Get Github or Gitlab user key: ```console $ curl https://github.com/.keys $ curl https://gitlab.com/.keys ``` Enter a namespace, for example LXD (which is in a NS by Snap). ```console $ nsenter -t $(cat /var/snap/lxd/common/lxd.pid) -m ``` SSH into a machine without checking host key. Useful when servers are in a rescue mode. ```console $ ssh -o "UserKnownHostsFile=/dev/null" -o "StrictHostKeyChecking=no" -o "GlobalKnownHostsFile=/dev/null" ``` Certbot manual example. ```console # certbot certonly --non-interactive --webroot --webroot-path /var/www/html/ -d foo.bar -d www.foo.bar ``` GPG-agent list SSH key and remove. ``` gpg-connect-agent KEYINFO --ssh-list --ssh-fpr DELETE_KEY $HASH ``` Show md5 fingerprint of SSH key. ```console $ ssh-keygen -l -E md5 -f .ssh/key.pub ``` Password recovery. At grub stage, press `e` to edit the kernel line and add `init=/bin/bash`. It will drop you in a shell before init system (systemd). ```console # mount -o remount,rw / # passwd ``` Mount partitions on an image file using losetup. ```console # losetup -P -f --show my.img ``` List all software installed from particular component (non-free, contrib) ```console $ dpkg-query -W -f='${Section}\t${Package}\n' | grep ^non-free ``` Manually rotate a file without logrotate, with savelog(8). ```console $ savelog ``` What processes uses swap? ```console $ for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less ``` MySQL "fast" shutdown. ```console > set global innodb_max_dirty_pages_pct = 0; $ mysqladmin ext -i10 | grep dirty ``` mkfs.ext4 for old systems in rescue mode (Debian Wheezy, …). ```console # mkfs.ext4 -O ^64bit,^metadata_csum ``` Send a mail from queue. ```console $ postcat -q ID > mail $ < mail sendmail -f FROM TO ``` Python Simple HTTP Server (useful for Munin for example). ```console $ cd /var/cache/munin/www $ python -m SimpleHTTPServer 8080 ``` Show custom certs (not a link) and expiration in `/etc/ssl/certs`. ```console # find /etc/ssl/certs/ -type f -print -exec openssl x509 -text -in {} \; | grep --color=auto -e etc -e CN= -e DNS: -e After; ``` Edit Bind DNS serial (needs modifications, not generic). ```console $ sed -ri 's/^\s*[0-9]+\s*; serial/\t\t\t 2017041010\t ; serial/' db.* ``` After Debian/Ubuntu upgrade, merge local config files according to config files shipped in packages. ```console # for file in $(find /etc -iname '*.dpkg-dist'); do vimdiff ${file%%.dpkg-dist} $file; rm $file; done # for file in $(find /etc -iname '*.dpkg-old'); do vimdiff ${file%%.dpkg-old} $file; rm $file; done # for file in $(find /etc -iname '*.dpkg-new'); do vimdiff ${file%%.dpkg-new} $file; rm $file; done # for file in $(find /etc -iname '*.ucf-dist'); do vimdiff ${file%%.ucf-dist} $file; rm $file; done # for file in $(find /etc -iname '*.ucf-old'); do vimdiff ${file%%.ucf-old} $file; rm $file; done # for file in $(find /etc -iname '*.ucf-new'); do vimdiff ${file%%.ucf-new} $file; rm $file; done ``` Debug php with strace and php-cgi (especially useful for wp multisites). ```console $ HTTP_HOST=www.site.com SCRIPT_FILENAME=index.php REDIRECT_STATUS=CGI SERVER_NAME=www.site.com strace -s 65535 -o /tmp/strace php-cgi -f index.php ``` `ps` with long user fields (here 20). ```console $ ps axo user:20,pid,pcpu,pmem,vsz,rss,tty,stat,start,time,comm ``` WTF is happening in apache (or other)? Let's strace all apache processes. ```console # strace -p $(ps auwwwx | grep apache | tr -s '\t' ' ' | cut -d' ' -f2 | tr '\n' ' ' | sed 's/ / -p /g') 9999 ``` WTF is happening? Let's tail all logs. ```console # tail -f $(lsof | grep -F .log | tr -s '\t' ' ' | cut -d' ' -f10 | sort | uniq | tr -s '\n' ' ') ``` Search for suspects POST in apache.log (often attacks). ```console # grep -Eo '"POST .*.php' access.log | grep -ve cron -e login -e admin -e xmlrpc -e trackback -e comment -e 404 | sort -u ``` Check for crashed MySQL table in syslog and launch a repair. ```bash #!/bin/bash tables=$(grep crashed /var/log/syslog | grep -Eo \'\./.*\' --color=auto | sed s#\'./## | sed s#\'## | uniq | tr -s '\n' ' ') for tableC in $tables; do db=${tableC%/*} table=${tableC#*/} mysqlcheck --auto-repair --check $db $table done ``` Get the groups of an user and add another user into these groups. ```console # for group in $(grep user1 /etc/group | cut -d':' -f1 | sed '/user1/d'); do adduser user2 $group; done ``` Get the last acceded URLs in Squid Access list. ```console # tail -n100 /var/log/squid3/access.log | grep -oE 'http.*' | cut -d ' ' -f1 | sort | uniq ``` Migrate MySQL users. ```console # #SRC Server # mysql mysql -e "select * from user WHERE USER='user1' OR USER='user2' INTO OUTFILE '/tmp/mysql_user';" # mysql mysql -e "select * from db WHERE USER='user1' OR USER='user2' INTO OUTFILE '/tmp/mysql_db';" # #DST Server # scp server:/tmp/mysql_{db,user} /tmp # chmod 664 /tmp/mysql_{db,user} # mysql mysql -e "LOAD DATA INFILE '/tmp/mysql_user' INTO TABLE user;" # mysql mysql -e "LOAD DATA INFILE '/tmp/mysql_db' INTO TABLE db;" ``` Find userid of mails in mailq. ```console $ for i in $(mailq | grep -Eo [A-F0-9]{10} | tr -s '\n' ' '); do postcat -q $i | grep userid | grep -Eo "[0-9]{4,}" >> tmp/userid; done $ sort -n /tmp/userid | uniq ``` Kill every MySQL SELECT older than X seconds – Original: https://anothersysadmin.wordpress.com/2008/10/29/kill-every-mysql-select-older-than-x-seconds/ ```bash #!/bin/bash # From https://anothersysadmin.wordpress.com/2008/10/29/kill-every-mysql-select-older-than-x-seconds/ SEC=$1 IFS='|' if [[ $SEC -lt 1 ]]; then echo "Usage: $0 SECONDS" exit 1 fi mysqladmin proc -v|grep Query|grep -Evi "delete|update|insert|alter table" |while read dummy qid qusr qhost qdb qstat qsec qstat2 query; do if [ $qsec -gt $SEC ]; then echo "Killing query $qid..." mysqladmin kill $qid fi done ``` List of contacts when sending a mail for technical purpose on a domain which doesn't announce their technical contacts in a whois. ``` abuse@, admin@, administrator@, contact@, info@, postmaster@, support@, webmaster@ ``` itk change rights. ```console # find /tmp/ -user www-user.old -exec chown www-user:user {} \; # find /tmp/ -user user.old -exec chown user:user {} \; * Détecter les fichiers non lisibles par Apache (lecture sur le groupe) : find ./ -type f ! -perm /g=r -exec ls -l {} \; * Détecter les répertoires non lisibles par Apache (lecture/exécution sur le groupe) : find ./ -type d \( ! -perm /g=r -o ! -perm /g=x \) -exec ls -ld {} \; * Détecter les fichiers/répertoires accessibles en écriture par Apache (écriture sur le groupe) : find ./ -perm /g=w * Détecter les fichiers/répertoires accessibles en écriture par tous : find ./ -perm -007 -o -type f -perm -006 ``` Get useradd command for migrating account. ```console # for i in user1 user2 user3...; do echo -n 'useradd -m -s /bin/bash -u '$(grep -E "^$i" /etc/passwd | cut -d':' -f3) && echo -en ' -p' \'$(grep -E "^$i" /etc/shadow | cut -d ':' -f2)\' $i '\n'; done Output : useradd -m -s /bin/bash -u USERID -p 'USERPWD' username ``` Find files newert than (mtime) a precise date, and execute an action. ```bash # find . ! -newermt '2012-09-19 11:40:00' -exec cp {} /tmp/mails \; ```