Legacy BIOS vs UEFI, Partition table:GPT vs MBR, Boot Loaders: GRUB, GRUB2, LILO Booting process legacy vs uefi Initramfs, Intitramrd, vmlinuz runlevels, targets, sysvinit, systemd, process id 1, Anaconda, kickstart, cfengine, Boot troubelshooting, Installing grub, manual booting, RHEL 6vs7vs8, Updating Kernel, Kernel panics, Package management, repositories,
LINKS:
Legacy BIOS vs UEFI
MBR vs GPT partition table
GRUB vs GRUB2
more
more
updating grub
Initrd and Initramfs
Complete boot process
more
Post bootup
init vs systemd
rt-kernel
kernel panic
kernel upgrade manually
booting issue
RHEL 6vs7vs8
Types of shells, env_varibales, global/local scope, export command, profiles and bashrc files, standard streams, redirections, regexs, scripting, config files, cron, anacron,
LINKS:
shell, rc and profiles files,
shell redirections
REGEX
Differnt types shells
Special variables
Environment variables
bash scripting cheatsheet
shell config files
crontab more
anacron more\
nice, renice, zombie, orphan, IPC's, system calls, process states, Exit code, kernel and user space, cache, buffer, Avg load, steal time, top, -namespaces, cgroups
LINKS:
Process priority - nice - renice
Zombie, Orphan process
IPC basic
IPC basics2
system calls vs interupts
sockets
Best read for IPC
Process, states, signals
Process signals
exit code
Kernel and user space
buffer cache
clear cache
top command
Top command memory usage
steal time
cgroups and namespaces
swapiness
paging vs swapping
Changing swappiness value
File permissions, attributes-chattr/lsattr, umask, special permissions, sticky bits, umask, ACL's, Xfs, ext2/3/4, btrfs, inodes, hard/soft links, fdisk, parted, lvm, raid, encrypted filesystem, Luks, DRBD, fstab, df ,du,swap, /proc filesys, multipath, device mapper, dmsetup, nfs, iscsi, backups and restorations
LINKS:
File permissions
File attributes
umask more
special perms suid,sgid,sticky bits
ACL's
ext/btrfs/xfs
ext2,ext3,ext4
hard link
hard link/soft link
inodes
Create partition using fdisk
parted vs fdisk
LVM-redhat
LVM-thegeekdiary
RAID
Encrypted partition
LUKS
DRBD
fstab
df command
du vs df One more
du
swap
swapiness
/proc more /proc
multipath
device mapper
[File descriptor]
[ulimit]
Selinux, iptables, firewalld, polkit, ACL's, sudo, SSL/TLS, md5,sha, System hardening
LINKS:
SELINUX P1, P2, P3
iptables, 1, 2
firewalld
polkit
[ACL's]-Basic, Detailed
SSL,TLS
Hardening
md5,sha
Find, locate, grep, awk, sed, cut, wc, sort, tar, zip, bzip, gzip, zcat, lsof, curl, wget, dd, hexdump, nohup, screen, atime, mtime, ctime, ssh, strace
LINKS\
Find 1, find 2
find empty file and delete
find mtime perm examples
locate
grep
awk
sed 1, sed 2
cut , wc
sort, uniq
gzip vs bzip2
tar, gzip
zcat
lsof
wget
dd
hexdump
nohup
screen vs nohup
atime,ctime,mtime
strace 1 2
ssh
Local logs, rsyslogs, remote/central logs, logratate, log-levels, journalctl,
LINKS:
Linux logging 1 2
syslog vs rsyslog vs syslog-ng
remote/centralised logging One more
logrotate
log level
journalctl\
user, group, password management, sudoer, LDAP, AD, kerberos auth,
LINKS:
useradd groupadd
chgrp usermod
passwd file passwd command
getent
sudoers
restricting sudo
authentication protocols
LDAP vs Kerb
Kerberos
LDAP
AD connection
*Configuring nic, ip command, setting route/gateway, adding dns entries, hosts file, hostname, teaming, bonding, bond modes, bridges
OSI model, subnet calculation, TCP/UDP pros and cons, TCP handshake, TCP flags, MTU, MSS, tcp packet capture, Window size, sequence number, socket states, graceful/forceful diconnection, checksums, fragmentations
Routing - Dynamic, static. NAT, subnetting, ICMP, ARP, Broadcast, multicast, unicast, OSPF, BGP
Switching - VLAN, MAC table
Troubleshooting - Slow/No network, routing, TCP connection, tools like ping, traceroute, MTR, IPref, netstat, wireshark, etc.
LINKS:\
*DNS, DHCP, HTTPD, Mysql, LoadBalancer, AD, LDAP, *
LINKS:
AD\
Disk, Process, Network, Web server, Memory,
What is laod average and how to interpret the values
LINKS:
Trooubleshooting 101
Basic tools/commands
fuser - https://www.tecmint.com/learn-how-to-use-fuser-command-with-examples-in-linux/ strace - significance of /etc/groups /etc/passwd /etc/shadow files. sudo, sudoer
Networking: https://www.redhat.com/sysadmin/7-great-network-commands
Performance: Benchmarking tools
Interview questions: https://javarevisited.blogspot.com/2011/05/unix-command-interview-questions.html#axzz70Qbi7t7y