctl -p 4
Warning logs.
Backup & recovery
321 rule
3 copies of data.(working data, backup on server weekly, offline in hdd)
rsync remote sync
rsync syntax:rsync [options] [local path] [[remote host:remote path] or [target path
or use sftp client to download compress data.
Syncing backup in local & remote
local
mkdir /root/etc_baks
rsync -aAvr /etc/ /root/etc_baks/
DD to Recovery Images
system updates & package management
system updates & install update packages
linux disruption upgrade
sudo apt-get update && sudo apt-get upgrade
Installing packages or additional softwares
add dependency or repository
To install precomiled softwares for yiur linux distribution.
or manually downloaing & compile & install.
sudo apt-get remove curl
autoclean options are there.
Shell scripting
a bit knowledge of programming required.
Like logical operators, variables, condition statements, & loops .
Linux Volume management(LVM)
physical disk = dev/ sda
partioned physical disk dev / sda1 dev/sda2
Volume group (group of physical volume by physical disks) 2disk each 1tb in a sysyem 2tb is the volume group.
Logical volume
LVM tools such as the System Storage Manager: lsblk, parted, and mkfs.xfs.
lsblk is a great tool for getting disk information
disks on this system: sda, sdb, and sdc.
sda has linux so,
parted /dev/sdb mklabel GPT
all data will ve deleted
Create the Partition
parted -a opt /dev/sdb mkpart primary ext4 0% 100%
any warnings
Update fstab
/etc/fstab
Make files system
(Which linux file system useful for you)
xfs filesystem
mkfs.xfs -f /dev/sdb1
Lets verify
lsblk -o NAME,FSTYPE
Mounting
mount -o defaults /dev/sdb1 /mnt/sdb
mount on boot we need to edit fstab.
Or ssm
apt install system-storage-manager
ssm list
To know the volumes
create -p NEW_POOL /dev/sdb1 /dev/sdc1
One large disk from freespace
or 3seperateeach 3.3gb out of 10gb.
[email protected] rdc]# ssm create -n disk001 –fs xfs -s 3GB -p NEW_POOL