wbsouza · April 21, 2022 13:07 · Apr 21, 2022 · Feb 17, 2022 · Jul 5, 2021 · May 21, 2021
diff --git a/linux b/linux
@@ -5,6 +5,9 @@ yum clean all
 yum makecache
 yum update
 
+# reload sysctl configs
+sudo sysctl --system
+
 
 # force all the files in /var/www/html to be under the nginx group
 chown user:nginx -fR /var/www/html

diff --git a/linux b/linux
@@ -172,3 +172,10 @@ $ pigz -dk -p8 image.gz
  ffmpeg -i ./test.mkv -acodec cop test.mp4
 
 
+# force reinstall packages
+sudo apt-get remove --purge ufw
+sudo apt-get -o Dpkg::Options::="--force-confmiss" install --reinstall ufw
+systemctl enable ufw
+ufw enable
+
+
diff --git a/linux b/linux
@@ -168,5 +168,7 @@ $ pigz -k -p8 image.png
 # Decompress
 $ pigz -dk -p8 image.gz
 
-
+ # Convert video .mkv to mp4
+ ffmpeg -i ./test.mkv -acodec cop test.mp4
+
 
diff --git a/linux b/linux
@@ -22,6 +22,15 @@ sed -i 's+regex+new-text+g' file.txt
 
 find -type  f -print0 | xargs -0 sed -i '/real_date_done/s/real_date_done/done_date/g'
 
+
+# Renaming files
+apt-get install rename
+
+find . -name "* *" -type d | rename 's/ /_/g'    # do the directories first
+find . -name "* *" -type f | rename 's/ /_/g'
+
+
+
 # Using sed to remove lines
 sed -i '/KeyRegenerationInterval/d' /etc/ssh/sshd_config
 sed -i '/ServerKeyBits/d' /etc/ssh/sshd_config

diff --git a/linux b/linux
@@ -0,0 +1,163 @@
+# force yum to update all the caches avoiding the error
+#  [Errno 14] HTTP Error 404 - Not Found
+echo "http_caching=packages" >> /etc/yum.conf
+yum clean all
+yum makecache
+yum update
+
+
+# force all the files in /var/www/html to be under the nginx group
+chown user:nginx -fR /var/www/html
+find /var/www/html -type d | awk '{ printf("\"%s\"\n", $0); }' | xargs chmod 2775
+sudo setfacl -Rdm g:adm:rwx /var/www/html
+
+# Using sed to replace text in files
+sed 's/word1/word2/g' input.file
+## *bsd/macos sed syntax#
+sed 's/word1/word2/g' input.file > output.file
+sed -i 's/word1/word2/g' input.file
+sed -i -e 's/word1/word2/g' -e 's/xx/yy/g' input.file
+## use + separator instead of / ##
+sed -i 's+regex+new-text+g' file.txt
+
+find -type  f -print0 | xargs -0 sed -i '/real_date_done/s/real_date_done/done_date/g'
+
+# Using sed to remove lines
+sed -i '/KeyRegenerationInterval/d' /etc/ssh/sshd_config
+sed -i '/ServerKeyBits/d' /etc/ssh/sshd_config
+sed -i '/RSAAuthentication/d' /etc/ssh/sshd_config
+
+
+# finding the biggest directory
+du -a /home | sort -n -r | head -n 5
+
+
+# updating SELinux rules to accept nginx reverse proxy
+cat /var/log/audit/audit.log | grep nginx | grep denied | audit2allow -M nginx
+sudo semodule -i nginx.pp
+
+# reinstalling and updating SELinux
+setenforce 0
+yum erase selinux\*
+rm -rf /etc/selinux
+yum install selinux-policy-targeted 
+touch /.autorelabel
+reboot
+
+# show the oscap profiles
+oscap info /usr/share/xml/scap/ssg/content/ssg-centos7-ds.xml 
+
+# generate an oscap report
+oscap xccdf eval --profile xccdf_org.ssgproject.content_profile_pci-dss --results-arf arf.xml \
+  --report /var/lib/reports/$(hostname)-scap-report-$(date +%Y%m%d).html \
+  --oval-results /usr/share/xml/scap/ssg/content/ssg-centos7-ds.xml 
+
+# run an oscap ansible script to update the linux system 
+ls /usr/share/scap-security-guide/ansible
+ansible-playbook -i "localhost," -c local /usr/share/scap-security-guide/ansible/ssg-centos7-role-pci-dss.yml 
+
+# secure the files under the /etc/pam.d location ##
+chattr +i -R /etc/pam.d
+lsattr -d /etc/pam.d
+lsattr -l /etc/pam.d
+cd /etc/pam.d
+
+## Try to add or delete something ##
+echo "test" > foo.txt
+mkdir foo
+ls -l
+rm system-auth
+
+## remove the immutable attributes again ##
+cd /etc/pam.d
+chattr -i -R  /etc/pam.d
+lsattr -d  /etc/pam.d
+
+# fixing the umount for a pendrive takes forever
+# edit your /etc/rc.local and add
+echo $((16*1024*1024)) > /proc/sys/vm/dirty_background_bytes
+echo $((48*1024*1024)) > /proc/sys/vm/dirty_bytes
+
+
+# show IPs associated with the network interfaces
+show_iface_ips() {
+  ip addr | awk '/^[0-9]+:/ {  sub(/:/,"",$2); iface=$2 } /^[[:space:]]*inet / {  split($2, a, "/"); print iface":"a[1] }'
+}
+# or in two steps
+net_device=$(ip route | grep default | grep -v tun | awk '{ print $5 }' | sed -z 's/\n//')
+ip_address=$(ip route| grep $net_device | grep -v default | grep src | awk '{ print $9 }' | sed -z 's/\n//')
+echo $ip_address
+
+
+# Show the main IP from the machine
+ifconfig | grep -E "([0-9]{1,3}\.){3}[0-9]{1,3}" | grep -v 127.0.0.1 | awk '{ print $2 }' | cut -f2 -d: | head -n1
+
+
+# Expanding an volume partition
+1) Use fdisk to add an extra partition
+2) vgextend centos /dev/sda3 # (adding a partition to the Volume Group)
+3) lvcreate -n home -L261GB centosID
+
+# show the current partitions with their respective uuids
+blkid
+
+# checking for errors and fixing them
+e2fsck -f  /dev/nvme1n1p1 
+
+# change the uuid partition 
+tune2fs /dev/nvme1n1p1 -U $(uuidgen)
+
+# utility to allow change the uuid / PARUUID
+gdisk /dev/nvme0n1   # PRESS x => expert, c => change PARUUID, w => write and exit
+
+# changing the PTUUID (unique identifier for the entire disk)
+fdisk /dev/nvme0n1 <<EOF > /dev/null
+p
+x
+i
+0x${PTUUID}
+r
+p
+w
+EOF
+
+
+# compressing directory and transfering the stream via ssh and decompressing 
+ssh user@host "cd /tmp/media; tar -cz Music" | tar xvz
+
+# or upload directory the same way
+tar -cz ./Music | ssh user@host "tar zx -C /new/path/to/data/"
+
+# copy partitions from different computers
+ssh root@source_host  "dd if=/dev/sda1 " | pv | dd of=/dev/vda1
+
+# split a big file into smal and compressed files
+ split --bytes=1024M --filter='gzip > $FILE.gz' ./source/file.dat ./output/path
+
+#---------------- mounting partition inside of a raw image from a disk ----------------
+# The filesystem itself starts on sector 63. You can also view this with fdisk -l:
+fdisk -l harddrive.img
+                    Device Boot      Start         End      Blocks   Id  System
+harddrive.img                *          63    33640109    16820023+  83  Linux
+
+# We need to skip 63 sectors, and each sector is 512 bytes long
+# So, we need to use an offset of 32,256 bytes.
+mount -o ro,loop,offset=32256 harddrive.img /mnt/loop
+mount | grep harddrive.img
+  /root/harddrive.img on /mnt/loop type ext3 (ro,loop=/dev/loop1,offset=32256)
+
+
+# reset number of invalid authentications 
+pam_tally --reset --user <USERNAME> 
+pam_tally2 --reset --user <USERNAME>.
+
+#===== GZip parallell compression
+# Compress
+# Always use -k to keep the original file
+$ pigz -k -p8 image.png
+
+# Decompress
+$ pigz -dk -p8 image.gz
+
+
+
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