MDEV-23580: WSREP_SST: [ERROR] rsync daemon port has been taken

This commit contains a large set of further bug fixes and
improvements to SST scripts for Galera, continuing the work
that was started in MDEV-24962 to make SST scripts work smoothly
in different network configurations (especially using ipv6) and
with different environment settings:

 1) The ipv6 addresses were incorrectly handled in the SST script
    for rsync (incorrect address substitution for establishing a
    connection, incorrect address substitution for bind, and so on);
 2) Checking the locality of the ip-address in SST scripts did not
    support ipv6 addresses (such as "[::1]"), which were falsely
    identified as non-local ip, which further did not allow running
    two SSTs on different local addresses on the same machine.
    On the other hand, this bug masked some other errors (related
    to handling ipv6 addresses);
 3) The code for checking the locality of the ip address was different
    in the SST scripts for rsync and for mysqldump, with individual
    flaws. This code is now made common and moved to wsrep_sst_common;
 4) Waiting for the start of the transport channel (socat, nc, rsync,
    stunnel) in the wait_for_listen() and check_pid_and_port() functions
    did not process ipv6 addresses correctly in all cases (not for all
    branches);
 5) Waiting for the start of the transport channel (socat, nc, rsync,
    stunnel) in the wait_for_listen() and check_pid_and_port() functions
    for some code branches could give a false positive result due to
    the textual match of prefixes in the port number and/or PID of
    the process;
 6) Waiting for the start of the transport channel (socat, nc, rsync,
    stunnel) was supported through different utilities in SST scripts
    for mariabackup and for rsync, and with various minor flaws in
    the code. Now the code is still different in these scripts, but
    it supports a common set of utilities (lsof, ss, sockstat) and
    is synchronized across patterns that used to check the output
    of  these utilities;
 7) In SST via mariabackup, the signal about readiness to receive data
    is sometimes sent too early - immediately after listen(), and not
    after accept() (which are called by socat or netcat utility).
 8) Checking availability of the some options of some utilities was
    done using the grep pattern, which easily gives false positives;
 9) Common name (CN) for local addresses, if not explicitly specified,
    is now always replaced to "localhost" to avoid the need to generate
    many separate certificates for local addresses of one machine and
    not to depend on which the local address is currently used in test
    (ipv4 or ipv6, etc.);
10) In tests galera_sst_mariabackup_encrypt_with_key_server and
    galera_sst_rsync_encrypt_with_key_server the correct certificate
    is selected to avoid commonname (CN) mismatch problems;
11) Further refactoring to protect against spaces in file names.
12) Further general refactoring to eliminate bash-specific constructs
    or to improve code readability;
13) The code for setting options for the nc (netcat) utility was
    different in different scripts for SST - now it is made identical.
14) Fixed long-time broken encryption via xbcrypt in combination with
    mariabackup and added support for key-based encryption via openssl
    utility, which is now enabled by default for encrypt=1 mode (this
    default mode can be changed using a new configuration file option
    "encypt-format=openssl|xbcrypt", which can be placed in the [mysqld],
    [sst] or in the [xtrabackup] section) - this change will allow us
    to use and to test the encypt=1 encryption without installing
    non-standard third-party utilities.

1 files changed, 268 insertions, 206 deletions

diff --git a/scripts/wsrep_sst_mariabackup.sh b/scripts/wsrep_sst_mariabackup.sh
index 8b05217b2fa..de789dc1728 100644
--- a/scripts/wsrep_sst_mariabackup.sh
+++ b/scripts/wsrep_sst_mariabackup.sh
@@ -1,6 +1,6 @@
 #!/bin/bash -ue
-# Copyright (C) 2013 Percona Inc
 # Copyright (C) 2017-2021 MariaDB
+# Copyright (C) 2013 Percona Inc
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -17,14 +17,15 @@
 # MA  02110-1335  USA.
 
 # Documentation:
-# http://www.percona.com/doc/percona-xtradb-cluster/manual/xtrabackup_sst.html
+# https://mariadb.com/kb/en/mariabackup-overview/
 # Make sure to read that before proceeding!
 
-. $(dirname $0)/wsrep_sst_common
+. $(dirname "$0")/wsrep_sst_common
 wsrep_check_datadir
 
-OS=$(uname)
+OS="$(uname)"
 ealgo=""
+eformat=""
 ekey=""
 ekeyfile=""
 encrypt=0
@@ -32,7 +33,7 @@ nproc=1
 ecode=0
 ssyslog=""
 ssystag=""
-XTRABACKUP_PID=""
+MARIABACKUP_PID=""
 SST_PORT=""
 REMOTEIP=""
 tcert=""
@@ -47,7 +48,7 @@ lsn=""
 ecmd=""
 rlimit=""
 # Initially
-stagemsg="${WSREP_SST_OPT_ROLE}"
+stagemsg="$WSREP_SST_OPT_ROLE"
 cpat=""
 speciald=1
 ib_home_dir=""
@@ -59,8 +60,8 @@ strmcmd=""
 tfmt=""
 tcmd=""
 payload=0
-pvformat="-F '%N => Rate:%r Avg:%a Elapsed:%t %e Bytes: %b %p' "
-pvopts="-f -i 10 -N $WSREP_SST_OPT_ROLE "
+pvformat="-F '%N => Rate:%r Avg:%a Elapsed:%t %e Bytes: %b %p'"
+pvopts="-f -i 10 -N $WSREP_SST_OPT_ROLE"
 STATDIR=""
 uextra=0
 disver=""
@@ -79,23 +80,22 @@ readonly SECRET_TAG="secret"
 # 5.6.21 PXC and later can't donate to an older joiner
 sst_ver=1
 
-if pv --help 2>/dev/null | grep -q FORMAT;then
-    pvopts+=$pvformat
+if [ -x "$(command -v pv)" ] && pv --help | grep -qw -- '-F'; then
+    pvopts="$pvopts $pvformat"
 fi
 pcmd="pv $pvopts"
 declare -a RC
 
 set +e
 MARIABACKUP_BIN="$(command -v mariabackup)"
-if [ -z "$MARIABACKUP_BIN" ]; then
+if [ ! -x "$MARIABACKUP_BIN" ]; then
     wsrep_log_error 'mariabackup binary not found in $PATH'
     exit 42
 fi
 set -e
 MBSTREAM_BIN=mbstream
-XBCRYPT_BIN=xbcrypt # Not available in MariaBackup
 
-DATA="${WSREP_SST_OPT_DATA}"
+DATA="$WSREP_SST_OPT_DATA"
 INFO_FILE="xtrabackup_galera_info"
 IST_FILE="xtrabackup_ist"
 MAGIC_FILE="$DATA/$INFO_FILE"
@@ -112,7 +112,7 @@ timeit(){
     local cmd="$@"
     local x1 x2 took extcode
 
-    if [[ $ttime -eq 1 ]];then
+    if [ $ttime -eq 1 ]; then
         x1=$(date +%s)
         wsrep_log_info "Evaluating $cmd"
         eval "$cmd"
@@ -137,19 +137,21 @@ get_keys()
     fi
 
     if [ $encrypt -eq 0 ]; then
-        if $MY_PRINT_DEFAULTS xtrabackup | grep -q -- "--encrypt"; then
-            wsrep_log_error "Unexpected option combination. SST may fail. Refer to http://www.percona.com/doc/percona-xtradb-cluster/manual/xtrabackup_sst.html"
+        if [ -n "$ealgo" -o -n "$ekey" -o -n "$ekeyfile" ]; then
+            wsrep_log_error "Options for encryption are specified, " \
+                            "but encryption itself is disabled. SST may fail."
         fi
         return
     fi
 
     if [ $sfmt = 'tar' ]; then
-        wsrep_log_info "NOTE: Xtrabackup-based encryption - encrypt=1 - cannot be enabled with tar format"
+        wsrep_log_info "NOTE: key-based encryption (encrypt=1) " \
+                       "cannot be enabled with tar format"
         encrypt=-1
         return
     fi
 
-    wsrep_log_info "Xtrabackup based encryption enabled in my.cnf - Supported only from Xtrabackup 2.1.4"
+    wsrep_log_info "Key based encryption enabled in my.cnf"
 
     if [ -z "$ealgo" ]; then
         wsrep_log_error "FATAL: Encryption algorithm empty from my.cnf, bailing out"
@@ -161,17 +163,49 @@ get_keys()
         exit 3
     fi
 
-    if [ -z "$ekey" ]; then
-        ecmd="$XBCRYPT_BIN --encrypt-algo='$ealgo' --encrypt-key-file='$ekeyfile'"
+    if [ "$eformat" = 'openssl' ]; then
+        get_openssl
+        if [ -z "$OPENSSL_BINARY" ]; then
+            wsrep_log_error "If encryption using the openssl is enabled, " \
+                            "then you need to install openssl"
+            exit 2
+        fi
+        ecmd="'$OPENSSL_BINARY' enc -$ealgo"
+        if "$OPENSSL_BINARY" enc -help 2>&1 | grep -qw -- '-pbkdf2'; then
+            ecmd="$ecmd -pbkdf2"
+        elif "$OPENSSL_BINARY" enc -help 2>&1 | grep -qw -- '-iter'; then
+            ecmd="$ecmd -iter 1"
+        elif "$OPENSSL_BINARY" enc -help 2>&1 | grep -qw -- '-md'; then
+            ecmd="$ecmd -md sha256"
+        fi
+        if [ -z "$ekey" ]; then
+            ecmd="$ecmd -kfile '$ekeyfile'"
+        else
+            ecmd="$ecmd -k '$ekey'"
+        fi
+    elif [ "$eformat" = 'xbcrypt' ]; then
+        if [ ! -x "$(command -v xbcrypt)" ]; then
+            wsrep_log_error "If encryption using the xbcrypt is enabled, " \
+                            "then you need to install xbcrypt"
+            exit 2
+        fi
+        wsrep_log_info "NOTE: xbcrypt-based encryption, " \
+                       "supported only from Xtrabackup 2.1.4"
+        if [ -z "$ekey" ]; then
+            ecmd="xbcrypt --encrypt-algo='$ealgo' --encrypt-key-file='$ekeyfile'"
+        else
+            ecmd="xbcrypt --encrypt-algo='$ealgo' --encrypt-key='$ekey'"
+        fi
     else
-        ecmd="$XBCRYPT_BIN --encrypt-algo='$ealgo' --encrypt-key='$ekey'"
+        wsrep_log_error "Unknown encryption format='$eformat'"
+        exit 2
     fi
 
     if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
         ecmd="$ecmd -d"
     fi
 
-    stagemsg+="-XB-Encrypted"
+    stagemsg="$stagemsg-XB-Encrypted"
 }
 
 get_transfer()
@@ -179,27 +213,27 @@ get_transfer()
     TSST_PORT="$SST_PORT"
 
     if [ $tfmt = 'nc' ]; then
-        wsrep_check_programs nc
         wsrep_log_info "Using netcat as streamer"
-
+        wsrep_check_programs nc
+        tcmd="nc"
         if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
-            if nc -h 2>&1 | grep -q ncat; then
-                # Ncat
-                tcmd="nc -l $TSST_PORT"
-            elif nc -h 2>&1 | grep -qw -- '-d\>'; then
-                # Debian netcat
+            if nc -h 2>&1 | grep -q 'ncat'; then
+                wsrep_log_info "Using Ncat as streamer"
+                tcmd="$tcmd -l"
+            elif nc -h 2>&1 | grep -qw -- '-d'; then
+                wsrep_log_info "Using Debian netcat as streamer"
+                tcmd="$tcmd -dl"
                 if [ $WSREP_SST_OPT_HOST_IPv6 -eq 1 ]; then
                     # When host is not explicitly specified (when only the port
                     # is specified) netcat can only bind to an IPv4 address if
                     # the "-6" option is not explicitly specified:
-                    tcmd="nc -dl -6 $TSST_PORT"
-                else
-                    tcmd="nc -dl $TSST_PORT"
+                    tcmd="$tcmd -6"
                 fi
             else
-                # traditional netcat
-                tcmd="nc -l -p $TSST_PORT"
+                wsrep_log_info "Using traditional netcat as streamer"
+                tcmd="$tcmd -l -p"
             fi
+            tcmd="$tcmd $TSST_PORT"
         else
             # Check to see if netcat supports the '-N' flag.
             # -N Shutdown the network socket after EOF on stdin
@@ -208,33 +242,28 @@ get_transfer()
             # transfer and cause the command to timeout.
             # Older versions of netcat did not need this flag and will
             # return an error if the flag is used.
-            #
-            tcmd_extra=""
-            if nc -h 2>&1 | grep -qw -- -N; then
-                tcmd_extra="-N"
+            if nc -h 2>&1 | grep -qw -- '-N'; then
+                tcmd="$tcmd -N"
                 wsrep_log_info "Using nc -N"
             fi
             # netcat doesn't understand [] around IPv6 address
             if nc -h 2>&1 | grep -q ncat; then
-                # Ncat
                 wsrep_log_info "Using Ncat as streamer"
-                tcmd="nc $tcmd_extra $WSREP_SST_OPT_HOST_UNESCAPED $TSST_PORT"
-            elif nc -h 2>&1 | grep -qw -- '-d\>'; then
-                # Debian netcat
+            elif nc -h 2>&1 | grep -qw -- '-d'; then
                 wsrep_log_info "Using Debian netcat as streamer"
-                tcmd="nc $tcmd_extra $WSREP_SST_OPT_HOST_UNESCAPED $TSST_PORT"
             else
-                # traditional netcat
                 wsrep_log_info "Using traditional netcat as streamer"
-                tcmd="nc -q0 $tcmd_extra $WSREP_SST_OPT_HOST_UNESCAPED $TSST_PORT"
+                tcmd="$tcmd -q0"
             fi
+            tcmd="$tcmd $WSREP_SST_OPT_HOST_UNESCAPED $TSST_PORT"
         fi
     else
         tfmt='socat'
-        wsrep_check_programs socat
+
         wsrep_log_info "Using socat as streamer"
+        wsrep_check_programs socat
 
-        if [[ $encrypt -eq 2 || $encrypt -eq 3 ]] && ! socat -V | grep -q "WITH_OPENSSL 1";then
+        if [ $encrypt -eq 2 -o $encrypt -eq 3 ] && ! socat -V | grep -q -F 'WITH_OPENSSL 1'; then
             wsrep_log_error "Encryption requested, but socat is not OpenSSL enabled (encrypt=$encrypt)"
             exit 2
         fi
@@ -245,7 +274,7 @@ get_transfer()
                 wsrep_log_error "Both PEM and CRT files required"
                 exit 22
             fi
-            stagemsg+="-OpenSSL-Encrypted-2"
+            stagemsg="$stagemsg-OpenSSL-Encrypted-2"
             if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
                 wsrep_log_info "Decrypting with cert=${tpem}, cafile=${tcert}"
                 tcmd="socat -u openssl-listen:$TSST_PORT,reuseaddr,cert='$tpem',cafile='$tcert'$sockopt stdio"
@@ -259,7 +288,7 @@ get_transfer()
                 wsrep_log_error "Both certificate and key files required"
                 exit 22
             fi
-            stagemsg+="-OpenSSL-Encrypted-3"
+            stagemsg="$stagemsg-OpenSSL-Encrypted-3"
             if [ -z "$tcert" ]; then
                 # no verification
                 if [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
@@ -278,6 +307,8 @@ get_transfer()
                     CN_option=""
                     if [ -n "$WSREP_SST_OPT_REMOTE_USER" ]; then
                         CN_option=",commonname='$WSREP_SST_OPT_REMOTE_USER'"
+                    elif is_local_ip "$WSREP_SST_OPT_HOST_UNESCAPED"; then
+                        CN_option=',commonname=localhost'
                     fi
                     wsrep_log_info "Encrypting with cert=${tpem}, key=${tkey}, cafile=${tcert}"
                     tcmd="socat -u stdio openssl-connect:$REMOTEIP:$TSST_PORT,cert='$tpem',key='$tkey',cafile='$tcert'$CN_option$sockopt"
@@ -297,13 +328,13 @@ get_footprint()
 {
     pushd "$WSREP_SST_OPT_DATA" 1>/dev/null
     payload=$(find . -regex '.*\.ibd$\|.*\.MYI$\|.*\.MYD$\|.*ibdata1$' -type f -print0 | du --files0-from=- --block-size=1 -c | awk 'END { print $1 }')
-    if $MY_PRINT_DEFAULTS xtrabackup | grep -q -- "--compress";then
+    if $MY_PRINT_DEFAULTS xtrabackup | grep -q -- "--compress"; then
         # QuickLZ has around 50% compression ratio
         # When compression/compaction used, the progress is only an approximate.
         payload=$(( payload*1/2 ))
     fi
     popd 1>/dev/null
-    pcmd+=" -s $payload"
+    pcmd="$pcmd -s $payload"
     adjust_progress
 }
 
@@ -320,9 +351,9 @@ adjust_progress()
 
     if [ -n "$progress" -a "$progress" != '1' ]; then
         if [ -e "$progress" ]; then
-            pcmd+=" 2>>'$progress'"
+            pcmd="$pcmd 2>>'$progress'"
         else
-            pcmd+=" 2>'$progress'"
+            pcmd="$pcmd 2>'$progress'"
         fi
     elif [ -z "$progress" -a -n "$rlimit" ]; then
             # When rlimit is non-zero
@@ -331,25 +362,26 @@ adjust_progress()
 
     if [ -n "$rlimit" -a "$WSREP_SST_OPT_ROLE" = 'donor' ]; then
         wsrep_log_info "Rate-limiting SST to $rlimit"
-        pcmd+=" -L \$rlimit"
+        pcmd="$pcmd -L \$rlimit"
     fi
 }
 
+encgroups='--mysqld|sst|xtrabackup'
+
 check_server_ssl_config()
 {
-    local section="$1"
-    tcert=$(parse_cnf "$section" 'ssl-ca')
-    tpem=$(parse_cnf "$section" 'ssl-cert')
-    tkey=$(parse_cnf "$section" 'ssl-key')
+    tcert=$(parse_cnf "$encgroups" 'ssl-ca')
+    tpem=$(parse_cnf "$encgroups" 'ssl-cert')
+    tkey=$(parse_cnf "$encgroups" 'ssl-key')
 }
 
 read_cnf()
 {
-    sfmt=$(parse_cnf sst streamfmt "mbstream")
-    tfmt=$(parse_cnf sst transferfmt "socat")
+    sfmt=$(parse_cnf sst streamfmt 'mbstream')
+    tfmt=$(parse_cnf sst transferfmt 'socat')
 
-    encrypt=$(parse_cnf 'sst' 'encrypt' 0)
-    tmode=$(parse_cnf 'sst' 'ssl-mode' 'DISABLED' | tr [:lower:] [:upper:])
+    encrypt=$(parse_cnf "$encgroups" 'encrypt' 0)
+    tmode=$(parse_cnf "$encgroups" 'ssl-mode' 'DISABLED' | tr [:lower:] [:upper:])
 
     if [ $encrypt -eq 0 -o $encrypt -ge 2 ]
     then
@@ -363,11 +395,7 @@ read_cnf()
         then # backward-incompatible behavior
             if [ -z "$tpem" -a -z "$tkey" -a -z "$tcert" ]
             then # no old-style SSL config in [sst]
-                check_server_ssl_config 'sst'
-                if [ -z "$tpem" -a -z "$tkey" -a -z "$tcert" ]
-                then # no new-stype SSL config in [sst], try server-wide SSL config
-                    check_server_ssl_config '--mysqld'
-                fi
+                check_server_ssl_config
             fi
             if [ 0 -eq $encrypt -a -n "$tpem" -a -n "$tkey" ]
             then
@@ -380,29 +408,21 @@ read_cnf()
                 [ "${tmode#VERIFY}" != "$tmode" ] || tcert=""
             fi
         fi
+    elif [ $encrypt -eq 1 ]; then
+        ealgo=$(parse_cnf "$encgroups" 'encrypt-algo')
+        eformat=$(parse_cnf "$encgroups" 'encrypt-format' 'openssl')
+        ekey=$(parse_cnf "$encgroups" 'encrypt-key')
+        ekeyfile=$(parse_cnf "$encgroups" 'encrypt-key-file')
     fi
 
-    if [ $encrypt -eq 1 ]; then
-        # Refer to http://www.percona.com/doc/percona-xtradb-cluster/manual/xtrabackup_sst.html
-        ealgo=$(parse_cnf xtrabackup encrypt "")
-        if [ -z "$ealgo" ]; then
-            ealgo=$(parse_cnf sst encrypt-algo "")
-            ekey=$(parse_cnf sst encrypt-key "")
-            ekeyfile=$(parse_cnf sst encrypt-key-file "")
-        else
-            ekey=$(parse_cnf xtrabackup encrypt-key "")
-            ekeyfile=$(parse_cnf xtrabackup encrypt-key-file "")
-        fi
-    fi
-
-    wsrep_log_info "SSL configuration: CA='"$tcert"', CERT='"$tpem"'," \
-                   "KEY='"$tkey"', MODE='"$tmode"', encrypt="$encrypt
+    wsrep_log_info "SSL configuration: CA='$tcert', CERT='$tpem'," \
+                   "KEY='$tkey', MODE='$tmode', encrypt='$encrypt'"
 
     sockopt=$(parse_cnf sst sockopt "")
     progress=$(parse_cnf sst progress "")
     ttime=$(parse_cnf sst time 0)
     cpat=$(parse_cnf sst cpat '.*galera\.cache$\|.*sst_in_progress$\|.*\.sst$\|.*gvwstate\.dat$\|.*grastate\.dat$\|.*\.err$\|.*\.log$\|.*RPM_UPGRADE_MARKER$\|.*RPM_UPGRADE_HISTORY$')
-    [[ $OS == "FreeBSD" ]] && cpat=$(parse_cnf sst cpat '.*galera\.cache$|.*sst_in_progress$|.*\.sst$|.*gvwstate\.dat$|.*grastate\.dat$|.*\.err$|.*\.log$|.*RPM_UPGRADE_MARKER$|.*RPM_UPGRADE_HISTORY$')
+    [ $OS = 'FreeBSD' ] && cpat=$(parse_cnf sst cpat '.*galera\.cache$|.*sst_in_progress$|.*\.sst$|.*gvwstate\.dat$|.*grastate\.dat$|.*\.err$|.*\.log$|.*RPM_UPGRADE_MARKER$|.*RPM_UPGRADE_HISTORY$')
     scomp=$(parse_cnf sst compressor "")
     sdecomp=$(parse_cnf sst decompressor "")
 
@@ -415,26 +435,20 @@ read_cnf()
     stimeout=$(parse_cnf sst sst-initial-timeout 300)
     ssyslog=$(parse_cnf sst sst-syslog 0)
     ssystag=$(parse_cnf mysqld_safe syslog-tag "${SST_SYSLOG_TAG:-}")
-    ssystag+="-"
+    ssystag="$ssystag-"
     sstlogarchive=$(parse_cnf sst sst-log-archive 1)
-    sstlogarchivedir=$(parse_cnf sst sst-log-archive-dir "/tmp/sst_log_archive")
+    sstlogarchivedir=$(parse_cnf sst sst-log-archive-dir '/tmp/sst_log_archive')
 
-    if [[ $speciald -eq 0 ]];then
+    if [ $speciald -eq 0 ]; then
         wsrep_log_error "sst-special-dirs equal to 0 is not supported, falling back to 1"
         speciald=1
     fi
 
-    if [[ $ssyslog -ne -1 ]];then
-        if $MY_PRINT_DEFAULTS mysqld_safe | grep -q -- "--syslog";then
+    if [ $ssyslog -ne -1 ]; then
+        if $MY_PRINT_DEFAULTS mysqld_safe | grep -q -- "--syslog"; then
             ssyslog=1
         fi
     fi
-
-    if [[ $encrypt -eq 1 ]]; then
-        wsrep_log_error "Xtrabackup-based encryption is currently not" \
-            "supported with MariaBackup"
-        exit 2
-    fi
 }
 
 get_stream()
@@ -461,7 +475,7 @@ get_proc()
 {
     set +e
     nproc=$(grep -c processor /proc/cpuinfo)
-    [[ -z $nproc || $nproc -eq 0 ]] && nproc=1
+    [ -z $nproc -o $nproc -eq 0 ] && nproc=1
     set -e
 }
 
@@ -477,7 +491,7 @@ cleanup_joiner()
     local estatus=$?
     if [ $estatus -ne 0 ]; then
         wsrep_log_error "Cleanup after exit with status:$estatus"
-    elif [ "${WSREP_SST_OPT_ROLE}" = 'joiner' ]; then
+    elif [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]; then
         wsrep_log_info "Removing the sst_in_progress file"
         wsrep_cleanup_progress_file
     fi
@@ -495,10 +509,10 @@ cleanup_joiner()
 
     # This means no setsid done in mysqld.
     # We don't want to kill mysqld here otherwise.
-    if [[ $$ -eq $pgid ]];then
+    if [ $$ -eq $pgid ]; then
         # This means a signal was delivered to the process.
         # So, more cleanup.
-        if [[ $estatus -ge 128 ]];then
+        if [ $estatus -ge 128 ]; then
             kill -KILL -$$ || true
         fi
     fi
@@ -509,7 +523,7 @@ cleanup_joiner()
 check_pid()
 {
     local pid_file="$1"
-    [ -r "$pid_file" ] && ps -p $(cat "$pid_file") >/dev/null 2>&1
+    [ -r "$pid_file" ] && ps -p $(cat "$pid_file") 2>&1 >/dev/null
 }
 
 cleanup_donor()
@@ -520,11 +534,11 @@ cleanup_donor()
         wsrep_log_error "Cleanup after exit with status:$estatus"
     fi
 
-    if [ -n "$XTRABACKUP_PID" ]; then
-        if check_pid $XTRABACKUP_PID
+    if [ -n "$MARIABACKUP_PID" ]; then
+        if check_pid $MARIABACKUP_PID
         then
-            wsrep_log_error "xtrabackup process is still running. Killing..."
-            kill_xtrabackup
+            wsrep_log_error "mariabackup process is still running. Killing..."
+            kill_mariabackup
         fi
     fi
 
@@ -550,10 +564,10 @@ cleanup_donor()
 
     # This means no setsid done in mysqld.
     # We don't want to kill mysqld here otherwise.
-    if [[ $$ -eq $pgid ]];then
+    if [ $$ -eq $pgid ]; then
         # This means a signal was delivered to the process.
         # So, more cleanup.
-        if [[ $estatus -ge 128 ]];then
+        if [ $estatus -ge 128 ]; then
             kill -KILL -$$ || true
         fi
     fi
@@ -561,24 +575,57 @@ cleanup_donor()
     exit $estatus
 }
 
-kill_xtrabackup()
+kill_mariabackup()
 {
-    local PID=$(cat "$XTRABACKUP_PID")
+    local PID=$(cat "$MARIABACKUP_PID")
     [ -n "$PID" -a "0" != "$PID" ] && kill $PID && (kill $PID && kill -9 $PID) || :
-    wsrep_log_info "Removing xtrabackup pid file $XTRABACKUP_PID"
-    rm -f "$XTRABACKUP_PID" || true
+    wsrep_log_info "Removing mariabackup pid file ($MARIABACKUP_PID)"
+    rm -f "$MARIABACKUP_PID" || true
 }
 
 setup_ports()
 {
     SST_PORT="$WSREP_SST_OPT_PORT"
-    if [ "$WSREP_SST_OPT_ROLE" = "donor" ]; then
-        REMOTEIP="${WSREP_SST_OPT_HOST}"
-        lsn="${WSREP_SST_OPT_LSN}"
-        sst_ver="${WSREP_SST_OPT_SST_VER}"
+    if [ "$WSREP_SST_OPT_ROLE" = 'donor' ]; then
+        REMOTEIP="$WSREP_SST_OPT_HOST"
+        lsn="$WSREP_SST_OPT_LSN"
+        sst_ver="$WSREP_SST_OPT_SST_VER"
     fi
 }
 
+check_port()
+{
+    local PORT="$1"
+    local UTILS="$2"
+
+    local port_info is_util
+
+    if [ $lsof_available -ne 0 ]; then
+        port_info=$(lsof -i ":$PORT" -Pn 2>/dev/null | \
+            grep -F '(LISTEN)')
+        is_util=$(echo "$port_info" | \
+            grep -E "^($UTILS)[^[:space:]]*[[:space:]]+[0-9]+[[:space:]]+")
+    elif [ $sockstat_available -ne 0 ]; then
+        port_info=$(sockstat -p "$PORT" 2>/dev/null | \
+            grep -F 'LISTEN')
+        is_util=$(echo "$port_info" | \
+            grep -E "[[:space:]]+($UTILS)[^[:space:]]*[[:space:]]+[0-9]+[[:space:]]+")
+    elif [ $ss_available -ne 0 ]; then
+        port_info=$(ss -H -p -n -l "( sport = :$PORT )" 2>/dev/null)
+        is_util=$(echo "$port_info" | \
+            grep -E "users:\\(.*\\(\"($UTILS)[^[:space:]]*\".*\<pid=[0-9]+\>.*\\)")
+    else
+        wsrep_log_error "unknown sockets utility"
+        exit 2 # ENOENT
+    fi
+
+    if [ -z "$is_util" ]; then
+        return 1
+    fi
+
+    return 0
+}
+
 # waits ~10 seconds for nc to open the port and then reports ready
 # (regardless of timeout)
 wait_for_listen()
@@ -586,16 +633,16 @@ wait_for_listen()
     local PORT="$1"
     local ADDR="$2"
     local MODULE="$3"
+
     for i in {1..50}
     do
-        if [ "$OS" = "FreeBSD" ];then
-            sockstat -46lp $PORT | grep -qE "^[^ ]* *(socat|nc) *[^ ]* *[^ ]* *[^ ]* *[^ ]*:$PORT" && break
-        else
-            ss -p state listening "( sport = :$PORT )" | grep -qE 'socat|nc' && break
+        if check_port "$PORT" 'socat|nc'
+        then
+            break
         fi
         sleep 0.2
     done
-    echo "ready ${ADDR}/${MODULE}//$sst_ver"
+    echo "ready $ADDR/$MODULE//$sst_ver"
 }
 
 check_extra()
@@ -606,10 +653,10 @@ check_extra()
         if [ "$thread_handling" = 'pool-of-threads' ]; then
             local eport=$(parse_cnf '--mysqld' 'extra-port')
             if [ -n "$eport" ]; then
-                # Xtrabackup works only locally.
-                # Hence, setting host to 127.0.0.1 unconditionally.
+                # mariabackup works only locally, hence,
+                # setting host to 127.0.0.1 unconditionally:
                 wsrep_log_info "SST through extra_port $eport"
-                INNOEXTRA+=" --host=127.0.0.1 --port=$eport"
+                INNOEXTRA="$INNOEXTRA --host=127.0.0.1 --port=$eport"
                 use_socket=0
             else
                 wsrep_log_error "Extra port $eport null, failing"
@@ -620,7 +667,7 @@ check_extra()
         fi
     fi
     if [ $use_socket -eq 1 -a -n "$WSREP_SST_OPT_SOCKET" ]; then
-        INNOEXTRA+=" --socket='$WSREP_SST_OPT_SOCKET'"
+        INNOEXTRA="$INNOEXTRA --socket='$WSREP_SST_OPT_SOCKET'"
     fi
 }
 
@@ -630,7 +677,7 @@ recv_joiner()
     local msg="$2"
     local tmt=$3
     local checkf=$4
-    local ltcmd
+    local wait=$5
 
     if [ ! -d "$dir" ]; then
         # This indicates that IST is in progress
@@ -640,28 +687,34 @@ recv_joiner()
     pushd "$dir" 1>/dev/null
     set +e
 
-    if [ $tmt -gt 0 -a -x "$(command -v timeout)" ]; then
-        if timeout --help | grep -q -- '-k'; then
-            ltcmd="timeout -k $(( tmt+10 )) $tmt $tcmd"
-        else
-            ltcmd="timeout -s9 $tmt $tcmd"
+    local ltcmd="$tcmd"
+    if [ $tmt -gt 0 ]; then
+        if [ -x "$(command -v timeout)" ]; then
+            if timeout --help | grep -qw -- '-k'; then
+                ltcmd="timeout -k $(( tmt+10 )) $tmt $tcmd"
+            else
+                ltcmd="timeout -s9 $tmt $tcmd"
+            fi
         fi
-        timeit "$msg" "$ltcmd | $strmcmd; RC=( "\${PIPESTATUS[@]}" )"
-    else
-        timeit "$msg" "$tcmd | $strmcmd; RC=( "\${PIPESTATUS[@]}" )"
     fi
 
+    if [ $wait -ne 0 ]; then
+        wait_for_listen "$SST_PORT" "$ADDR" "$MODULE" &
+    fi
+
+    timeit "$msg" "$ltcmd | $strmcmd; RC=( "\${PIPESTATUS[@]}" )"
+
     set -e
     popd 1>/dev/null
 
-    if [[ ${RC[0]} -eq 124 ]];then
+    if [ ${RC[0]} -eq 124 ]; then
         wsrep_log_error "Possible timeout in receiving first data from " \
                         "donor in gtid stage: exit codes: ${RC[@]}"
         exit 32
     fi
 
-    for ecode in "${RC[@]}";do
-        if [[ $ecode -ne 0 ]];then
+    for ecode in "${RC[@]}"; do
+        if [ $ecode -ne 0 ]; then
             wsrep_log_error "Error while getting data from donor node: " \
                             "exit codes: ${RC[@]}"
             exit 32
@@ -672,14 +725,14 @@ recv_joiner()
         if [ ! -r "$MAGIC_FILE" ]; then
             # this message should cause joiner to abort
             wsrep_log_error "receiving process ended without creating " \
-                            "'${MAGIC_FILE}'"
+                            "'$MAGIC_FILE'"
             wsrep_log_info "Contents of datadir"
-            wsrep_log_info "$(ls -l ${dir}/*)"
+            wsrep_log_info $(ls -l "$dir/"*)
             exit 32
         fi
 
         # check donor supplied secret
-        SECRET=$(grep "$SECRET_TAG " "$MAGIC_FILE" 2>/dev/null | cut -d ' ' -f 2)
+        SECRET=$(grep -- "$SECRET_TAG " "$MAGIC_FILE" 2>/dev/null | cut -d ' ' -f 2)
         if [ "$SECRET" != "$MY_SECRET" ]; then
             wsrep_log_error "Donor does not know my secret!"
             wsrep_log_info "Donor:'$SECRET', my:'$MY_SECRET'"
@@ -687,7 +740,7 @@ recv_joiner()
         fi
 
         # remove secret from magic file
-        grep -v "$SECRET_TAG " "$MAGIC_FILE" > "$MAGIC_FILE.new"
+        grep -v -- "$SECRET_TAG " "$MAGIC_FILE" > "$MAGIC_FILE.new"
         mv "$MAGIC_FILE.new" "$MAGIC_FILE"
     fi
 }
@@ -703,8 +756,8 @@ send_donor()
     set -e
     popd 1>/dev/null
 
-    for ecode in "${RC[@]}";do
-        if [[ $ecode -ne 0 ]];then
+    for ecode in "${RC[@]}"; do
+        if [ $ecode -ne 0 ]; then
             wsrep_log_error "Error while sending data to joiner node: " \
                             "exit codes: ${RC[@]}"
             exit 32
@@ -717,11 +770,11 @@ monitor_process()
     local sst_stream_pid=$1
 
     while true ; do
-        if ! ps -p "${WSREP_SST_OPT_PARENT}" &>/dev/null; then
+        if ! ps -p "$WSREP_SST_OPT_PARENT" &>/dev/null; then
             wsrep_log_error "Parent mysqld process (PID:${WSREP_SST_OPT_PARENT}) terminated unexpectedly."
             exit 32
         fi
-        if ! ps -p "${sst_stream_pid}" &>/dev/null; then
+        if ! ps -p "$sst_stream_pid" &>/dev/null; then
             break
         fi
         sleep 0.1
@@ -730,7 +783,7 @@ monitor_process()
 
 wsrep_check_programs "$MARIABACKUP_BIN"
 
-rm -f "${MAGIC_FILE}"
+rm -f "$MAGIC_FILE"
 
 if [ "$WSREP_SST_OPT_ROLE" != 'joiner' -a "$WSREP_SST_OPT_ROLE" != 'donor' ]; then
     wsrep_log_error "Invalid role ${WSREP_SST_OPT_ROLE}"
@@ -740,15 +793,15 @@ fi
 read_cnf
 setup_ports
 
-if "${MARIABACKUP_BIN}" --help 2>/dev/null | grep -q -- '--version-check'; then
+if "$MARIABACKUP_BIN" --help 2>/dev/null | grep -qw -- '--version-check'; then
     disver='--no-version-check'
 fi
 
-iopts+=" --databases-exclude='lost+found'"
+iopts="$iopts --databases-exclude='lost+found'"
 
 if [ ${FORCE_FTWRL:-0} -eq 1 ]; then
     wsrep_log_info "Forcing FTWRL due to environment variable FORCE_FTWRL equal to $FORCE_FTWRL"
-    iopts+=' --no-backup-locks'
+    iopts="$iopts --no-backup-locks"
 fi
 
 # if no command line argument and INNODB_DATA_HOME_DIR environment variable
@@ -769,11 +822,9 @@ fi
 
 cd "$OLD_PWD"
 
-if [[ $ssyslog -eq 1 ]];then
+if [ $ssyslog -eq 1 ]; then
 
-    if [ ! -x "$(command -v logger)" ]; then
-        wsrep_log_error "logger not in path: $PATH. Ignoring"
-    else
+    if [ -x "$(command -v logger)" ]; then
         wsrep_log_info "Logging all stderr of SST/mariabackup to syslog"
 
         exec 2> >(logger -p daemon.err -t ${ssystag}wsrep-sst-$WSREP_SST_OPT_ROLE)
@@ -787,6 +838,8 @@ if [[ $ssyslog -eq 1 ]];then
         {
             logger -p daemon.info -t ${ssystag}wsrep-sst-$WSREP_SST_OPT_ROLE "$@"
         }
+    else
+        wsrep_log_error "logger not in path: $PATH. Ignoring"
     fi
 
     INNOAPPLY="2>&1 | logger -p daemon.err -t ${ssystag}innobackupex-apply"
@@ -795,10 +848,9 @@ if [[ $ssyslog -eq 1 ]];then
 
 else
 
-if [[ "$sstlogarchive" -eq 1 ]]
+if [ $sstlogarchive -eq 1 ]
 then
     ARCHIVETIMESTAMP=$(date "+%Y.%m.%d-%H.%M.%S.%N")
-    newfile=""
 
     if [ -n "$sstlogarchivedir" ]
     then
@@ -812,11 +864,12 @@ then
     then
         if [ -n "$sstlogarchivedir" ]
         then
-            newfile="$sstlogarchivedir/$(basename '$INNOAPPLYLOG').$ARCHIVETIMESTAMP"
+            newfile=$(basename "$INNOAPPLYLOG")
+            newfile="$sstlogarchivedir/$newfile.$ARCHIVETIMESTAMP"
         else
             newfile="$INNOAPPLYLOG.$ARCHIVETIMESTAMP"
         fi
-        wsrep_log_info "Moving ${INNOAPPLYLOG} to ${newfile}"
+        wsrep_log_info "Moving '$INNOAPPLYLOG' to '$newfile'"
         mv "$INNOAPPLYLOG" "$newfile"
         gzip "$newfile"
     fi
@@ -825,11 +878,12 @@ then
     then
         if [ -n "$sstlogarchivedir" ]
         then
-            newfile="$sstlogarchivedir/$(basename '$INNOMOVELOG').$ARCHIVETIMESTAMP"
+            newfile=$(basename "$INNOMOVELOG")
+            newfile="$sstlogarchivedir/$newfile.$ARCHIVETIMESTAMP"
         else
             newfile="$INNOMOVELOG.$ARCHIVETIMESTAMP"
         fi
-        wsrep_log_info "Moving ${INNOMOVELOG} to ${newfile}"
+        wsrep_log_info "Moving '$INNOMOVELOG' to '$newfile'"
         mv "$INNOMOVELOG" "$newfile"
         gzip "$newfile"
     fi
@@ -838,11 +892,12 @@ then
     then
         if [ -n "$sstlogarchivedir" ]
         then
-            newfile="$sstlogarchivedir/$(basename '$INNOBACKUPLOG').$ARCHIVETIMESTAMP"
+            newfile=$(basename "$INNOBACKUPLOG")
+            newfile="$sstlogarchivedir/$newfile.$ARCHIVETIMESTAMP"
         else
             newfile="$INNOBACKUPLOG.$ARCHIVETIMESTAMP"
         fi
-        wsrep_log_info "Moving ${INNOBACKUPLOG} to ${newfile}"
+        wsrep_log_info "Moving '$INNOBACKUPLOG' to '$newfile'"
         mv "$INNOBACKUPLOG" "$newfile"
         gzip "$newfile"
     fi
@@ -868,7 +923,7 @@ setup_commands()
 get_stream
 get_transfer
 
-if [ "$WSREP_SST_OPT_ROLE" = "donor" ]
+if [ "$WSREP_SST_OPT_ROLE" = 'donor' ]
 then
     trap cleanup_donor EXIT
 
@@ -881,18 +936,18 @@ then
             exit 93
         fi
 
-        if [ -z "$(parse_cnf --mysqld tmpdir)" -a \
-             -z "$(parse_cnf xtrabackup tmpdir)" ]; then
-            xtmpdir=$(mktemp -d)
+        tmpdir=$(parse_cnf "$encgroups" 'tmpdir')
+        if [ -z "$tmpdir" ]; then
+            xtmpdir="$(mktemp -d)"
             tmpopts="--tmpdir='$xtmpdir'"
-            wsrep_log_info "Using $xtmpdir as xtrabackup temporary directory"
+            wsrep_log_info "Using $xtmpdir as mariabackup temporary directory"
         fi
 
-        itmpdir=$(mktemp -d)
+        itmpdir="$(mktemp -d)"
         wsrep_log_info "Using $itmpdir as mariabackup temporary directory"
 
         if [ -n "$WSREP_SST_OPT_USER" ]; then
-           INNOEXTRA+=" --user='$WSREP_SST_OPT_USER'"
+           INNOEXTRA="$INNOEXTRA --user='$WSREP_SST_OPT_USER'"
            usrst=1
         fi
 
@@ -927,10 +982,11 @@ then
             tcmd="$ecmd | $tcmd"
         fi
 
-        send_donor "$DATA" "${stagemsg}-gtid"
+        send_donor "$DATA" "$stagemsg-gtid"
 
         tcmd="$ttcmd"
 
+        # Restore the transport commmand to its original state
         if [ -n "$progress" ]; then
             get_footprint
             tcmd="$pcmd | $tcmd"
@@ -944,26 +1000,32 @@ then
 
         wsrep_log_info "Streaming the backup to joiner at ${REMOTEIP}:${SST_PORT}"
 
+        # Add compression to the head of the stream (if specified)
         if [ -n "$scomp" ]; then
             tcmd="$scomp | $tcmd"
         fi
 
+        # Add encryption to the head of the stream (if specified)
+        if [ $encrypt -eq 1 ]; then
+            tcmd="$ecmd | $tcmd"
+        fi
+
         setup_commands
         set +e
-        timeit "${stagemsg}-SST" "$INNOBACKUP | $tcmd; RC=( "\${PIPESTATUS[@]}" )"
+        timeit "$stagemsg-SST" "$INNOBACKUP | $tcmd; RC=( "\${PIPESTATUS[@]}" )"
         set -e
 
         if [ ${RC[0]} -ne 0 ]; then
             wsrep_log_error "${MARIABACKUP_BIN} finished with error: ${RC[0]}. " \
                             "Check syslog or ${INNOBACKUPLOG} for details"
             exit 22
-        elif [[ ${RC[$(( ${#RC[@]}-1 ))]} -eq 1 ]]; then
+        elif [ ${RC[$(( ${#RC[@]}-1 ))]} -eq 1 ]; then
             wsrep_log_error "$tcmd finished with error: ${RC[1]}"
             exit 22
         fi
 
         # mariabackup implicitly writes PID to fixed location in $xtmpdir
-        XTRABACKUP_PID="$xtmpdir/xtrabackup_pid"
+        MARIABACKUP_PID="$xtmpdir/xtrabackup_pid"
 
     else # BYPASS FOR IST
 
@@ -984,19 +1046,19 @@ then
             tcmd="$ecmd | $tcmd"
         fi
 
-        strmcmd+=" '$IST_FILE'"
+        strmcmd="$strmcmd '$IST_FILE'"
 
-        send_donor "$DATA" "${stagemsg}-IST"
+        send_donor "$DATA" "$stagemsg-IST"
 
     fi
 
-    echo "done ${WSREP_SST_OPT_GTID}"
+    echo "done $WSREP_SST_OPT_GTID"
     wsrep_log_info "Total time on donor: $totime seconds"
 
-elif [ "${WSREP_SST_OPT_ROLE}" = "joiner" ]
+elif [ "$WSREP_SST_OPT_ROLE" = 'joiner' ]
 then
-    [[ -e "$SST_PROGRESS_FILE" ]] && wsrep_log_info "Stale sst_in_progress file: $SST_PROGRESS_FILE"
-    [[ -n "$SST_PROGRESS_FILE" ]] && touch "$SST_PROGRESS_FILE"
+    [ -e "$SST_PROGRESS_FILE" ] && wsrep_log_info "Stale sst_in_progress file: $SST_PROGRESS_FILE"
+    [ -n "$SST_PROGRESS_FILE" ] && touch "$SST_PROGRESS_FILE"
 
     ib_home_dir="$INNODB_DATA_HOME_DIR"
 
@@ -1015,7 +1077,7 @@ then
 
     ib_undo_dir="$INNODB_UNDO_DIR"
 
-    stagemsg="Joiner-Recv"
+    stagemsg='Joiner-Recv'
 
     sencrypted=1
     nthreads=1
@@ -1041,42 +1103,41 @@ then
                 exit 42
             fi
             CN=$("$OPENSSL_BINARY" x509 -noout -subject -in "$tpem" | \
-                 tr "," "\n" | grep "CN =" | cut -d= -f2 | sed s/^\ // | \
+                 tr "," "\n" | grep -F 'CN =' | cut -d= -f2 | sed s/^\ // | \
                  sed s/\ %//)
         fi
-        MY_SECRET=$(wsrep_gen_secret)
+        MY_SECRET="$(wsrep_gen_secret)"
         # Add authentication data to address
         ADDR="$CN:$MY_SECRET@$ADDR"
     else
         MY_SECRET="" # for check down in recv_joiner()
     fi
 
-    wait_for_listen "$SST_PORT" "$ADDR" "$MODULE" &
-
     trap sig_joiner_cleanup HUP PIPE INT TERM
     trap cleanup_joiner EXIT
 
     if [ -n "$progress" ]; then
         adjust_progress
-        tcmd+=" | $pcmd"
+        tcmd="$tcmd | $pcmd"
     fi
 
     get_keys
     if [ $encrypt -eq 1 -a $sencrypted -eq 1 ]; then
-        if [ -n "$sdecomp" ]; then
-            strmcmd="$sdecomp | $ecmd | $strmcmd"
-        else
-            strmcmd="$ecmd | $strmcmd"
-        fi
-    elif [ -n "$sdecomp" ]; then
-            strmcmd="$sdecomp | $strmcmd"
+        strmcmd="$ecmd | $strmcmd"
+    fi
+
+    if [ -n "$sdecomp" ]; then
+        strmcmd="$sdecomp | $strmcmd"
     fi
 
-    STATDIR=$(mktemp -d)
+    check_sockets_utils
+
+    STATDIR="$(mktemp -d)"
     MAGIC_FILE="$STATDIR/$INFO_FILE"
-    recv_joiner "$STATDIR" "${stagemsg}-gtid" $stimeout 1
 
-    if ! ps -p ${WSREP_SST_OPT_PARENT} &>/dev/null
+    recv_joiner "$STATDIR" "$stagemsg-gtid" $stimeout 1 1
+
+    if ! ps -p "$WSREP_SST_OPT_PARENT" &>/dev/null
     then
         wsrep_log_error "Parent mysqld process (PID:${WSREP_SST_OPT_PARENT}) terminated unexpectedly."
         exit 32
@@ -1090,12 +1151,12 @@ then
             rm -rf "$DATA/.sst"
         fi
         mkdir -p "$DATA/.sst"
-        (recv_joiner "$DATA/.sst" "${stagemsg}-SST" 0 0) &
+        (recv_joiner "$DATA/.sst" "$stagemsg-SST" 0 0 0) &
         jpid=$!
         wsrep_log_info "Proceeding with SST"
 
         wsrep_log_info "Cleaning the existing datadir and innodb-data/log directories"
-        if [ "${OS}" = "FreeBSD" ]; then
+        if [ "$OS" = 'FreeBSD' ]; then
             find -E ${ib_home_dir:+"$ib_home_dir"} \
                     ${ib_undo_dir:+"$ib_undo_dir"} \
                     ${ib_log_dir:+"$ib_log_dir"} \
@@ -1128,13 +1189,13 @@ then
 
         get_proc
 
-        if [[ ! -s "$DATA/xtrabackup_checkpoints" ]];then
+        if [ ! -s "$DATA/xtrabackup_checkpoints" ]; then
             wsrep_log_error "xtrabackup_checkpoints missing, failed mariabackup/SST on donor"
             exit 2
         fi
 
         # Compact backups are not supported by mariabackup
-        if grep -q 'compact = 1' "$DATA/xtrabackup_checkpoints"; then
+        if grep -q -F 'compact = 1' "$DATA/xtrabackup_checkpoints"; then
             wsrep_log_info "Index compaction detected"
             wsrel_log_error "Compact backups are not supported by mariabackup"
             exit 2
@@ -1149,13 +1210,12 @@ then
                 exit 22
             fi
 
-            if [[ -n "$progress" ]] && pv --help | grep -q 'line-mode';then
+            if [ -n "$progress" ] && pv --help | grep -qw -- '--line-mode'; then
                 count=$(find "$DATA" -type f -name '*.qp' | wc -l)
                 count=$(( count*2 ))
-                if pv --help | grep -q FORMAT;then
-                    pvopts="-f -s $count -l -N Decompression -F '%N => Rate:%r Elapsed:%t %e Progress: [%b/$count]'"
-                else
-                    pvopts="-f -s $count -l -N Decompression"
+                pvopts="-f -s $count -l -N Decompression"
+                if pv --help | grep -qw -- '-F'; then
+                    pvopts="$pvopts -F '%N => Rate:%r Elapsed:%t %e Progress: [%b/$count]'"
                 fi
                 pcmd="pv $pvopts"
                 adjust_progress
@@ -1169,10 +1229,10 @@ then
             timeit "Joiner-Decompression" "find '$DATA' -type f -name '*.qp' -printf '%p\n%h\n' | $dcmd"
             extcode=$?
 
-            if [[ $extcode -eq 0 ]];then
+            if [ $extcode -eq 0 ]; then
                 wsrep_log_info "Removing qpress files after decompression"
                 find "$DATA" -type f -name '*.qp' -delete
-                if [[ $? -ne 0 ]];then
+                if [ $? -ne 0 ]; then
                     wsrep_log_error "Something went wrong with deletion of qpress files. Investigate"
                 fi
             else
@@ -1199,7 +1259,7 @@ then
 
         wsrep_log_info "Preparing the backup at ${DATA}"
         setup_commands
-        timeit "Xtrabackup prepare stage" "$INNOAPPLY"
+        timeit "mariabackup prepare stage" "$INNOAPPLY"
 
         if [ $? -ne 0 ]; then
             wsrep_log_error "${MARIABACKUP_BIN} apply finished with errors. Check syslog or ${INNOAPPLYLOG} for details"
@@ -1208,8 +1268,8 @@ then
 
         MAGIC_FILE="$TDATA/$INFO_FILE"
         wsrep_log_info "Moving the backup to ${TDATA}"
-        timeit "Xtrabackup move stage" "$INNOMOVE"
-        if [[ $? -eq 0 ]];then
+        timeit "mariabackup move stage" "$INNOMOVE"
+        if [ $? -eq 0 ]; then
             wsrep_log_info "Move successful, removing ${DATA}"
             rm -rf "$DATA"
             DATA="$TDATA"
@@ -1229,7 +1289,9 @@ then
         wsrep_log_error "SST magic file ${MAGIC_FILE} not found/readable"
         exit 2
     fi
-    wsrep_log_info "Galera co-ords from recovery: $(cat '${MAGIC_FILE}')"
+
+    coords=$(cat "$MAGIC_FILE")
+    wsrep_log_info "Galera co-ords from recovery: $coords"
     cat "$MAGIC_FILE" # Output : UUID:seqno wsrep_gtid_domain_id
 
     wsrep_log_info "Total time on joiner: $totime seconds"