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covelus/GNU_Linux_main_config_files_and_commands.sh

Created March 29, 2020 10:24
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GNU/Linux, main config files or debug ones & related commands
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GNU_Linux_main_config_files_and_commands.sh
# --------------------- PACKAGE MANAGEMENT ---------------------
# DPKG
$ dpkg -S /etc/file.conf # what package this file belongs to
$ dpkg -L <package> # package info (inc. files it contains)
$ dpkg -V <package> # verify
$ dpkg -r <package> # remove
# APT (apt = apt-get)
$ apt [-u] upgrade # -u show upgraded
$ sudo apt autoremove
$ sudo apt-get clean # will save space
$ sudo apt-get remove <package>
$ sudo apt-get --purge remove <package> # remove pkg + config
$ apt-cache search <package-name>
$ apt-cache search -n <installed-package-name> #installed and available
$ apt-cache show <package>
$ apt-cache [r]depends bash # normal and Reverse dependencies
$ apt-cache search metapackage
# --------------------- Standard CONFIG files ---------------------
RHEL 6: /etc/sysconfig/
Debian: /etc/default/
SuSE/RHEL 7: both
# --------------------- GRUB 2 ---------------------
/boot/grub[2]/grub.cfg #edit through:
/etc/default/grub
$ update-grub
/etc/grub.d/
# --------------------- INIT: SysVinit ---------------------
/etc/inittab
$ runlevel
$ telinit <num>
/etc/rc.d/[rc<num>.d/]
rc.local
$ chkconfig
$ service [<name> [status | ... ] | --status-all]
# Debian/Ubuntu:
# apt install sysvinit-utils chkconfig
# sudo status <name>
# --------------------- INIT: Systemd ---------------------
Ex:
/etc/hostname
/etc/vconsole.conf
/etc/sysctl.d/*.conf
/etc/os-release
$ systemctl
$ systemctl list-units -t service [--all]
$ sudo systemctl [ daemon-reload | [start | stop | enable | disable is-enabled] <serv-name>.service]
# FS: BOOT
/boot/
- vmlinuz
- initramfs
- config
- System.map
# FS: pseudo-fs's
/dev
/proc
/sys #sysfs
[/tmp, /run]
# --------------------- Kernel MODULES ---------------------
/lib/modules/$(uname -r)
/sys/module/<module-name>[/parameters]
/etc/modprobe.d/
# --------------------- Devices & UDEV ---------------------
$ mknod [-m mode] /dev/<name> <type> <major> <minor>
/dev/
# udev: libudev, udevd, udevadm
/etc/udev/udev.conf
/etc/udev/rules.d/<rulename>.rules
# --------------------- STORAGE/part ---------------------
#0.- boot code: , 446 Bi
#1..3.- part i: 16 Bi
#4.- part 4: 16 Bi, 0x55AA
$ fdisk
$ mkfs.ext4 /dev/...
$ blkid /dev/...
$ lsblk -i
$ dd if=... of=... bs=... count=...
$ partprobe -s # with summary. Not until restarting
# partprobe informs OS of partition table changes
$ cat /proc/partitions
# --------------------- FILESYSTEMS ---------------------
/proc/filesystems
$ sudo mount [-t <fs>] [[<dev>|UUID=|-U ]<uuid>] [[LABEL=|-L ]<label>] </mount-point>
$ sudo mount -o remount,ro </mount-point>
$ umount [dev | mount-point]
/etc/fstab
# <device> <dir> <type> <options> <dump> <fsck>
# /dev/sda11 /mnt/tempdir ext4 defaults 1 2
$ lsattr <filename>
$ chattr [+|-|=mode] <filename>
# i Immutable, also, no hard links
# a Append-only
# d Do-dump, ignored when 'dump' runs
# A: no-Atime
$ ln [-s] <file> <new_link> # link: hard (pointing inode in same FS) or, with -s, soft (if you move original, you lose the reference, but works accross FS's)
/sbin/mkfs*
$ sudo mkfs -t <fs> <dev>
$ sudo mkfs.<fs> <dev>
/sbin/fsck*
$ sudo fsck -t <fs> [options] <dev>
$ sudo fsck.<fs> <dev>
$ sudo touch /forcefsck; sudo reboot
$ e4defrag
$ dumpe2fs # show Ext FS info
$ tune2fs
$ tune2fs -c 30 <fs> # sets max count in 30
$ tune2fs -i 3w # Sets interval between checks to 3w
# Quota
$ quota
/etc/fstab:
/dev/sda11 /mnt/tempdir ext4 usrquota 1 2
$ sudo mount -o remount /mnt/tempdir
$ sudo quotacheck -u /mnt/tempdir
$ sudo quotaon -u /mnt/tempdir
$ sudo chown student.student /mnt/tempdir # optional
$ sudo edquota -u student
# TMPFS:
$ df -Th /dev/shm/ # -T type
$ sudo mount -t tmpfs none /mnt/tmpfs # creates a tmpfs, also:
$ sudo mount -t tmpfs -o size=1G none /mnt/tmpfs
# FS Loop Mechanism:
# setup, method 1
$ sudo mount -o loop imagefile mntpoint/
# setup, method 2:
$ sudo losetup /dev/loop2 imagefile
$ sudo mount /dev/loop2 mntpoint
$ sudo umount mntpoint
$ sudo losetup -d /dev/loop2
/proc/swaps
$ free -o
# --------------------- PROCESES # ---------------------
# ID = 1 --> init
/proc/sys/kernel/pid_max
$ ulimit [-a | -n 1600] #process limits & 1 example
# SystemV IPC:
# 1.- shared memory segments
# 2.- semaphores
# 3.- message queues
$ ipcs # SystemV IPC activity
$ ipcs -p # proceses that created them
$ ps -elf #procesos kernel
# fork vs exec
#Modif valor nice:
$ nice
$ nice -n 10 bash # enter in a new bash with priority 10
/etc/security/limits.conf # allow users to reduce niceness
$ renice [+|- <num>] <pid> # establece a prio en ±num, non suma ou resta
$ renice 15 -p <pid>
Shared libraries:
$ ldd /.../<bin-file> # shared libs required by this process
/usr/lib64/*.so*
$ ldconfig
/etc/ld.so.conf # used by ldconfig
# --------------------- SIGNALS ---------------------
$ kill [-l | [- signal] <pid>]
$ killall
$ pkill [-signal] [options] [pattern]
# --------------------- SYSTEM MONITORING ---------------------
$
# --------------------- USERS ---------------------
$ useradd [-s <shell>] [-m] [-k <skels>] [-c "Name Surname"] <username>
/etc/skel
/etc/login.defs
/etc/passwd # 644
/etc/shadow # 400
pam_cracklib
/etc/nologin.txt
$ userdel <u>
$ usermod [-L] <u>
$ chage -E <date> <u>
$ chage [-m mindays] [-M maxdays] [-d lastday] [-I inactive] [-E expiredate] [-W warndays] [-l] <u>
$ chage -d 0 <u>
$ bash -r # or rbash, restricted shell
# Root remote login
/etc/securetty #& associated module pam_securetty.so
/etc/ssh/sshd_config
# SSH:
$
# --------------------- GROUPS ---------------------
/etc/group
/etc/gshadow
$ groupadd
# e.g: groupadd -r -g 215 staff
$ groupmod
# e.g: groupmod -g 101 blah
$ groupdel <groupname>
$ usermod -G <groups> <user> # max 15
# e.g: usermod -G user1, group1, group2 user1
/etc/profiles # umask
# --------------------- FILE PERMISSIONS ---------------------
$ chmod
$ chown [-R] <user>[:group] <file>
$ chgrp
$ umask [number]
# default permissions at creation: 0666 files, 0777 directories, but just before applying umask (0002):
# (0666 | 0777) & ~0002 = (0664 | 0775)
# --------------------- ACLs ---------------------
$ getfacl [file|dir]
$ setfacl [ops] [permissions] [file | dir]
$ setfacl -m u: username:rx /home/u/fl1
# --------------------- PAM ---------------------
# config files
/etc/pam.d/
# type control mod-path mod-args
# type: auth, account, password, sessio n
# auth: required, requisite, optional, sufficient, include, substack
# libpam*
/lib/security
/lib/x86_64-linux-gnu
/lib64/security
# Apps must be individually configured individually in a file in /etc/pam.d
# --------------------- LDAP ---------------------
# config files:
/etc/openldap/ldap.conf
/etc/pam_ldap.conf
/etc/nslcd.conf
/etc/sssd/sssd.conf
/etc/nsswitch.conf
# Uses PAM + system-config-authentication | autoconf-tui
$ system-config-authentication
$ autoconf-tui
# --------------------- BACKUPS ---------------------
$ cpio
# $ ls | cpio --create -O /dev/st0
#$ cpio -t -I /dev/st0
$ tar
# tar -cvf <destination> /root
# tar -cMf <destination> /root # M = multiple volumes
# tar --compare --vervose --file /dev/st0
# tar --list --file <destination>
# tar xvf /dev/st0 somefile
# tar --extract --same-permissions --verbose --file /dev/st0
#BZIP2, GZIP, XZ...
$ tar zcvf file.tar.gz source
$ tar jcvf file.tar.bz2 source
$ tar Jcvf file.tar.xz source
$ tar x[zjJ]vf file.tar...
$ dd if=in-file of=out-file [options]
$ rsync [ops] src dest
$ sudo dump -0uf /tmp/backup /boot #level 0 backup, uncompress with restore
$ sudo restore -rfv /tmp/backup
$ tar xvf file.tar...
SYSTEM MONITORING
#/proc & /sys pseudo-fs's
/proc/sys/
‎ abi/ #binary app info, not very used
‎ debug/
‎ dev/ #devices
‎ fs/
‎ kernel/
‎ threads-max
‎‎ ‎ # sudo bash -c 'echo 10000 > /proc/sys/kernel/threads-max'
‎ ‎‎ ‎ # sudo sysctl kernel.threads-max=10000
‎ net/
‎ vm/
# process & load
# procps package
$ top
$ uptime
$ ps
# -A or-e Select all processes
# -N Negate selection (means do the opposite)
# -C Select by command name
# -G Select by real group ID (also supports names)
# -U Select by real user ID (also supports names)
$ ps -o pid,pri,ni,cmd
$ ps -C <command> -o pid,cmd,pri,ni,stat # info & status of process
# psmiscs/pstree package
$ pstree
# systat package
$ mpstat # multi-processor status (usage)
$ iostat # CPU utilization & I/O stats
$ sar # sys activity reporter
# (same name packages)
$ numasat # Non-Uniform Mem Arch status
$ strace # syscalls trace
$ <comand> & # start in foreground
$ fg # recovers <command> from foreground
$ jobs
# Mem
# procps package
$ free
$ vmstat
$ pmap
# I/O
# systat package
$ iostat
$ sar [ops] [interval] [reps]
$ vmstat
# Network
$ netstat
$ iotraf
$ tcpdump
$ wireshark
# --------------------- MEMORY MONITORING & TUNING ---------------------
$ cat /proc/meminfo
# procps package
$ free
$ vmstat [ops] [delay] [repetitions]
$ vmstat -SM -a 2 4
$ vmstat -s # stats
$ vmstat -d # disk
$ vmstat -p /dev/sd... 2 4
$ pmap
$ sudo swapoff -a
$ sudo swapon -a
/proc/sys/vm # tunable knobs, change directly or with:
$ sysctl
# at boot time:
/etc/sysctl.conf
# Mem overcommit & OOM Killer
/proc/sys/vm/overcommit_memory #0 = permit excepting obvious, 1 = all allowed, 2 = off
/proc/sys/vm/overcommit_ratio
/proc/[pid]/oom_score
# --------------------- I/O MONITORING AND TUNING ---------------------
# system I/O-bound if CPU waits for I/O to complete
$ iostat [-k | -m] #KB | MB -N #show by dev name -x # extending (detailed)
$ sudo iotop [-o] # for show continuously static activity for all active I/O tasks
$ ionice [-c class] [-n prio] [-p pid] [cmd [args]] # only with CFQ I/O scheduler
$ ionice -c 2 -n 3 -p 30003
$ bonnie++ # I/O benchmarking program
# --------------------- I/O SCHEDULING ---------------------
# elevator (for rotational devs):
# SSD?
$ cat /sys/block/sda/queue/rotational
#linux ... elevator=[ cfq | deadline | noop ]:
$ cat /sys/block/sda/queue/scheduler # --> noop deadline [cfq]
$ echo noop > /sys/block/sda/queue/scheduler # persistence
# tunables
$ /sys/block/<dev>/queue/iosched
# flush cache
$ echo 3 > /proc/sys/vm/drop_caches
# --------------------- NETWORKING ---------------------
$ hostname # non-persistant
/etc/hostname # Deb
‎ /etc/sysconfig/hostname # RHEL6
$ hostnamectl set-hostname [...] # systemd
$ ifconfig #non-persistent
$ ifconfig | grep [env | wl] # eth0, eth1 | wlan0
$ ip [ops] <OBJECT> [command | help] #non-persistent
$ ip [-force] -batch filename
‎# OBJECT = {address, link, maddress, monitor, route, rule, tunnel}
‎/etc/sysconfig/network #RHEL
‎ /network-scripts/ifcfg-ethX:Y
‎/etc/network/interfaces # Debian
$ nmcli
# Name resolution
$ [dig | host | nslookup] <address.com>
$ search <address.com>
$ nameserver [IP]
$ ping
$ traceroute <IP | address.com>
$ mrt <address.com>
# --------------------- Firewalls ---------------------
$ sudo systemctl status firewalld
$ firewall-cmd [--help]
$ sudo firewall-cmd [--get-default-zone | --get-active-zones | --get-zones | --set-default-zone=[trusted|public]
‎$ sudo firewall-cmd [--zone=internal --change-interface=eno1 --permanent --zone=internal --change-interface=eno1 ] # last is permanent --> creates:
‎ /etc/firewalld/zones/internal.xml
‎$ sudo firewall-cmd --get-zone-of-interface=eno1
‎$ sudo firewall-cmd --zone=public --list-all
‎$ sudo firewall-cmd --permanent --zone=trusted --add-source=192.168.1.0/24
‎$ sudo firewall-cmd --permanent --zone=trusted --list-sources
‎$ sudo firewall-cmd [--get-services | --list-services --zone=public ]
‎$ sudo firewall-cmd --permanent --zone=home --add-service=dhcp
‎$ sudo firewall-cmd --reload
‎$ sudo firewall-cmd --zone=home --add-port=21/tcp
‎$ sudo firewall-cmd --zone=home --list-ports
‎$ grep "21/tcp" /etc/services
# --------------------- SECURITY ---------------------
#SELinux
$ getenforce
$ sudo setenforce Permisive
# Contexts: User, Role, Type (most common), Level
# Type --> _t, e.g: kernel_t
$ restorecon -Rv <file># reset files context based on dir settings
# --------------------- ALTERNATIVES ---------------------
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.7 1
sudo update-alternatives --install /usr/bin/pip pip /usr/bin/pip3 1
sudo update-alternatives --install /usr/bin/vim vim /usr/bin/vim.tiny 1
# MATH in Shell
$ expr <op1> <operation> <op2>
$ expr 1814400 / 60 / 60 / 24 / 7 # 3 weeks = 1814400 seconds
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